Dynamic muscle quality of the plantar flexors is impaired in claudicant patients with peripheral arterial disease and associated with poorer walking endurance
- Publisher: Elsevier
mesheuropmc: human activities
Objectives: Peripheral arterial disease and intermittent claudication (PAD-IC) negatively affects physical activity and function. There is evidence for plantarflexor muscle dysfunction and weakness, however, the extent to which this dysfunction can be attributed to reduced muscle size and/or quality is not yet known. This study investigated whether in vivo plantarflexor muscle quality during static and dynamic contractions are altered by PAD-IC and whether such changes are associated with impaired walking endurance (according to initial and absolute claudication distances). Methods: A total of 22 participants were recruited, consisting of 10 healthy controls and 12 claudicants with occlusion of the superficial femoral artery (seven unilateral and five bilateral). Muscle quality of the combined gastrocnemius muscles during static contractions was calculated by normalising the estimated maximal potential muscle force to the physiological cross-sectional area of both lateral and medial gastrocnemius. Muscle quality during dynamic contractions of the combined plantarflexor muscles was calculated as the ratio of peak voluntary concentric plantarflexor power and the summed volume of lateral and medial gastrocnemius. Results: Dynamic muscle quality was 24% lower in both the claudicating-limb and asymptomatic-limb groups compared to controls (P=.017 and P=.023). The differences were most apparent at the highest contraction velocity (180°/s). Dynamic muscle quality was associated with reduced walking endurance (R=.689, P=.006 and R=.550, P=.042 for initial and absolute claudication distance, respectively). The claudicating-limb group demonstrated a trend towards reduced static muscle quality compared to controls (22%, P=.084). The relative contribution of the soleus muscle to plantarflexion maximum voluntary contraction was significantly higher in both claudicating-limb and asymptomatic-limb groups compared to controls (P=.012 and P=.018). Conclusions: The muscle strength of the plantarflexors in those with PAD-IC appears to be impaired at high contraction velocities. This may be explained by some reduction in gastrocnemii muscle quality and a greater reliance on the prominently type I fibred soleus muscle. The reduced dynamic capability of the plantarflexor muscles was associated with disease severity and walking ability, therefore efforts to improve plantarflexor power through dynamic exercise intervention are vital to maintain functional performance.