We investigated the effect of occluding of femoral blood flow on the post-exercise ventilatory response of both the sub- and supra-anaerobic threshold (AT) leg cycling in humans. Seven healthy subjects (aged 21-44 years) volunteered to participate in this study. The protocol consisted of 6 min constant-load upright cycling at either a sub-AT (80% of AT) or supra-AT (midway between AT and over(V, ̇) O2 max) work rate and a subsequent 6 min rest period either with or without femoral blood flow being occluded by a rapid cuff inflation to 250 Torr during the first 2 min of recovery. Blood lactate levels at the cessation of the sub- and supra-AT exercise averaged 1.8 ± 0.2 and 4.9 ± 0.4 mequiv. l-1 (mean ± S.E.M.), respectively. Compared to spontaneous recovery, the circulatory occlusion significantly reduced ventilation irrespective of the intensity of the preceding exercise. The relative contribution of the ventilatory deficit to the total spontaneous ventilation (defined as the difference between the cumulative ventilation with and without cuff inflation during the first 2 min of recovery) was significantly greater supra-AT (18.0 ± 3.9%) than sub-AT (9.3 ± 2.9%, P < 0.05). The subsequent release of occlusion was accompanied by a rapid increase in ventilation that began on the first breath after release. We concluded that the relatively greater speeding of ventilatory decline with occlusion during the first 2 min of recovery from supra-AT exercise argues against a significant role for an intramuscular chemoreflex-induced hyperpnoea. Rather, mechanisms related to the hemodynamic effects of suddenly altered muscle perfusion seem more consistent with this phenomenon.
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