Time-Course Changes in Dorsiflexion Range of Motion, Stretch Tolerance, and Shear Elastic Modulus for 20 Minutes of Hot Pack Application.

The application of thermal agents via hot packs is a commonly utilized method. However, the time-course changes in the range of motion (ROM), stretch sensation, shear elastic modulus, and muscle temperature during hot pack application are not well understood. This study aimed to investigate the time-course changes in these variables during a 20-minute hot pack application. Eighteen healthy young men (21.1 ± 0.2 years) participated in this study. We measured the dorsiflexion (DF) ROM, passive torque at DF ROM (an indicator of stretch tolerance), and shear elastic modulus (an indicator of muscle stiffness) of the medial gastrocnemius before and every 5 minutes during a 20-minute hot pack application. The results showed that hot pack application for ≥5 minutes significantly (p < 0.01) increased DF ROM (5 minutes: d = 0.48, 10 minutes: d = 0.59, 15 minutes: d = 0.73, 20 minutes: d = 0.88), passive torque at DF ROM (5 minutes: d = 0.71, 10 minutes: d = 0.71, 15 minutes: d = 0.82, 20 minutes: d = 0.91), and muscle temperature (5 minutes: d = 1.03, 10 minutes: d = 1.71, 15 minutes: d = 1.74, 20 minutes: d = 1.66). Additionally, the results showed that hot pack application for ≥5 minutes significantly (p < 0.05) decreased shear elastic modulus (5 minutes: d = 0.29, 10 minutes: d = 0.31, 15 minutes: d = 0.30, 20 minutes: d = 0.31). These results suggest that hot pack application for a minimum 5 minutes can increase ROM and subsequently decrease muscle stiffness.

Effects of 5-Week Foam Rolling Intervention on Range of Motion and Muscle Stiffness.

ABSTRACT: Kiyono, R, Onuma, R, Yasaka, K, Sato, S, Yahata, K, and Nakamura, M. Effects of 5-week foam rolling intervention on range of motion and muscle stiffness. J Strength Cond Res 36(7): 1890-1895, 2022-In clinical and sports settings, foam rolling (FR) intervention is widely used to increase the range of motion (ROM). However, the chronic effects of FR on ROM and muscle stiffness are unclear. The aim of this study was to investigate the effects of 5-week FR intervention on dorsiflexion ROM (DFROM) and shear elastic modulus of the medial gastrocnemius (MG) muscle. Accordingly, 30 healthy young adults were enrolled and randomly assigned to either the FR or control group with the former receiving 90 seconds of FR thrice per week over 5 weeks. Thereafter, DFROM, passive torque at DFROM, and shear elastic modulus of the MG during passive ankle dorsiflexion were assessed using a dynamometer and ultrasonography before and after 5 weeks. Our results showed that the FR group exhibited a significant increase in DFROM (Δ = 11.7%, p < 0.05, effect size = 0.39), but no changes in passive torque at DFROM, and shear elastic modulus at 0° and 10° dorsiflexion. Moreover, significant correlations were observed between change in DFROM and change in passive torque at DFROM in the FR group (rs = 0.607, p = 0.016). These results suggested that FR was an effective method to increase DFROM given its ability to change passive torque at DFROM (stretch tolerance) without altering muscle stiffness.

Effects of a high-volume static stretching programme on plantar-flexor muscle strength and architecture.

PURPOSE: Static stretching (SS) is performed in various settings, but there is no consensus about the effects of SS programmes on changes in muscle morphofunction. This study aimed to investigate the effects of a high-volume SS programme on muscle strength and architecture. METHODS: Sixteen healthy young male adults participated, and the dominant leg was defined as the intervention side, with the non-dominant leg as the control side. Stretching exercises were performed two times per week (6 sets of 5 min, totally 30 min per session,) for 5-week using a stretching board under the supervision of the research team. Before and after SS intervention programme, plantar-flexor strength (maximum voluntary isometric contraction, MVC-ISO; maximum voluntary concentric contraction, MVC-CON) and architecture (muscle thickness, pennation angle, and fascicle length) were measured via dynamometer and ultrasound, respectively. RESULTS: Following the SS-training programme, significant increases were observed for stretching side in MVIC-ISO at neutral ankle position (p = 0.02, d = 0.31, Δ = 6.4 ± 9.9%) and MVC-CON at 120°/s (p = 0.02, d = 0.30, Δ = 7.8 ± 9.1%), with no significant change on the control side. There was no significant change in any measure of muscle architecture for both intervention and control sides. CONCLUSION: Five-week high-volume SS induced positive changes on some measures of muscle strength but not hypertrophy of plantar-flexor muscles. Even with a volume much greater than already tested, the low strain offered by the SS per set seems be insufficient to induce architectural changes on skeletal muscle.

The Acute and Prolonged Effects of Different Durations of Foam Rolling on Range of Motion, Muscle Stiffness, and Muscle Strength.

"Foam Rolling" has been used in sports settings to increase range of motion and decrease muscle stiffness without decreasing muscle strength and athletic performance. However, there has been no study investigating the acute and prolonged effect of different durations of foam rolling intervention on muscle stiffness, and the minimum foam rolling intervention duration required to decrease muscle stiffness is unclear. Therefore, the purpose of this study was to investigate the acute and prolonged effect of different durations of foam rolling intervention on ROM, muscle stiffness, and muscle strength. The 45 participants were randomly allocated to 1 of 3 groups (30 s × 1 times group vs 30 s × 3 times group vs 30 s× 10 times group). The outcome measures were dorsiflexion range of motion, shear elastic modulus of medial gastrocnemius, and muscle strength before, 2 min and 30 min after foam rolling intervention. There were no significant differences before and 2 min after foam rolling intervention in 30 s×1 time group, whereas dorsiflexion range of motion was increased in both 30 s×3 times group (p = 0.042, d = 0.26) and 30 s× 10 times group (p < 0.01, d = 0.33). However, the increase in dorsiflexion range of motion was returned to baseline value after 30 minutes in both 30 s × 3 times group and 30 s × 10 times group. In addition, there were no significant changes in shear elastic modulus and muscle strength in all groups. This study suggested that foam rolling for more than 90 s or more of foam rolling was effective in order to increase the range of motion immediately without changing muscle stiffness and muscle strength.

Effect of Rest Duration Between Static Stretching on Passive Stiffness of Medial Gastrocnemius Muscle In Vivo.

CONTEXT: In clinical and sports settings, static stretching (SS) is usually performed to increase range of motion (ROM) and decrease passive muscle stiffness. Recently, the shear elastic modulus was measured by ultrasonic shear wave elastography as an index of muscle stiffness. Previous studies reported that the shear elastic modulus measured by ultrasound shear wave elastography decreased after SS, and the effects of SS on shear elastic modulus were likely affected by rest duration between sets of SS. OBJECTIVE: To investigate the acute effects of SS with different rest durations on ROM and shear elastic modulus of gastrocnemius and to clarify whether the rest duration between sets of SS decreases the shear elastic modulus. DESIGN: A randomized, repeated-measures experimental design. SETTING: University laboratory. PARTICIPANTS: Sixteen healthy males volunteered to participate in the study (age 21.3 [0.8] y; height 171.8 [5.1] cm; weight 63.1 [4.5] kg). MAIN OUTCOME MEASURES: Each participant underwent 3 different rest interval durations during SS (ie, long rest duration: 90 s; normal rest duration: 30 s; and short rest duration: 10 s). This SS technique was repeated 10 times, thus lasting a total of 300 seconds with different rest durations in each protocol. The dorsiflexion ROM and shear elastic modulus were measured before and after SS. RESULTS: Our results revealed that dorsiflexion ROM and shear elastic modulus were changed after 300-second SS; however, no effects of the rest duration between sets of SS were observed. CONCLUSIONS: In terms of decreasing the shear elastic modulus, clinicians and coaches should not focus on the rest duration when SS intervention is performed.

One-repetition maximum can be estimated with a handheld dynamometer and circumference in community-dwelling older adults.

[Purpose] One-repetition maximum is an essential statistic for physical therapists and coaches in rehabilitation and athletic settings. In a previous study, we showed that one-repetition maximum of the knee extensor could be predicted more accurately with the combination of maximal voluntary isometric contraction strength, as measured by a handheld dynamometer, muscle thickness, and thigh circumference, in young adults. However, there has been no study in older adults investigating the relationship between one-repetition maximum and maximal voluntary isometric contraction strength, or muscle thickness, and thigh circumference. Therefore, the aim of this study was to investigate the relationship between one-repetition maximum and maximal voluntary isometric contraction strength, or muscle thickness, and thigh circumference in older adults. [Participants and Methods] Twenty-eight older community-dwelling adults (18 males and 10 females) participated in this study. Muscle strength of the knee extensor was measured using one-repetition maximum and maximal voluntary isometric contraction strength. In addition, muscle thicknesses of the refutes femoris and the vastus intermedius, and thigh circumference were measured using ultrasonography and measuring tape, respectively. [Results] Stepwise regression analysis revealed that body mass, gender, thigh circumference at 15 cm above the patella, and maximal voluntary isometric contraction strength were significant and independent determinants (R2=0.868). [Conclusion] One-repetition maximum could be predicted more accurately using a combination of maximal voluntary isometric contraction strength, as measured with a handheld dynamometer, and thigh circumference in older adults.

The effect of low-intensity resistance training after heat stress on muscle size and strength of triceps brachii: a randomized controlled trial.

BACKGROUND: The purpose of this study was to clarify whether there is a synergistic effect on muscular strength and hypertrophy when low-intensity resistance training is performed after heat stress. METHODS: Thirty healthy young male volunteers were randomly allocated to either the low-intensity resistance training with heat stress group or the control group. The control group performed low-intensity resistance training alone. In the low-intensity resistance training with heat stress group, a hot pack was applied to cover the muscle belly of the triceps brachii for 20 min before the training. The duration of the intervention was 6 weeks. In both groups, the training resistance was 30% of the one repetition maximum, applied in three sets with eight repetitions each and 60-s intervals. The one repetition maximum of elbow extension and muscle thickness of triceps brachii were measured before and after 6 weeks of low intensity resistance training. RESULTS: There was no significant change in the one-repetition maximum and muscle thickness in the control group, whereas there was a significant increase in the muscle strength and thickness in the low-intensity resistance training with heat stress group. CONCLUSION: The combination of heat stress and low-intensity resistance training was an effective method for increasing muscle strength and volume. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry (UMIN000036167; March 11, 2019).

Efficacies of ultrasound and a handheld dynamometer to predict one-repetition maximum.

[Purpose] It is important to accurately measure one-repetition maximum to determine the training load and number of repetitions. However, huge and expensive equipment, such as a torque machine and/or dynamometer, is needed to measure one-repetition maximum. Therefore, a more accessible and affordable method has been developed to predict one-repetition maximum. In this study, we aimed to investigate whether one-repetition maximum of the knee extensor could be predicted more accurately with a combination of muscle strength, measured using a handheld dynamometer, muscle thickness, and thigh circumference. [Participants and Methods] Participants were sixty-four non-athletic healthy adult volunteers (33 males and 31 females). Muscle strength of the knee extensor measured using one-repetition maximum, maximal voluntary isometric contraction measured using a handheld dynamometer, muscle thickness of the quadriceps and/or thigh circumference measured on ultrasonography. [Results] The stepwise regression analysis revealed that body mass, gender, muscle thickness at 15 cm above the patella, and maximal voluntary isometric contraction were the significant and independent determinants (R2=0.813). [Conclusion] One-repetition maximum could be predicted more accurately with a combination of maximal voluntary isometric contraction measured using a handheld dynamometer and muscle thickness.

The Effect of Capacitive and Resistive Electric Transfer Intervention on Delayed-Onset Muscle Soreness Induced by Eccentric Exercise.

This study aimed to investigate the acute effect of capacitive and resistive electric transfer (CRet) intervention on eccentrically damaged muscle. A total of 28 healthy and sedentary male volunteers were randomly allocated to either CRet intervention or control groups. The participants performed a bout of eccentric exercise of the knee extensors with the dominant leg and received 30 min of CRet intervention of the quadriceps 48 h after the exercise. The dependent variables for the analysis were knee flexion range of motion (ROM), muscle soreness and maximum voluntary isometric (MVC-ISO), and concentric contraction (MVC-CON) torque of the knee extensors. These were measured prior to exercise (baseline) and before and after CRet intervention (48 h after the exercise). The results showed that knee flexion ROM, muscle strength (MVC-ISO and MVC-CON), and muscle soreness significantly improved after CRet intervention. CRet intervention may improve muscle soreness and loss of muscle function in an eccentrically damaged muscle.

Relationship between Nordic hamstring strength and maximal voluntary eccentric, concentric and isometric knee flexion torque.

Nordic hamstring exercise is performed to prevent knee flexor muscle strain injuries and used to assess their injury risks. However, what exactly Nordic hamstring strength indicates is not clear. We investigated the relationship between Nordic hamstring strength and maximal voluntary contraction (MVC) torque of the knee flexors measured by an isokinetic dynamometer. Sixteen healthy young men who had not experienced hamstring strain injuries participated in the study. In Nordic hamstring, each participant was instructed to lean forward as far as possible in 3 s (approximately 30°/s), and force at the ankle joint of the dominant leg was measured during the movement. The force was multiplied by lower leg length and converted into torque. MVC torque of the knee flexors was measured isometrically at 30°, 45°, 60°, and 90° knee flexion joint angles, and concentrically and eccentrically at 30°/s and 60°/s in 10°-90° knee flexion for the dominant leg in a prone position. Correlations among the dependent variables were assessed using Pearson's correlation coefficients. Peak Nordic hamstring torque ranged 96.8-163.5 Nm, and peak MVC eccentric torque ranged 50.7-109.4 Nm at 30°/s and 59.2-121.2 Nm at 60°/s. No significant correlations were evident between the peak Nordic hamstring torque and peak eccentric knee flexion torque (r = 0.24-0.3, p = 0.26-0.4). This was also the case for the Nordic hamstring torque and MVC torque of isometric (r = -0.03-0.1, p = 0.71-0.92) and concentric contractions (r = 0.28-0.49, p = 0.053-0.29). These results show that Nordic hamstring strength is not associated with the knee flexor torque measured by an isokinetic dynamometer. It may be that other factors than static and dynamic hamstring strengths affect Nordic hamstring strength.

The Associations between Rapid Strength Development and Muscle Stiffness in Older Population.

BACKGROUND: Previous studies suggest that the capacity for rapid force production of ankle plantar flexors is essential for the prevention of falls in the elderly. In healthy young adults, there were significant associations between rate of force development and muscle stiffness measured by shear wave elastography. However, there has been no study investigating the association of rate of force development with shear elastic modulus in older adults. METHODS: The muscle strength and shear elastic modulus of the medial gastrocnemius muscle in both legs were measured in 17 elderly men and 10 elderly women (mean ± SD; 70.7 ± 4.1 years; 160.6 ± 8.0 cm; 58.7 ± 9.5 kg). We investigated the rate of force development of plantar flexors and shear elastic modulus of medial gastrocnemius muscle using by shear wave elastography. RESULTS: Our results showed that there were no significant associations between normalized rate of force development and shear elastic modulus of medial gastrocnemius muscle. CONCLUSION: This suggests that the capacity of rapid force production could be related not to muscle stiffness of the medial gastrocnemius muscle, but to neuromuscular function in older individuals.

Cross-education and detraining effects of eccentric vs. concentric resistance training of the elbow flexors.

BACKGROUND: Unilateral resistance training increases the strength of the contralateral non-trained homologous muscles known as the cross-education effect. We tested the hypothesis that unilateral eccentric resistance training (ET) would induce greater and longer-lasting cross-education effect when compared with concentric resistance training (CT). METHODS: Young (20-23 y) participants were allocated to ET (5 males, 4 females) or CT (5 males, 4 females) group that performed unilateral progressive ET or CT of the elbow flexors, twice a week for 5 weeks (10 sessions) followed by a 5-week detraining, and control group (7 males, 6 females) that did not perform any training. Maximum voluntary isometric contraction torque of the elbow flexors (MVIC), one-repetition maximum of concentric dumbbell curl (1-RM), and biceps brachii and brachialis muscle thickness (MT) were measured from the trained and non-trained arms before, several days after the last training session, and 5 weeks later. A ratio between the trained and non-trained arms for the change in MVIC or 1-RM from pre- to post-training (cross-body transfer ratio) was compared between ET and CT groups. RESULTS: The control group did not show significant changes in any variables. Both ET and CT increased (P < 0.05) MVIC (22.5 ± 12.3 % vs. 26.0 ± 11.9 %) and 1-RM (28.8 ± 6.6 % vs. 35.4 ± 12.9 %) of the trained arm without a significant difference between groups. MVIC was maintained after detraining for ET but returned to the baseline for CT, and 1-RM was maintained after detraining for both ET and CT. For the non-trained arm, MVIC (22.7 ± 17.9 % vs. 12.2 ± 10.2 %) and 1-RM (19.9 ± 14.6 % vs. 24.0 ± 10.6 %) increased similarly (P > 0.05) after ET and CT, and MVIC returned to the baseline after detraining, but 1-RM was maintained for both groups. An increase (P < 0.05) in MT was found only after ET for the trained arm (7.1 ± 6.1 %). The cross-body transfer ratio for MVIC was greater (P < 0.05) for ET (90.9 ± 46.7 %) than CT (49.0 ± 30.0 %). CONCLUSIONS: These results did not support the hypothesis and showed similar changes in the most of the variables between ET and CT for the trained and non-trained arms, and strong cross-education effects on MVIC and 1-RM, but less detraining effect after ET than CT on MVIC of the trained arm. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry (UMIN000044477; Jun 09, 2021).

Comparison of the Acute Effects of Hold-Relax and Static Stretching among Older Adults.

Various stretching techniques are generally recommended to counteract age-related declines in range of motion (ROM) and/or increased muscle stiffness. However, to date, an effective stretching technique has not yet been established for older adults. Consequently, we compared the acute effects of hold relax stretching (HRS) and static stretching (SS) on dorsiflexion (DF) ROM and muscle stiffness among older adults. Overall, 15 elderly men and nine elderly women (70.2 ± 3.9 years, 160.8 ± 7.8 cm, 59.6 ± 9.7 kg) were enrolled, and both legs were randomized to either HRS or SS stretching. We measured DF ROM and muscle stiffness using a dynamometer and ultrasonography before and after 120 s of HRS or SS interventions. Our multivariate analysis indicated no significant interaction effects, but a main effect for DF ROM. Post-hoc tests revealed that DF ROM was increased after both HRS and SS interventions. Moreover, multivariate analysis showed a significant interaction effect for muscle stiffness. Post-hoc tests revealed that muscle stiffness was decreased significantly after only SS intervention. Taken together, our results indicated that both HRS and SS interventions are recommended to increase ROM, and SS is recommended to decrease muscle stiffness in older adults.

Acute Effect of Vibration Roller With and Without Rolling on Various Parts of the Plantar Flexor Muscle.

A single use of a vibration foam roller likely increases the range of motion (ROM) without decreasing muscle strength and athletic performance. However, to date, no study compared the effects of a vibration roller with and without rolling on various parts of the plantar flexor muscle. Therefore, this study aimed to compare the effects of the vibration foam roller with rolling or without rolling at the muscle-tendon junction (MTJ) or the muscle belly on dorsiflexion (DF) ROM, passive torque at DF ROM, shear elastic modulus, muscle strength, and jump performance. Fifteen healthy young males performed the following three conditions: (1) vibration rolling over the whole muscle-tendon unit, (2) static vibration on muscle belly, and (3) static vibration on MTJ for three-set 60-s vibration in random order. In this study, DF ROM, passive torque, shear elastic modulus, muscle strength, and single-leg drop jump were measured before and immediately after the interventions. The DF ROM and passive torque at DF ROM were increased after all three conditions, whereas the shear elastic modulus was decreased after vibration rolling and static vibration on the muscle belly, but not following static vibration of the MTJ. In addition, there were no significant changes in muscle strength and jump performance in any group. Our results showed that vibration with rolling or static vibration on muscle belly could be effective to improve ROM and muscle stiffness without adverse effects of muscle strength and athletic performance.

Association between the Range of Motion and Passive Property of the Gastrocnemius Muscle-Tendon Unit in Older Population.

Range of motion has been widely known to decrease with age; however, factors associated with its decrease in the elderly population and especially its gender difference have been unclear. Therefore, this study aimed to investigate the factors associated with ankle dorsiflexion range of motion in the older population. Both male (n = 17, mean ± SD; 70.5 ± 4.2 years; 165.4 ± 5.3 cm; 63.8 ± 7.7 kg) and female (n = 25, 74.0 ± 4.0 years; 151.2 ± 4.9 cm; 50.1 ± 5.6 kg) community-dwelling older adults participated in this study. The ankle dorsiflexion and passive torque of both legs were measured using a dynamometer, and shear elastic modulus of the medial gastrocnemius muscle at 0° ankle angle was measured using ultrasonic shear wave elastography. In this study, we defined the passive torque at dorsiflexion range of motion (DF ROM) as the index of stretch tolerance, and shear elastic modulus as the index of passive muscle stiffness. The partial correlation coefficient adjusted by age, height, weight, and side (dominant or nondominant side) was used to analyze the relationship between DF ROM and passive torque at DF ROM or shear elastic modulus of MG in each male and female participant, respectively. Our results revealed that dorsiflexion range of motion was significantly associated with passive torque at dorsiflexion range of motion in both male (r = 0.455, p = 0.012) and female (r = 0.486, p < 0.01), but not with shear elastic modulus in both male (r = -0.123, p = 0.519) and female (r = 0.019, p = 0.898). Our results suggested that the ankle dorsiflexion range of motion could be related to the stretch tolerance, but not to passive muscle stiffness in community-dwelling elderly population regardless of gender.

Local and Non-local Effects of Foam Rolling on Passive Soft Tissue Properties and Spinal Excitability.

In sports and clinical settings, roller massage (RM) interventions are used to acutely increase range of motion (ROM); however, the underlying mechanisms are unclear. Apart from changes in soft tissue properties (i.e., reduced passive stiffness), neurophysiological alterations such as decreased spinal excitability have been described. However, to date, no study has investigated both jointly. The purpose of this trial was to examine RM's effects on neurophysiological markers and passive tissue properties of the plantar flexors in the treated (ROLL) and non-treated (NO-ROLL) leg. Fifteen healthy individuals (23 ± 3 years, eight females) performed three unilateral 60-s bouts of calf RM. This procedure was repeated four times on separate days to allow independent assessments of the following outcomes without reciprocal interactions: dorsiflexion ROM, passive torque during passive dorsiflexion, shear elastic modulus of the medial gastrocnemius muscle, and spinal excitability. Following RM, dorsiflexion ROM increased in both ROLL (+19.7%) and NO-ROLL (+13.9%). Similarly, also passive torque at dorsiflexion ROM increased in ROLL (+15.0%) and NO-ROLL (+15.2%). However, there were no significant changes in shear elastic modulus and spinal excitability (p > 0.05). Moreover, significant correlations were observed between the changes in DF ROM and passive torque at DF ROM in both ROLL and NO-ROLL. Changes in ROM after RM appear to be the result of sensory changes (e.g., passive torque at DF ROM), affecting both rolled and non-rolled body regions. Thus, therapists and exercise professionals may consider applying remote treatments if local loading is contraindicated.

High-Intensity Static Stretching in Quadriceps Is Affected More by Its Intensity Than Its Duration.

A previous study reported that 3-min of high-intensity static stretching at an intensity of 120% of range of motion (ROM) did not change the muscle stiffness of the rectus femoris, because of the overly high stress of the stretching. The purpose of this study was to examine the effects of high-intensity static stretching of a shorter duration or lower intensity on the flexibility of the rectus femoris than that of the previous study. Two experiments were conducted (Experiment 1 and 2). In Experiment 1, eleven healthy men underwent static stretching at the intensity of 120% of ROM for two different durations (1 and 3 min). In Experiment 2, fifteen healthy men underwent 3-min of static stretching at the intensity of 110% of ROM. The shear elastic modulus of the quadriceps were measured. In Experiment 1, ROM increased in both interventions (p < 0.01), but the shear elastic modulus of the rectus femoris was not changed. In Experiment 2, ROM significantly increased (p < 0.01), and the shear elastic modulus of the rectus femoris significantly decreased (p < 0.05). It was suggested that the stretching intensity (110%) is more important than stretching duration to decrease the muscle stiffness of the rectus femoris.

Elbow Joint Angles in Elbow Flexor Unilateral Resistance Exercise Training Determine Its Effects on Muscle Strength and Thickness of Trained and Non-trained Arms.

The present study compared two unilateral arm curl resistance exercise protocols with a different starting and finishing elbow joint angle in the same ROM for changes in elbow flexors strength and muscle thickness of the trained and non-trained arms. Thirty-two non-resistance trained young adults were randomly assigned to one of the three groups: extended joint training (0°-50°; EXT, n = 12); flexed joint training (80°-130°; FLE, n = 12); and non-training control (n = 8). The exercise training was performed by the dominant arms twice a week for 5 weeks with gradual increases in the training volume over 10 training sessions, and the non-dominant (non-trained) arms were investigated for the cross-education effect. Maximal voluntary contraction torque of isometric (MVC-ISO), concentric (MVC-CON), and eccentric contractions (MVC-ECC), and thickness (MT) of biceps brachii and brachialis of the trained and non-trained arms were assessed at baseline and 4-8 days after the last training session. The control group did not show significant changes in any variables. Significant (P < 0.05) increases in MVC-ISO torque (16.2 ± 12.6%), MVC-CON torque (21.1 ± 24.4%), and MVC-ECC torque (19.6 ± 17.5%) of the trained arm were observed for the EXT group only. The magnitude of the increase in MT of the trained arm was greater (P < 0.05) for EXT (8.9 ± 3.9%) than FLE (3.4 ± 2.7%). The cross-education effect was evident for MVC-ISO (15.9 ± 14.8%) and MVC-CON (16.7 ± 20.0%) torque of the EXT group only. These results suggest that resistance training at the extended elbow joint induces greater muscle adaptations and cross-education effects than that at flexed elbow joint.

Comparison Between Contract-Relax Stretching and Antagonist Contract-Relax Stretching on Gastrocnemius Medialis Passive Properties.

Antagonist contract-relax stretching and contract-relax stretching is commonly used in sports practice and rehabilitation settings. To date, no study has compared these modalities regarding muscle stiffness and stretch tolerance. This study aimed to investigate the effects of contract-relax and antagonist contract-relax stretching on dorsiflexion range of motion (ROM), stretch tolerance, and shear elastic modulus. Forty healthy participants (24 men and 16 women) took part in the study. Participants were randomly assigned to perform either contract-relax stretching or antagonist contract-relax stretching for 2 min. Outcomes were assessed on ROM, stretch tolerance, and shear elastic modulus before and after stretching. The ROM and stretch tolerance significantly increased after both contract-relax stretching (+ 5.4 ± 5.8°, p < 0.05; + 3.5 ± 8.0 Nm, p < 0.05) and antagonist contract-relax stretching (+ 6.1 ± 4.9°, p < 0.05; + 4.2 ± 6.4 Nm, p < 0.05); however, no significant difference was found between the two groups. Alternatively, the shear elastic modulus significantly decreased after both contract-relax (-31.1 ± 22.6 kPa, p < 0.05) and antagonist contract-relax stretching (-11.1 ± 22.3 kPa, p < 0.05); however, contract-relax stretching (-41.9 ± 19.6%) was more effective than antagonist contract-relax stretching (-12.5 ± 61.6%). The results of this study suggest that contract-relax stretching instead of antagonist contract-relax stretching should be conducted to decrease muscle stiffness. However, either contract-relax or antagonist contract-relax stretching can increase ROM.