DarrylH wrote:Re the previous mention of hyponatremia in Pedal Power magazine, my interpretation was that they drank too much water, rather than getting too little salt - 10 L of water over that distance is a LOT. Any medicos care to comment?
I think it's a balancing act.
The amount of water consumed should be dependent up on the environment, and nature of the amount being sweated. Ideally you should be approx replacing the amount of sweat with water + sodium. Yes they drank a lot of water but that probably wouldn't have been a problem if they'd been replacing salt as well. 10L seems like a lot, but depends on how much the sweat and how long they were out there.
Good article:
http://www.uni.edu/dolgener/Advanced_Sp ... intake.pdf
Fluid and fuel intake during exercise
EDWARD F. COYLE
The Human Performance Laboratory, Department of Kinesiology and Health Education, The University of Texas at
Austin, Austin, TX 78712, USA
Accepted 7 August 2003
The amounts of water, carbohydrate and salt that athletes are advised to ingest during exercise are based upon
their effectiveness in attenuating both fatigue as well as illness due to hyperthermia, dehydration or
hyperhydration. When possible, fluid should be ingested at rates that most closely match sweating rate. When
that is not possible or practical or sufficiently ergogenic, some athletes might tolerate body water losses
amounting to 2% of body weight without significant risk to physical well-being or performance when the
environment is cold (e.g. 5–108C) or temperate (e.g. 21–228C). However, when exercising in a hot environment
( >30C), dehydration by 2% of body weight impairs absolute power production and predisposes individuals to
heat injury. Fluid should not be ingested at rates in excess of sweating rate and thus body water and weight
should not increase during exercise. Fatigue can be reduced by adding carbohydrate to the fluids consumed so
that 30–60 g of rapidly absorbed carbohydrate are ingested throughout each hour of an athletic event.
Furthermore, sodium should be included in fluids consumed during exercise lasting longer than 2 h or by
individuals during any event that stimulates heavy sodium loss (more than 3–4 g of sodium). Athletes do not
benefit by ingesting glycerol, amino acids or alleged precursors of neurotransmitter. Ingestion of other
substances during exercise, with the possible exception of caffeine, is discouraged. Athletes will benefit the most
by tailoring their individual needs for water, carbohydrate and salt to the specific challenges of their sport,
especially considering the environment’s impact on sweating and heat stress.
Keywords: carbohydrate, dehydration, fatigue, gastrointestinal function, hyperthermia, sodium.