Heterogeneous antioxidant responses to exercise in middle-aged men: A six-month study of amateur soccer players

Abstract

Physical exercise exerts a dual influence on redox homeostasis, capable of inducing both adaptive antioxidant responses and detrimental oxidative stress, with outcomes critically dependent on exercise intensity and individual physiological tolerance. This balance is especially pertinent for middle-aged individuals, a demographic at a pivotal juncture for long-term health, where personalized exercise strategies are key for promoting successful aging. However, practical and non-invasive tools for routine redox monitoring remain underutilized in amateur sports settings. This pilot study, therefore, evaluated the heterogeneous effects of a sixmonth amateur soccer training program on salivary antioxidant capacity in middle-aged men under controlled dietary conditions, utilizing a non-invasive spectrophotometric approach. Twelve participants (aged 45–60 years) completed the structured training. Saliva samples were collected before and immediately after a standardized high-intensity session at the program’s conclusion. Total antioxidant capacity was assessed via the 1,1′-diphenyl- 2-picrylhydrazyl (DPPH) radical scavenging assay under standardized analytical conditions, with all samples processed using the same reagent batch to ensure consistency. The primary outcome was the intra-individual change (Δ) in absorbance. The results revealed marked interindividual heterogeneity in post-exercise redox responses. Specifically, half of the cohort exhibited a decrease in post-exercise absorbance (negative Δ values), indicating enhanced antioxidant activity, while the other half showed an increase (positive Δ values), suggesting a reduction in antioxidant capacity or an increased pro-oxidant load. The magnitude of change varied considerably among participants. These findings underscore the threshold-dependent duality of intense exercise and highlight the significant role of individual redox physiology in mediating its net effect, independent of dietary confounding in this study. The study provides clear proof-of-concept evidence for the feasibility and relevance of using non-invasive salivary DPPH testing as a practical tool to monitor exercise-induced oxidative balance. This supports the rational development of personalized training regimens guided by objective biochemical feedback, aiming to optimize health benefits and mitigate oxidative risks in middle-aged amateur athletes. The approach has direct implications for applied sports science, preventive health strategies, and the move toward more individualized exercise prescription in community-based settings.