The effect of cognitive fatigue and hypoxia on repeated arm bike sprint performance: A combined and individual stressors approach

Abstract

High‐altitude ascent can expose individuals to both physical and cognitive stress in combination. Despite this, limited research has investigated the combined influence of low oxygen concentrations and cognitive fatigue on high‐intensity exercise performance. The aim of the present study was to investigate the combined effects of cognitive fatigue and normobaric hypoxia on repeated arm bike sprint ability. Six active healthy males completed four experimental conditions in a balanced order (mean ± SD; age: 25.2 ± 2.9 years, body fat percentage: 14.4 ± 1.6%, max power during 5‐s arm bike sprint: 380 ± 77 W). All conditions were completed at 17°C environmental temperature, 50% relative humidity, with a wind speed 0.4 m.s−1. The four experimental conditions were: 1) normobaric normoxia (0.209 FiO2) with no prior cognitive fatigue (CON), 2) normobaric normoxia (0.209 FiO2) with cognitive fatigue induced using an individualised 16‐min dual‐task cognitive test prior to performance test (CF), 3) normobaric hypoxia (0.12 FiO2) with no prior cognitive fatigue (HYP), 4) normobaric hypoxia (0.12 FiO2) with cognitive fatigue induced as before (HYP+CF). To assess physical performance for each condition, participants completed 10 × 20‐s ‘all‐out’ arm sprints, followed by a 60‐s isometric bicep maximal voluntary contraction (MVC) at 100% maximal voluntary strength. Central and peripheral fatigue were assessed using Supramaximal Nerve Stimulation (400 V square wave, 10 ms spaced doublets, 37 ± 5 mA), with stimulations superimposed every 10‐s during the 60‐s MVC using the twitch interpolation method. Voluntary activation percentage (VA) and resting potentiated twitch force (Qtw,pot) were calculated. Near Infra‐Red Spectroscopy (NIRS), heart rate, oxygen consumption and subjective ratings of perceived exertion, physical discomfort and thermal sensation, were also measured. Cognitive fatigue was successfully induced prior to the performance test as verified (p≤0.001) using the Brunel Mood Scale (BRUMS), Stanford Sleepiness Scale (SSS) and the Visual Analogue Scale of Fatigue (VASF). High‐altitude resulted in decreased (p=0.002) NIRS muscle oxygenation by 9.7 ± 3.8%. Individually, cognitive fatigue (p=0.032) and hypoxia (p=0.037) lowered power output across all ten sprints by 7.3 ± 6.4 W and 10.5 ± 8.8 W respectively, when compared to control conditions (CON: 188 ± 22 W, HYP: 182 ± 16 W, CF: 185 ± 18 W, HYP+CF: 170 ± 16 W). Exposure to both stressors in combination produced a greater decline in average power output, and the effect was additive for the two stressors (no interaction, p=0.127). Post‐exercise perceptual and subjective sensations, as well as MVC force, VA and Qtw,pot were not different between trials (p≥0.126). In conclusion, separate exposure to cognitive fatigue and hypoxia significantly impaired self‐paced physical performance during repeated arm bike sprints. When combined, exposure to cognitive fatigue and hypoxia diminished performance additively for the two stressors.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.