Purpose: This paper aimed to investigate the effects of upper-body high-intensity interval training (HIIT) on energy metabolism and maximal oxygen uptake (VO2max) in elite swimmers. Methods: A randomized controlled trial was conducted, in which elite swimmers were stratified and randomly assigned to either an upper-body HIIT group or an upper-body moderate-intensity continuous training (MICT) group. The HIIT group performed upper-body HIIT sessions lasting 60 min, including a warm-up, main workout, and cool-down at a 2:3:1 time ratio. The main workout consisted of circuit-based HIIT involving eight exercises, each performed for 20 s with 10 s of rest, totaling 230 s per circuit, with 3-min interset intervals, repeated for three sets. The MICT group followed a similar session structure except that the main workout involved eight continuous exercises performed for 60 s each with 20-s rest intervals and 20-s interset intervals and also repeated for three sets. Pre- and post-intervention assessments included upper-body cycle ergometry to evaluate the VO2 max and indices of energy metabolism. Repeated-measure ANOVA was used to analyze changes in VO2max and energy metabolism indicators. Results: Prior to the intervention, no significant differences in VO2max or energy metabolism indices between the two groups were noted. After 4 weeks of training, the HIIT group exhibited significant improvements in VO2max and energy metabolism parameters as assessed by upper-body ergometry (p < 0.05). By contrast, the MICT group showed no significant changes in these indicators (p > 0.05). A significant interaction effect was observed between time and group (p < 0.05). Conclusion: A 4-week program of upper-body HIIT significantly enhances energy metabolism and VO2 max in elite swimmers. These findings provide a theoretical basis for incorporating upper-body HIIT into the training regimens of competitive swimmers to optimize aerobic capacity and metabolic efficiency.
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