Myosin ATPase activity after strengthening exercise
Jaweed, M.M.; Herbison, G.J.; Ditunno, J.F.
Journal of Anatomy 124(Pt 2): 371-381
1977
ISSN/ISBN: 0021-8782 PMID: 145422 Document Number: 120802
Two grades of high intensity weight lifting were used in this experiment to test the possibility of a histochemical change in myosin ATPase activity of the rat soleus. Adult Wistar rats were trained to carry weights on their backs for 6 wk, either once on a 45 cm long ladder (group A) or twice on a 90 cm long ladder (group B) set at 50.degree. angle. The former represented the high intensity short duration and the latter high intensity prolonged duration exercise. A significant muscle hypertrophy (23-26%, P < .05) in both the exercise groups was found. Group A muscles showed a relative increase in the number of type II or fast twitch-oxidative-glycolytic (FOG) fibers accompanied by a hypertrophy of the type I or slow-twitch-oxidative (SO) fibers (13.7%, P < .05). The soleus muscles in group B showed a significant decrease (8.2%; P < .01) in the number of type II (FOG) fibers, presumably owing to a conversion of type II (FOG) to type I (SO) fibers. The stimulus of high intensity weight lkfting may command a selective recruitment of the fiber types and thereby stimulated the synthesis of specific myosin ATPase: the fast type in brief or static work and the slow type in prolonged or more dynamic high intensity work. The O2 supply to muscle fibers may regulate the synthesis of specific contractile protein(s).