Post-Exercise Circulatory Occlusion Differently Affects Soleus Spinal/Supraspinal Excitability

Post-exercise circulatory occlusion allows the investigation of the effects of group III/IV muscle afferent feedback on central nervous system responsiveness. This study explored the effects of post-exercise circulatory occlusion on soleus H- and V-wave excitability. Following a randomized-crossover design, in 1 day, 16 healthy men (24.6±3.5 y) completed a 3-minute sustained plantar-flexion contraction at 40% of maximal voluntary isometric contraction. Then, for testing, a cuff was inflated around the ipsilateral thigh (at 300 mm Hg) ~5 seconds before exercise termination. On the other day, testing was completed without previous fatiguing contraction and under free-flowing conditions. Maximal voluntary isometric contraction, electromyographic amplitude, H-reflex recruitment curve and V-wave normalized amplitude were determined. Leg pain intensity (0-10-point scale) and mean arterial pressure were also recorded. During post-exercise circulatory occlusion, maximal voluntary isometric contraction (-29.7±15.5%; p<0.001) and V-wave normalized amplitude (-42.7±45.9%; p=0.02) decreased, despite no changes in electromyography (p=0.19). Also, neither H-reflex threshold (p=0.53), slope (p=0.83), nor maximal amplitude (p=0.68) was affected. The muscle pain rated+5.8 points (p<0.001) and the mean arterial pressure was higher 22.4±2.8 mm Hg (p<0.001) with post-exercise circulatory occlusion. Thus, the lower-limb group III/IV afferent feedback inhibits supraspinal, but not spinal, pathway.