Performance, hydration status, urinary biomarkers, and cardiovascular response during a repeated short-distance swimrun race
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Abstract
Objective: This study aimed to evaluate the performance, hydration status, urinary biomarkers, and heart rate during a repeated short distance swimrun composed of four continuous rounds of swimming and running. Method: This was a descriptive, observational, and repeated-measures study. The sample was convenience-based, comprising 20 adult recreational athletes. The swimrun consisted of laps, completing 1200 m of swimming followed by 6 km of running (i.e., 4 × [300 m swim + 1.5 km run]). Urinary variables were assessed with reagent strips before and immediately after the event, and heart rate was monitored continuously and expressed in absolute terms and as a percentage of age-predicted maximal heart rate. Effect sizes are reported with 95% confidence intervals (CI). Results: A significant increase in urinary protein and a significant decrease in urinary pH were observed, both with large effect sizes (protein: p = .014, r = .85; pH: p = .014, r = −.85). Women showed consistently higher heart rates, especially in 2nd and 3rd lap (g = −0.86), though these differences were not statistically significant (p > .05); in swimming, women showed significantly higher heart rates in the 2nd and 3rd laps (g = −1.62 and −1.14; p = .010 and .046) and higher relative intensity throughout (80.6 vs 69.2 % HRmax in swimming and 93.2 vs 85.6 % HRmax in running). Strong inter-lap HR correlations were found, especially between run 2nd and 3rd laps (r = .87) and run 1st and 2nd laps (r = .82). Age and weight showed moderate negative correlations with heart rate. Conclusions: Overall, repeated short distance swimrun challenges elicit measurable yet moderate physiological stress in recreational athletes, with implications for hydration strategies, performance pacing, and individual monitoring during multisport events. Given the small convenience sample, and particularly the subgroup of seven women, the sex-related comparisons should be regarded as exploratory and hypothesis-generating rather than confirmatory.
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European Social Fund Plus
Grant numbers grant number: PO_24148
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