Search

The adolescent population with Down syndrome (DS) appears to show higher levels of body fat and lower levels of cardiorespiratory fitness or muscle strength than their peers without disabilities. There is a need to create physical activity programs to improve these data. The aim of this research was to determine the effects of a 16-week swimming program, strength program, and combined program (swimming and strength training) on body composition and health-related physical fitness on adolescents with DS and to assess whether there are differences in the results of the different training programs. Forty-five adolescents (17 female and 28 male; average age 15.5 [1.53] years) with DS were recruited and randomized to three groups (swim [n = 15], strength [n = 15], and combined [n = 15]). Results showed that the swim group had significant improvements in all health-related physical fitness variables and there was an improvement in some body-composition variables (p <.05). The strength and combined groups obtained minor improvements in the variables analyzed. In summary, a 16-week swim program consisting of three sessions of 60 min is able to improve levels of body composition and health-related physical fitness in adolescents with DS. The swim training program seems to be more effective in improving body composition and health-related physical fitness than the strength or combined program. These findings could be useful in different special-education centers due to the predisposition shown by the population with DS to this sport modality. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of 6-week barbell weighted-jump-squat (WJS) training with and without eccentric load reduction on explosive performance. Methods: Twenty well-trained male athletes were randomly assigned to either an experimental group (n = 10) or a control group (n = 10). Participants completed 12 WJS training sessions (6 sets of 5 repetitions of barbell back squat at 30% of 1-repetition maximum [1RM]) twice a week over a 6-week period. While the control group used 0% eccentric loading (ie, traditional WJS), the experimental group utilized a 50% eccentric loading reduction with a mechanical braking unit (ie, eccentric load set at 15% of 1RM). Performance assessments, including countermovement jump, 20-m sprint, standing long jump, and 1RM barbell back squat, were conducted both before (pretests) and after (posttests) the intervention. Results: Both the experimental group and the control group demonstrated a significant increase in countermovement-jump height (+6.4% [4.0%] vs +4.9% [5.7%]; P <.001) and peak power output (+2.3% [2.7%] vs +1.9% [5.1%]; P =.017), faster 20-m sprint times (+9.4% [4.8%] vs +9.2% [5.5%]; P <.001), longer standing long jump (+3.1% [2.5%] vs +3.0% [3.3%]; P <.001), and higher 1RM back squat (+6.4% [4.0%] vs +4.9% [5.7%]; P <.001) from pretests to posttests. However, there was no significant condition × time interaction for any variable (all P ≥.294). Conclusions: Both WJS training methods, with and without load reduction in the eccentric phase, effectively enhance explosive performance. Nevertheless, athletes in later stages of injury rehabilitation or intense training may find reducing eccentric load a more tolerable strategy for achieving similar performance gains compared with traditional isoinertial loading. [ABSTRACT FROM AUTHOR]

Purpose: This study explored the effects of 4 bench-press (BP) training programs with different velocity-loss (VL) thresholds (0%, 15%, 25%, and 50%) on strength gains and neuromuscular adaptations. Methods: Forty-six resistance-trained men (22.8 [4.4] y) were randomly assigned into 4 groups that differed in the VL allowed within the set: 0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50). Training loads (40%–55% 1-repetition maximum), frequency (2 sessions/wk), number of sets (3), and interset recovery (4 min) were identical for all groups. Participants completed the following tests before and after an 8-week (16-session) BP training program: (1) maximal isometric test, (2) progressive loading test, and (3) fatigue test in the BP exercise. During all tests, triceps brachii muscle electromyography was assessed. Results: After completing the resistance-training program, no significant group × time interactions were noticed for isometric and dynamic BP strength variables. The dose–response relationship exhibited an inverted U-shaped relationship pattern, with VL25 showing the greatest effect sizes for almost all strength variables analyzed. The total number of repetitions performed during the training program increased as the VL magnitude increased. Conclusions: The group that trained with high VL threshold (50%), which performed a total of 876 repetitions, did not experience additional strength gains compared with those experienced by the 0%, 15%, and 25% of VL groups, which performed significantly fewer repetitions (48, 357, and 547, respectively). These findings suggest that when light loads (40%–55% 1-repetition maximum) are used, low and moderate VL thresholds (0%–25%) provide a higher training efficiency. [ABSTRACT FROM AUTHOR]

Objective: The study aimed to investigate the effects of the level of contraction during isometric shoulder abduction at different abduction angles on muscle thickness and stiffness of the shoulder girdle in asymptomatic individuals. Design: Measurement properties study. Setting: Biomechanics and motion analysis lab. Participants: Twenty individuals volunteered to participate in this study. Main Outcome Measure: The subjects were tested for morphological and mechanical properties, expressed by thickness and stiffness of the supraspinatus tendon and muscle, and upper trapezius muscle. Moreover, acromiohumeral distance was also evaluated using B-mode ultrasound and shear-wave elastography. Intervention: The thickness and stiffness of the supraspinatus and upper trapezius muscle were assessed at 3 angles of abduction (0°, 60°, and 90°) and 3 levels of contraction (0%, 10%, and 20% of the maximal voluntary isometric contraction) using ultrasonography with shear-wave imaging. Moreover, the acromiohumeral distance was measured to establish the occupation ratio during passive movement. Results: The supraspinatus and upper trapezius muscle thickness and stiffness were significantly greater at 60° shoulder abduction compared with 0°, and 90° compared with 60°, as well as significantly greater at 20% maximal voluntary isometric contraction compared with 0% and 10% maximal voluntary isometric contraction. Thickness and stiffness were significantly greater in the supraspinatus compared with the upper trapezius muscle at all 3 angles of shoulder abduction for all 3 level of contractions. The acromiohumeral distance decreased significantly from 0° to 60° and from 60° to 90°. Conclusion: Morphological and mechanical properties of the supraspinatus and upper trapezius muscles depended on the relative level of muscle contraction and the angle of shoulder abduction. [ABSTRACT FROM AUTHOR]

Context: The Hip Stability Isometric Test (HipSIT) is commonly employed in clinical settings for evaluating the hip posterolateral muscle strength. In this study, we introduced the "Field Hip Stability Isometric Test" (F-HipSIT) and assessed the intrarater and interrater reliability of this strength assessment specifically designed for sports settings. Design: Reliability study. Methods: Two independent raters (A and B) went to athletes' training facilities to conduct 2 sessions of F-HipSIT spaced at least 1 week apart. The average peak force value from 3 valid attempts of each leg was recorded and normalized by the participant's body mass for statistical analysis. Results: Thirty male and 30 female amateur athletes took part in this study. Rater A obtained similar values in the first (0.39 [0.05] and 0.44 [0.07] kg·f/kg) and second (0.39 [0.06] and 0.45 [0.07] kg·f/kg) testing days for men and women, respectively. Rater B also found similar values in the first (0.35 [0.06] and 0.42 [0.08] kg·f/kg) and second (0.36 [0.06] and 0.45 [0.08] kg·f/kg) testing days for men and women, respectively. Excellent intrarater intraclass correlation coefficient (ICC) values were found for men (ICC =.922) and women (ICC =.930), with coefficient of variation of 6% to 8% and minimal detectable change of 0.06 to 0.10 kg·f/kg. The F-HipSIT presented good interrater reliability for men (ICC =.857) and women (ICC =.868), with coefficient of variation of 5% and minimal detectable change of 0.05 to 0.06 kg·f/kg. Conclusion: The F-HipSIT intrarater and interrater reliability among male and female recreational athletes supports this field test as a quick and convenient screening tool to monitor hip posterolateral muscle strength in sports settings. [ABSTRACT FROM AUTHOR]

Context: Poor knee biomechanics contribute to knee joint injuries. Neuromuscular control over knee position is partially derived from the hip. It is unknown whether isolated activation training of the gluteal muscles improves lower-extremity frontal plane mechanics. This study examined if a home-based hip muscle activation program improves performance on the Forward Step-Down Test as well as increases surface electromyography (sEMG) activation of the gluteal muscles. Design: The study utilized a single-group repeated-measures design. Methods: Thirty-five participants (24 females, mean age = 23.17 [SD 1.36] years) completed an 8-week hip muscle activation program. The Forward Step-Down Test score and sEMG of gluteus maximus and medius were assessed preintervention and postintervention. Results: Forward Step-Down Test scores improved significantly from preintervention (Mdn = 3.5) to postintervention (Mdn = 3.0, T = 109, P =.010, r =.31.), but this result did not meet clinical significance. sEMG analysis revealed a significant increase in mean gluteus maximus activation (P =.028, d = 1.19). No significant dose–response relationship existed between compliance and the Forward Step-Down Test scores or sEMG results. Conclusions: A home-based hip activation program increases gluteus maximus activation without clinically significant changes in frontal plane movement quality. Future studies may find clinical relevance by adding motor learning to the activation training program to improve functional muscle use. [ABSTRACT FROM AUTHOR]

Context: The hip adductor and abductor muscles play vital roles as stabilizers in the lower-extremity. Their activation during soccer-specific actions is essential, but local muscular fatigue can hinder athletic performance and increase the risk of injury. Design: This study aimed to observe the variations in frontal plane hip strength in female college soccer players before and after a high-workload soccer-specific training session. Furthermore, the study sought to compare the relative changes in hip strength with the internal and external load measures obtained during that session. Methods: Twenty female college soccer players participated in a retrospective observational study. Isometric hip adductor and abductor strength were measured before and after a training session in the college spring season. Measurements were taken with a handheld dynamometer (MicroFET 2) while the players were supine. Global positioning system sensors (Catapult Vector S7), commonly worn by players during training sessions and competitive matches, were used to measure external and internal loads. Statistical analyses were performed using paired samples t test to assess hip adductor and abductor strength changes before and after the training session. Spearman rank was used to identify correlation coefficients between global positioning system data and isometric hip strength. Results: The findings revealed significant decreases in the strength of the right hip adduction (P =.012, −7% relative change), right abduction (P =.009, −7.6% relative change), and left abduction (P =.016, −4.9% relative change) after the training session. Furthermore, relative decreases in hip isometric adduction and abduction strength are related to the distance covered at high speeds. Conclusion: The results of this study highlight that hip isometric adduction and abduction strength tend to decrease after exposure to high workloads during soccer-specific training. [ABSTRACT FROM AUTHOR]

Context: The aim of this study was to investigate the effects of 8-week ballistic-strength-training program using a validated specific throwing device (ie, Arm/Shoulder Specific Strength Device), on isokinetic shoulders' rotation muscle-torques and ratios as well as range of motion in team handball players. Design: A repeated-measures experimental design with a randomized controlled trial was used. Methods: Twenty-six high-level competitive male U-19 team handball players were randomly assigned into training (TG, n = 15) and control (n = 11) groups. The TG undertook a twice a week for 8-week periodized throws program with an individually predetermined optimal load. The program incorporated shackled eccentric and concentric exercises using the Arm/Shoulder Specific Strength Device. Peak torques, functional, and conventional ratios for both arms at different angular velocities (60°·s−1, 180°·s−1, and 300°·s−1) were assessed over time and between groups, using an isokinetic dynamometer. Results: A significant improvement for TG (P <.01; d = 1.13 [moderate]; +20.2%) of the concentric peak torques for dominant arm in external rotation was observed at 300°·s−1. Significant (P <.05–.01) increases were also noted for nondominant arm at the 3 studied angular velocities. In addition, 300°·s−1 eccentric peak torques of the dominant arm and nondominant arm have significantly improved for both external and internal rotations (P <.05; d =.99 [moderate] and d = 1.21 [large]; +15.7% and + 17.9%, respectively) with small changes at the other angular assessed velocities. Posttraining, TG's dominant arm showed significant improvements (P <.05–.01) in functional and conventional ratios at all velocities. Notably, significant differences (P <.05–.01) were observed at 60°·s−1 and across all velocities when comparing the TG with the control group. TG showed significant increase for internal rotation and external rotation shoulder range of motions (P <.05; d = 1.22–1.27 [large]), +5.0% and +7.7%, respectively). Conclusions: The specific 8-week throwing training program on the Arm/Shoulder Specific Strength Device showed significant performance improvements in almost all assessed isokinetic concentric and eccentric peak torques as well as internal and external range of motion increase for both arms while ensuring rotator cuff torque ratios and shoulder mobility in team handball real sport-specific condition. [ABSTRACT FROM AUTHOR]

Purpose: The optimal approach to hamstring training is heavily debated. Eccentric exercises reduce injury risk; however, it is argued that these exercises transfer poorly to improved hamstring function during sprinting. Some argue that other exercises, such as isometric exercises, result in better transfer to running gait and should be used when training to improve performance and reduce injury risk. Given the performance requirements of the hamstrings during the terminal swing phase, where they are exposed to high strain, exercises should aim to improve the torque production during this phase. This should improve the hamstrings' ability to resist overlengthening consequently, improving performance and limiting strain injury. Most hamstring training studies fail to assess running kinematics postintervention. Of the limited evidence available, only eccentric exercises demonstrate changes in swing-phase kinematics following training. Studies of other exercise modalities investigate effects on markers of performance and injury risk but do not investigate changes in running kinematics. Conclusions: Despite being inconsistent with principles of transfer, current evidence suggests that eccentric exercises result in transfer to swing-phase kinematics. Other exercise modalities may be effective, but the effect of these exercises on running kinematics is unknown. [ABSTRACT FROM AUTHOR]

Following anterior cruciate ligament reconstruction (ACLR), patients exhibit abnormal walking mechanics and quadriceps dysfunction. Quadriceps dysfunction has been largely attributed to muscle atrophy and weakness. While important, these factors do not capture intrinsic properties of muscle that govern its ability to generate force and withstand load. While fascicle abnormalities after ACLR have been documented in early stages of recovery (<12 mo), long-term effects of ACLR on fascicle mechanics remain unexplored. We evaluated quadriceps fascicle mechanics during walking 3 years post-ACLR and examined the relationship with knee mechanics. Participants included 24 individuals with ACLR and 24 Controls. Linear mixed models compared the ACLR, Contralateral, and Controls limbs for (1) quadriceps strength, (2) fascicle architecture and mechanics, and (3) knee mechanics. No difference in strength or overall fascicle length excursions was found between limbs. The ACLR limb exhibited longer fascicles at heel strike and peak knee extension moment (P <.001–.004), and smaller fascicle angles at heel strike, peak knee extension moment, and overall suppressed fascicle angle excursions (P <.001–.049) relative to the Contralateral and/or Control limb. This indicates an abnormality in fascicle architecture and mechanics following ACLR and suggests abnormalities in contractile function that cannot be explained by muscle weakness and may contribute to long-term gait irregularities. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the influence of knee joint range of motion (RoM) on the torque–velocity relationship and fatigue in the knee extensor muscles of 7 young (median = 26 y) and 7 older (68 y) adults. Each leg was assigned a RoM (35° or 75°) over which to perform a torque–velocity protocol (maximal isokinetic contractions, 60–300°·s−1) and a fatigue protocol (120 maximal contractions at 120°·s−1, 0.5 Hz). Six older participants were unable to reach 300°·s−1 over 35°. Therefore, the velocity eliciting 75% of peak torque at 60°·s−1 (V75, °·s−1) was calculated for each RoM from a fit of individual torque–velocity curves (60–240°·s−1), and ΔV75 (35°–75°) was determined. Fatigue (final torque/initial torque) was used to calculate Δfatigue (35°–75°). ΔV75 was not different from 0 in young (−28.3°·s−1 [−158.6 to 55.7], median [range], P =.091) or older (−18.5°·s−1 [−95.0 to 23.9], P =.128), with no difference by age (P =.710). In contrast, fatigue was greater for 75° in young (Δfatigue = 25.9% [17.5–30.3], P =.018) and older (17.2% [11.9–52.9], P =.018), with no effect of age (P =.710). These data indicate that, regardless of age, RoM did not alter the torque–velocity relationship between 60 and 240°·s−1, and fatigue was greater with a larger RoM. [ABSTRACT FROM AUTHOR]

Clinical Scenario: Existing studies have posited that incorporating abdominal enhancement techniques during lower-extremity exercises might mitigate compensatory pelvic motions and enhance the engagement of specific hip muscles. Clinical Question: Does performing lower-extremity exercises with abdominal enhancement techniques increase hip muscle activation levels in healthy individuals? Summary of Key Finding: After the literature review, 4 cross-sectional studies met the inclusion criteria and were included in this critically appraised topic. Clinical Bottom Line: There is moderate evidence to support that prone hip extension with abdominal enhancement may increase gluteus maximus and hamstring muscle activity. Gluteus medius activity may not be affected by abdominal enhancement during hip abduction exercises. Strength and Recommendation: The collective findings from the 4 cross-sectional trials indicate that the incorporation of abdominal enhancement techniques during lower-extremity exercises may have the potential to enhance targeted muscle activation levels in healthy individuals. Further research is recommended to establish more robust conclusions. [ABSTRACT FROM AUTHOR]

Clinical Scenario: The fascial relationship between scapular muscles and abdominal muscles has been documented from previous studies. However, it is not yet clear whether voluntary abdominal contraction has a beneficial effect on scapular muscle activity during shoulder exercises. Clinical Question: Do scapulothoracic muscle activation levels increase if shoulder exercises are performed with voluntary abdominal activation? Summary of Key Finding: After the literature review, 4 cross-sectional studies met the inclusion criteria and were included in this critically appraised topic. Clinical Bottom Line: There is moderate evidence to support dynamic shoulder exercises with voluntary abdominal contraction can increase trapezius and serratus anterior muscle activation level in asymptomatic shoulders. Strength and Recommendation: Findings from 4 cross-sectional trials indicate that there is moderate evidence supporting that dynamic shoulder exercises performed with voluntary abdominal contraction can increase scapular muscle activity. [ABSTRACT FROM AUTHOR]

Stimulation of sympathetic nerves in the vas deferens yields biphasic contractions consisting of a rapid transient component resulting from activation of P2X1 receptors by ATP and a secondary sustained component mediated by activation of α1-adrenoceptors by noradrenaline. Noradrenaline can also potentiate the ATP-dependent contractions of the vas deferens, but the mechanisms underlying this effect are unclear. The purpose of the present study was to investigate the mechanisms underlying potentiation of transient contractions of the vas deferens induced by activation of α1-adrenoceptors. Contractions of the mouse vas deferens were induced by electric field stimulation (EFS). Delivery of brief (1s duration) pulses (4 Hz) yielded transient contractions that were inhibited tetrodotoxin (100 nM) and guanethidine (10 µM). α,β-meATP (10 µM), a P2X1R desensitising agent, reduced the amplitude of these responses by 65% and prazosin (100 nM), an α1-adrenoceptor antagonist, decreased mean contraction amplitude by 69%. Stimulation of α1-adrenoceptors with phenylephrine (3 µM) enhanced EFS and ATP-induced contractions and these effects were mimicked by the phorbol ester PDBu (1 µM), which activates PKC. The PKC inhibitor GF109203X (1 µM) prevented the stimulatory effects of PDBu on ATP-induced contractions of the vas deferens but only reduced the stimulatory effects of phenylephrine by 40%. PDBu increased the amplitude of ATP-induced currents recorded from freshly isolated vas deferens myocytes and HEK-293 cells expressing human P2X1Rs by 93%. This study indicates that: (1) potentiation of ATP-evoked contractions of the mouse vas deferens by α1-adrenoceptor activation were not fully blocked by the PKC inhibitor GF109203X and (2) that the stimulatory effect of PKC on ATP-induced contractions of the vas deferens is associated with enhanced P2X1R currents in vas deferens myocytes.

Context: The hamstrings are the most commonly injured muscle in sports and are especially injury prone in lengthened positions. Measuring knee muscle strength in such positions could be relevant to establish injury risk. Handheld dynamometry has been shown to be a valid, reliable, and practical tool to measure isometric muscle strength clinically. The aim of this study was to assess the validity and reliability of the assessment of isometric knee muscle strength with a handheld dynamometer (HHD) at various muscle lengths, by modifying the hip and knee angles during testing. Design: Concurrent validity and test--retest reliability. Methods: Thirty young healthy participants were recruited. Hamstring and quadriceps isometric strength was measured with a HHD and with an isokinetic dynamometer, over 2 testing sessions, in a randomized order. Isometric strength was measured on the right lower limb in 6 different positions, with the hip at either 0° or 80° of flexion and the knee at either 30°, 60°, or 90° of flexion. Pearson and Spearman correlations were used to assess the validity, and intraclass correlation coefficients were calculated to establish the test--retest reliability of the HHD. Results: Good to excellent reliability and moderate to high validity were found in all the tested muscle length positions, except for the hamstrings in a seated position with the knee extended at 30°. Conclusions: The use of a HHD is supported in the clinical setting to measure knee muscle strength at varying muscle lengths in healthy adults, but not for the hamstrings in a lengthened position (hip flexed and knee extended). These results will have to be confirmed in sport-specific populations. [ABSTRACT FROM AUTHOR]

Context: Injury-related fear and quadriceps strength are independently associated with secondary anterior cruciate ligament (ACL) injury risk. It is not known whether injury-related fear and quadriceps strength are associated, despite their individual predictive capabilities of secondary ACL injury. The purpose of this study was to examine the association between injury-related fear and quadriceps strength in individuals at least 1 year after ACL reconstruction (ACLR). Design: Cross-sectional study. Methods: Forty participants between the ages of 18 and 35 years at least 1 year post unilateral primary ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) and a standard isokinetic quadriceps strength assessment using the Biodex Isokinetic Dynamometer. Pearson Product-Moment correlations were used to examine the linear association between the TSK-11 scores and peak torque (in nanometers per kilogram) for each limb and between the TSK-11 scores and limb symmetry indices for each limb. Pearson Product-Moment correlation coefficients (r) were interpreted as very high (.90--1.00), high (.70--.90), moderate (.50--.70), low (.30--.50), and no correlation (.00--.30). Results: The average TSK-11 score was 18.2 (5.3), average ACLR peak quadriceps torque was 1.9 (0.50) N·m/kg, average contralateral peak quadriceps torque was 2.3 (0.48) N·m/kg, and average limb symmetry index was 85.3% (12.6%). There was no statistically significant correlation between the TSK-11 and peak quadriceps torque on the ACLR limb (r = .12, P = .46), the TSK-11 and contralateral limb (r = .29, P = .07), or the TSK-11 and limb symmetry index (r = -.18, P = .27). Conclusions: There was no association between kinesiophobia and peak isokinetic quadriceps strength in individuals at least 1 year post-ACLR. Both factors, independently, have been shown to influence risk of secondary injury in patients after ACLR. [ABSTRACT FROM AUTHOR]

Context: The purpose of the study was to develop normative ranges and standards for knee and shoulder isokinetic and anthropometric values. These standards can be qualitatively interpreted and allow practitioners to classify isokinetic and anthropometric values more objectively for university-level netball players. Design: Posttest only observational study design. All players were only evaluated once during the in-season to generate normative ranges. Methods: A total of 51 female players volunteered. Participants were evaluated on an isokinetic dynamometer at 60° per second to obtain knee-extensor and knee-flexor values as well as shoulder-flexor and shoulder-extensor values. A total of 16 anthropometric variables were collected including stature, body mass, 8 skinfolds, and 6 circumferences. Between-group differences were calculated to determine whether playing level was a differentiating factor in data. Results: Normative standards were developed for isokinetic parameters associated with the knee and shoulder joints as well as skinfolds and circumference measures. No statistically significant between-group differences were evident (χKruskal-Wallis²[2] = 3.96, P = .140). Conclusion: These standards can be used by coaches and practitioners to set attainable goals for individual players or those from secondary leagues, classify individual and team-based performances, and facilitate decision-making processes. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r >.770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance. [ABSTRACT FROM AUTHOR]

Knowledge of how the different types of sedentary behaviors (SB) are associated with functional limitations can guide professionals who work with older adults on better recommendations about the amount of daily time that should be encouraged in each type of SB. The objective was to estimate the associations between two SB typologies (SB television [TV] and SB computer/internet) and the presence of handgrip strength, lower limb strength, gait speed, and balance limitations in Brazilian community-dwelling older adults. This is a cross-sectional study with 1,298 community-dwelling older adults (≥60 years). SB was assessed by self-reporting daily time spent watching TV or using computer/internet (categorized into <2, 3–4, and ≥5 hr/day). Outcomes were handgrip strength, lower limb strength, gait speed, and balance limitations considering referenced cutoff points. Older adults in SB TV ≥5 hr/day had 1.75 (95% confidence interval [CI] [1.07, 2.86]) and 1.88 (95% CI [1.02, 3.46]) times more chances of handgrip strength and gait speed limitations, respectively. On the other hand, those who spent 3–4 and ≥5 hr/day in SB computer/internet had 0.45 (95% CI [0.20, 0.99]) and 0.37 (95% CI [0.15, 0.93]) had less chances of lower limb strength and balance limitations, respectively. In conclusion, functional limitations would be associated differently depending on the type of SB in the older adults sampled. [ABSTRACT FROM AUTHOR]

Context: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). Design: A correlation study. Methods: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. Results: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between −.3 and.1). Conclusions: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump. [ABSTRACT FROM AUTHOR]

Purpose: This study examined performance and physiological adaptations following 3 weeks of repeated-sprint training (RST) with blood-flow restriction (BFR) or without (non-BFR). Methods: Twenty-six semiprofessional and amateur adult male team-sport players were assessed for repeated-sprint ability, anaerobic capacity, leg lean mass, neuromuscular function, and maximal aerobic capacity before and after RST. Participants completed 9 cycling RST sessions (3 sets of 5–7 × 5-s sprints, 25-s passive recovery, 3-min rest) over a 3-week period with BFR or non-BFR. Results: During RST sessions, the BFR group demonstrated lower mean power output compared with non-BFR (−14.5%; g = 1.48; P =.001). Significant improvements (P <.05) in mean and peak power output during repeated-sprint ability (+4.1%; g = 0.42, and + 2.2%; g = 0.25, respectively) and anaerobic capacity (+4.8%; g = 0.47, and + 4.7%; g = 0.32, respectively) tests, leg lean mass (+2.0%; g = 0.16), and peak aerobic power (+3.3%; g = 0.25) were observed from pretesting to posttesting without any between-groups differences. No significant changes (P >.05) were observed for maximal isometric voluntary contraction and maximal aerobic capacity. Peak rate of force development decreased (P =.003) in both groups following RST (−14.6%; g = 0.65), without any between-groups differences. Conclusions: Repeated-sprint ability, anaerobic capacity, leg lean mass, and peak aerobic power improved following 3 weeks of RST; however, the addition of BFR did not further enhance adaptations. Interestingly, comparable improvements were achieved between groups despite lower external loads experienced during RST sessions with BFR. [ABSTRACT FROM AUTHOR]

Objective: To determine the criterion validity and test–retest reliability of isometric finger-strength testing in 6 differentiated grip techniques for the assessment of bouldering ability among male climbers. Methods: We recruited participants at climbing gyms in Sweden and through online advertisements. We included climbers over 15 years of age with a minimum bouldering performance level of 17 International Rock Climbing and Research Association (IRCRA) for men and 15 IRCRA for women. We tested unilateral, maximal isometric peak finger strength in the front 3 drag, half crimp, closed crimp, 35 sloper, 45 × 90-mm, and 90 × 90-mm pinch through maximal force deloaded of a force plate. We analyzed criterion validity, test–retest reliability, and capacity to determine bouldering performance ability using a stepwise multivariable regression model. Results: Women were excluded from the analysis due to insufficient sample size (n = 16). Thirty-two male participants were included in the primary analysis. The median (interquartile range) age in the advanced and elite group was 27 (25; 35) and 23 (22; 32) years, respectively. The half crimp for the participants' weak and strong hand displayed the highest ability to determine bouldering grade performance, explaining 48% to 58% of the variance. In the stepwise regression, maximal strength in the half crimp and the front 3 drag collectively explained 66% of the variance for performance. Conclusion: Strength in the half crimp proved the most important performance indicator. The results of this study provide a reliable and valid framework for maximal isometric peak finger-strength testing in advanced and elite male boulderers. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the postactivation performance-enhancement effect of maximal voluntary isometric contraction (MVIC) at the starting position on power-clean performance over a series of contrast sets. Methods: Eighteen male (age: 31 [3.7] y, body mass: 76.8 [9.1] kg, height: 175.0 [5.2] cm) and 2 female (age: 27.5 [3.5] y, body mass: 53.3.8 [2.0] kg, height: 158.5 [4.9] cm) resistance-trained individuals performed a contrast postactivation performance-enhancement protocol (isometric contrast training condition [ISO]) consisting of 3 sets of 3 MVICs alternated with 3 power cleans, with an intracontrast rest period of 1 minute. A control protocol consisted of 3 sets of 3 power cleans were performed in a separate session. Barbell velocity during the power clean was measured as an indicator of performance. Results: A significant time effect was observed for both mean velocity (MV; P <.001) and peak velocity (PV; P =.008). Time × group (P =.415–.444) and group (P =.158–.210) effects showed no significant difference for either MV or PV. However, differences in MV and PV between the corresponding sets of ISO and control condition exceeded the minimum worthwhile change, showing a small to moderate effect (MV: d = 0.38–0.50, PV: d = 0.35–0.50) in favor of ISO. There was no significant difference in rating of perceived exertion between conditions (P =.385, d = 0.22). Conclusion: Power-clean performance was potentiated after 1 minute of rest following 3 repetitions of MVIC across 3 sets. Furthermore, the ISO protocol did not result in greater perception of exertion. These results indicate that coaches may incorporate MVICs as the postactivation performance-enhancement stimulus during contrast training involving the power-clean exercise. [ABSTRACT FROM AUTHOR]

Inherited mutations in human beta-cardiac myosin (M2β) can lead to severe forms of heart failure. The E525K mutation in M2β is associated with dilated cardiomyopathy (DCM) and was found to stabilize the interacting heads motif (IHM) and autoinhibited super-relaxed (SRX) state in dimeric heavy meromyosin. However, in monomeric M2β subfragment 1 (S1) we found that E525K enhances (threefold) the maximum steady-state actin-activated ATPase activity (k cat) and decreases (eightfold) the actin concentration at which ATPase is one-half maximal (K ATPase). We also found a twofold to fourfold increase in the actin-activated power stroke and phosphate release rate constants at 30 μM actin, which overall enhanced the duty ratio threefold. Loaded motility assays revealed that the enhanced intrinsic motor activity translates to increased ensemble force in M2β S1. Glutamate 525, located near the actin binding region in the so-called activation loop, is highly conserved and predicted to form a salt bridge with another conserved residue (lysine 484) in the relay helix. Enhanced sampling molecular dynamics simulations predict that the charge reversal mutation disrupts the E525-K484 salt bridge, inducing conformations with a more flexible relay helix and a wide phosphate release tunnel. Our results highlight a highly conserved allosteric pathway associated with actin activation of the power stroke and phosphate release and suggest an important feature of the autoinhibited IHM is to prevent this region of myosin from interacting with actin. The ability of the E525K mutation to stabilize the IHM likely overrides the enhanced intrinsic motor properties, which may be key to triggering DCM pathogenesis.

Context: With the high prevalence of anterior cruciate ligament rupture among young and active individuals, rehabilitation after the injury and surgery should meet the current evidence-based recommendations to restore knee function and reduce the risk of further injury. This study aimed to investigate the current rehabilitation practices and return to sports (RTS) criteria after anterior cruciate ligament reconstruction (ACLR) among physical therapists in Saudi Arabia. Design: Online cross-sectional survey-based study. Methods: A total of 177 physical therapists in Saudi Arabia participated in this survey. The survey included questions about the preferred postoperative timing and frequency of rehabilitation, current views on the importance of preoperative and postoperative rehabilitation to the overall outcomes, the timeframe of RTS, and the decision-making process to RTS. Results: Most therapists (96.6%) believed preoperative rehabilitation was essential/important to postoperative outcomes. Two-thirds encouraged patients to start rehabilitation program within 1 to 4 days immediately post-ACLR. RTS was permitted 6 to 9 months post-ACLR by 60% of therapists if satisfied with patient progress and capacity. Factors considered before RTS included knee strength (72.9%), functional capacity (86.4%), lower limb and trunk mechanics (62.7%), and psychological readiness (42.2%). Knee strength was assessed by manual muscle testing (39%), handheld dynamometry (15.3%), and isokinetic dynamometer (13.6%). While 60% of the therapists used single-limbed hop for distance for evaluating functional capacity, only 27.1% used a hop test battery. Conclusions: The surveyed physical therapists in Saudi Arabia demonstrated variations in the current rehabilitation practices and RTS criteria post-ACLR. Over half of the surveyed therapists considered preoperative rehabilitation essential to postoperative outcomes. However, the therapists should update their perspective with current evidence-based practice regarding the RTS timeframe, psychological readiness assessment for RTS, and knee strength evaluation using objective measurements. [ABSTRACT FROM AUTHOR]

Context: The aim of this study was to analyze the muscle activity of the hamstring muscles and the lateral gastrocnemius during different variants of the single-leg bridge (SLB) in futsal players. Design: Cross-sectional study. Methods: Twenty-two futsal players (age = 24.8 [3.9] y) volunteered to participate in this study. The participants performed 3 variations of the SLB with the knee flexed at 45°. The first position was performed with the ankle in plantar position with flat support, the second with the ankle in dorsiflexion (DF) with heel support, and the third with the ankle in DF and external rotation (ER) with heel support. The Wilcoxon rank-sum test assessed the difference between variables for samples with the rank-biserial correlation effect size. Spearman correlation coefficients were used to examine the associations of the percentage maximal voluntary isometric contraction for each muscle with peak force and rate of force development with 3 different variances of the SLB. Results: The variation of ankle DF and ER with heel support generated higher muscle activity in BF in concentric (P<.01, effect size [ES] = -0.613); isometric (P<.042, ES = -0.494); and eccentric (P<.005, ES = -0.668) contraction than ankle DF with heel support. In contrast, the variation of ankle DF and ER with heel support generated fewer muscle activity in lateral gastrocnemius in concentric (P < .001, ES = 0.779); isometric (P < .003, ES = 0.708); and eccentric (P < .014, ES = 0.589) contraction than ankle DF with heel support. Conclusions: The position of DF and ER was the best position in SLB to train the BF. It could be convenient to start rehabilitation of the BF with flat foot postition or ankle in DF with heel support and progress with the position of the ankle in DF and ER with heel support. [ABSTRACT FROM AUTHOR]

Prior studies have explored the relationship between knee valgus and musculoskeletal variables to formulate injury prevention programs, primarily for females. Nonetheless, there is insufficient evidence pertaining to professional male soccer players. Here, the aim was to test the correlation of lateral trunk inclination, hip adduction, hip internal rotation, ankle dorsiflexion range of motion, and hip isometric strength with knee valgus during the single-leg vertical jump test. Twenty-four professional male soccer players performed a single-leg vertical hop test, hip strength assessments, and an ankle dorsiflexion range of motion test. A motion analysis system was employed for kinematic analysis. Maximal isometric hip strength and ankle dorsiflexion range of motion were tested using a handheld dynamometer and a digital inclinometer, respectively. The correlation of peak knee valgus with peak lateral trunk inclination was.43 during the landing phase (P =.04) and with peak hip internal rotation was −.68 (P <.001). For knee valgus angular displacement, only peak lateral trunk inclination presented a moderate positive correlation (r =.40, P =.05). This study showed that trunk and hip kinematics are associated with knee valgus, which could consequently lead to increased knee overload in male professional soccer players following a unilateral vertical landing test. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether there are bilateral and interdigit differences in the maximal force production of experienced climbers and whether these differences are mediated by ability level or preferred style of climbing. Methods: Thirty-six male climbers (age 30 [9.4] y) took part in a single-session trial to test their maximal force production on both hands. The tests included a one-arm maximal isometric finger flexor strength test (MIFS) and a one-arm individual MIFS. Bilateral differences were analyzed by strongest hand (defined as the hand that produced the highest MIFS value) and dominance (defined as the writing hand). Results: A pairwise t test found that MIFS was significantly greater for the strongest hand (mean difference = 4.1%, 95% CI, −0.052 to 0.029, P <.001), with handedness explaining 89% of the variation. A 2-way mixed-model analysis of variance determined that there were no interactions between preferred style (bouldering or sport climbing) and MIFS or between ability level (advanced or elite) and MIFS. Conclusions: Climbers have significant finger flexor strength bilateral asymmetries between their strongest and weakest hand. Moreover, when dominance is controlled, this difference in strength is present, with the dominant hand producing more force. Neither preferred style of climbing nor the ability level of the climbers could explain these asymmetries. As such, practitioners should consider regularly monitoring unilateral strength, aiming to minimize the likelihood of large bilateral asymmetry occurring. [ABSTRACT FROM AUTHOR]

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of a Nordic hamstring exercise intervention on biceps femoris long head, semitendinosus, and semimembranosus muscle's activity and relative contributions through multichannel electromyography. Twenty-four injury-free male basketball players (mean age 20 [3] y) were randomly assigned to a 12-week intervention (n = 13) or control group (n = 11). The primary outcome measures were normalized muscle activity (percentage of maximal voluntary isometric contraction, %MVIC) and relative contribution of hamstring muscles over 12 weeks. No effects were found on any of the primary outcome measures. Between-group differences over 12 weeks were 2.7%MVIC (95% confidence interval 95% CI, −0.7 to 6.1) for the biceps femoris long head, 3.4%MVIC (95% CI, −1.4 to 8.2) for the semitendinosus, and 0.8%MVIC (95% CI, −3.0 to 4.6) for the semimembranosus, P =.366. Between-group differences over 12 weeks were 1.0% relative contribution (%con; 95% CI, −3.0 to 5.1) for the biceps femoris long head, 2.2% relative contribution (95% CI, −2.8 to 7.2) for the semitendinosus, and −3.3% relative contribution (95% CI, −6.4 to −0.1) for the semimembranosus P =.258. A positive value implies a higher value for the Nordic group. A Nordic hamstring exercise intervention did not affect the level of muscle activity and relative contribution of hamstring muscles in performance of the Nordic hamstring exercise. [ABSTRACT FROM AUTHOR]

TRAAK, TREK-1, and TREK-2 are mechanosensitive two-pore domain K+ (K2P) channels that contribute to action potential propagation, sensory transduction, and muscle contraction. While structural and functional studies have led to models that explain their mechanosensitivity, we lack a quantitative understanding of channel activation by membrane tension. Here, we define the tension response of mechanosensitive K2Ps using patch-clamp recording and imaging. All are low-threshold mechanosensitive channels (T10%/50% 0.6-2.7 / 4.4-6.4 mN/m) with distinct response profiles. TRAAK is most sensitive, TREK-1 intermediate, and TREK-2 least sensitive. TRAAK and TREK-1 are activated broadly over a range encompassing nearly all physiologically relevant tensions. TREK-2, in contrast, activates over a narrower range like mechanosensitive channels Piezo1, MscS, and MscL. We further show that low-frequency, low-intensity focused ultrasound increases membrane tension to activate TRAAK and MscS. This work provides insight into tension gating of mechanosensitive K2Ps relevant to understanding their physiological roles and potential applications for ultrasonic neuromodulation.

Details of the anatomy and behavior of the structures responsible for human eye movements have been extensively elaborated since the first modern biomechanical models were introduced. Based on these findings, a finite element model of human ocular adduction is developed based on connective anatomy and measured optic nerve (ON) properties, as well as active contractility of bilaminar extraocular muscles (EOMs), but incorporating the novel feature that globe translation is not otherwise constrained so that realistic kinematics can be simulated. Anatomy of the hemisymmetric model is defined by magnetic resonance imaging. The globe is modeled as suspended by anatomically realistic connective tissues, orbital fat, and contiguous ON. The model incorporates a material subroutine that implements active EOM contraction based on fiber twitch characteristics. Starting from the initial condition of 26° adduction, the medial rectus (MR) muscle was commanded to contract as the lateral rectus (LR) relaxed. We alternatively modeled absence or presence of orbital fat. During pursuit-like adduction from 26 to 32°, the globe translated 0.52 mm posteriorly and 0.1 mm medially with orbital fat present, but 1.2 mm posteriorly and 0.1 mm medially without fat. Maximum principal strains in the optic disk and peripapillary reached 0.05-0.06, and von-Mises stress 96 kPa. Tension in the MR orbital layer was ~ 24 g-force after 6° adduction, but only ~ 3 gm-f in the whole LR. This physiologically plausible simulation of EOM activation in an anatomically realistic globe suspensory system demonstrates that orbital connective tissues and fat are integral to the biomechanics of adduction, including loading by the ON.

Muscle contraction at the macrolevel is a physiological process that is ultimately due to the interaction between myosin and actin proteins at the microlevel. The actin–myosin interaction involves slow attachment and detachment responses and a rapid temporal change in protein conformation called power-stroke. Jump-diffusion models that combine jump processes between attachment and detachment with a mechanical description of the power-stroke have been proposed in the literature. However, the current formulations of these models are not fully compatible with the principles of thermodynamics. To solve the problem of coupling continuous mechanisms with discrete chemical transitions, we rely on the mathematical formalism of Poisson random measures. First, we design an efficient stochastic formulation for existing muscle contraction partial differential equation models. Then, we write a new jump-diffusion model for actin–myosin interaction. This new model describes both the behavior of muscle contraction on multiple time scales and its compatibility with thermodynamic principles. Finally, following a classical calibration procedure, we demonstrate the ability of the model to reproduce experimental data characterizing muscle behavior on fast and slow time scales. [ABSTRACT FROM AUTHOR]

Context: Hip and groin injuries are common in field sports such as football, with measurement of hip strength and range of motion (ROM) recommended for assessment of these conditions. We aimed to report hip strength, hip ROM, and functional task performance in young elite Australian football athletes. Design: Cross-sectional study. Methods: Fifty-eight newly drafted Australian Football League athletes completed hip abduction, adduction, internal rotation, external rotation, and flexion strength testing with an adjustable stabilized or hand-held dynamometer. Hip internal rotation and external rotation, bent knee fall out, and ankle dorsiflexion ROM were also measured. Players completed hop for distance, side bridge, and star excursion balance functional tests. We compared findings between the dominant and nondominant limbs. Results: We found small deficits unlikely to be clinically meaningful in the dominant limb for hip abduction and adduction strength, and a small deficit in the nondominant limb for external rotation strength and side bridge time. Athletes had lower hip internal rotation (mean difference 2.56°; 95% confidence interval, 0.87 to 4.26) and total rotation ROM (2.03°; 95% confidence interval, 0.06 to 4.01) on the dominant limb. Conclusions: There were no meaningful differences between dominant and nondominant limbs for hip strength, ROM, or functional tests. Our results may be used for benchmarking young male Australian football athletes when targeting optimal strength and returning from injury. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of graded hypoxia during exhaustive intermittent cycling on subsequent rapid and maximal torque-production capacity. Methods: Fifteen well-trained cyclists repeated intermittent cycling bouts (15 s at 30% of anaerobic power reserve; rest = 45 s) until exhaustion at sea level (FiO2 ∼0.21/end-exercise arterial oxygen saturation ∼96%), moderate hypoxia (FiO2 ∼0.16/∼90%), and severe hypoxia (FiO2 ∼0.12/∼79%). Rapid (rate of torque development [RTD]) and maximal isometric torque-production capacities of the knee extensors were assessed at baseline (visit 1) and exhaustion (visits 2–4). Results: Exercise capacity decreased with hypoxia severity (39 [30], 22 [13], and 13 [6] cycle efforts in sea level, moderate hypoxia, and severe hypoxia, respectively; P =.002). Changes in maximal-voluntary-contraction torque between baseline and postexercise in all conditions were not statistically significant (pooled values: −2.6% [5.7%]; P =.162). Peak RTD measured postexercise was reduced below baseline in all conditions (–21.5% [5.1%]; P ≤.015). Compared with baseline, absolute RTD values were lower at 0- to 30-millisecond (–35.1% [5.3%], P ≤.020), 0- to 50-millisecond (–40.0% [3.9%], P ≤.002), 0- to 100-millisecond (–30.7% [3.7%], P ≤.001), and 0- to 200-millisecond (–18.1% [2.4%], P ≤.004) time intervals in all conditions. Conclusions: Exhaustive intermittent cycling induces substantial yet comparable impairments in RTD of knee extensors between normoxia and moderate to severe hypoxia. [ABSTRACT FROM AUTHOR]

Purpose: After anterior cruciate ligament reconstruction (ACL-R), knee muscle strength symmetry is used as part of the return-to-sport criteria. However, little is known about the changes in the force–velocity (F–V) relationship, which could affect athletic performance. This study investigated the F–V relationship of knee muscles at 4 and 8 months after ACL-R, using the 2-point method tested by isokinetic dynamometry. Methods: A total of 103 physically trained individuals (24.6 [9.3] y, 59.2% male) who underwent primary ACL-R were included. Demographic information and surgery characteristics were collected at 6 weeks postoperatively. Isokinetic knee flexors' and extensors' peak torques were measured at 60° and 240° per second in the concentric mode at 4 and 8 months postoperative. Peak torques and angular velocities were converted to force and linear velocity for calculating maximum isometric force (F0) and the slope of the regression line (F–V slope). Results: At 4 and 8 months postoperative, F0 was significantly lower and F–V slope was significantly less steep (less negative) on the operated leg compared with the nonoperated leg for knee extensors (P <.001) and flexors (P <.001–.002). The limb symmetry index calculated using F0 was lower than the limb symmetry indexes assessed at 60° and 240° per second, especially for knee flexors (P <.001). The use of patellar tendon grafts was associated with lower F0 and a less steep F–V slope compared with hamstring tendon grafts (P <.010). Conclusion: The isokinetic 2-point model assessing the F–V relationship provides additional and relevant insight for evaluating knee muscle strength after ACL-R. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the contribution of splenius capitis, sternocleidomastoid, and upper fibers of trapezius activation to the gains in rate of force development (RFD) of the head and neck during maximum voluntary ballistic contractions. Methods: RFD gain was facilitated by a single-session intervention for maximum voluntary ballistic contractions in the anterior direction, oriented at 45° to the midsagittal plane, which require active restraint of axial rotation. Muscle activation for the agonist (sternocleidomastoid) and 2 antagonists (splenius capitis and upper fibers of trapezius) was evaluated. The study sample included 12 physically active men (mean age, 22.6 y). RFD (N·m·s−1; 0–100 ms) and integrated muscle activity (50 ms before and 100 ms after force onset) were measured at 10 minutes, 20 minutes, and 2 days postintervention, relative to baseline. Muscle activation predictive of RFD gains was evaluated by linear regression analysis. RFD reproducibility was evaluated using the coefficient of variation of the typical error. Results: The intervention yielded a 1.95- to 2.39-fold RFD gain (P ≤.05), with greater RFD gain for participants with a lower peak moment of force (<10.9 N·m) than those with a higher peak moment (≥10.9 N·m) at baseline (P ≤.002). For the low group, 65% to 74% of the RFD gain was predicted by ipsilateral sternocleidomastoid activation, with ipsilateral splenius capitis activation predicting 77% to 92% of RFD gain for the high group. Absolute peak and impulse of static force were greater for the high than for the low group (P ≤.04). RFD reproducibility was high (coefficient of variation of the typical error ≤ 14.4%). Conclusions: The agonist- and antagonist-focused synergies might reflect different functional priorities, higher RFD gain compared with higher head–neck force. [ABSTRACT FROM AUTHOR]

Background: Low-intensity resistance exercise therapy (LIRET) based on myofascial chains, applied to both affected and nonlocal joints, is an effective method for knee osteoarthritis (OA) rehabilitation. This study applied LIRET in a comparison of prevalues and postvalues of lower-limb tension in female patients with knee OA and asymptomatic participants. Methods: Twenty-four female participants with knee OA and 20 asymptomatic women took part in a 3-month long application of LIRET. Participants' ankle passive torque and ankle range of motion in the sagittal plane were assessed with an isokinetic dynamometer. The collected values were used to estimate the sagittal-plane lower-limb tension. Results: Compared with the asymptomatic group, participants with knee OA presented decreased maximum ankle dorsiflexion (P <.001), decreased ankle plantar flexion range (P =.023), ankle resting position more inclined to dorsiflexion (P =.017), increased ankle dorsiflexion stiffness (P =.005), and lower ankle plantar flexion stiffness (P =.034). After exercise intervention, the knee OA group self-reported less knee pain (P <.001), improved physical function (P <.001), increased maximum dorsiflexion (P =.021), and increased plantar flexion range (P <.001). While plantar flexion stiffness increased (P =.037), dorsiflexion stiffness decreased (P =.015) and ankle resting position moved toward dorsiflexion (P =.002). Results suggest possible decreased anterior leg tension and possible increased posterior leg tension in patients with knee OA. Conclusions: The results supported that knee OA patients present imbalanced myofascial tension of lower limbs. LIRET based on myofascial chains appears to decrease pain, and stiffness, and improve physical function of patients with knee OA and change their lower-limb tension. [ABSTRACT FROM AUTHOR]

Context: Hip muscle imbalance, especially between gluteal muscles and tensor fasciae latae (TFL), is one of the risk factors for developing low back pain which should be considered in rehabilitation programs. This study compared the effect of exercises with gluteal-to-TFL muscle activation index above and below 50 on pain intensity, disability, and lower limbs' range of motion (ROM) in patients with nonspecific chronic low back pain. Design: A semiexperimental intervention study with a pretest and posttest. Methods: A total of 45 patients with nonspecific chronic low back pain were randomly divided into 2 experimental groups of gluteal-to-TFL muscle activation index above 50 (n = 15), below 50 (n = 15), and a control group (n = 15). Pain intensity (visual analog scale), disability (Roland–Morris Disability Questionnaire), and lower limbs' ROM including hip extension, hip abduction, hip external rotation, and knee extension (goniometer) were assessed at pretest and after 8 weeks of intervention. Results: Within-group comparison showed significant improvement of pain, disability, and ROMs in both experimental groups. No significant changes were observed in the control group. In between-group analysis, significant differences were observed in group of gluteal-to-TFL muscle activation index above 50 for only pain (P =.03) and disability (P =.01). For ROMs, although clinical improvement of lower limbs' ROMs was higher in group of gluteal-to-TFL muscle activation index above 50, no statistically significant differences were found between 2 experimental groups. Both experimental groups were superior to the control group for all outcomes. Conclusions: Findings indicate the statistically and clinically superior effectiveness of exercises with a gluteal-to-TFL muscle activation index above 50 in the reduction of pain and disability. Based on the clinical significance of exercises with a gluteal-to-TFL muscle activation index above 50 for improving ROMs, utilizing specific exercises that more activated gluteal muscle compared to TFL is recommended for patient with restricted lower limbs' ROMs. [ABSTRACT FROM AUTHOR]

Context: Different resistance exercise determinants modulate the musculotendinous adaptations following eccentric hamstring training. The Nordic Hamstring Exercise (NHE) can be performed 2-fold: the movement velocity irreversibly increases toward the end of the range of motion or it is kept constant. Design: This cross-sectional study aimed to investigate if the downward acceleration angle (DWAangle) can be used as a classification parameter to distinguish between increasing and constant velocity NHE execution. Furthermore, the kinetic and kinematic differences of these 2 NHE execution conditions were examined by analyzing the DWAangle in relation to the angle of peak moment. Methods: A total of 613 unassisted NHE repetitions of 12 trained male sprinters (22 y, 181 cm, 76 kg) were analyzed. Results: The majority of analyzed parameters demonstrated large effects. NHEs with constant velocity (n = 285) revealed significantly higher impulses (P <.001; d = 2.34; + 61%) and fractional time under tension (P <.001; d = 1.29; +143%). Although the generated peak moments were significantly higher for constant velocity (P =.003; d = 0.29; +4%), they emerged at similar knee flexion angles (P =.167; d = 0.28) and revealed on average just low relationships to the DWAangle ( R mean 2 = 22.4 %). DWAangle highly correlated with the impulse ( R mean 2 = 60.8 %) and δ (DWAangle–angle of peak moment; R mean 2 = 83.6 %). Conclusions: Relating DWAangle to angle of peak moment assists to distinguish between significantly different NHE execution, which will potentially elicit different musculotendinous adaptations. These insights are essential for coaches and athletes to understand how to manipulate eccentric hamstring training to change its purpose. [ABSTRACT FROM AUTHOR]

Context: Long-lever shoulder strength tests may aid clinical decision-making regarding return to sport after a shoulder injury. The Athletic Shoulder Test (AST) was developed to measure force production in 3 positions of shoulder abduction (90°, 135°, and 180°) using force plates. However, handheld dynamometers (HHDs) are more portable, affordable, and may provide valid and reliable results which would increase the clinical utility of long-lever tests. HHDs vary in shape, design, and their capacity to report parameters such as rate of force production and require further investigation. The aim of this study was to examine the intrarater reliability of the Kinvent HHD and assess its validity against Kinvent force plates in the AST. Peak force (in kilograms), torque (in Newton meters), and normalized torque (in Newton meters per kilogram) were reported. Design: Validity and reliability study. Methods: Twenty-seven participants with no history of upper limb injury performed the test in a randomized order using the Kinvent HHD and force plates. Each condition was assessed 3 times, and peak force was recorded. Arm length was measured to calculate peak torque. Normalized peak torque was calculated by dividing torque by bodyweight (in kilograms). Results: The Kinvent HHD is reliable when measuring force (intraclass correlation coefficient [ICC] ≥.80), torque (ICC ≥.84), and normalized torque (ICC ≥.64) during the AST. The Kinvent HHD is also valid when compared with the Kinvent force plates for force (ICC ≥.79; r ≥.82), torque (ICC ≥.82; r ≥.76), and normalized torque (ICC ≥.71; r ≥.61). There were no statistically significant differences across the 3 trials on analyses of variance (P >.05). Conclusions: The Kinvent HHD is a reliable tool when used to measure force, torque, and normalized torque in the AST. Furthermore, given the lack of significant difference between trials, clinicians can use one test to accurately report relative peak force/torque/normalized torque rather than average 3 separate trials. Finally, the Kinvent HHD is valid when compared with Kinvent force plates. [ABSTRACT FROM AUTHOR]

Background Interventions using vibration stimulation have been recognized for their potential for increasing range of motion (ROM) without compromising muscle strength. Handheld vibration massagers can efficiently deliver vibration therapy to the shoulder joint and may be a potential treatment. Purpose To evaluate the effects of vibration massage using a handheld device on the soft tissues of the posterior shoulder joint, particularly on internal rotation (IR) passive ROM and external rotation (ER) muscle strength. Study Design Crossover study design. Methods A crossover study with a 5-min vibration massage and passive control condition was conducted in healthy male volunteers (mean age 20.5 ± 1.7 years). Vibration massage was applied to the posterior shoulder soft tissues of the dominant arm, with no intervention under control conditions. IR-ROM (vertebral level and in abduction) and strength of the external rotators (isometric and isokinetic) were measured before and immediately after the intervention. Vertebral levels were calculated as a ratio of lengths (ratio decreases with increased mobility). IR-ROM in abduction, the angle was measured. Statistical analysis was performed with two-way repeated measures ANOVA and paired t-test (Bonferroni correction). Results Vibration application decreased (improved) vertebral level IR ROM by -4.1% (p < 0.01, d = 0.445) and increased abduction position IR ROM by 11.4° (p < 0.01, d = 0.694). These changes exceeded the 95% confidence interval for the minimum detectable change. By contrast, the control condition produced no changes. IR-ROM (vertebral level and abduction) immediately after the intervention showed significant differences between the control and vibration conditions (p = 0.036, d = 0.273; p = 0.048, d = 0.483, respectively). Muscle strength did not show any interaction, time, or between-condition effects. Conclusions A massage using a handheld vibration massager applied to the posterior shoulder soft tissues increased IR-ROM without negatively affecting muscle strength, suggesting its potential use as a means of warming up. Level of Evidence Level 3 [ABSTRACT FROM AUTHOR]

Introduction Adductor-related groin pain involves an injury to the common aponeurosis connecting the rectus abdominus and adductor longus to the pubis. It commonly occurs in sports that require cutting and pivoting and can result in significant loss of playing time. Platelet-Rich Plasma (PRP) is often indicated for treatment of musculoskeletal disorders and may represent an alternative treatment for patients with adductor-related groin pain. The purpose of this case report is to describe the non-surgical management of adductor-related groin pain in a competitive soccer player with a with an ultrasound (US)-guided PRP injection and physical therapy management. Case Description A 17-year-old male competitive soccer player with right-sided adductor-related groin pain was treated with an US-guided PRP and a multi-phased physical therapy regimen based on tissue healing and individual patient/criteria progression. The patient completed 12 physical therapy sessions over six weeks post PRP injection. Outcomes At the end of treatment, clinically meaningful improvements were observed in pain intensity, passive range of motion, strength (handheld dynamometry, Biodex), functional tests, psychosocial (OSPRO-YF) and patient-reported outcomes (HAGOS, LEFS). The subject returned to sport at six weeks post injection without limitation and at three months follow up, the subject reported that he had returned to 95% of his previous level of play. Discussion This case report may offer support for PRP as an alternative treatment in the management of adductor-related groin pain. Incorporation of PRP as an adjunct to physical therapy led to improvements on all outcomes that surpassed the clinical significance change criteria. [ABSTRACT FROM AUTHOR]

Unloader braces are a treatment modality for medial compartment knee osteoarthritis. The functional mechanisms involved are not yet fully understood. Therefore, this two-part systematic review examines the following research questions: How is muscle activation altered by medial compartment knee osteoarthritis, and do medial tibiofemoral compartment unloader braces alter muscle activation? If so, could this alteration be part of the unloading mechanism by affecting the altered muscle activity in medial compartment knee osteoarthritis? A systematic literature search was conducted using PubMed, LIVIVO, Web of Science, Google Scholar, and CENTRAL for articles published until August 2023. The first systematic review, examining neuromuscular alterations, identified 703 articles, with a final inclusion of 20. The second systematic review, which evaluated the neuromuscular effects of unloader braces, identified 123 articles with the final inclusion of 3. Individuals with medial compartment knee osteoarthritis demonstrated increased activity and co-contraction of the periarticular knee muscles, whereas medial tibio-femoral compartment unloader braces seemed to reduce activity and co-contraction. In contrast to the belief that unloader braces result in muscle weakness as they decrease muscle activity and co-contraction, our limited insights indicate that they rather might reduce the pathological increase. This may result in joint load reduction due to lower compressive forces. However, further investigation is required. [ABSTRACT FROM AUTHOR]

Summary: Associations between different sarcopenia definitions and the risk of injurious falls were investigated in 75–80-year-old women in the Swedish SUPERB cohort. Only sarcopenia according to the Sarcopenia Definitions and Outcomes Consortium (SDOC) definition was associated with incident injurious falls with and without fractures in older women. Purpose: To investigate the association between three commonly used sarcopenia definitions and the risk of injurious falls in a population of older Swedish women. Methods: A total of 2,883 75–80-year-old women with complete data on relevant sarcopenia definitions from the Swedish SUPERB cohort were studied. Sarcopenia was defined based on the Sarcopenia Definitions and Outcomes Consortium (SDOC: low handgrip strength and gait speed), revised European Working Group on Sarcopenia in Older People (EWGSOP2: low appendicular lean mass index (ALMI, dual-energy X-ray absorptiometry (DXA)-derived), appendicular lean mass (kg)/height (m2), hand grip strength (kg), or low chair stand time (s)), and Asian Working Group for Sarcopenia (AWGS: low ALMI and hand grip strength (kg) or low gait speed (m/s)). Questionnaires captured the occurrence of falls in the past 12 months. Incident injurious falls were identified using national registers. Cox regression (hazard ratios (HR) and 95% confidence intervals (CI)) analyses were performed without adjustment and after adjustment for age, body mass index, previous falls, and the Charlson comorbidity index. Results: During a median (IQR) follow-up time of 7.06 (6.2–7.9) years, there were 491 injurious falls without fracture and 962 injurious falls when also including falls resulting in a fracture. Sarcopenia according to EWGSOP2 and AWGS was not associated with an increased risk of injurious falls. Individuals with sarcopenia defined by SDOC had a higher risk of injurious falls with and without fracture (HR 2.11; 95% CI, 1.63–2.73 and HR, 2.16; 95% CI, 1.55–3.02, respectively). Conclusion: Sarcopenia definitions confined to muscle function and strength such as SDOC, rather than including DXA-determined ALMI (EWGSOP2 and AWGS), are associated with incident injurious falls with and without fractures in older women. [ABSTRACT FROM AUTHOR]

Summary: We assessed multiple components of muscle function in ten adults with X-linked hypophosphatemia (XLH) receiving burosumab treatment. Lower limb power (+ 9%), short physical performance battery (SPPB) score (+ 1.2 points), and physical activity (+ 65%) increased following 6 months of treatment, and hand grip increased (+ 10%) between 6 and 12 months of treatment. Purpose: X-linked hypophosphatemia (XLH) is a rare genetic disorder of phosphate metabolism. Burosumab is a monoclonal antibody treatment shown to improve phosphate homeostasis and improve symptoms as well as fracture healing when used as a therapy for XLH in adults. However, little is known about its effects on the large deficits in multiple components of physical function previously reported in XLH. Methods: Ten adults (6 females, age 41.1 ± 15.7 y) were recruited from specialist centres in London and Bristol. During clinical visits for initial burosumab treatment and at 6-month and 12-month follow-up, physical function, and physical activity (PA) assessments were performed. In detail, lower limb power was assessed by mechanography via a countermovement jump, mobility by short physical performance battery (SPPB), functional capacity by 6-min walk test (6MWT), upper limb strength by hand grip dynamometry, and PA via an International Physical Activity Questionnaire (IPAQ). Differences between baseline and 6-month follow-up, and in a subset of 5 patients between 6- and 12-month follow-up, were assessed. Results: Lower limb power increased by 9% (P = 0.049) from baseline to 6 months, as did SPPB score (+ 1.2 points, P = 0.033) and total PA (+ 65%, P = 0.046) although hand grip and 6MWT did not differ. Only for hand grip was a significant improvement (+ 10%, P = 0.023) seen between 6 and 12 months. Conclusions: Burosumab treatment is associated with improved lower limb function and mobility at 6 months, with improvement in hand grip strength at 12 months. Future studies should explore the underlying mechanisms and describe on function and other patient outcomes. [ABSTRACT FROM AUTHOR]

Background: The literature is unclear about how the different attachment systems for overdentures impact the maximum bite force, the masticatory efficiency and how this impact in the oral health self‐perception in patients. Objective: To evaluate the effect of two attachment systems (O‐ring and Locator) for mandibular overdenture using single implant on quality of life, maximum bite force (BF) and masticatory efficiency (ME). Methods: Twenty‐eight completely edentulous denture wearers with a mandibular symphysis implant were randomly selected and allocated into two groups in a crossover study, considering O‐ring and Locator attachment types. The quality of life and self‐perception of oral health were assessed using the Oral Health Impact Profile (OHIP‐Edent) and Geriatric Index of Determination of Oral Health (GOHAI) questionnaires, respectively. BF was measured using a gnathodynamometer and ME by chewing silicone cubes and almonds in different numbers of cycles. Results: There was no difference between the attachment systems about self‐perceived oral health and impact on quality of life (p >.05). The O‐ring‐type system obtained a significantly higher BF than the locator‐type system (p =.04). Regardless of the food chewed, no statistically significant difference was observed with the type of attachment (p >.05). The ME was directly proportional to the masticatory cycles only for almonds (p <.01). Conclusions: Locator and O‐ring inserts had a similar impact on patients' quality of life, self‐perception of oral health and ME. Additionally, the O‐ring system exhibited superior properties in the BF. [ABSTRACT FROM AUTHOR]

The ability to hold objects relies on neural processes underlying grip force control during grasping. Brain activity lateralized to contralateral hemisphere averaged over trials is associated with grip force applied on an object. However, the involvement of neural variability within-trial during grip force control remains unclear. We examined dependence of neural variability over frontal, central, and parietal regions of interest (ROI) on grip force magnitude using noninvasive electroencephalography (EEG). We utilized our existing EEG dataset comprised of healthy young adults performing an isometric force control task, cued to exert 5, 10, or 15% of their maximum voluntary contraction (MVC) across trials and received visual feedback of their grip force. We quantified variability in EEG signal via sample entropy (sequence-dependent) and standard deviation (sequence-independent measure) over ROI. We found lateralized modulation in EEG sample entropy with force magnitude over central electrodes but not over frontal or parietal electrodes. However, modulation was not observed for standard deviation in the EEG activity. These findings highlight lateralized and spatially constrained modulation in sequence-dependent, but not sequence-independent component of EEG variability. We contextualize these findings in applications requiring finer precision (e.g., prosthesis), and propose directions for future studies investigating role of neural entropy in behavior. [ABSTRACT FROM AUTHOR]

Objective: To examine the effect of concurrent physical and cognitive demands as well as age on indicators of muscle fatigue at the wrist. Background: There are few studies examining risk indicators for musculoskeletal disorders associated with work-related physical and cognitive demands that often occur simultaneously in the workplace. Methods: Twenty-four gender-balanced older and 24 gender-balanced younger (mean age 60 and 23 years) participants performed four 30 min dual tasks. Tasks differed by the muscular load level during force tracking: 5% and 10% of maximum voluntary contraction force (MVC) and concurrent cognitive demands on the working memory: easy and difficult. Muscle fatigue was assessed by MVC decline and changes in surface electromyography (increased root mean square: RMS, decreased median frequency: MF) at the extensor digitorum (ED) and extensor carpi ulnaris (EU). Results: A decline in MVC was found in all participants when tracking was performed at 10% MVC (mean ± SD: 137.9 ± 49.2 – 123.0 ± 45.3 N). Irrespective of age, muscular, or cognitive load, RMS increased (ED 12.3 ± 6.5 – 14.1 ± 7.0% MVE, EU 15.4 ± 7.6 – 16.9 ± 8.6% MVE) and MF decreased (ED 85.4 ± 13.6 – 83.2 ± 12.8 Hz, EU 107.2 ± 17.1 – 104.3 ± 16.7 Hz) in both muscles. However, changes in MF of EU tended to be more pronounced in the older group at higher cognitive and lower muscular load, without reaching statistical significance. Conclusion: Maximum voluntary contraction indicated no interaction between muscle fatigue, cognitive load, or age. However, the tendencies toward altered muscle activity due to an increase in cognitive load and older age suggest muscular adaptations while maintaining tracking performance during the onset of fatigue signs in the sEMG signal. Application: If the tendencies in muscle activity are confirmed by further studies, ergonomic assessments in industrial workplaces should consider cognitive load and age when describing the risk of musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Objective: Standardized executive functioning (EF) measures do not reliably capture EF-related difficulties reported in daily life. We aim to determine if an ecologically relevant neuropsychological battery is more strongly associated with self-reported everyday EF impairments than classically used tests. Method: Fifty-nine adults aged 18–49 self-rated their EF abilities using the Barkley Deficits in EF Scale (BDEFS) and were randomly assigned to complete either a test battery composed of EF measures with hypothesized ecological relevance (Six Elements, Zoo Map, Hayling Sentence Completion, Iowa Gambling, and Auditory Startle Tasks) or one composed of traditional EF tasks (Card Sorting, Trail Making, Color-Word Interference, and Verbal Fluency). Associations were examined using linear regression. Results: There were no strong associations between BDEFS subscales and performance on either test battery. Only the regression model predicting Emotional Regulation from ecological tasks was significant. Iowa Gambling Task performance and corrugator muscle contraction in the Auditory Startle Task individually contributed significantly to the model, with small and moderate effect sizes respectively. Conclusion: Results align with evidence that self-reported EF difficulties are not adequately captured by formal neuropsychological measures, even for performance-based measures which directly tap everyday constructs. Findings are interpreted cautiously in the context of a small, high-functioning sample. [ABSTRACT FROM AUTHOR]