Kensuke Oba

Background: Static stretching is widely accessible across the lifespan and commonly prescribed to improve flexibility. However, whether flexibility improvements following chronic static stretching are moderated by participant characteristics or the targeted muscle group in lower-limb remains uncertain. Objectives: We primarily aimed to determine whether the effects of chronic static stretching on flexibility are moderated by age, sex, training status, baseline flexibility, and muscle group. Methods: We searched PubMed, Web of Science, and Scopus for randomized controlled trials published before June 2025 that examined the chronic effects of static stretching on lower limb flexibility outcomes (compared with non-stretching or passive control conditions) in healthy populations. Meta-analysis was performed using a random-effects model, with effect sizes expressed as standardized mean differences corrected for small-sample bias (Hedges’ g). Subgroup analyses were conducted to examine the potential moderation by age (children and adolescents vs young vs middle-aged vs older adults), sex (male vs female), training status (athlete/trained vs recreationally active vs sedentary), baseline flexibility (with tightness vs without tightness and not reported), and muscle group (knee flexors vs knee extensors vs ankle plantar flexors). Methodological quality was assessed using the Physiotherapy Evidence Database (PEDro) scale, and potential small-study effects were evaluated using Egger’s regression test and trim-and-fill analysis. Results: Seventy-nine studies (n = 3287) were included in the analysis. Chronic static stretching produced a moderate improvement in flexibility (Hedges’ g = 0.851, 95% confidence interval 0.710 to 0.991; SE = 0.0718; Z = 11.845; p < 0.001), with substantial heterogeneity (τ ² = 0.249; I ² = 66.1%). No significant moderating effects were observed for age, sex, training status, baseline flexibility, or target muscle group. Egger’s regression test indicated potential small-study effects ( p < 0.001); however, trim-and-fill analysis did not impute any potentially missing studies and the adjusted pooled estimate remained unchanged. The mean PEDro score was 6.15 ± 0.90 (range 4–8), indicating moderate-to-good study quality. Conclusions: Chronic static stretching yielded significant, moderate improvements in lower-limb flexibility; however, substantial heterogeneity and potential small-study effects were observed. These effects did not appear to be meaningfully moderated by age, sex, baseline flexibility, training status, or target muscle group. Overall, chronic static stretching may improve lower-limb flexibility across diverse healthy individuals and target muscle groups, although the results should be interpreted cautiously given the heterogeneity, potential small-study effects, and methodological variability among the included studies.

Dynamic stretching (DS) comprises repetitive movements throughout the joint range of motion, and DS speed is known to affect athletic performance. However, it is unclear how DS speed affects musculotendinous stiffness (MTS). This study aimed to compare the DS effects at three different speeds on the maximum ankle dorsiflexion angle, maximum passive torque, and MTS. Based on sample size calculation (f = 0.25, α = 0.05, power = 0.80), 12 participants were needed, and 12 healthy university male athletes enrolled. DS to ankle plantar flexors was performed under the following conditions: low-speed (30 reps/min), moderate-speed (60 reps/min), high-speed (120 reps/min), and control (no DS). DS was performed for 15 reps × four sets with a 30 s rest. To assess musculotendinous extensibility, the maximum ankle dorsiflexion angle, maximum passive torque, and MTS were measured before and after DS. The maximum ankle dorsiflexion angle significantly increased after all DS (p = 0.001–0.006, d_z = 0.98–1.38) and was significantly larger in the high-speed DS than in the control condition (p = 0.039). MTS significantly increased after high-speed DS (p = 0.038, d = 0.68) but significantly decreased after moderate-speed DS (p = 0.025, d_z = −0.75) compared to baseline values. Maximal passive torque significantly increased after low-, moderate-, and high-speed DS (p < 0.001 to p = 0.011, d_z = 0.89–1.89) and was significantly higher after high-speed DS than after control (p = 0.004, d = 0.58). These results indicate that DS increases the ankle dorsiflexion angle regardless of speed and is effective in decreasing MTS at moderate speed.

Purpose Dynamic stretching (DS), characterized by repeated movements through the joint range of motion via antagonist muscle contraction, is thought to reduce muscle stiffness through mechanisms such as reciprocal inhibition. However, whether DS effectively decreases muscle stiffness remains unclear. This study aimed to investigate the acute effects of DS on triceps surae muscle stiffness using shear wave elastography. Methods Sixteen healthy young adults performed both 120-s DS and control (no stretching) tasks. Shear wave velocities of the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL) muscles were measured as indicators of muscle stiffness before and after DS. Results Our findings indicated that DS significantly reduced the shear wave velocity in the MG. However, no significant changes were observed in the shear wave velocities of the LG and SOL. Conclusion DS effectively decreased MG stiffness, with no observed effects in the LG or SOL. These findings highlight inter-muscular variability in response to DS and suggest that DS may be particularly beneficial for targeting stiffness in the MG of the triceps surae muscles.

Dynamic stretching (DS) uses a controlled movement through the range of motion (ROM) of the active joint(s) by contracting the agonist muscles without being held in an end position. In contrast, ballistic stretching (BS) typically uses uncontrolled movements of a higher velocity with bouncing actions. However, BS is often considered to be a form of DS. When considered together, DS and BS reportedly increase flexibility, evidenced by single- and multiple-joint ROM improvements and other measurements. However, a meta-analysis with subgroup analyses revealing the acute effects of DS and BS on flexibility in detail, independently of other stretching methods, has yet to be conducted. The purpose of this meta-analysis was to investigate the acute effects of DS and BS on flexibility in healthy participants. The PubMed, Web of Science, and Scopus databases were searched for eligible papers published before September 9, 2024; 17 papers were included in the meta-analysis. The main meta-analysis was performed with a random-effect model, and subgroup analyses were performed to examine the effects of age (young vs. middle-aged and older), sex (male vs. mixed sex), stretching methods (DS vs. BS), stretched muscles (hamstrings vs. plantar flexors vs. multiple muscles), and flexibility outcomes (single-joint ROM vs. straight-leg raise test vs. sit-and-reach test). A small increase in flexibility was found following DS and BS (considered together) (effect size = 0.372, Z = 3.936, 95% confidence interval = 0.187–0.557, p < 0.001, I2 = 27%). Subgroup analyses revealed no significant differences between age (p = 0.24), sex (p = 0.76), stretching method (p = 0.83), stretched muscle (p = 0.20), or flexibility outcome (p = 0.34) groups. Our results suggest that DS and BS effectively provide acute, small-magnitude improvements in flexibility that are not significantly affected by individual characteristics, stretching methods, stretched muscles, or flexibility outcomes.

Background: Static stretching (SS) is effective in increasing flexibility and neuromuscular function, leading to changes in postural control. Objective: This study aimed to examine the acute effects of SS on ankle plantar flexors and dynamic postural control during a maximum forward-leaning task in young and older adults. Methods: Twenty-eight university students and 22 community-dwelling older adults were included in this study. The participants performed 5 sets of 1-min SS for the ankle plantar flexors of both legs with standing on a stretching board. Ankle dorsiflexion range of motion (ROM) and center of pressure (COP) during the maximum forward-leaning task, the COP area, and the anterior limit of stability were assessed before and after SS. Results: SS increased ankle dorsiflexion ROM, COP velocity, and anterior limit of stability, whereas changes in the COP area were not significant after SS. Furthermore, there were no differences in the changes in postural control between young and older adults, whereas ROM increase was greater in older adults than in young adults. Conclusions: These findings suggest that SS can improve postural control and can serve as a simple, low-risk intervention to reduce the risk of falls in older, at-risk adult populations.

Dynamic stretching (DS) is performed as a warm-up to improve the range of motion and athletic performance. However, the effect of different amounts of DS on muscle performance remains unclear. This study investigated the effects of DS repetitions with one or four sets of 30 s on musculotendinous extensibility and muscle strength. Fourteen healthy men (23.6 ± 1.5 years) underwent DS to ankle plantar flexors for one set (fifteen repetitions) or four sets after warm-up. The maximal ankle dorsiflexion angle, musculotendinous stiffness (MTS), passive torque, peak plantarflexion torque during maximal isometric contraction, and muscle temperature were measured before and after stretching. A significant effect of time was observed on the maximal ankle dorsiflexion angle, MTS, passive torque, and muscle temperature (p < 0.001). However, no interactions or effects between the conditions were observed. After DS, the maximal ankle dorsiflexion angle and muscle temperature significantly increased (p < 0.01), while the MTS and passive torque significantly decreased (p < 0.01). The maximal muscle strength showed no significant effects or interactions (p = 0.198−0.439). These results indicated that one and four sets of DS effectively increased musculotendinous extensibility. Thus, one set of DS may have similar effects as a warm-up before four sets of DS.