Fig. 1.

Schematic representation of the study phases and exercise protocols.

Forty-three physically active participants (30 males and 13 females) were recruited for the study. After fulfilling inclusion criteria, a DEXA scan was performed after a 12-h overnight fast. On another visit, participants performed a familiarization session with the cycle ergometer exercise protocols that included submaximal cycling exercise, an incremental test until exhaustion with verification, a 30-s Wingate test and post-exercise occlusion of the circulation. On a third visit, participants carried out a test to assess VO₂max and the VO₂/intensity relationship. At least one week apart, the subjects were submitted to a resting muscle biopsy, which was separated by a minimum of one week from the performance of the maximal functional reserve tests (MFR). The MFR sessions consisted in two experimental sessions. In each of them, after a standardized warm-up, subjects performed six bouts of supramaximal constant intensity exercise at 120% of VO₂max until exhaustion, interspersed either with 20 s of recovery periods with application of immediate post-exercise ischaemia at exhaustion (ischaemic recovery session) or with 20 s of recovery with free circulation (free circulation recovery session), in random order. At the start of the 2nd to 6th bouts in the ischaemic recovery session, the cuffs were deflated instantaneously, to allow for restoration of the circulation during the subsequent bout. The cuffs located around the two thighs were instantaneously inflated at 300 mmHg during the sessions with ischaemic recovery to elicit total occlusion of the circulation of both lower extremities and impede metabolic recovery. The schematic presented for the MFR test corresponds to the ischemic session. In 13 volunteers a muscle biopsy was obtained before and immediately after the ISR test.