title: Time course of changes in human skeletal muscle succinate dehydrogenase and cytochrome oxidase activities and maximal oxygen uptake with physical activity and inactivity.
abstract: Succinate dehydrogenase (SDH) and cytochrome oxidase activities in the lateral vastus of the human quadriceps femoris muscle together with total body VO2 max were followed during an 8-10 week period of endurance training (n = 13) and a successive 6 week period without training (n = 8). During the training period there was a gradual increase in both VO2 max and muscle oxidative enzyme activities, all being significantly different from the pre-training levels after 3 weeks of training. After 8 weeks of training VO2 max was 19%, vastus lateralis SDH 32%, and cytochrome oxidase activity 35% above the pre-training levels respectively. 6 weeks post training VO2 max was still 16% above the pre-training level, and not significantly different from the level at the end of training (p greater than 0.2). In contrast vastus lateralis SDH activity had returned to the pre-training level. Cytochrome oxidase activity had returned to the pre-training level within two weeks post-training. The significantly faster post-training decline in skeletal muscle oxidative enzyme activities in contrast to that of the VO2 max indicates that an enhancement of the oxidative potential in skeletal muscle is not a necessity for a high VO2 max. Moreover, the fast return to the pre-training level of both SDH and cytochrome oxidase activities indicate a high turnover rate of enzymes in the TCA cycle as well as the respiratory chain.
mesh_terms: D000328:Adult; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006801:Humans; D008297:Male; D008451:Maximal Voluntary Ventilation; D009132:Muscles / Q000201:enzymology*; D010101:Oxygen Consumption; D005082:Physical Exertion; D013385:Succinate Dehydrogenase / Q000378:metabolism*
chemical_list: D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV