Tissue Oxygenation in Men and Women During Repeated-Sprint Exercise

Abstract

Purpose:To understand the role of O2 utilization in the sex differences of fatigue during intermittent activity, we compared the cerebral (prefrontal lobe) and muscle (vastus lateralis) oxygenation of men and women during repeated-sprint exercise (RSE).Methods:Ten men and 10 women matched for initial-sprint mechanical work performed ten, 10 s cycle sprints (with 30 s of rest) under normoxic (NM: 21% FIO2) and acute hypoxic (HY: 13% FIO2) conditions in a randomized single-blind and crossover design. Mechanical work was calculated and arterial O2 saturation (SpO2) was estimated via pulse oximetry during every sprint. Cerebral and muscle oxy- (O2Hb) and deoxy-hemoglobin (HHb) were monitored continuously by near-infrared spectroscopy.Results:Compared with NM, work decrement was accentuated (P = 0.01) in HY for both men (–16.4 ± 10.3%) and women (–16.8 ± 9.0%). This was associated with lower SpO2 and lower cerebral Δ[O2Hb] in both sexes (–13.6 ± 7.5%, P = .008, and –134.5 ± 73.8%, P = .003, respectively). These HY-induced changes were nearly identical in these men and women matched for initial-sprint work. Muscle Δ[HHb] increased 9-fold (P = .009) and 5-fold (P = .02) in men and women, respectively, and plateaued. This muscle deoxygenation was not exacerbated in HY.Conclusions:Results indicate that men and women matched for initial-sprint work experience similar levels of fatigue and systemic, cerebral, and peripheral adjustments during RSE performed in NM and HY. These data suggest that cerebral deoxygenation imposes a limitation to repeated-sprint performance.

No Improved Performance With Repeated-Sprint Training in Hypoxia Versus Normoxia: A Double-Blind and Crossover Study

“…Provided that ∆[tHb] reflects blood perfusion, it is suggested that RS performance is not primarily limited by oxygen delivery to skeletal muscle, as this is indeed supported in the literature [24][25][26][27] , neither by blood flow-related removal of metabolites. Rather, RS performance is considered to be predominantly determined by neuromuscular factors 24-28 , including, but not limited to, neural drive, muscle excitability, PCr stores and recovery rate 28 .…”

Repeated sprint training in normobaric hypoxia

“…This may relate to reduced cerebral oxygenation, since studies in hypoxia have demonstrated that diminished cerebral oxygen availability is associated with decreased central drive and fatigue. Specifically during RS exercise, decreased cerebral oxygenation was associated with decreased work capacity 38 39…”

Update in the understanding of altitude-induced limitations to performance in team-sport athletes

“…For example, total mechanical work during ten 10 s cycle sprints interspersed with 30 s of rest was reduced (−8%) in hypoxic (FiO 2 0.13, ∼3600 m) versus normoxic conditions 13. In hypoxia, a ∼9-fold to 10-fold increase in deoxygenation of active muscles (assessed via near-infrared spectroscopy) occurs rapidly during the first repetition of a series of sprints 13 39. However, as this deoxygenation quickly plateaus, and is relatively similar in normoxia and hypoxia, the results have been interpreted to mean that the level of muscle deoxygenation per se, and presumably muscle O 2 extraction, is unlikely to limit CAC 13 39.…”

“…In hypoxia, a ∼9-fold to 10-fold increase in deoxygenation of active muscles (assessed via near-infrared spectroscopy) occurs rapidly during the first repetition of a series of sprints 13 39. However, as this deoxygenation quickly plateaus, and is relatively similar in normoxia and hypoxia, the results have been interpreted to mean that the level of muscle deoxygenation per se, and presumably muscle O 2 extraction, is unlikely to limit CAC 13 39. On the other hand, the capacity of the muscle to get reoxygenated during recovery periods between efforts has been incriminated in the performance decline in hypoxia 40.…”