Associations of resting plasma adenosine triphosphate, antioxidant capacity, and oxidative stress biomarkers with cardiorespiratory fitness in combat sport athletes: a pilot cross-sectional study
Jinling Huang, Lüfeng Miao, Yangjun Liu · Frontiers in Physiology · 2026
Background: and study
Aim: Combat sports involve repeated high-intensity efforts separated by short recovery periods, creating substantial demands on aerobic function and recovery. However, little is known about whether resting metabolic and redox-related biomarkers are associated with cardiorespiratory fitness in combat sport athletes. This pilot cross-sectional study examined the associations of resting plasma adenosine triphosphate (ATP), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GPX) with maximal oxygen uptake (VO 2 max) and relative VO 2 max.
Materials and methods: Resting venous blood samples were collected once after at least 8 h of fasting and before a graded treadmill exercise test; no post-exercise samples were obtained. Cardiorespiratory fitness was evaluated using a graded treadmill exercise test, with VO 2 max, relative VO 2 max, respiratory exchange ratio, exercise heart rate, and exercise duration recorded. Statistical analyses included descriptive statistics, Spearman and partial correlations, multiple linear regression, and decision tree modeling, with additional robustness checks using Bootstrap confidence intervals and permutation tests.
Results: Twenty-one combat sport athletes were included. Mean VO 2 max was 2937.19 ± 643.93 mL/min, and mean relative VO 2 max was 42.38 ± 8.80 mL/kg/min.s. T-AOC was strongly positively correlated with both VO 2 max (Spearman’s ρ = 0.723, p < 0.01) and relative VO 2 max (Spearman’s ρ = 0.678, p < 0.01), and these associations remained significant in partial correlation analyses adjusted for age, sex, height, and body mass. MDA was moderately correlated with relative VO 2 max (ρ = 0.454, p < 0.05). In multivariable models, T-AOC was the only biomarker significantly associated with VO 2 max and, together with MDA, was associated with relative VO 2 max. Partial correlation, decision tree, Bootstrap, and permutation analyses consistently supported T-AOC as the most stable signal across analytical approaches, suggesting that its association with cardiorespiratory fitness was not model-specific. By contrast, ATP, SOD, and GPX showed limited independent explanatory value.
Conclusions: Combat sport athletes in this pilot sample demonstrated high cardiorespiratory fitness. In this pilot sample, resting T-AOC showed the most consistent positive association with VO 2 max and relative VO 2 max, while MDA showed an exploratory association with relative VO 2 max. Because biomarkers were measured once before exercise, these
results represent baseline cross-sectional associations and do not establish causality, acute exercise responses, or recovery status. Larger longitudinal studies are needed to confirm these
Findings: .