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This study examined whether the association between hamstring (H) and quadriceps (Q) strength with size depends on the region and the muscle used to examined cross-sectional area (CSA). Maximum isometric contraction knee extension and flexion torque was obtained from 20 young participants while Q and H CSA was recorded using extended field of view ultrasonography at four sections along the thigh. Stepwise linear regression models using the maximum CSA of individual muscles showed a significant association of quadriceps (R 2  = 0.793) and hamstring (R 2  = 0.275) CSA with MVC torque (p < 0.05). The association was lower when maximum or section-specific muscle group CSAs were used as indices of size. The H:Q CSA ratio showed a significant association (R 2  = 0.275, p < 0.05) and a moderate correlation (r = 0.48) with H:Q torque ratio. These results indicated that the association between muscle CSA and strength differs between the knee extensors and flexors. Amongst the various indices of muscle size, the combination of maximum CSA values of each muscle displayed the greatest relationship between strength and CSA. The H:Q CSA ratio can explain a significant but small part of the H:Q isometric strength ratio.

Background: The aim of this study was to investigate whether the application of the integrated neuromuscular inhibition technique (INIT) combined with therapeutic exercise (TE) can provide faster and greater improvement in maximum isometric strength and isometric endurance of the neck muscles in patients with chronic mechanical neck pain (CMNP)., Methods: In this 10-week, single-blind clinical trial, 40 participants (men and women) with CMNP were divided into two groups. The intervention group (IG) followed a TE program in combination with the INIT, while the control group (CG) followed the same TE program without the INIT technique. Changes in maximum isometric strength and isometric endurance of the neck muscles were evaluated before, during, and after the intervention, with follow-up measurements taken at 1, 3, and 6 months after the intervention. Analysis of variance with repeated measures was applied., Results: Both groups showed a significant improvement in all dependent measures after the intervention (p < .05). These changes were maintained for both groups 6 months after the intervention. However, the IG showed a greater improvement in the maximum isometric strength of neck flexion and an improved craniocervical flexion test score compared with the CG., Conclusion: The combination of TE and INIT had a positive effect on neck muscle strength and endurance in individuals suffering from CMNP as compared with TE alone., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

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.

Background and Purpose: People with knee osteoarthritis (OA) display limitations in daily activities and a lower quality of life. The purpose of this study was to investigate the differences in strength balance and activation during maximum strength efforts between women with knee OA and asymptomatic women., Methods: Twelve women with knee OA (age 60.33 ± 6.66 years) and 11 controls (age 56.54 ± 5.46 years) performed maximum isokinetic eccentric and concentric knee extension and flexion tests at 60°/s, 120°/s, and 150°/s. Surface electromyography (EMG) was recorded from the biceps femoris (BF), vastus lateralis (VL), and vastus medialis (VM). Hamstrings-to-quadriceps moment ratios (H/Q), the synergetic (VL/VM), and co-contraction (BF/[VM + VL]) EMG ratios were calculated., Results: Analysis-of-variance designs showed that women experiencing knee OA had significantly higher H/Q moment ratios and VM/VL EMG ratios than controls (P < 0.05). The co-contraction index was significantly lower in the OA group only during knee flexion (P < 0.05)., Conclusions: Women with knee OA showed a higher H/Q moment ratios probably because of the need for better joint stability or a lower quadriceps capacity. This deficiency was accompanied by a higher VM activation, which probably serves to stabilize the patella upon maximum contraction as well as a higher activation of antagonist muscles.

The purpose of the study was to examine the effects of a resistance exercise program on soccer kick biomechanics. Twenty male amateur soccer players were divided in the experimental group (EG) and the control group (CG), each consisting of 10 players. The EG followed a 10-week resistance exercise program mainly for the lower limb muscles. Maximal instep kick kinematics, electromyography, and ground reaction forces (GRFs) as well as maximum isometric leg strength were recorded before and after training. A 2-way analysis of variance showed significantly higher ball speed values only for the EG (26.14 ± 1.17 m·s vs. 27.59 ± 1.49 m·s before and after training, respectively), whereas no significant differences were observed for the CG. The EG showed a decline in joint angular velocities and an increase in biceps femoris electromyography of the swinging leg during the backswing phase followed by a significant increase in segmental and joint velocities and muscle activation of the same leg during the forward swing phase (p < 0.05). The EG also showed significantly higher vertical GRFs and rectus femoris and gastrocnemius activation of the support leg (p < 0.05). Similarly, maximum and explosive isometric force significantly increased after training only for the EG (p < 0.05). These results suggest that increases in soccer kicking performance after a 10-week resistance training program were accompanied by increases in maximum strength and an altered soccer kick movement pattern, characterized by a more explosive backward-forward swinging movement and higher muscle activation during the final kicking phase.

The aim of this study was to assess the effects of a hippotherapy program on static balance and strength in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either an experimental group (n=10) or a control group (n=9). The experimental group attended a 10-week hippotherapy program. To assess static balance, three tasks of increasing difficulty (Double-Leg Stance with opened or closed eyes, and One-Leg Stance with opened eyes) were performed while standing on an EPS pressure platform (Loran Engineering S.r.I., Bologna, Italy). The strength measurements consisted of three maximal isometric half-squats from the seating position (knee joint at 90°). The hippotherapy intervention program resulted in significant improvements in strength parameters, and on the more complex balance task (i.e. standing on one leg). In conclusion, this study provides evidence that hippotherapy can be used as an effective intervention for improving balance and strength in individuals with ID, and could thus influence functional activities and quality of life., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The aim of this study was to examine the effects of incline plyometrics training on muscle activation and architecture during vertical jumping and maximum strength. Twenty male participants were divided in two training groups which followed after a 4 week training program. The incline plyometrics group (n = 10) trained by performing consecutive jumps on an inclined surface (15°) while the plane plyometrics (PP) group (n = 10) performed the same jumps on a plane surface. Both groups trained four times per week and performed 8 sets of 10 jumps in each session. Subjects performed squat jumps, counter movement jumps and drop jumps (DJ) prior to and immediately after the training period, while the electromyographic activity of the medial gastrocnemius (MGAS) and tibialis anterior muscles and the architecture of MGAS were recorded. Maximal isokinetic and isometric strength of the plantar flexors were performed. Analysis of variance showed that only the IP group improved fast DJ height performance by 17.4 and 14.4% (20 and 40 cm, p < 0.05). This was accompanied by a significantly higher MGAS activity during the propulsion phase (24% from 20 cm and 50% from 40 cm, p < 0.05) of the DJ and a longer working fascicle length (5.08%, p < 0.05) compared with the PP group. There were no significant changes in isokinetic and isometric strength of the plantar flexors after training for both groups. The increase of jumping performance, after incline plyometrics should be taken into consideration by coaches, when they apply hopping exercise to improve explosiveness of the plantar flexors.

This study examined fatigue profile during intermittent exercise in 10 men with mild to moderate mental retardation (MR) and 10 men without mental retardation (C). They performed 4 x 30s maximal knee extensions and flexions with 1-min rest on an isokinetic dynamometer. Peak torque of flexors (PTFL) and extensors (PTEX), total work (TW), and lactate were measured. Fatigue was calculated as the magnitude of decline (%) in PTFL, PTEX, and TW and as rate of decline (linear slope) in TW from 1st to 4th set. MR had lower PTFL, PTEX, TW, and lactate throughout the protocol than C, while pre-motor time was greater in MR vs. C (p<0.05). MR demonstrated a delayed pattern of reduction in muscular performance. Lower values were observed in MR vs. C in the magnitude of decline for PTEX and TW and the rate of decline for TW. In conclusion, MR exhibit a different fatigue profile during intermittent exercise than C. The lower magnitude and decline rate in neuromuscular performance in MR during intermittent exercise is associated with their lower peak strength, short-term anaerobic capacity, and lactate accumulation. Rehabilitation and sport professionals should consider the differences in fatigue profile when designing intermittent exercise programs for MR., (Copyright 2009 Elsevier Ltd. All rights reserved.)

The aim of this study was to examine the differences in muscle architecture during isometric tests between children and adults. Eight boys (age= 11.2 +/- 0.26 years) and eight men (age= 22.3 +/- 2.01 years) performed plantar flexion isometric efforts at angles of -15 degrees, 0 degrees, 15 degrees at 0%, 40%, 60%, 80% of MVC. Analysis of variance tests indicated that adults showed greater fascicle length from rest to 80% of MVC (p < .05), greater pennation angle at 80% and 100% of MVC (p < .05) and greater aponeuroses displacement at levels of effort greater than 60% of MVC (p < .05). These differences observed in MG would appear to favor better utilization of the force-length and the force-velocity relationships, of the muscle in adults compared with children.

Plyometric training improves vertical jump height (VJH). However, the effectiveness of plyometric training depends on various factors. A meta-analysis of 56 studies with a total of 225 effect sizes (ESs) was carried out to analyze the role of various factors on the effects of plyometrics on VJH performance. The inclusion criteria for the analysis were a) studies using plyometric programs for lower-limb muscles, b) studies employing true experimental designs and valid and reliable measurements, and c) studies including enough data to calculate ESs. Subjects with more experience in sport obtained greater enhancements in VJH performance (p < 0.01). Subjects in either good or bad physical condition benefit equally from plyometric work (p < 0.05), although men tend to obtain better power results than women after plyometric training (p < 0.05). With relation to the variables of performance, training volumes of more than 10 weeks and more than 20 sessions, using high-intensity programs (with more than 50 jumps per session), were the strategies that seemed to maximize the probability of obtaining significantly greater improvements in performance (p < 0.05). To optimize jumping enhancement, the combination of different types of plyometrics (squat jump + countermovement jump + drop jump) is recommended rather than using only 1 form (p < 0.05). However, no extra benefits were found to be gained from doing plyometrics with added weight. The responses identified in this analysis are essential and should be considered by strength and conditioning professionals with regard to the most appropriate dose-response trends for optimizing plyometric-induced gains.

Despite ongoing efforts, the relationship between groin strength and injury remains unclear. The challenge of accurately predicting injuries presents an opportunity for researchers to develop prevention strategies to reduce the occurrence of such injuries. Consequently, this issue requires further investigation to obtain insights into effective mitigation strategies. In 120 male soccer players, the maximum isometric strength of the hip muscle groups was measured, and the strength ratios were calculated. Previous injury and anthropometric data were registered. Injury data were collected following the FIFA/UEFA consensus. k-nearest neighbor (k-NN) was used to predict the incidence of injury, while the significant predictive variables of the k-NN algorithm were fitted into a multivariate logistic regression model (LR) to analyze the likelihood of players sustaining a groin injury. The LR model determined two variables as significant predictors of groin injury. Players were less likely to sustain a groin injury by 76% for each decrease of the adductor/abductor isometric strength ratio in the non-dominant limb (OR = 0.238, CI 95% = [(0.098–0.572]). Players with a history of previous injury had a 67% greater risk of sustaining an injury (OR = 0.333, CI 95% = [(0.1068–1.038]). Isometric hip adductor and abductor strength imbalances of the non-dominant lower limb and a history of previous injury were risk factors for groin injury in soccer players. [ABSTRACT FROM AUTHOR]

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]

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]

BACKGROUND: After ankle sprains, therapists may use proprioceptive training programs to manage residual symptoms and reduce the risk for recurrent injuries. However, evidence on program effectiveness is limited. OBJECTIVE: To investigate effectiveness of balance and proprioceptive neuromuscular facilitation (PNF) programs in individuals with sprain. METHODS: Participants were recruited from a rehabilitation center and were randomly allocated to a balance or PNF group. Both groups received 10 training sessions, within a six-week period. Ankle position sense, isokinetic strength and EMG activity were assessed by a blinded investigator at baseline, at the end of training and eight weeks after training. Recurrent injuries were recorded 12 months after training. RESULTS: Twenty participants provided follow-up data. Eight weeks after training, significant (p < 0.017) gains were found in most strength measures for both groups, apart from dorsiflexion strength (p > 0.05). For the balance group, there were no recurrent injuries and for the PNF group the recurrent injury rate was 20%. Eight weeks after training, the balance group significantly (p < 0.017) improved plantar flexion position sense and EMG activity of peroneus longus muscle and the PNF group significantly (p < 0.017) improved EMG activity of tibialis anterior muscle. CONCLUSIONS: For individuals with sprain, balance and PNF programs are recommended for ankle strengthening. They may also be effective in reducing the risk for recurrent injuries. [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]

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.

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]

Exercise responses and injury rates differ between individual hamstrings and this may be linked with their morphology. The aim of this study was to compare muscle length and tendon dimensions between the individual hamstrings at two knee joint angles using free hand three-dimensional ultrasound (3D US). Muscle-tendon length and distal tendon cross-sectional area (CSA), volume, length and echogenicity of biceps femoris long (BFlh) and short (BFsh) head, semimembranosus (SM) and semitendinosus (ST) of 16 individuals were measured using free-hand 3D US at 0° (full extension) and 45° of knee flexion. ST showed the greatest length than all muscles and BFsh the lowest (p < 0.05). No difference was observed between SM and BFlh length (p > 0.05). Of the four muscles, ST tendon was longer, with less volume and CSA but greater echogenicity than the other tendons. In contrast, SM and BFlh showed shorter tendons and lower echogenicity but a greater volume and CSA than ST (p < 0.05). Muscle and tendon lengthened from 45° to 0° knee flexion angle (p < 0.05) but this change was not statistically different between individual hamstrings (p > 0.05). Freehand 3D US indicated that hamstring muscle length and distal tendon dimensions differ between individual hamstrings. All muscles and tendons lengthened as the knee was extended but this change was similar for all individual hamstrings. [ABSTRACT FROM AUTHOR]

Background and Purpose. Improving functional performance in patients with chronic low back pain is of primary importance. The purpose of this study was to examine the effects of 2 pr.oprioceptive neuromuscular facilitation (PNF) programs on trunk muscle endurance, flexibility, and functional performance in subjects with chronic low back pain (CLBP). Subjects. Eighty-six women (40.2±11.9 [X±SD] years of age) who had complaints of CLBP were randomly assigned to 3 groups: rhythmic stabilization training, combination of isotonic exercises, and control. Methods. Subjects trained with each program for 4 weeks with the aim of improving trunk stability and strength. Static and dynamic trunk muscle endurance and lumbar mobility were measured before, at the end of, and 4 and 8 weeks after training. Disability and back pain intensity also were measured with the Oswestry Index. Results. Multivariate analysis of variance indicated that both training groups demonstrated significant improvements in lumbar mobility (8.6%-24.1%), static and dynamic muscle endurance (23.6%-81%), and Oswestry Index (29.3%-31.8%) measurements. Discussion and Conclusion. Static and dynamic PNF programs may be appropriate for improving short-term trunk muscle endurance and trunk mobility in people with CLBP. [ABSTRACT FROM AUTHOR]

Isokinetic dynamometers are extensively used to monitor strength development in young soccer players. The purpose of this study was to examine the effects of age, velocity and leg of preference on the peak moments in young soccer players. One hundred and fifty eight soccer players (age [ABSTRACT FROM AUTHOR]

Muscle strength imbalances around the knee are often observed in athletes after anterior cruciate ligament (ACL) surgery and hamstring muscle injury. This study examined three hamstrings-to-quadriceps (H:Q) strength ratio types (conventional, functional, and mixed) in thirteen female athletes with a history of hamstring injury, fourteen basketball players following ACL reconstruction and 34 controls. The conventional (concentric H:Q) peak torque ratio was evaluated at 120°·s−1 and 240°·s−1. The functional (eccentric hamstring to concentric quadriceps) torque ratio was evaluated at 120°·s−1. Finally, the mixed (eccentric hamstrings at 30°·s−1 to concentric quadriceps at 240°·s−1) torque ratio was calculated. Both ACL and the hamstring-injured groups showed a lower quadriceps and hamstrings strength compared with controls (p < 0.05). However, non-significant group differences in the H:Q ratio were found (p > 0.05). Isokinetic assessment of muscle strength may be useful for setting appropriate targets of training programs for athletes with a history of ACL surgery or hamstring strain. However, isokinetic evaluation of the H:Q ratio is not injury—specific and it does not vary between different methods of calculating the H:Q ratio. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the hamstring to quadriceps ratio (H:Q) obtained from three different hip flexion angles. Seventy-three young athletes performed maximum isokinetic concentric and eccentric knee extension and flexion efforts at 60 °·s−1 and 240 °·s−1 from hip flexion angles of 90°, 60°, and 120°. The conventional (concentric to concentric), functional (eccentric to concentric) and mixed (eccentric at 30 °·s−1 to concentric torque at 240 °·s−1) H:Q torque ratios and the electromyographic activity from the rectus femoris and biceps femoris were analyzed. The conventional H:Q ratios and the functional H:Q ratios at 60 °·s−1 did not significantly differ between the three testing positions (p > 0.05). In contrast, testing from the 90° hip flexion angle showed a greater functional torque ratio at 240 °·s−1 and a mixed H:Q torque ratio compared with the other two positions (p < 0.05). The hip flexion angle did not influence the recorded muscle activation signals (p > 0.05). For the range of hip flexion angles tested, routine isokinetic assessment of conventional H:Q ratio and functional H:Q ratio at slow speed is not angle-dependent. Should assessment of the functional H:Q ratio at fast angular velocity or the mixed ratio is required, then selection of hip flexion angle is important. [ABSTRACT FROM AUTHOR]

Highlights: [•] Individuals with ID require proper interventions such as hippotherapy. [•] Reaction time and muscle activation deficits might limit the individual's autonomy. [•] Hippotherapy can improve functional task performance by enhancing reaction time. [•] Hippotherapy is an effective training that provides a complex sensory motor stimulation. [ABSTRACT FROM AUTHOR]