In Vivo Rodent Models of Skeletal Muscle Adaptation to Decreased Use

Skeletal muscle possesses plasticity and adaptability to external and internal physiological changes. Due to these characteristics, skeletal muscle shows dramatic changes depending on its response to stimuli such as physical activity, nutritional changes, disease status, and environmental changes. Modulation of the rate of protein synthesis/degradation plays an important role in atrophic responses. The purpose of this review is to describe different features of skeletal muscle adaptation with various models of deceased use. In this review, four models were addressed: immobilization, spinal cord transection, hindlimb unloading, and aging. Immobilization is a form of decreased use in which skeletal muscle shows electrical activity, tension development, and motion. These results differ by muscle group. Spinal cord transection was selected to simulate spinal cord injury. Similar to the immobilization model, dramatic atrophy occurs in addition to fiber type conversion in this model. Despite the fact that electromyography shows unremarkable changes in muscle after hindlimb unloading, decreased muscle mass and contractile force are observed. Lastly, aging significantly decreases the numbers of muscle fibers and motor units. Skeletal muscle responses to decreased use include decreased strength, decreased fiber numbers, and fiber type transformation. These four models demonstrated different changes in the skeletal muscle. This review elucidates the different skeletal muscle adaptations in these four decreased use animal models and encourages further studies.

Effects of High-speed Elastic Band Training on Physical Fitness and Muscle Function in Rural Community-dwelling Elderly: a Single-blinded Randomized Controlled Trial

BACKGROUND: Aging related decrease in muscle strength and flexibility leads to functional loss of physical ability. Power training is known to improve these capacities and helps in performing daily routine better. Therefore, we modified previously proven and certified sarcopenia intervention exercise for elderly in rural community and applied them to examine the effects on physical fitness and muscle functions to show its applicability. METHODS: Subjects were divided into control and exercise group using single-blind method. Exercise group underwent high-speed elastic band training(concentric contraction in 1 second) 2 days per week for 12 weeks. Before and after the intervention, we performed body composition analysis, anthropometric measurement, blood test, blood pressure check, senior fitness test (SFT), upper body and lower body strength examination. Korean version of Physical Activity Scale for the Elderly (K-PASE), and Center for Epidemiological Studies- Depression Scale (CES-D) were also assessed. RESULTS: Body weight in control group was significantly increased (Paired t-test: P=0.008), although it was consistent in exercise group (GroupxTime: P=0.013). 30-second chair stand (P<0.001) and 30-second arm curl (P<0.001) of the senior fitness test were also significantly improved in exercise group compared to control. In addition, muscle strength of knee flexion (P=0.034) and K-PASE score (P<0.001) were improved in training group with statistical significance. CONCLUSIONS: The modified high-speed elastic band training for rural elderly improved muscle strength and daily physical performance. This result suggests a simple and easy to perform band training could be an excellent solution to prevent sarcopenia in rural elderly. It also supports the evidence that this program would be widely distributed.