Considerations in the Use of Body Mass Change to Estimate Change in Hydration Status During a 161-Kilometer Ultramarathon Running Competition In scientific literature and popular literature, they find indications of hydration that body mass losses of more than 2% should be avoided during the burden. In this work, we show that these guidelines are not applicable to longer loads of several hours, in which body mass loss does not reflect no equivalent loss of body water due to the impact of body mass change due to the substrate application, the release of the muscle-bound water and water. These impact on body mass loss required to maintain the body’s water balance are shown for a 161-km long ultramarathone, using data for total energy costs, exogenous energy consumption and percentage of any energy, the average body mass of the subscriber andUses the extent of the collection of soft tissue fluid during an ultramarathone. We assume that the total energy from proteins is between 5 and 10%. The entire exogenous energy is used to support the energy costs of the race. The glycogen consumption is between 300 and 500 g, the water associated with glycogen between 1 and 3 g per g of glycogen, and the mass of the bladder and the gastrointestinal tract is unchanged from the measurements before the race to measuring the body mass after the race.
These calculations show that an average participant of 68.8 kg must lose 1.9 to 5.0% body mass to maintain the water balance while avoiding excessive fluid intake at the same time. The whole work can be found under https://pubmed.ncbi.nlm.nih.gov/28895063/