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The Effects of Aging and Treadmill Running on Soleus and Gastrocnemius Muscle Morphology in the Senescence-Accelerated Mouse (SAMP1)

¹ School of Health Sciences
² Institute of Laboratory Animal Sciences, Kagoshima University, Japan.

Address correspondence to Harutoshi Sakakima, PT, PhD, Course of Physical Therapy, School of Health Sciences, Faculty of Medicine, Kagoshima University, 8-35-1, Sakuragaoka, Kagoshima, 890-8520 Japan. E-mail: sakaki{at}health.nop.kagoshima-u.ac.jp

We investigated the effects of aging on the soleus and gastrocnemius muscles in male SAMP1 (senescence-accelerated mouse prone 1). Body mass, muscle wet weight, fiber size, and the percent of type II fibers declined from 50 weeks of age. Voluntary motor behavior also significantly declined with age. Furthermore, we examined the effects of high (twice daily) and low (once daily) frequency treadmill running, for 6 weeks at 5 days per week, beginning when the mice were 50 weeks old. Muscle fiber size for the high frequency running significantly increased. Pathological fiber alterations in these mice were increased by running, especially by high frequency running. This suggests that age-related muscle morphological changes in SAMP1 occurs from 50 weeks of age, and that the decline in voluntary motor behavior is an important factor in aging muscle atrophy. In addition, high frequency running is more beneficial for aged muscle hypertrophy. This model is useful for studying the acceleration of the aging process in skeletal muscle of the SAM.

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