title: Creatine kinase MB and citrate synthase in type I and type II muscle fibres in trained and untrained men.
abstract: Total creatine kinase (CK), creatine kinase MB (CK-MB) and citrate synthase (CS) were determined in isolated and pooled type I and type II skeletal muscle fibres. Determinations were made on biopsies from 3 sedentary men, 3 junior cyclists and 2 elite cyclists. CS and CK-MB activities were higher in the trained groups in both fibre types. The total CK activity was not related to training status, although it was lower in type I fibres than in type II fibres (p less than 0.05). The reverse relation was observed for CS and CK-MB activities (p less than 0.01). The ratio of type I/type II for CS was not related to training status, while the corresponding ratio for CK-MB increased with a greater degree of endurance training. For a given increase in CS activity, the increase in CK-MB activity was greater in type I fibres than in type II fibres (p less than 0.01). Thus, with endurance training there seems to be a specific adaptation for CK-MB, particularly in type I fibres.
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling; D002950:Citrate (si)-Synthase / Q000378:metabolism*; D003402:Creatine Kinase / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000201:enzymology*; D007652:Oxo-Acid-Lyases / Q000378:metabolism*; D010101:Oxygen Consumption; D010807:Physical Endurance
chemical_list: D007527:Isoenzymes; D002950:Citrate (si)-Synthase; D003402:Creatine Kinase; D007652:Oxo-Acid-Lyases