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The purpose of this study was to examine the effect of pelvic tilt angle on maximum hip and knee muscles' strength and antagonist/agonist strength ratios. Twenty-one young males and females performed maximum isokinetic concentric knee extension–flexion and hip extension–flexion efforts at 60°·s−1, 120°·s−1, and 180°·s−1 from three positions: anterior, neutral, and posterior pelvic tilt. Peak torques and knee flexor-to-extensor and hip flexor-to-extensor torque ratios were analyzed. An analysis of variance showed that peak hip extensor torque was significantly greater in the anterior pelvic tilt condition compared to either neutral or posterior pelvic tilt angles (p > 0.05). No effects of changing pelvic tilt angle on hip flexor, knee flexor, or knee extension values were found (p > 0.05). The hip flexor-to-extensor torque ratio decreased (p < 0.05) in the anterior pelvic tilt position relative to the other positions, while no difference in the knee flexor-to-extensor ratio between pelvic positions was observed (p > 0.05). This study shows that an increased anterior pelvic tilt affects the maximum isokinetic strength of the hip extensors, supporting previous suggestions regarding the link between pelvic position and hip and knee muscle function. Isokinetic testing from an anterior pelvic tilt position may alter the evaluation of hip flexion/extension strength. [ABSTRACT FROM AUTHOR]

Core stability training is crucial for competitive athletes, individuals who want to improve their health and physical performance, and those undergoing clinical rehabilitation. This study compared the ultrasound (US) muscle thickness of the abdominals and lumbar multifidus (LM) muscles between seven popular trunk stability exercises performed using hollowing and bracing maneuvers. Forty-four healthy young adults, aged between 21 and 32 years, performed a plank, bird dog, beast crawl, dead bug, Pilates tap, bridge, and side planks using the bracing and the hollowing maneuver. The thickness of the transversus abdominis (TrA), internal oblique (IO), and LM muscles was measured simultaneously using two ultrasound machines. Analysis of variance designs indicated that during hollowing, the bird dog and side plank exercises resulted in the greatest increase in the muscle's relative thickness overall. The relative thickness of all muscles was significantly greater (p < 0.001) during hollowing (22.7 ± 7.80 to 106 ± 24.5% of rest) compared to bracing (18.7 ± 7.40 to 87.1 ± 20.9% of rest). The TrA showed the greatest increase in thickness (p < 0.001) compared to the IO and LM. Additionally, the IO had a greater increase in thickness (p < 0.001) than the LM. In conclusion, our findings indicate that the bird dog and side plank exercises, when performed with hollowing, showed the most significant total muscle thickness increase. Notably, the hollowing maneuver enhances the thickness of the TrA, IO, and LM muscles more than the bracing maneuver. This contributes to the discussion on optimal strategies for dynamic core stabilization. [ABSTRACT FROM AUTHOR]

Bridging exercises with abdominal hollowing are often used as a regimen for improving spinal stability. Lately, this type of training has become very popular among elite athletes, creating a need for more demanding exercises. The purpose of this study was to investigate whether the use of additional external resistance is beneficial for abdominal muscle recruitment during bridge exercise. Tissue movement of the transversus abdominis (TrA) and the rectus abdominis (RA) was recorded with the use of two synchronized ultrasonic devices, in 20 healthy college students. From the hook-lying position participants were examined in eight different exercise conditions: a) rest, b) abdominal drawing-in maneuver (ADIM), c) bridge, d) bridge- ADIM, e) bridge with 10KG, f) bridge- ADIM with 10KG, g) bridge with 20KG and h) bridge-ADIM with 20KG. Analysis of variance (ANOVA) showed a statistically significant increase in TrA thickness when performing the bridge exercise combined with ADIM compared to rest mode (p < .05). RA thickness decreased when the ADIM was performed, compared to rest (p < 0.05). No significant difference in TrA and RA thickness when exercising with and without external resistance was observed (p > 0.05). The main outcome of this study was that external loading provided some extra level of difficulty, yet it was not beneficial for abdominal muscle recruitment, when performing a supine bridge exercise. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of adding the integrated neuromuscular inhibition technique (INIT) to therapeutic exercise (TE) in individuals with chronic mechanical neck pain (CMNP). In this 34-week, assessor-blind randomized controlled trial, 40 participants (men and women) with CMNP with active or latent myofascial trigger points on the neck muscles were divided into 2 groups. The participants followed 4 treatments per week for 10 weeks. The intervention group followed a TE program in combination with the INIT, whereas the control group followed the same program without the INIT. Both protocols were applied by physiotherapists. Pain, disability, pressure pain threshold, active range of motion, and health-related quality of life were evaluated before, during, and after the intervention, whereas patients were followed for 6 months after completion of treatment. Repeated-measures ANOVA was applied. Both groups showed a significant improvement in all dependent measures after the intervention (P <.05). However, the intervention group showed greater improvement in the visual analog scale and neck disability index score, in the neck muscles pressure pain threshold, in the range of motion, and in the 36-Item Short Form Health Survey score, than the control group. In many of the above variables this improvement was seen from the second week and was maintained for 6 months after the intervention. The results of this preliminary study suggest that the addition of the INIT to a TE program had a positive effect on pain, functionality, and the quality of life in individuals with CMNP. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to examine the kinematic differences during instep soccer kicks between players who were blind and sighted controls. Eleven male soccer players who were blind and nine male sighted performed instep kicks under static and dynamic conditions. The results indicated significantly higher (p < .05) ball speed velocities (20.81m/sec) and ball/foot speed ratio values (1.35) for soccer players who were blind during the static kick compared with sighted players (16.16m/sec and 1.23, respectively). Significant group effect on shank and foot angular velocity was observed during the static kicking condition (p < .05), while no differences were found during the dynamic kicking condition (p > .05). Despite the absence of vision, systematic training could have beneficial effects on technical skills, allowing athletes who are blind to develop skill levels comparable to sighted athletes. [ABSTRACT FROM AUTHOR]

Background: Identifying combinations of the hip and knee joint angles which can selectively recruit specific hamstring muscles may be beneficial for injury prevention or rehabilitation. The purpose of this study was to examine the joint torque and electromyographic (EMG) activity of the semitendinosus (ST) and biceps femoris long head (BFlh). Methods: Twenty subjects performed maximum isokinetic concentric and eccentric knee flexor efforts at 60°s-1, 120°s-1 and 150°s-1 from three different hip joint angles while surface EMG of ST and BFlh was recorded. Results: Analysis of variance showed that there are no inter-muscular differences in EMG amplitude across testing conditions (p > .05). Peak EMG occurred near full knee extension for the BFLh and at a higher flexion angle for the ST while exercise from a prone position shifted the peak EMG towards higher knee flexion angle (p < 0.05). Conclusion: Maximal dynamic knee flexion exercises do not induce a higher EMG amplitude of BFlh or ST. Exercising from a higher hip flexion angle near full knee extension may selectively activate the BFlh. Level of evidence: IIb. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pilates programs are widely used as a form of regular exercise in a broad range of populations investigating their effectiveness for chronic low back pain (CLBP) treatment. OBJECTIVE: The aim of this study was to compare the effects of a Pilates program and a trunk strengthening exercise program on functional disability and health-related quality of life (HRQOL) in women with nonspecific CLBP. METHODS: A total of 101 volunteer women with CLBP provided data with a 3-month follow-up. They were randomized to either a Pilates (n = 37), trunk strengthening exercise (n = 36) or a control group (n = 28), exercising for a period of 8 weeks, three times a week. Data were collected on HRQOL using the Short-Form 36 Health Survey (SF-36v2), and functional disability using the Roland Morris Disability Questionnaire prior to program initiation, mid-intervention, immediately after program termination, and three months post-intervention. RESULTS: The Pilates participants reported greater improvements on self-reported functional disability and HRQOL compared with participants in the trunk strengthening exercise and control groups (p < 0.05). The effects were retained for a period of three months after program termination for the Pilates group and to a lesser extent for the trunk strengthening exercise group. CONCLUSIONS: An 8-week Pilates program improved HRQOL and reduced functional disability more than either a trunk strengthening exercise program or controls among women with CLBP. [ABSTRACT FROM AUTHOR]

Soccer kicking training should be adjusted to the characteristics of the athletes. Therefore, examination of differences in kicking kinematics of females and pubertal players relative to males is worthwhile. The purpose of the study was to compare kicking kinematics and segmental sequence parameters between male, female, and pubertal players. Ten adult male, ten adult female, and ten male pubertal players participated in the study. Participants performed five consecutive kicking trials of a stationary ball, as powerful as they could. Analysis of variance showed significantly higher ball velocity, higher joint linear velocities for the knee and the hip, and higher angular velocities of the knee and the ankle for males compared to female and pubertal players (p < 0.05). Similarly, the peak joint velocity was achieved significantly closer to ball impact in males compared to other groups (p < 0.05). Males also showed a more plantarflexed ankle immediately before ball impact (p < 0.05). Females and pubertal players may benefit from skill training aiming to increase ankle plantarflexion and hip flexion prior to ball impact, and to adjust thigh and shank motion, such that the shank–foot segment travels through a higher range of motion and with a greater velocity. [ABSTRACT FROM PUBLISHER]

The article discusses a study which evaluates muscle strength and activity in women with knee osteoarthritis (OA) and those who are asymptomatic. It describes the methods used including the subjects, instrumentation and procedure, and discusses data and statistical analyses. Results of the study revealed inconsistencies in the evidence regarding coactivation ratios.

The semitendinosus (ST) consists of a long distal tendon and it is divided in two parts by a tendinous inscription (TI). The purpose of this study was to quantify strain and elongation of the TI and the distal tendon of ST. Fourteen subjects performed ramp isometric contractions of the knee flexors at 0°, 45° and 90° of knee flexion. Two ultrasound probes were used to visualize the displacement of the distal tendon and selected points across the TI and aponeuroses. Three-way analysis of variance designs indicated that: (a) strain and elongation of the ST distal muscle–tendon junction were higher than that of the aponeurosis – TI junction points (p <0.05) (b) the long arm of the TI reach strain of 49.86±7.77% which was significantly (p <0.05) higher than that displayed by the short arm (28.35±0.59%) (c) Strain of tendinous and TI-aponeuroses segments significantly increased from 90° to 0° of knee flexion while the inverse was observed for the TI arm length (p <0.05). (d) Tendon strain was significantly higher than strain of the TI-aponeuroses segments at 45° and 90° of knee flexion while the opposite was observed at 0° of knee flexion. The arrangement of TI along ST length results in differential local strains, indicating that the mechanical properties of the ST muscle are affected by tendon, aponeuroses and tendinous inscription interactions. [ABSTRACT FROM AUTHOR]

The article presents information on a study which analyzes the effects of a 10-week resistance exercise program on kick biomechanics and muscle strength in soccer players. The study included twenty male amateur soccer players who followed a resistance exercise program mainly for the lower limb muscles, and measured maximal instep kick kinematics, electromyography, and ground reaction forces (GRFs). The methods and results of the study are also discussed.

The article discusses research which was conducted to compare the effects an Olympic weightlifting (OL) and traditional weight (TW) training program had on muscle coactivation around the knee joint during vertical jump tests. Researchers evaluated 26 men. They found that the Olympic weightlifting improves jump performance via a constant knee muscle coactivation index, whereas the traditional weight training caused an increased coactivation index, probably to enhance joint stability.

Cutting in soccer is a common skill used to avoid the opponent's pressure but the potential effects of such a skill on instep kicking performance have not been previously investigated. The purpose of this study was to examine the differences in lower limb biomechanics between straight approach soccer kicks and kicks performed following a cutting maneuver task. Ten young amateur soccer players performed, in a random order, instep kicks after a two-step straight approach run and kicks after a double 'faking' cutting maneuver task. The results showed that kicking after a cutting maneuver task displayed significantly lower ball speed values compared with the straight approach instep kicking (16.73 vs. 19.78 m/s, respectively; p < 0.05). Moreover, analysis of variance showed significant differences between the two kicking conditions in ankle, knee and hip joint displacements. The present study indicated that performing instep kicks after a double-cutting maneuver reduces ball and foot speed probably due to increasing joint frontal and transverse plane rotations. Improvements in the performance of the cutting maneuver task through training might result in better transfer of energy and speed to the kicking task thus permitting players to perform more powerful kicks under realistic game conditions. [ABSTRACT FROM AUTHOR]

Context: The effects of fatigue on impact loading during running are unclear, with some authors reporting increased impact forces and others reporting decreased forces. Objective: To examine the effects of isokinetic fatigue on muscle cocontraction ratios about the knee and ankle during running. Design: Cross-sectional study. Setting: Neuromechanics laboratory. Patients or Other Participants: Female middle-distance runners (age = 21.3 ± 1.93 years) with at least 5 years of training experience. Intervention(s): Participants ran on the treadmill at 3.61 m/s before and immediately after the fatigue protocol, which consisted of consecutive, concentric knee extension-flexion at 120°/s until they could no longer produce 307% of the maximum knee-extension moment achieved in the familiarization session for 3 consecutive repetitions. Main Outcome Measure(s): Electromyographic (EMG) amplitude of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GAS), and tibialis anterior (TA) was recorded using surface electrodes. Agonist:antagonist EMG ratios for the knee (VM:BF) and ankle (GAS:TA) were calculated for the preactivation (PR), initial loading response (LR1), and late loading response (LR2) phases of running. Hip-, knee-, and ankle-joint angular displacements at initial foot contact were obtained from 3-dimensional kinematic tracings. Results: Fatigue did not alter the VM:BF EMG ratio during the PR phase (P > .05), but it increased the ratio during the LR, phase (P < .05). The GAS:TA EMG ratio increased during the LR1 phase after fatigue (P < .05) but remained unchanged during the PR and LR2 phrases (P > .05). Conclusions: The increased agonist EMG activation, coupled with reduced antagonist EMG activation after impact, indicates that the acute decrease in muscle strength capacity of the knee extensors and flexors results in altered muscle-activation patterns about the knee and ankle before and after foot impact. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to examine whether muscle architecture of the long head of biceps femoris (BF) and semitendinosus (ST) muscles varies along their length. The ST and BF muscles were dissected and removed from their origins in eight cadaveric specimens (age range 67.8–73.4years). One-way analysis of variance designs were used to compare fascicle length (FL), pennation angle (PA) and muscle thickness (MT) between proximal, mid-belly and distal positions. Tendon and muscle length properties were also quantified. For the BF muscle, one-way analysis of variance tests showed a higher PA (23.96±3.82°) and FL (7.12±0.48cm) proximally than distal positions (PA=17.78±1.95° and FL=6.35±0.89cm, respectively). For the ST, there was a significantly (p <0.05) lower PA (8.81±1.22°) and FL (13.10±1.54cm) proximally than distally (PA=14.69±1.09° and FL=15.49±2.30cm, respectively). Muscle thickness significantly increased from distal to more proximal positions (p <0.05). These data suggest that the ST and BF architecture is not uniform and that measurement of these parameters largely depends on the measurement site. Modeling these muscles by assuming a uniform architecture along muscle length may yield less accurate representation of human hamstring muscle function. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to compare the three-dimensional kinematics of the lower extremities and ground reaction forces between the instep kick and the kick with the outside area of the foot (outstep kick) in pubertal soccer players. Ten pubertal soccer players performed consecutive kicking trials in random order after a two-step angled approach with the instep and the outstep portion of the foot. Three-dimensional data and ground reaction forces were measured during kicking. Paired t-tests indicated significantly higher (P < 0.05) ball speeds and ball/foot speed ratios for the instep kick compared with the outstep kick. Non-significant differences in angular and linear sagittal plane kinematic parameters, temporal characteristics, and ground reaction forces between the instep and outstep soccer kicks were observed (P > 0.05). In contrast, analysis of variance indicated that the outstep kick displayed higher hip internal rotation and abduction, knee internal rotation, and ankle inversion than the instep kick (P < 0.05). Our results suggest that the instep kick is more powerful than the outstep kick and that different types of kick require different types of skill training. [ABSTRACT FROM AUTHOR]

Introduction: Conflicting results have been reported on the functional role of the proximal and distal compartments of the semitendinosus (ST) muscle. This study compared the discharge characteristics of motor units (MU) in the two compartments at three knee joint angles (0°: long length; 45°: intermediate length; and 90°: short length). Methods: Twenty men (21.4 ± 2.3 yr) performed steady isometric contractions with the knee flexors at four target forces: 10%, 20%, 40%, and 60% of maximum voluntary contraction. High-density EMG signals were recorded to examine the MU discharge characteristics in the two compartments. Measurements included recruitment threshold, mean discharge rate, coefficient of variation (CoV) for interspike interval, and SD of filtered cumulative spike train (fCST). Additionally, the within- and between-compartment association of the neural drive was calculated. Results: ANOVA indicated that maximal force, absolute EMG amplitude during the maximum voluntary contractions, and force steadiness (CoV for force) were greater at the longest muscle length than the other two lengths (P < 0.05). Linear mixed models showed that both recruitment threshold and CoV for interspike interval were similar between compartments (P > 0.05) at each of the three knee joint angles. However, the mean discharge rate and the variability in neural drive were greater for the proximal than the distal compartment (P < 0.05). The between-compartment association in neural drive (filtered cumulative spike train) was relatively low. Conclusions: There were distinct differences in MU discharge characteristics between the proximal and the distal compartments of ST across its operating range of muscle lengths, and each compartment received a relatively distinct neural drive. These findings emphasize the importance of recognizing differences in neural control of the ST compartments to guide related interventions and to inform rehabilitation strategies. [ABSTRACT FROM AUTHOR]

Introduction: The aim of the study was to compare maximal force, force steadiness, and the discharge characteristics of motor units in the tibialis anterior (TA) muscle during submaximal isometric contractions for ankle dorsiflexion and adduction of the foot. Methods: Nineteen active young adults performed maximal and submaximal isometric dorsiflexion and adduction contractions at five target forces (5%, 10%, 20%, 40%, and 60% maximal voluntary contraction [MVC]). The activity of motor units in TA was recorded by high-density EMG. Results: The maximal force was similar between dorsiflexion and adduction, despite EMG amplitude for TA being greater (P < 0.05) during dorsiflexion than adduction. The coefficient of variation (CV) for force (force steadiness) during dorsiflexion was always less (P < 0.05) than during adduction, except of 5% MVC force. No differences were observed for mean discharge rate; however, the regression between the changes in discharge rate relative to the change of force was significant for dorsiflexion (R² = 0.25, P < 0.05) but not for adduction. Discharge variability, however, was usually less during dorsiflexion. The CV for interspike interval was less (P < 0.05) at 10%, 20%, and 40% MVC but greater at 60% MVC during dorsiflexion than adduction. Similarly, the SD values of the filtered cumulative spike train of the motor units in TA were less (P < 0.05) at 5%, 10%, 20%, and 40% MVC during dorsiflexion than adduction. Conclusions: Although the mean discharge rate of motor units in TA was similar during foot adduction and ankle dorsiflexion, discharge variability was less during dorsiflexion resulting in less accurate performance of the steady adduction contractions. The neural drive to bifunctional muscles differs during their accessory function, which must be considered for training and rehabilitation interventions. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the influence of habitual training history on force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Fifteen athletes whose training emphasized alternating actions (11 runners and 4 cyclists) and fifteen athletes who relied on bilateral actions with leg muscles (7 volleyball players, 8 weight-lifters) performed 2 maximal voluntary contractions (MVC) with the dorsiflexors, and 3 steady contractions at 8 target forces (2.5%, 5%, 10%, 20%, 30%, 40%, 50% and 60% MVC). The discharge characteristics of motor units in tibialis anterior were recorded using high-density electromyography grids. The MVC force and the absolute (standard deviation) and normalized (coefficient of variation) amplitudes of the force fluctuations at all target forces were similar between groups. The coefficient of variation for force decreased progressively from 2.5% to 20% MVC force, then it plateaued until 60% MVC force. Mean discharge rate of the motor units in tibialis anterior was similar at all target forces between groups. The variability in discharge times (coefficient of variation for interspike interval) and the variability in neural drive (coefficient of variation of filtered cumulative spike train) was also similar for the two groups. These results indicate that athletes who have trained with either alternating or bilateral actions with leg muscles has similar effects on maximal force, force control, and variability in the independent and common synaptic input during a single-limb isometric task with the dorsiflexors. [ABSTRACT FROM AUTHOR]

Backround The purpose of this study was to compare joint kinematics, knee and trunk muscle activation and co-activation patterns during a sit-to-stand movement in women with knee osteoarthritis and age-matched controls. Methods Eleven women with knee osteoarthritis (mean and standard deviation, age: 66.90, 4.51 years, height: 1.63, 0.02 m, mass: 77.63, 5.4 kg) and eleven healthy women (mean and standard deviation, age: 61.90, 3.12 years, height: 1.63 m, 0.03, mass: 78.30, 4.91 kg) performed a Sit to Stand movement at a self-selected slow, normal and fast speed. Three-dimensional joint kinematics of the lower limb, vertical ground reaction forces and electromyographic activity of the biceps femoris vastus lateralis and erectus spinae were recorded bilaterally. Findings A two-way ANOVA showed that the osteoarhtitis group performed the sit to stand task using a smaller knee and hip range of motion compared with the control group while no differences in temporal kinematics and ground reaction force-related parameters were observed. In addition, women with osteoarhtritis displayed significantly lower vastus lateralis coupled with a higher biceps feomoris electromyographic activity and higher agonist–antagonist co-contraction and co-activation than asymptomatic women. The activation of erectus spinae was not different between groups. Interpretation Results indicate that patients with moderate knee osteoarthritis rise from the chair using greater knee muscle co-contraction, earlier and greater activation of the hamstrings which results in reduced hip and knee range of motion. This may be a way to overcome the pain and potential muscle atrophy of knee extensor muscles without compromising overall task duration. [ABSTRACT FROM AUTHOR]