Increased wheel-running activity in the genetically skeletal muscle fast-twitch fiber-dominant rats

• Published in: Journal of applied physiology (1985) 2003-01, Vol.94 (1), p.185-192
• Main Authors: Suwa, Masataka, Nakano, Hiroshi, Higaki, Yasuki, Nakamura, Tomohiro, Katsuta, Shigeru, Kumagai, Shuzo
• Format: Article
• Language: English
• Subjects: Anatomy & physiology; Animals; Biological and medical sciences; Body Composition; Capillaries - anatomy & histology; Female; Fundamental and applied biological sciences. Psychology; Genes, Dominant; Genetics; Histocytochemistry; Hybridization, Genetic; Male; Motor Activity - physiology; Muscle Fibers, Fast-Twitch - physiology; Muscle Fibers, Fast-Twitch - ultrastructure; Muscle, Skeletal - blood supply; Muscle, Skeletal - physiology; Muscle, Skeletal - ultrastructure; Muscular system; Rats; Rats, Inbred Strains - genetics; Rodents; Space life sciences; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00295.2002

1  Institute of Health Science, Kyushu University, Kasuga, Fukuoka 816-8580; 2  Department of Human Development, Nakamura Gakuen University, Jonan-ku, Fukuoka 814-0198; 3  Department of Preventive Medicine, Saga Medical School, Saga 849-8501; 4  Department of General Education, Osaka Institute of Technology, Asahi-ku, Osaka 535-8585; and 5  Graduate School of Integrated Science and Art, University of East Asia, Shimonoseki, Yamaguchi 751-8503, Japan The purpose of the present study was to investigate whether genetic differences in muscle histochemical characteristics were related to the voluntary wheel-running activity level by using genetically fast-twitch fiber-dominant rats (FFDR) and control rats (CR). The rats were divided into four groups; sedentary CR (Sed-CR), wheel-running CR (WR-CR), sedentary FFDR (Sed-FFDR), and wheel-running FFDR (WR-FFDR). Wheel access was started at age 9 wk and lasted for 7 days. The FFDR showed a lower percentage of type I fibers of the deep portion of gastrocnemius and soleus muscles and a higher percentage of both type IIX fibers of the gastrocnemius muscle and type IIA fibers of the soleus muscle compared with CR. A higher capillary density and smaller fiber cross-sectional area were also observed in FFDR. The daily running distance in WR-FFDR was higher than in WR-CR for each 7 days. The total running distance for 7 days in WR-FFDR was 3.2-fold higher than in WR-CR. On day 7  of the 7-day test, the total number of active 1-min intervals for 24 h, the average rpm when they were active, and the maximum rpm for any single 1-min period in the WR-FFDR were significantly higher than in the WR-CR (1.5-,   2.9-, and 2.0-fold, respectively). These results suggest that mechanical or physiological muscle characteristics may thus affect the wheel-running activity level. activity pattern; capillary density; selection breeding; muscle fiber-type composition; wheel cage