plantar flexor muscles
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2021 ◽  
Vol 12 ◽  
Author(s):  
Masatoshi Nakamura ◽  
Riku Yoshida ◽  
Shigeru Sato ◽  
Kaoru Yahata ◽  
Yuta Murakami ◽  
...  

The purpose of this study was to compare two static stretching (SS) training programs at high-intensity (HI-SS) and low-intensity (LI-SS) on passive and active properties of the plantar flexor muscles. Forty healthy young men were randomly allocated into three groups: HI-SS intervention group (n = 14), LI-SS intervention group (n = 13), and non-intervention control group (n = 13). An 11-point numerical scale (0–10; none to very painful stretching) was used to determine SS intensity. HI-SS and LI-SS stretched at 6–7 and 0–1 intensities, respectively, both in 3 sets of 60 s, 3×/week, for 4 weeks. Dorsiflexion range of motion (ROM), gastrocnemius muscle stiffness, muscle strength, drop jump height, and muscle architecture were assessed before and after SS training program. The HI-SS group improved more than LI-SS in ROM (40 vs. 15%) and decreased muscle stiffness (−57 vs. −24%), while no significant change was observed for muscle strength, drop jump height, and muscle architecture in both groups. The control group presented no significant change in any variable. Performing HI-SS is more effective than LI-SS for increasing ROM and decreasing muscle stiffness of plantar flexor muscles following a 4-week training period in young men. However, SS may not increase muscle strength or hypertrophy, regardless of the stretching discomfort intensity.


2021 ◽  
Vol 154 (9) ◽  
Author(s):  
Nao Yamauchi ◽  
Iori Kimura ◽  
Yuki Ashida ◽  
Azuma Naito ◽  
Nao Tokuda ◽  
...  

Eccentric contractions, in which the muscle is stretched during contraction, cause substantially greater damage than isometric (ISO) contractions, in which the length of the muscle does not change during contraction. Here, we tested the hypothesis that ISO training improves fatigue resistance in skeletal muscle from dystrophin-deficient mdx52 mice (15–22 wk old). ISO training (100 Hz stimulation frequency, 0.25-s contractions every 0.5 s, 6 sets of 60 contractions) was performed on the left plantar flexor muscles in vivo with supramaximal electrical stimulation every other day for 4 wk. Compared with the normal control muscle, resistance to fatigue was reduced in the nontrained muscle from mdx52 mice, which was accompanied by a reduction in citrate synthase activity and the LC3BII/I ratio and an increase in the phosphorylation levels of Akt Ser473 and the expression levels of p62. ISO training restored these alterations and markedly increased in vivo fatigue resistance and PGC-1α expression in mdx52 muscles. Moreover, an increased number of Evans Blue dye-positive fibers was significantly reduced by ISO training in mdx52 muscles. In contrast, ISO training did not restore a reduction in the amount of SH3 and cysteine-rich domain 3 in mdx muscles. Thus, our data suggest that mitochondrial function is impaired in dystrophin-deficient muscles, which is likely to be induced by the defective autophagy due to persistent activation of Akt. ISO training inhibits the aberrant activation of Akt presumably by up-regulating the PGC-1α expression, which results in improved mitochondrial function and thus fatigue resistance in dystrophin-deficient muscles.


2021 ◽  
Vol 3 ◽  
Author(s):  
Yuto Miyake ◽  
Tadashi Suga ◽  
Masafumi Terada ◽  
Takahiro Tanaka ◽  
Hiromasa Ueno ◽  
...  

The plantar flexor torque plays an important role in achieving superior sprint performance in sprinters. Because of the close relationship between joint torque and muscle size, a simple assumption can be made that greater plantar flexor muscles (i.e., triceps surae muscles) are related to better sprint performance. However, previous studies have reported the absence of these relationships. Furthermore, to examine these relationships, only a few studies have calculated the muscle volume (MV) of the plantar flexors. In this study, we hypothesized that the plantar flexor MVs may not be important morphological factors for sprint performance. To test our hypothesis, we examined the relationships between plantar flexor MVs and sprint performance in sprinters. Fifty-two male sprinters and 26 body size-matched male non-sprinters participated in this study. On the basis of the personal best 100 m sprint times [range, 10.21–11.90 (mean ± SD, 11.13 ± 0.42) s] in sprinters, a K-means cluster analysis was applied to divide them into four sprint performance level groups (n = 8, 8, 19, and 17 for each group), which was the optimal number of clusters determined by the silhouette coefficient. The MVs of the gastrocnemius lateralis (GL), gastrocnemius medialis (GM), and soleus (SOL) in participants were measured using magnetic resonance imaging. In addition to absolute MVs, the relative MVs normalized to body mass were used for the analyses. The absolute and relative MVs of the total and individual plantar flexors were significantly greater in sprinters than in non-sprinters (all p < 0.01, d = 0.64–1.39). In contrast, all the plantar flexor MV variables did not differ significantly among the four groups of sprinters (all p > 0.05, η2 = 0.02–0.07). Furthermore, all plantar flexor MV variables did not correlate significantly with personal best 100 m sprint time in sprinters (r = −0.253–0.002, all p > 0.05). These findings suggest that although the plantar flexor muscles are specifically developed in sprinters compared to untrained non-sprinters, the greater plantar flexor MVs in the sprinters may not be important morphological factors for their sprint performance.


2021 ◽  
Vol 12 ◽  
Author(s):  
Marina Reiner ◽  
Markus Tilp ◽  
Gaël Guilhem ◽  
Antonio Morales-Artacho ◽  
Masatoshi Nakamura ◽  
...  

A single proprioceptive neuromuscular facilitation (PNF) stretching exercise can increase the range of motion (ROM) of a joint but can lead to a decrease in performance immediately after the stretching exercise. Post-stretching activation (PSA) exercises are known as a possible way to counteract such a drop in performance following a single stretching exercise. However, to date, no study has investigated the combination of PNF stretching with PSA. Thus, the aim of this study was to compare the effects of a PNF stretching exercise with and without PSA on the muscle function (e.g., ROM) and mechanical properties of the plantar flexor muscles. Eighteen physically active males volunteered in the study, which had a crossover design and a random order. The passive shear modulus of the gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) was measured in a neutral position with shear wave elastography, both pre- and post-intervention. Maximum voluntary isometric contraction (MVIC) peak torque, maximum voluntary dynamic contraction peak torque, dorsiflexion ROM, and passive resistive torque (PRT) were also measured with a dynamometer. The interventions were 4×30s of PNF stretching (5s of contraction) and two sets of three exercises with 20 or 40 fast ground contacts (PNF stretching+PSA) and PNF stretching only. ROM was found to have increased in both groups (+4%). In addition, the PNF stretching+PSA group showed a decrease in PRT at a given angle (−7%) and a decrease in GM and mean shear modulus (GM+GL; −6%). Moreover, the MVIC peak torque decreased (−4%) only in the PNF stretching group (without PSA). Therefore, we conclude that, if PNF stretching is used as a warm-up exercise, target-muscle-specific PSA should follow to keep the performance output at the same level while maintaining the benefit of a greater ROM.


PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0253276
Author(s):  
Lauren K. Sara ◽  
Savannah B. Gutsch ◽  
Sandra K. Hunter

Introduction The single-leg heel raise test (SLHR) is commonly used in clinical settings to approximate plantar flexor strength, yet this is neither validated nor supported physiologically. The purposes of this study were to: determine (1) associations between SLHR repetitions, maximal plantar flexor strength, and reductions in strength; and (2) whether sex differences exist in performance of the SLHR. Methods Twenty-eight young, healthy participants (14 males,14 females, 19–30 years) performed repeated single-leg heel raises to task failure. Pre- and post-task measures included maximal voluntary isometric contractions (MVIC), and voluntary activation and contractile properties of the plantar flexor muscles, assessed using peripheral electrical stimulation of the tibial nerve. Surface electromyography was recorded for the medial and lateral gastrocnemius, soleus, and anterior tibialis muscles. Results The SLHR resulted in 20.5% reductions in MVIC torque (p<0.001). However, the number of SLHR repetitions was not correlated with either the baseline MVIC (maximal strength; p = 0.979) or the reduction in MVIC following the SLHR (p = 0.23). There were no sex differences in either the number of SLHR repetitions (p = 0.14), baseline MVIC torque (p = 0.198), or the reduction of MVIC (p = 0.14). MVIC decline was positively associated with the reduction in voluntary activation (r = 0.841, p<0.001), but was not associated with the change in twitch amplitude (p = 0.597). Conclusions The SLHR was similar in young males and females yet was a poor predictor of maximal plantar flexor strength but evaluates performance fatigability of the lower extremity specific to dynamic contractions. The reduction in maximal strength at task failure was explained by reduced neural drive to the plantar flexor muscles in both males and females. Impact statement SLHR performance is not a clinical assessment of plantar flexor strength but assesses dynamic lower extremity fatigability that is similar in males and females. Alternate clinical measures for maximal plantar flexion strength need to be developed.


2021 ◽  
pp. 026921552110113
Author(s):  
Şerife Yoldaş Aslan ◽  
Sehim Kutlay ◽  
Ebru Düsünceli Atman ◽  
Atilla Halil Elhan ◽  
Haydar Gök ◽  
...  

Objective: To evaluate the effectiveness of radial extracorporeal shock wave therapy on ankle flexor spasticity in stroke survivors and to reveal changes in the fibroelastic components of muscle. Design: Randomized controlled trial. Setting: Inpatient neuro-rehabilitation clinic of a university hospital. Participants: Stroke patients with ankle flexor spasticity. Interventions: Patients were randomized to three groups; radial extracorporeal shock wave therapy, sham, or control. Active and sham therapy were administered two sessions/week for two weeks. All patients received conventional rehabilitation. Main measures: The primary outcome was Modified Ashworth Scale. Secondary outcomes were the Tardieu Scale and elastic properties of plantar flexor muscles assessed by elastography (strain index). All assessments were performed before, immediately after the treatment, and four weeks later at follow-up. Results: Fifty-one participants were enrolled (active therapy n = 17, sham n = 17, control n = 17). Modified Ashworth scores showed a significant decrease in the active therapy group (from 2.47 ± 0.72 to 1.41 ± 0.62) compared to sham (from 2.19 ± 1.05 to 2.06 ± 1.12) and control (from 2.06 ± 0.85 to 2.00 ± 0.73) groups immediately after the treatment ( P < 0.001). Tardieu results were also in concordance ( P < 0.001), however this effect was not preserved at follow-up. Elastic properties of the ankle flexors were improved in all groups at both assessments after the therapy showing significant decreases in strain index ( P < 0.001). However, there was no difference among the groups in terms of improvement in elastography. Conclusion: Radial extracorporeal shock wave therapy has short-term anti-spastic effects on ankle flexor muscles when used as an adjunct to conventional rehabilitation.


2021 ◽  
Vol 9 (8) ◽  
Author(s):  
Mehdi Datoussaid ◽  
Hasnae El Khalouqi ◽  
Charel Dahm ◽  
Nathalie Guissard ◽  
Stéphane Baudry

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