Isokinetic strength and endurance in peripheral arterial insufficiency with intermittent claudication

Isokinetic plantar flexor peak torques (PT) and contractional work (CW) of the triceps surae muscle have been measured in 24 patients with peripheral arterial insufficiency and intermittent claudication and in 15 controls. Tests were performed both during non-fatiguing (30-180 degrees/s) and fatiguing (200 repeated plantar flexions at 60 degrees/s) conditions. The electromyographic signals (iEMG) from all three heads of the triceps surae were measured. The patients were significantly weaker (PT) and produced significantly less contractional work (CW) than the controls. In contrast, similar iEMGs of the triceps surae heads indicated similar levels of activation. At 40 contractions the majority of the patients had already given up and the remainder showed significantly greater declines in PT (50%) and CW (55%) than did the controls (13% and 18%, respectively). The decline in muscular excitations was similar in both groups. The ratio CW/iEMG showed a dramatic decline in the patients but was virtually constant in the controls. These results indicate a fatigue of low-frequency type in the patient group. There were close correlations between maximum walking tolerance and total work production.