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It has been shown that stretching exercises can improve the flexibility and independence of the elderly. However, although these exercises commonly constitute training programs, the morphological adaptations induced by stretching exercises in aged skeletal muscle are still unclear. Objective To assess the acute effects of passive mechanical static stretching on the morphology, sarcomerogenesis and modulation of important components of the extracellular matrix of the soleus muscle of aged female rats. Methods Fifteen old female rats with 26 months were divided into two groups: stretching ( n = 8, SG) and control ( n = 7, CG): The stretching protocol consisted of 4 repetitions each of 1 min with 30 s interval between sets. Stretching was performed on the left soleus muscle, 3 times a week for 1 week. After three sessions, the rats were anesthetized to remove the left soleus muscle, and then euthanized. The following analyses were carried out: muscle fiber cross-sectional area and serial sarcomere number; immunohistochemistry for the quantification of collagen I, III and TGFβ-1. Results a decrease in muscle fiber cross-sectional area of the SG was observed when compared to the CG ( p = 0.0001, Kruskal–Wallis); the percentage of type I collagen was significantly lower in the SG when compared to the CG ( p = 0.01, Kruskal–Wallis), as well as the percentage of TGFβ-1 ( p = 0.04, Kruskal–Wallis); collagen III was significantly higher in the SG than in the CG (7.06 ± 6.88% vs 4.92 ± 5.30%, p = 0.01, Kruskal–Wallis). Conclusion Although the acute stretching induced muscle hypotrophy, an antifibrotic action was detected. [ABSTRACT FROM AUTHOR]

• Gastrocnemius muscle thickness has correlation with calf circumference in older women. • Excess weight is a limitation condition when using gastrocnemius muscle thickness. • Gastrocnemius muscle thickness might be a complementary measure of calf circumference. Calf circumference (CC) is an indirect method used to evaluate muscle mass in older adults. Ultrasound has also been studied as a method for measuring muscle mass. Therefore, the aim of the present study was to correlate CC and muscle thickness of the medial gastrocnemius muscle (MGM) in healthy older women. A cross-sectional study was conducted with 74 healthy older women. The MGM thickness was evaluated using an ultrasound device (Logiq Book XP, General Electric®). The reference value for adequate CC was ≥ 31 cm. Weight and height were measured for the calculation of the body mass index (BMI), which was dichotomized as with or without excess weight based on the cutoff points recommended by the World Health Organization (1995) ; Lipschitz (1994) and the Pan-American Health Organization (2001). All participants were ≥ 64 years of age. Mean weight and height were 66.19 kg (SD: 10.48) and 1.55 m (SD: 0.06), respectively. Half of the participants had a BMI higher than 27.53 kg/m2. Moderate positive correlations were found between CC and MGM thickness (ρ = 0.432; p < 0.001), MGM thickness and weight (r = 0.422; p < 0.001) and between MGM thickness and BMI (r = 0.438; p < 0.001). However, the correlation between CC and MGM thickness was non-significant among the women with excess weight. A moderate positive correlation between MGM thickness and CC was found in healthy older women. However, this correlation was weak and non-significant among those with excess weight. [ABSTRACT FROM AUTHOR]