Muscle adaptations in rat skeletal muscle from long term habitual exercise

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Muscle adaptations in rat skeletal muscle from long term habitual exercise


Author: Leung, Ka Chun
Title: Muscle adaptations in rat skeletal muscle from long term habitual exercise
Degree: M.Sc.
Year: 2013
Subject: Exercise -- Physiological aspects.
Musculoskeletal system.
Rats -- Physiology.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xiii, 99 leaves : ill. (some col.) ; 30 cm.
Language: English
Abstract: Regular physical activity has been known to bring benefits to our health in both physical and mental aspects. Although physical activity shows positive effects on different organs and systems in our bodies, it is strongly related to the exercise adaptations of skeletal muscle. The aim of the study is to examine the effects of long term habitual exercise on fibre type composition, fibre size, capillary density and mitochondrial density in skeletal muscle. The hypothesis is that long term habitual exercise is capable to improve muscle performance by inducing different skeletal muscle adaptations including fibre type transformation, hypertrophy, angiogenesis and mitochondrial biogenesis. The specific aim of the study is to determine whether this 20 weeks voluntary exercise protocol is capable to induce fast to slow twitch fibre transformation in varies muscles groups. Eighteen young adults Sprague Dawley rats with around 2 months old were randomly assigned to sedentary control group and exercise group with 20 weeks of experimental period. Rats in the exercise group were housed individually in cages with 24 hours free access to an in-cage running wheel with 38 cm in diameter. Magnetic digital counters were equipped on the running wheels to measure the number of revolutions each day. Rats in control group were housed in the cages without running wheels and located near the exercise animals. After the 20 weeks of experimental period, plantaris, red medial gastrocnemius (RMG) and white medial gastrocnemius (WMG) muscles were collected for analysis. Immunohistochemical staining was used to examine the effects of 20 weeks habitual voluntary running exercise on muscle fibre composition, muscle fibre cross-sectional area, capillary density and mitochondrial density in rat skeletal muscle. The results showed that 20 weeks of habitual running exercise is sufficient to induce type IIX to IIA fibre transformation in plantaris only, while further fast to slow transformation is not noticed. The type IIA fibre composition in plantaris muscle was increased significantly by 20.9%, while that of type IIB fibre was significantly reduced by 8.6%. The exercise protocol also induces non-fibre type specific hypertrophy and angiogenesis in all three muscle groups. However, an increase of mitochondrial density was only observed in RMG. This result demonstrated that long term habitual voluntary exercise is able to induce varies muscle adaptive responses on different skeletal muscle. However, it is not sufficient to induce fast to slow twitch fibre transformation with the 20 weeks exercise protocol.

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