Effects of dynamic ischaemic training on human skeletal muscle dimensions.

The effect of training under conditions of local leg ischaemia on muscle area and fibre dimensions was studied in nine males. Leg ischaemia was induced by enclosing the legs in a pressure chamber and sealing the opening with a rubber membrane at the level of the crotch. Air pressure over the legs was 50 mmHg. The subjects performed 16 sessions (45 min) of one-legged supine strenuous ischaemic training during 4 weeks. Exercise intensity was maintained as high as possible during the whole session. The contralateral leg served as a control leg and remained passive during exercise. Before and after the training period, muscle fibre dimensions were determined from biopsy samples taken from the m. vastus lateralis, and leg muscle dimensions were assessed by magnetic resonance imaging (MRI). In the trained leg, mean fibre area increased by 12% (P < 0.05). The MRI-assessed cross-sectional area of the vastus group increased by 4% (P = 0.01). In the control leg, mean fibre area and the cross-sectional area of the vastus group were unchanged, while those of the adductor muscle group decreased by 4% (P < 0.05). It is concluded that a short period of strenuous ischaemic endurance training increases the cross-sectional area of the ischaemically trained muscle group, as measured both by MRI and from muscle biopsy samples. In contrast, the adductor muscles in the contralateral thigh showed a decreased cross-sectional area (as assessed by MRI), possibly due to the effects of the strenuous contralateral training, by mechanisms that have yet to be identified.