How to rehydrate for athletes
Time to read: ~5mins
As an athlete your goal, when finished a training session/match, is to prepare for the next training session or game.
Your priorities should be as follows:
- Rehydrate
- Replenish
- Rebuild
In this article, we focus on rehydration.
When we exercise, to cope with the rise in temperature from physical work, our body loses heat through many ways, a major component of heat loss is sweating. Sweat is not just water, there are essential minerals that aid muscle function. These electrolytes are sodium, chloride and potassium. When acute fluid losses occur, an electrolyte imbalance is likely to occur (more lost than replaced), the principal electrolyte lost in sweat is sodium. [1, 2]
In healthy people, everyday hydration is regulated and balanced between thirst and urine losses. However, under conditions of stress (i.e. exercise) thirst may not be a sufficient prompt for maintaining fluid balance [3].
Why is rehydration taking priority over carb (replenish)/protein (rebuild) intake?
With progressive dehydration, as we experience in team sports where access to fluids is limited during training/match play, there’s a high level of fluid loss [4].
We lose fluid from both within (intracellular) and outside (extracellular) cells. Loss of fluid within the cells may impact our capacity to recover, reduced intracellular volume reduces rates of glycogen (carbohydrate) and protein synthesis (think of this as part of the replenishment/rebuild process).
How to rehydrate?
Even after you finish training or a match, you’ll continue to lose fluids, some due to the continued sweat loss but principally from urine losses. Successful rehydration is replacing the fluid loss associated with both exercise and urine losses.
It is important to start consuming small amounts of fluid as soon as possible after training, plan ahead & avoid drinking rapidly to avoid stimulating excessive urine production (as not all fluid is retained).
What helps us rehydrate?
The main factors that drive effective rehydration are the volume and contents of the fluid consumed. Optimal rehydration is only achieved when sodium, lost in sweat, is replaced as well as the fluid.
Water alone is not ideal to rehydrate, in particular, if rapid and complete rehydration is needed and when intake is fluids alone (multi-game tournament or back to back training etc).
Plasma, the fluid our blood cells are suspended in, is quicker and better restored if sodium chloride (salt) is added (0.45g/L) to the water consumed [5].
Sodium promotes quicker fluid absorption in the small intestine and allows the plasma sodium concentration to remain elevated when rehydrating; this helps maintain thirst and delays urination (fluid loss) [6]. Don’t forget that you will consume salt through your meals too.
The rehydration drink should also contain carbohydrate as this stimulates fluid absorption in the gut and improves taste.
Conclusion
150% of the weight lost (which is predominantly fluid), is needed to achieve complete rehydration over 6 hours after exercise [6-8].
Therefore, if you really wanted to be precise with your rehydration tactic; measure your body weight before and after your exercise (training/match) and multiply the loss of body mass by 1500 (ml) or 1.5 (L) to see how much fluid you should consume in the following 6 hours.
For example; After an intense match, I lost 2kg and need to consume 3000ml (3L) of fluids over 6 hours (500ml/hr).
I also made this handy calculator for use
Take-home:
Rehydration is of primary importance within the recovery process, rehydrate with an appropriate amount of fluid /sodium and complete rehydration over the course of ~6 hours.
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