title: Time course adaptations in cardiac and skeletal muscle to different running programs.
abstract: The effects of chronic "steady-state" and high-speed interval running were investigated on time-course changes in certain biochemical properties of cardiac and skeletal muscle fiber types of rats. Nine weeks of the interval program resulted in significant increased (15%) in both cardiac enlargement and ATPase activity of myofibrils; whereas increases in these parameters were only transient and not significant at the termination of the program involving steady-state running. Neither program induced appreciable alterations in citrate synthase and phosphofructokinase activity in cardiac muscle. In fast-twitch white fibers, "steady-state" training induced only a transient 45% increase in citrate synthase activity in contrast to a progressive twofold change with interval training. Both programs resulted in similar increases (45-50%) in citrate synthase activity in fast-twitch and slow-twitch red fibers. However, the patterns of increase for both fiber types differed between the two programs. These findings suggest that training programs incorporating elements of both "steady-state" incline and high-speed interval running can potentially induce respiratory enzyme adaptations in the greatest spectrum of rodent skeletal muscle fibers in addition to inducing adaptations to enhance contractile potential in cardiac muscle.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006332:Cardiomegaly; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D006593:Hexokinase / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D009132:Muscles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D010732:Phosphofructokinase-1 / Q000378:metabolism; D010805:Physical Conditioning, Animal; D051381:Rats; D012420:Running
chemical_list: D002950:Citrate (si)-Synthase; D006593:Hexokinase; D010732:Phosphofructokinase-1; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium