1. A group of eight male patients with moderate hemiparesis was studied at rest and during 40 min of exercise on four occasions. Both two-leg and one-leg exercise were performed and each leg was studied separately. Arterial concentrations and leg exchange of carbohydrate substrates and free fatty acids were examined. In addition, the concentrations of intramuscular metabolites for each leg were measured at rest and immediately after exercise.
2. In two-leg exercise, oxygen uptake for the paretic leg was significantly lower than for the non-paretic leg at rest (55%) as well as during exercise (40%). Glucose uptake by the paretic leg was smaller (25–50%) and there was no measurable net leg exchange for lactate. Recordings of pedal pressure indicated that the paretic leg did considerably less work than the non-paretic leg throughout the exercise period. The rate of uptake of oleic acid was lower for the paretic leg (50%) in the resting state but similar for the two legs during exercise. The recovery of 14CO2 from [14C]oleic acid during exercise was significantly reduced for the paretic leg.
3. During one-leg exercise, oxygen and glucose uptakes by the working leg were similar for the paretic and non-paretic leg but lactate release was significantly greater for the paretic leg during exercise (30–45%).
4. The concentrations of ATP and creatine phosphate in the basal state were similar for the two legs. ATP and creatine phosphate fell significantly in the two legs during both the two-leg and the one-leg exercise period. The most marked decrease in ATP was noted for the paretic leg during one-leg exercise. The pattern of glycogen depletion during one-leg exercise for the paretic leg indicated primarily activation of the type II fibres. In contrast, the depletion pattern for the non-paretic leg suggested mainly recruitment of type I fibres.
5. The results indicate that, during exercise, paretic muscle shows a reduced blood flow, an augmented lactate production and a diminished capacity to oxidize free fatty acids. These metabolic derangements may be referrable to an augmented number and increased activation of type II muscle fibres as well as to alterations in the structure of muscle mitochondria. In addition, the present study indicates that one-leg exercise should be preferred to two-leg exercise when studying leg muscle circulation and metabolism in hemiparetic patients.