Differences in Muscle Fiber Recruitment Patterns between Continuous and Interval Exercises.
We evaluated differences in muscle fiber recruitment patterns between continuous and interval training to develop an optimal training program for Thoroughbred horses. Five well trained female thoroughbred horses (3-4 years old) were used. The horses performed two different exercises on a 10% inclined treadmill: 90%VO2 max for 4 min (continuous) and 90% VO2 max for 2 min × 2 times with 10-min interval (interval). Muscle samples were obtained from the middle gluteal muscle before and immediately after the exercises. Four muscle fiber types (type I, IIA, IIA/X, and IIX) were immunohistochemically identified, and the optical density of periodic acid Schiff staining (OD-PAS) in each fiber type and glycogen content of the muscle sample were determined by quantitative histochemical and biochemical procedures, respectively. No significant differences were found in the OD-PASs and glycogen contents between the continuous and interval exercises, but the decreases in OD-PAS of fast-twitch muscle fibers were obvious after interval as compared to continuous exercise. Interval exercise may be a more effective training stimulus for the glycolytic capacity of fast-twitch muscle fiber. The data about muscle fiber recruitment can provide significant insights into the optimal training program not only for thoroughbred horses, but also for human athletes.
Science Research Center, Yamaguchi University, Japan.
Seiko
S
Yamano
Biological Sciences, Graduate School of Medicine, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8515, Japan.
Minako
M
Kawai
Biological Sciences, Graduate School of Medicine, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8515, Japan.
Yoshio
Y
Minami
The Equine Research Institute, Japan Racing Association, 321-4 Tokami-cho, Utsunomiya, Tochigi 320-0856, Japan.
Atsushi
A
Hiraga
Biological Sciences, Graduate School of Medicine, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8515, Japan.
Hirofumi
H
Miyata
Thoroughbred; glycogen; interval exercise; muscle fiber