Over 12 months, GPX showed substantial tracking (r = 0.714, ICC = 0.683) compatible with a trait-like component, while SOD showed no meaningful tracking (r = 0.057, ICC = 0.053) and greater state-like variability in trained youth athletes.
Key Findings
Results
GPX demonstrated substantial longitudinal tracking over 12 months, suggesting a comparatively stronger trait-like component in trained youth athletes.
GPX tracking was evaluated using Pearson correlation (r = 0.714, p < 0.001) and intraclass correlation coefficient (ICC = 0.683).
The study included 69 trained athletes aged 10–17 years from the MuCAYAplus study.
The tracking period was 12 months with repeated assessments of antioxidant enzyme activity.
These findings are described as 'compatible with a comparatively stronger trait-like component for GPX.'
Results
SOD showed no meaningful longitudinal tracking over 12 months, suggesting greater state-like variability.
SOD tracking yielded a Pearson correlation of r = 0.057 (p = 0.644) and an ICC of 0.053.
These values indicate essentially no stability of individual SOD rankings across the 12-month period.
The authors describe SOD as exhibiting 'greater state-like variability.'
This contrasts sharply with the substantial tracking observed for GPX in the same cohort.
Results
SOD activity decreased and GPX activity increased over the 12-month study period.
Both enzymes changed in opposite directions across the longitudinal assessment window.
SOD decreased while GPX increased over 12 months in the same cohort of trained youth athletes.
These directional changes were observed in 69 trained athletes aged 10–17 years.
The divergent trajectories occurred alongside the contrasting tracking stability profiles of the two enzymes.
Results
No statistically supported associations were detected between changes in training exposure or growth-related measures and changes in SOD or GPX.
Change-score regression models were used to test whether changes in training exposure, growth-related variables, sex interactions, and hematological parameters predicted enzyme changes.
Neither training-exposure changes nor growth-related variables were significantly associated with SOD or GPX changes.
Sex interactions were also tested and did not yield statistically supported associations with enzyme changes.
The analysis was conducted over a 12-month longitudinal window in 69 trained youth athletes.
Results
Exploratory analyses identified erythrocyte-related associations with SOD, while leukocyte and platelet changes were unrelated to either enzyme.
Hematological parameters were included in change-score regression models as potential predictors.
Erythrocyte-related parameters showed exploratory associations specifically with SOD.
Leukocyte and platelet changes were unrelated to SOD or GPX changes.
These findings were described as 'exploratory' and not as primary or confirmatory results.
Results
Cluster-based SOD/GPX redox phenotype analyses were not robust in this cohort.
Exploratory cluster-based redox phenotype stability was assessed using agreement statistics.
The combined SOD/GPX phenotype clusters did not show robustness across the 12-month period.
This suggests that classifying youth athletes into stable redox phenotype groups based on these two enzymes together was not supported by the data.
The analysis was part of the exploratory component of the study design.
Methods
The study used a longitudinal design within the MuCAYAplus study, assessing trained youth athletes aged 10–17 years over 12 months with repeated measurements of antioxidant enzymes, training exposure, body composition, and hematological parameters.
Sample size was 69 trained athletes.
Age range was 10–17 years.
Assessment duration was 12 months.
Longitudinal tracking was evaluated using both Pearson correlation and intraclass correlation coefficients (ICC).
Change-score regression models were used to test predictors of enzyme change.
What This Means
This research suggests that two key antioxidant enzymes — superoxide dismutase (SOD) and glutathione peroxidase (GPX) — behave quite differently in young trained athletes over time. GPX levels were relatively stable and consistent within individuals across a 12-month period, meaning that athletes who had higher GPX at the start tended to still have higher GPX a year later. SOD, by contrast, showed essentially no such consistency, fluctuating considerably in ways that did not track individual athletes' baseline levels. Both enzymes also moved in opposite directions overall: SOD tended to decrease while GPX tended to increase over the year.
The study also found that neither changes in training load nor changes related to growth and development were statistically linked to changes in either enzyme. Some exploratory findings suggested that red blood cell-related factors may be associated with SOD changes, but these were preliminary and not the primary focus. Attempts to classify athletes into distinct 'redox phenotype' groups based on both enzymes together did not yield stable, meaningful clusters.
This research suggests that GPX may reflect a more stable, individual biological characteristic — sometimes called a 'trait' — whereas SOD may be more sensitive to short-term or fluctuating influences, behaving more like a 'state' marker. For researchers and practitioners working with young athletes, this means that a single measurement of GPX may be more representative of an individual's typical antioxidant capacity than a single SOD measurement, though the practical significance of these enzyme differences in healthy youth athletes requires further study.
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Haferanke J, Dettenhofer M, Huber S, Mühlbauer F, Baumgartner L, Engl T, et al.. (2026). Enzyme-Specific Redox Stability and Plasticity in Trained Youth Athletes: Longitudinal Analysis of SOD and GPX.. International journal of molecular sciences. https://doi.org/10.3390/ijms27177813