The Effects of a High Carbohydrate Diet Combined with High Molecular Weight Carbohydrate Supplementation on Anaerobic Performance and Oxidative Stress in Elite Swimmers

<b>Background/Objectives</b>:Training periodization is fundamental to optimizing athletic performance, with carbohydrate metabolism playing a critical role in supporting high-intensity efforts by facilitating muscle glycogen resynthesis. Recent studies suggest that high carbohydrate diets and high molecular weight carbohydrate (HMWC) supplementation can improve both endurance and anaerobic performance, while potentially influencing oxidative stress. This study investigates the effects of a high carbohydrate diet combined with HMWC supplementation on anaerobic performance and oxidative stress markers in elite swimmers. <b>Methods</b>: Eight national-level swimmers (tier 3-4) completed a three-day training microcycle with dietary interventions. Anaerobic capacity was assessed using Wingate tests for upper and lower limbs, while swimming performance was evaluated through an 8 × 100 m exercise protocol. The study was conducted using a one group quasi-experimental design with a pre-test/post-test structure, with participants acting as their own controls. Baseline measurements were taken prior to the intervention, followed by the administration of the high carbohydrate diet and HMWC supplementation. Post-intervention assessments were performed using the same test protocols to assess changes in performance and oxidative stress markers (such as GSH, CK, MDA, FRAP), which were determined by ELISA. The samples were stored at -80 °C until the evaluations. STATISTICA 5.0 (StatSoft, Inc., 1995) was used for statistical analysis of the obtained results. <b>Results</b>: The obtained results demonstrated significant improvements in peak power output for the lower limbs following supplementation (<i>p</i> < 0.001) and a reduced time to peak power for the upper limbs (<i>p</i> < 0.001). Additionally, velocity during the final swimming segments increased significantly following the intervention (<i>p</i> < 0.001). However, no notable changes were observed in antioxidant enzyme activity (SOD, CAT, GPx, GR) or low molecular weight antioxidants, suggesting a potential ceiling effect in redox adaptations. Lipid peroxidation, measured by MDA levels, increased post-supplementation (<i>p</i> < 0.05), indicating oxidative stress associated with high-intensity training and supplementation. <b>Conclusions</b>: The findings underscore the efficacy of combined dietary strategies with HMWC in enhancing anaerobic performance in swimming, while highlighting the necessity for further exploration of oxidative stress dynamics.