Exercise-induced Oxidative Stress During Exercise And Recovery In Hot Condition

Abstract

Acute exercise of sufficient intensity and duration can result in oxidative stress (OS), characterized by elevated blood OS biomarkers. Unfortunately, the time course for the change in OS and its recovery (RC) has not been adequately determined in most studies. PURPOSE: This study investigated the pattern change in blood OS biomarkers (low density lipoproteins oxidized (LDLox) and glutathione ratio (oxidized glutathione (GSSG) to total glutathione (TGSH) during a 1 h bout of cycling and a 1 h RC period, compared to a rest condition. It was hypothesized that the blood OS biomarkers would be elevated within the first 30 min of exercise based on the predicted intensity with the OS biomarkers returning to baseline during RC. METHODS: Ten males (mean(SD)); age,24.4 (1) yrs; mass, 75.3 (2.1) kg; height 175.9 (1) cm; VO2max, 50.0 (1.8) ml·kg-1·min-1) arrived at 1800 h on two occasions and completed; an exercise (Ex) (70-75% max power output) or rest (RE) condition in a hot environment (40oC and 30% relative humidity), in a randomized order. Blood was sampled every 15 min during EX and at min 15, 30 and 60 mins during RC. Plasma LDLox and both reduced (GSH) and oxidized (GSSG) forms of glutathione status were assessed. Repeated measures ANOVAs (2 conditions x 4 times [EX] and 2 conditions x 4 times [RC]) determined if differences in LDLox, and GSSG/TGSH ratio occurred with an alpha set a priori p < .05. RESULTS: Mean HR for RE was 73 ± 3 bpm vs 165 ± 3 for EX overtime. Mean cycling power output was 151 ± 9 W during EX. There was no main effect for condition (p = 0.054) or time (p = 0.061) or interaction (time by condition) effect (p = 0.074) for LDLox during EX. The GSSG/TGSH ratio increased at 30 minutes regardless of condition (12.5% compared to 5% at 0 minutes in chamber). The GSSG/TGSH ratio had a main effect for time to increase at 60 min RC independent of condition (p = 0.02). CONCLUSIONS: The results did not support our hypothesis of an exercise-induced OS. Our findings were likely impacted by 1) the environmental conditions inducing a high heat stress at rest, 2) delayed recovery due to the high heat stress in combination with dehydration during recovery, and 3) and small sample size which could not overcome the large interindividual variability in LDLox values.