Passive repetitive stretching is associated with greater muscle mass and cross-sectional area in the sarcopenic muscle

Abstract

Mechanical stimulation has benefits for muscle mass and function. Passive stretching is widely performed in clinical rehabilitation medicine. However, the hypertrophic effects of passive repetitive stretching on senescent skeletal muscles against muscle atrophy remain unknown. We used senescence-accelerated model SAM-P8 mice. The gastrocnemius muscle was passively repetitive stretched by manual ankle dorsiflexion for 15 min, 5 days a week for 2 weeks under deep anesthesia. We examined the effects of passive stretching on muscle mass, myofiber cross-sectional area, muscle fiber type composition, satellite cell and myonuclei content, signaling pathways involved in muscle protein synthesis, and myogenic regulatory factors. The gastrocnemius muscle weight and fiber cross-sectional area of the stretched side was found greater compared with that of the unstretched side. Passive repetitive stretching increased the mRNA expression level of Akt, p70S6K, 4E-BP1, Myf5, myogenin, MuRF1.The phosphorylation level of p70S6K significantly increased in the stretched muscles, whereas of Akt and 4E-BP1 remained unchanged, compared to the unstretched side. The Pax7+ cells and myonuclei content did not differ between the stretched and unstretched muscles. These findings suggest that the hypertrophic or suppressed atrophic observation in the stretched muscles are mainly attributable to the protein turnover provoked by stretching. These findings are applicable to clinical muscle strengthening and sarcopenia prevention.

Cross‐sectional and longitudinal associations between body flexibility and sarcopenia

“…A recent study also revealed that 2 weeks of passive stretching (with a frequency of 15 min/ day for 5 days/week) prevented muscle loss in senescenceaccelerated mouse models. 26 The current results also found that increased flexibility during 4 years was associated with incident low muscle mass, low muscle strength and sarcopenia. Our findings suggested that maintaining high flexibility and monitoring the dynamic change of flexibility are both helpful in preventing sarcopenia.…”

“…In addition, we found that baseline flexibility was associated with 4‐year changes in SMI and HGS in the sensitivity analyses. A recent study also revealed that 2 weeks of passive stretching (with a frequency of 15 min/day for 5 days/week) prevented muscle loss in senescence‐accelerated mouse models 26 …”

“…A recent study also revealed that 2 weeks of passive stretching (with a frequency of 15 min/day for 5 days/week) prevented muscle loss in senescence‐accelerated mouse models. 26 …”

Critical evaluation of commonly used methods to determine the concordance between sonography and magnetic resonance imaging: A comparative study

“…For evaluation of MCSA the mean of the three highest MCSA values in the lateral and the medial head of the gastrocnemius were used to minimize potential error of location (Koppenhaver et al, 2009;Teyhen and Koppenhaver, 2011). Reliability of MRI measurements can be assumed as very high with r = 0.99 (Wirth et al, 2007;Wang et al, 2021).…”

Muscle preservation in proximal nerve injuries: a current update

“…In denervated muscles, stretching or contracting increases the expression of IGF-1 mRNA in myocytes and elevates the concentration of IGF-1, which activates Akt via an autocrine/paracrine mechanism (Agata et al., 2009). Akt activation facilitates muscle protein synthesis via mTOR, which also reduces the upregulation of ubiquitin-proteasome genes (activators of protein degradation) and maintains the level of runt-related transcription factor-1 (controls autophagy) (Hadj-Saïd et al., 2012), by negatively regulating forkhead-related transcription factor (Wang et al., 2021).…”