Abstract
Strenuous exercise in animal studies has been shown to cause acute oxidative stress due to the generation of oxygen-centered free radicals reflected in lower levels of glutathione (GSH), higher levels of glutathione disulfide (GSSG), and a drop in GSH:GSSG ratios, the maintenance of which is crucial for a variety of cell functions. Human studies on this topic are limited. The purpose of this study was to investigate the effects of a maximal graded exercise test GXTmax (modified Bruce protocol) on GSH as a marker of acute oxidative stress, and whether full recovery will occur at 60 minutes postexercise.
Eighty sedentary subjects were used as a sample of convenience. Venous blood samples for GSH and GSSG were collected directly before, immediately after, and 60 minutes post-GXTmax. Repeated-measures analysis of variance and Bonferroni adjusted t tests (post-GXTmax) versus resting, and 60 minutes recovery versus resting) were used for data analysis.
As an acute response to maximal exercise, the GSH levels dropped significantly from a resting baseline value of 1025.75 microM to an immediate post-GXTmax value of 893.30 microM (pooled SE = 7.17 microM). The GSSG levels significantly increased from 2.24 microM to 3.15 microM (pooled SE = 0.03 microM). The GSH:GSSG ratio levels significantly dropped from baseline 462.12 to 276.40 postexercise (pooled SE = 5.98). The blood GSH, GSSG, and GSH:GSSG ratio levels showed no significant difference at 60 minutes post-GXTmax when compared with resting values, indicating full recovery.
The current results indicated that in sedentary individuals, a maximal treadmill GXT is an effective technique for inducing acute oxidative stress as evidenced by GSH system responses, with full return to resting baseline levels within 60 minutes of recovery. The potential for using this model in assessing oxidative stress responses to cardiac and pulmonary rehabilitation is of clinical interest, with a need for further investigation.