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Abstract

New sports supplements with high amounts of sodium have started showing up on the market; thus, research examining how large-dose sodium intake affects cycling performance is necessary. PURPOSE: To evaluate the effect of a high dose of sodium on hydration measures during a 2-hour cycling bout in a hot (30°C) and humid (60% relative humidity) environment. METHODS: Nine recreationally active participants (6 males, 3 females; age = 22.22 ± 1.99yrs; weight = 79.93 ± 18.78 kg) completed 2-hours of cycling in an environmental chamber on two separate occasions with at least one week between trials. Participants were instructed to maintain their heart rate (HR) between 55-65% of their heart rate reserve (HRR). Participants were randomly given a large-dose sodium supplement (810mg sodium/serving) before one trial. After mixing the supplement in 532ml of water, participants drank 266ml 1 hour pre-trial; consuming the remainder within the first hour of cycling. Pre- and post-cycling urine samples and body mass measurements were collected to determine acute hydration status. Any urine following the pre- sample was collected in a urine volume container. Fluid intake was recorded every 30 minutes during cycling. At 120-minutes, participants completed a 2.5-minute cooldown and were instructed to remove wet clothing and towel off excess sweat before body mass was measured. Repeated measures ANOVA were used to analyze differences between condition and time. Descriptive statistics (mean ± standard deviation) were calculated for all data. Significance level was set at p<05. RESULTS: For all time points and between conditions, there were no significant differences found for urine specifc gravity (Usg) or body mass pre- to post-cycling (p>0.05). Pre-cycling averages for Usg were 1.018 ± 0.009 (supplement group) and 1.013±0.004 (control). Post-cycling averages for Usg were 1.019 ± 0.009 (supplement group) and 1.024 ± 0.029 (control). CONCLUSION: Large doses of sodium do not appear to significantly impact hydration status, as compared to the non-supplement trial. Although not significant, participants in the control group appeared to undergo further dehydration while the supplement group appears to maintain their hydration status, as evidenced by the minimal change in Usg pre-post.

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