Glycogen Storage and Glycogen Synthetase Activity in Trained and Untrained Muscle of Man

Bilateral biopsies from “one‐leg” trained subjects were analysed for glycogen content (G), total glycogen synthetase activity (GST), synthetase I‐form (GSI) and hexokinase (HK). Histochemical estimations were made of G, GST and GSI in slow twitch (ST) and fast twitch (FT) muscle fibres. Samples from the trained (T) and the untrained (U) legs were taken before and after acute exhaustive exercise and at different intervals during a 46 h recovery period when a carbohydrate enriched diet was given. Prior to exercise G levels were higher (32 %) in T‐leg than in U‐leg. Throughout the experiment T‐leg showed higher activity for GST (35%) and HK (18%). In both U‐ and T‐legs GSI activity increased (from 16 to 48 %) after exercise. The increase in GSI was histochemically found mainly in ST fibres in both T‐ and U‐leg, while the staining intensity for GST was similar in ST and FT fibres. During the recovery period, G was restored and GSI gradually declined to resting values. The rate of synthesis was the same in T‐ and U‐legs and in the two fibre types.