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:
Nine ultra-marathon trained runners (6 males, 3 females) 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 oz of water) and three trials with a hydration pack (0.5, 1.0 and 1.5 oz 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. Statistical analysis revealed a significant effect of water mass on CoT; every 1kg of added mass, CoT increased by 0.0516 J/kg/m, or 1.16% (p= .0145). Additionally, for every 1kg of added total mass, CoT increased by 0.04061 J/kg/m, or 0.9% (p= .0159). No significant effect between conditions was observed for commonly used hydration devices.
Conclusion:
The main findings from this study indicate that for every kg of water carried, irrespective of the container used, there is a 1.16% increase in CoT in horizontal level running, and when for every kg of total mass carried, that is: water mass plus the mass of the containers, there is a 0.9% increase in CoT in horizontal level running. This increase in CoT may slow an average-trained runner’s performance time for 100km distance between ~2.6 to 12.6 minutes when carrying between 0.25 L and 1.5 L of water, respectively. (This application is calculated based off of the 0.9% change due to the nature that water cannot be transported without one of the devices.)