Effects of dynamic ischaemic training on human skeletal muscle dimensions

The effect of training under conditions of local leg ischaemia on muscle ar ea and fibre dimensions was studied in nine males. Leg ischaemia was induce d 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 wa s 50 mmHg. The subjects performed 16 sessions (45 min) of one-legged supine strenuous ischaemic training during 4 weeks. Exercise intensity was mainta ined as high as possible during the whole session. The contralateral leg se rved as a control leg and remained passive during exercise. Before and afte r 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 fibr e area increased by 12% (P < 0.05). The MRI-assessed cross-sectional area o f the vastus group increased by 4% (P = 0.01). In the control leg, mean fib re area and the cross-sectional area of the vastus group were unchanged, wh ile those of the adductor muscle group decreased by 4% (P < 0.05). It is co ncluded that a short period of strenuous ischaemic endurance training incre ases the cross-sectional area of the ischaemically trained muscle group, as measured both by MRI and from muscle biopsy samples. In contrast, the addu ctor muscles in the contralateral thigh showed a decreased cross-sectional area (as assessed by MRI), possibly due to the effects of the strenuous con tralateral training, by mechanisms that have yet to be identified.