Document Type : Original Article
1. Introduction and Purpose
High-intensity intermittent exercise, characteristic of combat sports like boxing, significantly increases the production of reactive oxygen species (ROS) due to heightened aerobic and anaerobic metabolism. When the accumulation of ROS surpasses the neutralizing capacity of the body's endogenous antioxidant defense system, it induces a state known as oxidative stress. This condition is linked to cellular damage, accelerated muscle fatigue, and impaired athletic performance. The body's defense system consists of primary enzymatic defenses, such as superoxide dismutase (SOD) and catalase (CAT), as well as secondary non-enzymatic (exogenous) defenses. Studies suggest that boxing competitions can disrupt this balance. Conversely, the use of natural antioxidant supplements, like curcumin (the active compound in turmeric), has been proposed as a strategy to enhance the defense system and modulate exercise-induced oxidative stress. Curcumin operates through various mechanisms, including direct free radical scavenging, inhibition of lipid peroxidation, and upregulation of antioxidant enzyme expression. However, limited research has investigated the combined effect of a simulated high-intensity competition and curcumin supplementation on oxidative and antioxidant indices in elite boxers. Therefore, the primary objective of this study was to examine the effect of a simulated boxing competition and both short-term and acute curcumin supplementation on serum levels of oxidative markers, such as malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), as well as antioxidant markers, including the enzymes SOD and CAT, in male professional boxers.
2. Materials and Methods
This applied study utilized a quasi-experimental crossover design with one experimental group and was conducted with ethical approval (IR.UM.REC.1401.201). The statistical population consisted of male professional boxers in Mashhad city. After screening, 10 boxers (mean ± SD: age 23.3 ± 7 years, weight 67.55 ± 1.04 kg, body mass index 22.14 ± 2.83 kg/m²) were selected via purposive sampling. The study protocol was executed over four weeks: Week 1 involved baseline assessment without intervention; Week 2 included a 7-day consumption of an 80 mg daily nano-curcumin supplement before lunch, followed by a simulated boxing competition; Week 3 was a washout period; and Week 4 entailed acute consumption of the 80 mg supplement immediately after the simulated boxing competition. The standardized simulated boxing competition protocol consisted of three 3-minute rounds with one-minute rest intervals, during which participants performed Jab, Rear Straight, Rear Hook, and Lead Hook punches on a boxing bag in response to audio cues. Participants' diets were controlled throughout the study. Blood sampling was conducted at eight time points: A (baseline, Week 1), B (immediately post-competition, Week 1), C (48-hour recovery, Week 1), D (after one week of supplementation, Week 2), E (immediately post-competition, Week 2), F (48-hour recovery, Week 2), G (immediately after acute supplementation, Week 4), and H (48-hour recovery, Week 4), from the antecubital vein. Serum levels of MDA, H₂O₂, SOD, and CAT were measured using commercial ELISA kits (Zellbio, Germany) and the colorimetric method. Data were analyzed using repeated measures analysis of variance (ANOVA) and the Bonferroni post-hoc test in SPSS version 26 (significance level P < 0.05).
3. Results
The results from the repeated measures ANOVA indicated no significant within-group changes in serum levels of most investigated markers across the different phases of the study. The enzyme superoxide dismutase (SOD) showed no statistically significant differences between most stages, including comparisons of baseline (A) with post-competition (B) and acute post-supplementation (G) with recovery (H) (P > 0.05). The only exception was a significant decrease in SOD levels between the stage after one week of supplementation (D) and the stage immediately after the competition during the same period (E) (P = 0.049). Regarding the enzyme catalase (CAT), no significant changes in activity were observed between any of the eight sampling stages (P > 0.05 for all comparisons). The levels of malondialdehyde (MDA), as an index of lipid peroxidation, did not change significantly in response to the simulated boxing competition, curcumin supplementation, or their combination. Similarly, the serum concentration of hydrogen peroxide (H₂O₂) remained stable across all assessed stages (baseline, post-competition, post-supplementation, and recovery periods), with no significant statistical fluctuations recorded (P > 0.05 for all comparisons). In summary, the data indicated that neither the stimulus of the simulated boxing competition nor the curcumin supplementation intervention, according to the defined protocol, had a measurable impact on the serum profile of these oxidative and antioxidant markers in the studied population.
4. Conclusion
The findings of this study demonstrate that performing a simulated boxing competition using the applied protocol does not lead to a significant measurable disturbance in the serum oxidant-antioxidant balance of male professional boxers. Furthermore, short-term (7-day) and acute supplementation with 80 mg of nano-curcumin, under the conditions of this study, lacked considerable modulating effects on the levels of selected oxidative stress markers (MDA and H₂O₂) and the enzymatic antioxidant defense capacity (SOD and CAT). These results suggest that professional boxers experience strong and efficient physiological adaptations in their endogenous antioxidant system when subjected to repeated high-intensity activities, rendering a single challenge insufficient to disrupt this homeostasis. Additionally, the dose, duration, or bioavailability of the nano-curcumin formulation used may have been inadequate to induce detectable changes in the circulatory environment. The inconsistency of the results with some studies reporting positive effects of curcumin or intense exercise may be attributed to factors such as the athletes' fitness levels, the specific type and intensity of the exercise protocol, the timing of sampling, the dose and duration of supplementation, and the sensitivity of assessment methods. To further clarify the effect of curcumin, future studies should consider higher doses (e.g., 100-150 mg), longer supplementation periods (several weeks), assessment of concomitant inflammatory markers, and investigation of its effects in athletes with varying fitness levels or under training conditions with greater cumulative volume and intensity.
5. Acknowledgment & Funding
We thank and appreciate all the athletes who participated in this research. The present article is derived from a Master's thesis at Ferdowsi University of Mashhad.
6. Ethical Consideration
This study was approved by the Ethics Committee with the ethical code (IR.UM.REC.1401.201).
7. Authors' Contributions
All authors contributed to the article. All authors read and approved the final manuscript.
8. Conflict of Interest
The authors declare that there is no conflict of interest regarding this article.
