Low Intensity Training, Inactivity and Resumed Training in Sedentary Men

The effects of a low intensity training regimen, consisting of two 7-week periods with an interspersed 8-week inactivity period were investigated in 16 sedentary men. A follow-up was made on 7 subjects after 38 additional weeks' training. Systemic as well as local effects were studied using exercise tests and leg muscle biopsies. The two 7-week training periods both resulted in a 6% increase in Vo2 max and a lowered heart rate during submaximal work. No persisting training effects were detected by exercise tests after inactivity. In skeletal muscle, however, striking differences in enzyme activity pattern and ultrastructure were observed between the two periods, indicating that some training effect of importance for muscle metabolic adaptation might have persisted during inactivity. It is suggested that such an effect might be associated with the local oxygen supply. During the 38-week training period there was a large increase in muscle metabolic capacity, but no change in maximal oxygen uptake. This separation of systemic and local training effects indicates a lack of a direct causal relationship between muscle metabolic potential and max imal oxygen uptake. It is suggested that the elevated muscle oxidative capacity is of importance for an increased endurance capacity.