Cost Of Transport In Ultra-runners Utilizing Hand Bottle Vs. Hydration Pack

Abstract

Over the last 10 years, ultra-marathon running events have become increasingly popular. For these longer distances, it is common for runners to carry hydration devices with them. How different water carrying devices impact cost of transport (CoT) during running is unknown. PURPOSE: To examine differences in CoT in trained ultrarunners utilizing two popular hydration devices filled with various amounts of water. METHODS: Six ultra-marathon trained runners (5 males, 1 female) participated in this study after obtaining informed consent . Each subject completed six 10 min running trials at 15% below their lactate threshold over two days: one baseline trial (no water), two trials with a hand bottle (0.25 and 0.5 kg of water) and three trials with a hydration pack (0.5, 1.0 and 1.5 kg of water) on their back. Each subject’s running trials were randomized utilizing a Latin Square design. For each trial, we analyzed VO2 (ml/kg/min) and RER to obtain 2 minutes of steady state data to calculate CoT (J/kg/m). We used a linear mixed model to analyze the effects of water mass and hydration device on CoT. RESULTS: We found a statistically significant effect of water mass on CoT: every 1 kg of additional water mass increases CoT by 0.09 J/kg/m (1.92 %, p=0.03), but hydration device had no significant effect on CoT (p=0.31) (see Figure 1). CONCLUSIONS: : Our preliminary findings indicate that CoT increases by 1.92% for every additional 1 kg of water mass carried. This increase in CoT could have significant negative effects on ultramarathon running performance.Figure 1: Cost of transport (CoT, J/kg/m) as a function of water mass (kg) carried. The regression line is calculated using a linear mixed model: each subject was classified as a random effect; water mass was classified as fixed-effect; and CoT as the outcome variable.