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Can chronic stretching change the muscle-tendon mechanical properties? A review
Abstract and Figures
Purpose:
It is recognized that stretching is an effective method to chronically increase the joint range of motion. However, the effects of stretching training on the muscle-tendon structural properties remain unclear. This systematic review with meta-analysis aimed to determine whether chronic stretching alter the muscle-tendon structural properties.
Methods:
Published papers regarding longitudinal stretching (static, dynamic and/or PNF) intervention (either randomized or not) in humans of any age and health status, with more than 2 weeks in duration and at least 2 sessions per week, were searched in PubMed, PEDro, ScienceDirect and ResearchGate databases. Structural or mechanical variables from joint (maximal tolerated passive torque or resistance to stretch) or muscle-tendon unit (muscle architecture, stiffness, extensibility, shear modulus, volume, thickness, cross sectional area, and slack length) were extracted from those papers.
Results:
A total of 26 studies were selected, with a duration ranging from 3 to 8 weeks, and an average total time under stretching of 1165s per week. Small effects were seen for maximal tolerated passive torque, but trivial effects were seen for joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness. A large heterogeneity was seen for most of the variables.
Conclusion:
Stretching interventions with 3-8 weeks duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level. This article is protected by copyright. All rights reserved.
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... The American College of Sports Medicine recognises flexibility as one of five health-related components of physical fitness [4]. Muscle stretching, the primary way to improve flexibility, is widely used by coaches, athletes, and allied health, exercise and medical professionals to increase ROM [5], improve physical performance [6,7] and supposedly mitigate injury risk [8,9]. The most common, accessible and simplest form of stretching is static stretching, which involves moving a joint to near its end ROM (until a stretch sensation is felt in the muscle) and holding still [10][11][12][13]. ...
... Stretching is thought to improve flexibility by increasing stretch tolerance [14], changing the viscoelastic properties of the musculotendinous tissues (i.e. musculotendon stiffness) [5], or changing the muscle architecture (i.e. muscle fascicle length and pennation angle) [15]. ...
... Warneke et al. [68] found that statically stretching the ankle plantar flexors with an extended knee for 60 min/day led to significantly greater improvements in ankle dorsiflexion ROM when assessed in knee extension compared with 30 min and 10 min/day over a 6-week period. It has been proposed that such high-volume long-duration static stretching is necessary to elicit the morphological adaptations in the muscle-tendon unit that were elusive in earlier reviews [5,15]. More studies investigating the effects of longer duration static stretching on flexibility are needed to increase the confidence in the dose-response relationship suggested by the current review and to identify the physiological mechanisms underpinning these improvements in flexibility. ...
Background
Static stretching is widely used to increase flexibility. However, there is no consensus regarding the optimal dosage parameters for increasing flexibility.
Objectives
We aimed to determine the optimal frequency, intensity and volume to maximise flexibility through static stretching, and to investigate whether this is moderated by muscle group, age, sex, training status and baseline level of flexibility.
Methods
Seven databases (CINAHL Complete, Cochrane CENTRAL, Embase, Emcare, MEDLINE, Scopus, and SPORTDiscus) were systematically searched up to June 2024. Randomised and non-randomised controlled trials investigating the effects of a single session (acute) or multiple sessions (chronic) of static stretching on one or more flexibility outcomes (compared to non-stretching passive controls) among adults (aged ≥ 18 years) were included. A multi-level meta-analysis examined the effect of acute and chronic static stretching on flexibility outcomes, while multivariate meta-regression was used to determine the volume at which increases in flexibility were maximised.
Results
Data from 189 studies representing 6654 adults (61% male; mean [standard deviation] age = 26.8 ± 11.4 years) were included. We found a moderate positive effect of acute static stretching on flexibility (summary Hedges’ g = 0.63, 95% confidence interval 0.52–0.75, p < 0.001) and a large positive effect of chronic static stretching on flexibility (summary Hedges’ g = 0.96, 95% confidence interval 0.84–1.09, p < 0.001). Neither effect was moderated by stretching intensity, age, sex or training status, or weekly session frequency and intervention length (chronic static stretching only) [p > 0.05]. However, larger improvements were found for adults with poor baseline flexibility compared with adults with average baseline flexibility (p = 0.01). Furthermore, larger improvements in flexibility were found in the hamstrings compared with the spine following acute static stretching (p = 0.04). Improvements in flexibility were maximised by a cumulative stretching volume of 4 min per session (acute) and 10 min per week (chronic).
Conclusions
Static stretching improves flexibility in adults, with no additional benefit observed beyond 4 min per session or 10 min per week. Although intensity, frequency, age, sex and training status do not influence improvements in flexibility, lower flexibility levels are associated with greater improvement following both acute and chronic static stretching. These guidelines for static stretching can be used by coaches and therapists to improve flexibility.
Clinical Trial Registration
PROSPERO CRD42023420168.
... Mechanical theories of increasing flexibility involve muscle viscoelasticity (6) . Shear wave elastography (SWE) is a technique that makes it possible to quantitatively measure elasticity as a value such as the Young's modulus (7) and is expected to be useful for determining the effectiveness of stretching (8) . SWE has been used to examine the immediate effects of static stretching. ...
... The stretching program was developed based on review articles that examined the effects of chronic stretching (8,12) . The participants were instructed to perform voluntary static stretching of the right rectus femoris muscle five times a week for four weeks. ...
... Several weeks of static stretching can decrease the Young's modulus of muscle and increase the joint range of motion. Modified sensation seems to be primarily responsible for the increase in flexibility with stretching within eight weeks, while the muscle properties do not seem to change (8) . However, this study indicates a change in the Young's modulus of muscle. ...
Aim
The study aimed to quantitatively clarify the effects of several weeks of static stretching on the flexibility of the rectus femoris muscle using shear wave elastography.
Material and methods
Fifteen healthy men (age: 26.4 ± 2.2 years) were instructed to perform 5 min of voluntary static stretching of their right rectus femoris muscles five times a week for four weeks. The participants adjusted their stretching inrectus femoris muscle tensity to a point immediately before experiencing discomfort or pain. The Young’s modulus of the rectus femoris muscle and the knee-flexion range of motion were measured as indicators of flexibility. The Young’s modulus was measured using shear wave elastography. Measurements were performed at baseline, as well as at two and four weeks after the stretching program started. A generalized linear mixed model was used to assess the change in the Young’s modulus after the stretching program and the effects of the Young’s modulus on the knee-flexion range of motion.
Results
The Young’s modulus of the rectus femoris muscle decreased after two and four weeks of stretching compared with the baseline (p = 0.0004 and p <0.0001, respectively). The Young’s modulus of the rectus femoris muscle and the four-week duration of stretching affected the knee-flexion range of motion (p = 0.0242 and 0.0016, respectively).
Conclusions
Shear wave elastography quantitatively revealed that several weeks of static stretching increased the flexibility of the rectus femoris muscle in healthy men. A four-week static stretching regimen reduced the Young’s modulus of the rectus femoris muscle and increased the knee-flexion range of motion.
... A meta-analysis including 446 healthy adults engaged in a long-term stretching protocol, lasting between 2 and 8 weeks, revealed that stretching enhances the maximal tolerated stretch. Nevertheless, it did not significantly modify the stiffness of the MTU, tendon stiffness, muscle stiffness, or muscle architectural parameters, such as pennation angle, and fiber length [17]. These findings seem to favor the sensory theory, the stretching protocols might be too short to observe an MTU adaptation. ...
... It is consistent with the systematic review on the effect of longitudinal stretching in young and healthy individuals. Indeed, Freitas et al. in their meta-analysis about healthy and mostly young individuals showed a small but significant effect on maximally tolerated resistance after long-term static stretching [17]. Specifically, Marshal et al. reported a 43.5% increase in maximal tolerable resistance after longterm hamstring stretching program (6 min × 5 times/week for 4 weeks) [41]. ...
... Specifically, Marshal et al. reported a 43.5% increase in maximal tolerable resistance after longterm hamstring stretching program (6 min × 5 times/week for 4 weeks) [41]. Our study shows greater effects size than Freitas et al., suggesting that stretching might have a greater impact on stretching tolerance for elderly individuals [17]. However, there are several differences between the studies included in their meta-analysis and our own, particularly in terms of the muscles stretched. ...
Purpose
Long-term static stretching is commonly employed in elderly rehabilitation to enhance range of motion (RoM), which is crucial for fall prevention and improving gait parameters. A RoM increase can result from enhanced stretch tolerance and/or musculotendinous (MTU) adaptations. Previous studies have also shown muscle hypertrophy following long-term stretching protocols in deconditioned populations. Mechanisms underlying RoM increase due to stretching in the elderly are scarce. This review aims to provide an overview of the long-term effects of static stretching on the structure and mechanical properties of the MTU in older adults.
Methods
Systematic searches were performed on three databases (PubMed, Epistemonikos, and Scopus), and cross-referencing, according to the PICO method. Meta-analyses were conducted to examine the impact of long-term stretching on range of motion, maximally tolerated resistance, and MTU stiffness.
Results
Meta-analysis in older adults unveil that long-term static stretching increases the passive stiffness of the MTU (effect size = 0.61; 95% confidence interval = [0.10 1.12], p = 0.02, I² = 0), increases maximal tolerated resistance (effect size = 0.70; 95% confidence interval = [0.27 1.14], p < 0.01, I² = 0) and increases RoM (effect size = 0.67; 95% confidence interval = [0.24 1.11], p < 0.01, I² = 0).
Conclusion
Improvement of flexibility among elderly individuals following long-term passive stretching procedures is due to enhanced stretch tolerance and MTU modification. It underscores the critical role of stretching in both restoring functional mobility and muscle retraining. More studies are needed to establish stronger evidence.
... Similarly, much is known about clinical consequences related to incorrect values of the pelvic tilt. We also note a development of various therapeutic concepts aiming to restore the balance within the muscles stabilising the pelvis in order to bring it to its correct position [4,19,28,43,45,55,56]. Most often they are based, to a greater or lesser degree, on the concept of muscular imbalance developed by Janda. ...
... It seems well confirmed how incorrect pelvis position affects the locomotive system, both in the biomechanical context [7,51] and in terms of its clinical consequences [3][4][5]19,52,53]. Various forms of therapy are developed aiming to restore correct anatomical and biomechanical conditions within the lumbar-pelvic-hip complex, starting from the administration of various pharmacological measures [54] to various systems of exercise restoring correct tone and length of pelvis stabilisers [4,19,28,43,45,55,56]. ...
Purpose
The objective of the study was to initially validate the hypothesis about the relationship between the pelvic tilt angle in the saggital plane and the functional state of muscles stabilising the lumbo-pelvic-hip (LPH) complex expressed as a change in their stiffness in a tensiomyography examination.
Materials and methods
Forty five women aged 19–30 years took part in an observational (cross-sectional) study. The examination involved measurements using the tensiomyography method (TMG). The stiffness of muscles stabilising the LPH complex expressed as a maximal muscle displacement (Dm variable) was assessed and the relationship between muscle stiffness and the value of the pelvic tilt (PT) in the sagittal plane was determined.
Results
The analysis showed significant differences in the values of medians of the muscle displacement (Dm) values in groups identified in terms of the value of pelvic tilt (Table 1) for Erector Spinae (ES) muscles (p = 0.0012), Gluteus Maximus (GM) muscles (p = 0.0004), Rectus Abdominis (RA) muscles (p = 0.0005), Obliquus abdominis externus (OAE) muscles (p = 0.0002*) and Rectus Femoris (RF) muscles (p = 0.0071). The results of the correlation analysis performed using the Spearman rho correlation coefficient between the value of pelvic tilt and muscle stiffness (Dm) show the following significant relations for ES muscles (p = 0<0.0001), GM muscles (p<0.0001), RA muscles (p<0.0001) and OAE muscles (p<0.0001). However, a clear direction of changes in stiffness in accordance with the description of relations defined as Lower Crossed Syndrome was not confirmed.
Conclusions
A tensiomyographic examination did not show clear relations between the value of pelvic tilt and stiffness of muscles stabilising the lumbar-pelvic-hip complex. The mechanism of Lower Crossed Syndrome (LCS) may be not the only model explaining the relations between musculofascial structures of the hip-lumbar area. The implications of the LCS should not be the only basis for the therapy of disorders resulting from an incorrect position of the pelvis in the sagittal plane.
... It could be that longer sessions, such as 30 min as used in this study, are needed to effectively decrease muscle stiffness. In a similar vein, literature suggests that lower volumes of static stretching only affect the stretch tolerance, while prolonged and intense stretching is needed to change muscle mechanical properties such as muscle stiffness (39). A recent study reported that achieving a positive impact on the UT muscle stiffness may require the application of stronger pressure during massage sessions (29). ...
... In contrast, studies on stretching (40,41) and foam rolling (26,42), reported mixed results for muscle stiffness reduction in various muscles, with no clear correlation between stretching duration and stiffness levels. While larger volumes of stretching are likely needed to elicit changes in muscle stiffness (39), the effects seem to be dependent on the nature of the intervention and the specific muscle under consideration (26,(40)(41)(42)(43). Further studies should also explore the importance of weekly frequency and duration in massage interventions. ...
Introduction
Massage is an effective treatment for reducing pain, swelling, stiffness, and improving muscle mobility. Although self-reported benefits on muscle stiffness and pain are well-known, studies measuring muscle stiffness objectively are scarce.
Methods
A randomized controlled trial involving 30 recreationally active young women (22.3 ± 0.4 years) was conducted. The participants were randomly assigned to either the control group or the intervention group which received a series of five 30-min whole back therapeutic massage sessions over 5 weeks. Shear wave elastography was used to assess muscle stiffness (erector spinae (ESp) and upper trapezius (UT) muscles) before and after the intervention and at 3-week follow-up.
Results
For ESp, there was no statistically significant time × group interaction ( F = 2.908; p = 0.063). However, there was a statistically significant and large time × group interaction for UT ( F = 13.533; p = 0.006; η ² = 0.19). Post-hoc testing for time indicated that the shear modulus in the intervention group was reduced at follow-up ( p = 0.005; d = 1.02), while the difference between baseline and post-intervention measurements were not statistically significant ( p = 0.053; d = 0.75).
Conclusion
In conclusion, massage significantly reduced proximal UT stiffness both 3 days and 3 weeks after the intervention. However, it had no significant effect on the distal part of UT or the ESp muscle.
... Increased stretch (pain) tolerance has been widely attributed as a primary mechanism underlying stretched and non-stretched joint ROM increases [16,18,19,24,26,[37][38][39][40]. Increased stretch tolerance effects to increase contralateral ROM have been attributed to diffuse noxious inhibitory control and gate control theory of pain due to stimulation of nociceptors from the SS which may suppress the sensation of pain [16,18,41,42]. ...
Introduction: Increases in contralateral range of motion (ROM) have been shown following acute high-intensity and high-duration static stretching (SS) with no significant change in contralat-eral force, power, and muscle activation. There are currently no studies comparing the effects of a high-intensity, short-duration (HISD) or low-intensity, long-duration (LILD) SS on contralateral performance. Purpose: The aim of this study was to examine how HISD and LILD SS of the dominant leg hamstrings influence contralateral limb performance. Methods: Sixteen trained participants (eight females, eight males) completed three SS interventions of the dominant leg hamstrings; (1) HISD (6 × 10 s at maximal point of discomfort), (2) LILD (6 × 30 s at initial point of discomfort), and (3) control. Dominant and non-dominant ROM, maximal voluntary isometric contraction (MVIC) forces, muscle activation (electromyography (EMG)), and unilateral CMJ and DJ heights were recorded pre-test and 1 min post-test. Results: There were no significant contralateral ROM or performance changes. Following the HISD condition, the post-test ROM for the stretched leg (110.6 ± 12.6 •) exceeded the pre-test (106.0 ± 9.0 •) by a small magnitude effect of 4.2% (p = 0.008, d = 0.42). With LILD, the stretched leg post-test (112.2 ± 16.5 •) exceeded (2.6%, p = 0.06, d = 0.18) the pre-test ROM (109.3 ± 16.2 •) by a non-significant, trivial magnitude. There were large magnitude impairments, evidenced by main effects for testing time for force, instantaneous strength, and associated EMG. A significant ROM interaction (p = 0.02) showed that with LILD, the stretched leg significantly (p = 0.05) exceeded the contralateral leg by 13.4% post-test. Conclusions: The results showing no significant increase in contralateral ROM with either HISD or LILD SS, suggesting the interventions may not have been effective in promoting crossover effects.
... Static stretching (SS) is frequently used in athletic, fitness, and clinical settings to increase joint range of motion (ROM) [1,2]. Additionally, SS aims to mitigate injury incidence [3][4][5] and improve athletic performance [5][6][7]. ...
Background
The chronic effect of static stretching (SS) on muscle hypertrophy is still unclear. This study aimed to examine the chronic effects of SS exercises on skeletal muscle hypertrophy in healthy individuals.
Methods
A systematic literature search was conducted in the PubMed, Web of Science, Cochrane Library, and SPORTDiscus databases up to July 2023. Included studies examined chronic effects of SS exercise compared to an active/passive control group or the contralateral leg (i.e., utilizing between- or within-study designs, respectively) and assessed at least one outcome of skeletal muscle hypertrophy in healthy individuals with no age restriction.
Results
Twenty-five studies met the inclusion criteria. Overall, findings indicated an unclear effect of chronic SS exercises on skeletal muscle hypertrophy with a trivial point estimate (standardised mean difference [SMD] = 0.118 [95% prediction interval [95% PI] = − 0.233 to 0.469; p = 0.017]) and low heterogeneity (I² = 24%). Subgroup analyses revealed that trained individuals (β = 0.424; 95% PI = 0.095 to 0.753) displayed larger effects compared to recreationally trained (β = 0.115; 95% PI = − 0.195 to 0.425) and sedentary individuals (β = − 0.081; 95% PI = − 0.399 to 0.236). Subanalysis suggested the potential for greater skeletal muscle hypertrophy in samples with higher percentages of females (β = 0.003, [95% confidence interval [95% CI] = − 0.000 to 0.005]). However, the practical significance of this finding is questionable. Furthermore, a greater variety of stretching exercises elicited larger increases in muscle hypertrophy (β = 0.069, [95% CI = 0.041 to 0.097]). Longer durations of single stretching exercises (β = 0.006, [95% CI = 0.002 to 0.010]), time under stretching per session (β = 0.006, [95% CI = 0.003 to 0.009]), per week (β = 0.001, [95% CI = 0.000 to 0.001]) and in total (β = 0.008, [95% CI = 0.003 to 0.013]) induced larger muscle hypertrophy. Regarding joint range of motion, there was a clear positive effect with a moderate point estimate (β = 0.698; 95% PI = 0.147 to 1.249; p < 0.001) and moderate heterogeneity (I² = 43%). Moreover, findings indicated no significant association between the gains in joint range of motion and the increase in muscle hypertrophy (β = 0.036, [95% CI = − 0.123 to 0.196]; p = 0.638).
Conclusions
This study revealed an overall unclear chronic effect of SS on skeletal muscle hypertrophy, although interpretation across the range of PI suggests a potential modest beneficial effect. Subgroup analysis indicated larger stretching-induced muscle gains in trained individuals, a more varied selection of SS exercises, longer mean duration of single stretching exercise, increased time under SS per session, week, and in total, and possibly in samples with a higher proportion of females. From a practical perspective, it appears that SS exercises may not be highly effective in promoting skeletal muscle hypertrophy unless a higher duration of training is utilized.
PROSPERO registration number: CRD42022331762.
... Increased stretch (pain) tolerance has been widely attributed as a primary mechanism underlying stretched and non-stretched joint ROM increases (Magnusson et al. 1996;Konrad & Tilp 2014;Weppler et al. 2010;Freitas et al. 2018;Chaouachi et al. 2017;Behm et al. 2019;Hadjizadeh Anvar et al. 2023). Increased stretch tolerance effects to increase contralateral ROM has been attributed to diffuse noxious inhibitory control (DNIC) and gate control theory of pain due to stimulation of nociceptors from the SS which may suppress the sensation of pain (LeBars et al. 1992;Behm et al. 2019Pud et al. 2009). ...
Introduction: Increases in contralateral range of motion (ROM) have been shown following acute high-intensity and high-duration static stretching (SS) with no significant change in contralateral force, power, and muscle activation. There are currently no studies comparing the effects of a high-intensity, low-duration (HILD) or low-intensity, high-duration (LIHD) SS on contralateral performance. Purpose: The aim of this study was to examine how HILD and LIHD SS of the dominant leg hamstrings influence contralateral limb performance. Methods: Sixteen trained participants (8 females, 8 males) completed three SS interventions of the dominant leg hamstrings; 1) HILD (6x10s at maximal point of discomfort (POD)), 2) LIHD (6x30s at initial POD), and 3) control. Dominant and non-dominant ROM, maximal voluntary isometric contraction (MVIC) forces, muscle activation (electromyography (EMG)), unilateral CMJ and DJ heights were recorded pre-test and 1-minute post-test. Results: There were no significant contralateral ROM or performance changes. Following the HILD condition, the post-test ROM for the stretched leg (110.612.60) exceeded the pre-test (106.09.00) by 4.2% (p=0.008). Similarly, with LIHD, the stretched leg post-test (112.216.50) also exceeded (p=0.06) the pre-test ROM (109.316.20) by 2.6%. There were large magnitude impairments, evidenced by main effects for testing time for force, instantaneous strength, and associated EMG. A significant ROM interaction (p=0.02) showed that with LIHD, the stretched leg significantly (p=0.05) exceeded the contralateral leg by 13.4% post-test. Conclusion: The results showing no significant increase in contralateral ROM with either HILD or LIHD SS suggesting the interventions may not have been effective in promoting crossover effects.
The relaxation of trapezius muscles is widely believed to alleviate fatigue or injury of the trapezius muscles and reduce the risk of shoulder and neck pain. This study aims to examine the effects of different muscle relaxation techniques on the physical properties of the trapezius muscle and to explore how changes in the physical properties of the upper trapezius muscle affect those of the middle trapezius muscle. Twenty-four healthy males (mean age: 23.08 ± 0.97 years; height: 172.42 ± 4.61 cm; weight: 66.38 ± 6.68 kg; and body mass index: 22.30 ± 1.81 kg/m ² ), randomly divided into four groups: stretching relaxation group (ST, n = 6), mechanical vibration massage (MV, n = 6), pulse massage (PU, n = 6), and control (CO, n = 6). Measurements using the Myoton digital muscle assessment system were conducted daily over 2 weeks. The experimental groups demonstrated a notable decrease in tension and stiffness, accompanied by heightened elasticity in the upper trapezius muscles. Conversely, the control group exhibited contrasting trends. Although no significant variances were detected among the relaxation techniques, all proved efficacious compared to the control group ( P < 0.05). Moreover, relaxation of the upper trapezius muscles significantly influenced the middle trapezius muscles ( P < 0.05). Various relaxation methods positively influenced trapezius muscle attributes over 2 weeks, with inter-regional effects noted.
Stretching is widely used in sport training and clinical practice with the aim of increasing muscle-tendon extensibility and joint range of motion. The underlying assumption is that extensibility increases as a result of increased passive tension applied to muscle-tendon units. In some stretching protocols, this condition is not always met sufficiently to trigger adaptation within the muscle-tendon unit. For example, there is experimental evidence that both acute and chronic stretching interventions may increase the maximal range of motion in the absence of changes in the passive torque-angle curve. We contend that these results are partly explained by the influence of non-muscular structures that contribute only marginally to the passive torque. The potential candidates are the nervous system and fasciae, which would play an important role in the perception of the stretch and in the limitation of the range of motion of the maximal joints. At least in part, this may explain the lack of a significant effect of some chronic stretching interventions to change passive muscle tension.
The aim of the current study was to investigate the influence of static stretching on hamstring flexibility in healthy young adults by means of systematic review and meta-analysis. The search strategy included MEDLINE, PEDro, Cochrane CENTRAL, EMBASE, LILACS, and manual search from inception to June 2015. Randomized and controlled clinical trials studies that have compared static stretching to control group, and evaluated range of motion (ROM), were included. On the other hand, studies that have worked with special population such as children, elderly people, athletes, and people with any dysfunction/disease were excluded, as well as articles that have used contralateral leg as control group or have not performed static stretching. The meta-analysis was divided according to three types of tests. Nineteen studies were included out of the 813 articles identified. In all tests, the results favored static stretching compared to control group: passive straight leg raise (12.04; 95% CI: 9.61 to 14.47), passive knee extension test (8.58; 95% CI: 6.31 to 10.84), and active knee extension test (8.35; 95% CI: 5.15 to 11.55). In conclusion, static stretching was effective in increasing hamstring flexibility in healthy young adults.
Purpose:
It remains unclear whether the acute effect of stretching on passive muscle stiffness differs among the synergists. We examined the muscle stiffness responses of the medial (MG) and lateral gastrocnemii (LG), and soleus (Sol) during passive dorsiflexion before and after a static stretching by using ultrasound shear wave elastography.
Methods:
Before and after a 5-min static stretching by passive dorsiflexion, shear modulus of the triceps surae and the Achilles tendon (AT) during passive dorsiflexion in the knee extended position were measured in 12 healthy subjects.
Results:
Before the static stretching, shear modulus was the greatest in MG and smallest in Sol. The stretching induced significant reductions in shear modulus of MG, but not in shear modulus of LG and Sol. The slack angle was observed at more plantar flexed position in the following order: AT, MG, LG, and Sol. After the stretching, the slack angles of each muscle and AT were significantly shifted to more dorsiflexed positions with a similar extent. When considering the shift in slack angle, the change in MG shear modulus became smaller.
Conclusion:
The present study indicates that passive muscle stiffness differs among the triceps surae, and that the acute effect of a static stretching is observed only in the stiff muscle. However, a large part of the reduction of passive muscle stiffness at a given joint angle could be due to an increase in the slack length.
Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanical properties of nerves remain largely unexplored. The primary aim of this study was to characterize the effect of passive dorsiflexion on sciatic nerve shear wave velocity (an index of stiffness) when the knee was in 90° flexion (knee 90°) or extended (knee 180°). The secondary aim was to determine the effect of five repeated dorsiflexions on the nerve shear wave velocity. Nine healthy participants were tested. The repeatability of sciatic nerve shear wave velocity was good for both knee 90° and knee 180° (ICCs≥0.92, CVs≤8.1%). The shear wave velocity of the sciatic nerve significantly increased (p<0.0001) during dorsiflexion when the knee was extended (knee 180°), but no changes were observed when the knee was flexed (90°). The shear wave velocity-angle relationship displayed a hysteresis for knee 180°. Although there was a tendency for the nerve shear wave velocity to decrease throughout the repetition of the five ankle dorsiflexions, the level of significance was not reached (p=0.055). These results demonstrate that the sciatic nerve stiffness can be non-invasively assessed during passive movements. In addition, the results highlight the importance of considering both the knee and the ankle position for clinical and biomechanical assessment of the sciatic nerve. This non-invasive technique offers new perspectives to provide new insights into nerve mechanics in both healthy and clinical populations (e.g., specific peripheral neuropathies).
Objective
To explore changes in muscle architectural parameters of the muscle-tendon unit of soleus and medial gastrocnemius (GM) in patients with chronic hemiparesis, after 1 year of rehabilitation.
Material/Patients and methods
In this prospective study, 20 chronic hemiparetic patients (8 W, mean age: 56 [12], time since lesion 9 [8]) were evaluated. Muscle architectural parameters including muscle fascicle length, pennation angle, thickness, tendon and muscle belly lengths were evaluated in vivo using ultrasonography in passive condition (verified by electromyographic recording) in a seated patient with ankle, knee and hip on the paretic side at 90°. Following the biomechanical analysis, each patient benefited from the Five Step Assessment (FSA), involving the measure of XV1, angle of arrest at slow and strong stretch, which estimates soft tissue extensibility around each muscle. Four muscles of interest in the lower limb were selected for this measure: soleus (XV1Sol), medial gastro-soleus complex (XV1GSC), gluteus maximus (XV1GM) and rectus femoris (XV1RF). Biomechanical and clinical analyses were performed at the beginning and after 1 year of treatment. Two treatments were implemented:
– conventional rehabilitation (50%);
– guided Self-rehabilitation contract (GSC, 50%).
Patients in the GSC group were prescribed a daily self-stretch program with static (> 10 min/muscle/day) and eccentric stretch. Changes in architectural parameters and clinical muscle extensibility of overall patients before and after 1 year of rehabilitation were analyzed (Student's).
Results
After 1 year, muscle fascicle length and thickness increased respectively by 6.1 mm (14.2%, P = 0.05), 1.8 mm (13.6%, P = 0.06) in soleus, and by 2.9 mm (9.1%, P = 0.04) and 1.7 mm (13.2%, P = 0.03) in MG. Muscle belly length of MG increased by 2.9 cm (17%, P = 0.0001) and its tendon length decreased by 0.82 cm (5%, P = 0.04). XV1GSC increased by 4.8° (3.3%, P = 0.07), XV1GM by 4.1° (3.3%, P = 0.0004) and XV1RF by 7.2° (6%, P = 0.02).
Discussion - Conclusion
Stretch of soleus and medial gastrocnemius practiced over the long term in patients with spastic hemiparesis allowed structural changes, increasing muscle fascicle length and thickness. Muscle belly length of medial gastrocnemius also increased significantly while its tendon length decreased, suggesting that the tendon may adapt its length to the muscle length changes.
Context:
Static Stretching (SS) is commonly performed within a warm-up routine to increase the range of motion (ROM) of a joint and to decrease muscle stiffness. However, the time course of changes in ankle dorsiflexion (DF) ROM and muscle stiffness during a routine SS program is unclear.
Objective:
The present study investigated changes in ankle DF ROM, passive torque at DF ROM, and muscle stiffness during a routine SS program performed three times weekly for 4 weeks.
Design:
A quasi-randomized controlled trial design.
Participants:
The subjects comprised 24 male volunteers (age 23.8 ± 2.3 years; height 172.0 ± 4.3 cm; body mass 63.1 ± 4.5 kg) randomly assigned to either a group performing a 4-week stretching intervention program (SS group) or a control group.
Main outcome measures:
The DF ROM, passive torque, and muscle stiffness were measured during passive ankle dorsiflexion in both groups using a dynamometer and ultrasonography once weekly during the 4-week intervention period.
Results:
In the SS group, DF ROM and passive torque at DF ROM significantly increased after 2, 3, and 4 weeks compared with the initial measurements. Muscle stiffness also decreased significantly after 3 and 4 weeks in the SS group. However, there were no significant changes in the control group.
Conclusions:
Based on these results, the SS program effectively increased DF ROM and decreased muscle stiffness. Furthermore, an SS program greater than 2 weeks duration effectively increased DF ROM and changed the stretch tolerance, and an SS program greater than 3 weeks in duration effectively decreased muscle stiffness.
The aims of this study were to investigate the effects of a 4-week intervention of static stretching (SS) on muscle hardness of the semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) muscles. Shear elastic modulus was measured by using ultrasound shear wave elastography as the index of muscle hardness. Thirty healthy men (age 22.7 ± 2.2 years) volunteered for this study and were randomly assigned to the SS intervention group (n = 15) or the control group (n = 15). Participants in the SS intervention group received a 4-week stretch intervention for the hamstrings of their dominant leg. Shear elastic moduli of the hamstrings were measured at initial evaluation and after 4 weeks in both groups at a determined angle. In all muscles, the shear elastic modulus decreased significantly after SS intervention. The percentage change in the shear elastic modulus from the value at initial evaluation to after 4 weeks intervention was greatest in the SM. These results suggest that SS intervention has chronic effects on reducing hardness of the hamstring muscle components, especially the SM muscle.
Background/aim:
To investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI).
Methods:
Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data.
Results:
Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present.
Conclusions:
The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.