Oxygen availability affects exercise capacity, but not neuromuscular fatigue characteristics of knee extensors, during exhaustive intermittent cycling

Girard, Olivier, Buchheit, Martin, Goodall, Stuart and Racinais, Sebastian (2020) Oxygen availability affects exercise capacity, but not neuromuscular fatigue characteristics of knee extensors, during exhaustive intermittent cycling. European Journal of Applied Physiology. ISSN 1439-6319 (In Press)

[img] Text
Manuscript.pdf - Accepted Version
Restricted to Repository staff only until 5 September 2021.

Download (339kB) | Request a copy

Abstract

Purpose: To compare the effects of different hypoxia severities on exercise capacity, cardio-respiratory, tissue oxygenation and neuromuscular fatigue characteristics in response to exhaustive intermittent cycling. Methods: Eleven well-trained cyclists, repeated supra-maximal cycling efforts of 15 s (30 of anaerobic power reserve, 609±23 W), interspersed with 45 s of passive rest until task failure. The exercise was performed on separate days in normoxia (SL; simulated altitude/end-exercise arterial oxygen saturation = 0 m/~96), moderate (MH; 2,200 m/~90) and severe (SH; 4,200 m/~79) hypoxia in a cross-over design. Neuromuscular tests, during brief (5 s) and sustained (30 s) maximal isometric voluntary contractions of the knee extensors, were performed at baseline and exhaustion. Results: Exercise capacity decreased with hypoxia severity (23±9, 16±6 and 9±3 cycle efforts in SL, MH and SH, respectively P<0.001; η2=0.72). Both cerebral (P<0.001; η2=0.86) and muscle (P<0.01; η2=0.54) oxygenation decreased throughout the exercise, independent of condition (P≥0.45; η2≥0.14). Compared to SL, muscle oxygenation was globally lower in MH and SH (P=0.011; η2=0.36). Cardiovascular solicitation neared maximal values at exhaustion in all conditions. Peak twitch amplitude with single and paired electrical stimuli (P<0.001; η2≥0.87), maximal torque (P<0.001; η2≥0.48) and voluntary activation measured using transcranial magnetic stimulation (P≤0.034; η2≥0.31) during brief and sustained MVCs were all reduced at exhaustion, independent of condition (P≥0.196; η2≥0.15). Conclusions: Despite reduced exercise capacity with increasing severity of hypoxia during exhaustive intermittent cycling, neuromuscular fatigue characteristics were not different at task failure and cardiovascular solicitation neared maximum values.

Item Type: Article
Subjects: C600 Sports Science
Department: Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Depositing User: Elena Carlaw
Date Deposited: 24 Sep 2020 13:06
Last Modified: 24 Sep 2020 13:15
URI: http://nrl.northumbria.ac.uk/id/eprint/44246

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year

View more statistics