Time to failure and neuromuscular response to intermittent isometric exercise at different levels of vascular occlusion: a randomized crossover study
Objectives: The purpose this study was investigate the effects of different vascular occlusion levels (total occlusion (TO), partial occlusion (PO) or free flow (FF)) during intermittent isometric handgrip exercise (IIHE) on the time to failure (TF) and the recovery of the maximum voluntary isometric force (MVIF), median frequency (EMGFmed) and peak of EMG signal (EMGpeak) after failure. Methods: Thirteen healthy men (21 ± 1.71 year) carried out an IIHE until the failure at 45% of MVIF with TO, PO or FF. Occlusion pressure was determined previously to the exercise. The MVIF, EMGFmed and EMGpeak were measured before and after exercise. Results: TF (in seconds) was significantly different (p < 0.05) among all investigated conditions: TO (150 ± 68), PO (390 ± 210) and FF (510 ± 240). The MVIF was lower immediately after IIHE, remaining lower eleven minutes after failure in all cases (p <0.05), when compared to pre exercise. There was a greater force reduction (p <0.05) one minute after the failure in the PO (-45.8%) and FF (-39.9%) conditions, when compared to TO (-28.1%). Only the PO condition caused lower MVIF (p <0.05) than in the OT, eleven minutes after the task failure. PO caused a greater reduction in EMGFmed compared TO and greater increase in EMGpeak, when compared to TO and FF (p <0.05). Conclusions: TO during IIHE lead to a lower time to failure, but a faster MVIF recovery, while the PO seems to be associated to a slower neuromuscular recovery, when compared to other conditions.
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