Abstract
Objective
Fluid consumption and maintenance of body mass is crucial to exercise performance, particularly during ultraendurance events. The current study aimed to assess body mass change and hydration status during an 80.5-km treadmill time trial (TT).
Methods
Ultrarunners were recruited to complete 80.5 km on a motorized treadmill within an artificial laboratory environment. Body mass (BM) was determined prior to, at 16.1-km intervals, and on completion of an 80.5-km TT using bioelectrical impedance analysis (BIA). Ad libitum fluid intake was permitted during the trial, and total fluid consumption and gastrointestinal (GI) symptoms were noted throughout.
Results
Total fluid intake was 3294.4 ± 1402.9 mL with an average consumption of 386.9 ± 212.2 mL/h. Prerunning BM (72.59 ± 8.48 kg) was reduced throughout the TT. Overall exercise-induced BM loss averaged 2.78 ± 0.94 kg with a 4.01 ± 1.35% decrease over time, although some retention of BM occurred in the latter stages of the TT. Ambient conditions were maintained throughout with no significant fluctuations in temperature (20.8° ± 0.2°C; P > .05) or humidity (35.7 ± 1.3%; P > .05). Average time to completion was 7 hours 28 minutes 9 seconds ± 1 hour 25 minutes 12 seconds at an average speed of 10.8 ± 1.5 km/h.
Conclusion
The current study indicates that participants were unable to maintain prerunning BM following the completion of an 80.5-km TT with an average BM loss of 4%. Consensus guidelines state to avoid BM losses of >3%; therefore this emphasizes the importance of optimal hydration strategies in ultraendurance running.