Increased fatigability of the gastrocnemius medialis muscle in individuals with intermittent claudication.

BACKGROUND

We attempted to identify possible differences in the contractility of the gastrocnemius medialis (GM) muscle between healthy controls and individuals with peripheral arterial disease (PAD) and intermittent lower-limb claudication.

METHODS

The GM muscles of 17 PAD patients and 17 healthy controls were examined with tensiomyography. Single or multiple electrical impulses were used to trigger muscle contractions, and the time and amplitude of contractions were measured.

RESULTS

After single-impulse stimulation, the GM muscles of PAD patients showed significantly shorter contraction times (P < 0.001) than the GM muscles of controls. During 1 min of repetitive electrical stimulation, the contraction velocity of the controls' GM muscles typically showed a sustained increase throughout the stimulation period, whereas in PAD patients, a significant decrease in contraction velocity was observed after 30 s. The onset of muscle fatigue was unrelated to the ankle brachial index (ABI) of the examined leg. When the legs of PAD patients with higher and lower ABIs were compared to each other, no significant differences were found regarding the time and amplitude of contraction after single-impulse stimulation.

CONCLUSIONS

The GM muscles of individuals with intermittent claudication contract more quickly and fatigue earlier than the GM muscles of healthy controls. Because the contraction time, measured with tensiomyography, reflects the individual's muscle fibre composition, our findings may reflect a shift from type I fibres to type II fibres in the GM muscles of PAD patients. Our data support the idea that calf myopathy is present in claudication-prone patients and, in part, determines the clinical manifestations of PAD.