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This summary is from the IAAF 2nd International Consensus Conference on “Nutrition for Athletics“ held in Monaco from April 18-20, 2007. Copies of the CD and booklet are available from the IAAF website www.iaaf.org.
Fluid Needs for Training and Competition in Athletics
Presenter: Susan Sherriffs (GBR)
Hydration status affects performance. Different events have different fluid needs. General guidelines for all events are to ensure euhydration by consuming about 500ml of fluid with sodium or sodium containing foods 2 hours before exercise. In the hours after exercise, 150% of the water lost should be provided to adequately re-hydrate. A scale can be used to estimate sweat losses. Competition hydration plans should be practiced during training.
The main concern in the sprint events is that warm-up and pre-race activities might result in a sub-optimal hydration status. Also, training in a warm environment or wearing heavy clothing can result in dehydration. There might be some advantage in commencing a race somewhat dehydrated, since this can positively influence power-to-weight ratio. However, no more than 2-3% of body weight should be lost. A higher degree of dehydration will negatively impact performance.
Middle- and long-distance runners should always start their training and races euhydrated. For runs longer than 10km, there is a rationale for consuming fluids during exercise. Drinks should not have high energy density or osmolality. General guidelines for the amount of fluid replacement will be meaningless, since individual sweat rate and sweat sodium content vary greatly.
In the jumping events, no clear effect of mild dehydration has been found. If hypo-hydration does not reduce muscle force production or power then it may improve jumping performance. However, systematic research is required for confirmation.
There is no rationale for throwers to commence their competition hypo-hydrated. Studies show that accuracy, but not speed, of cricket bowlers was worse after dehydration. Throwers should aim to stay euhydrated, but beware not to over-drink during the long hours on the track.
Combined event athletes should aim to start their competition euhydrated and try to keep within 2% body weight loss during the day. Fluid can be ingested between attempts or between events. Athletes should beware not to over-drink, so that body weight is gained during the day. Sodium should be ingested in the form of sodium containing fluids or in the form of sodium containing foods. Recovery of body water lost during the first day of a combined event competition may be one of the recovery priorities for many of these athletes.
The above summary was written by Peter Res
If you wish to download this handy Grams and Calorie Calculator for Carbohydrate, Protein, and Fat, click here for the Excel spreadsheet.
This is part 9 of 14 in a series from the 2007 2nd IAAF International Consensus Conference “Nutrition for Athletics”