Most of us know that dehydration is, together with injuriesspecialty enemies of performance. But are we really aware of the extent to which this physiological phenomenon affects our athletic abilities?
How does dehydration affect performance?
Research of Subudi et al., (2013) thoroughly delves into all the implications and consequences of a state of dehydration. The study highlights the importance of maintaining an adequate state of hydration, given that “people can adapt to working in a hot environment and improve their ability to thermoregulate and conserve fluids, but they cannot adapt to dehydration“.
As the authors point out, a acute dehydration may reduce physical performance as well as thermoregulatory ability and increase the risk of heat illness. In turn, chronic dehydration may reduce metabolic and thermoregulatory efficiency and increase susceptibility to kidney disease.
The study, led by Andrew Subudi, a researcher at the University of Colorado, shows progressive physiological effects of dehydration on physical performance and pathophysiology of hypohydration.
As we can see in the following adaptation posted by Antelm Pujol, a doctor and broadcaster, on Twitter, a dehydration of 2% would already result in a drop in yield close to approximately 10%.
If we get to a 3% dehydration we are approaching one yield loss of almost 20%, what is considered a “critical decline”.
In the event that the rate continues to increase and we go to 4-6% dehydrationswe can stand up headache, irritability, lack of concentration and even a severe disturbance of thermoregulation.
Above these values, the consequences are much more serious: mental confusion, delirium, impending collapse, heart failure, kidney failure, or even death.
How can we ensure adequate hydration?
Although “the onset, extent and severity depend on the individual’s workload, fitness level, ambient temperature, relative humidity and degree of heat build-up”, the consequences are highly individual, the best way to avoid any problem is to ensure proper hydration.
To do this, American College of Sports Medicinein its position paper Exercise and Fluid Replacement Support (1996), recommends:
- A nutritionally balanced diet and adequate fluid intake in the 24-hour period before the eventespecially during the period that includes the pre-workout meal.
- Drink approximately 500 ml of fluid approximately 2 hours before training.
- During exercise, start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all water lost through sweat, or consume as much as you can tolerate.
- During exercise lasting less than 1 hour, there is little evidence of physiological or physical differences in performance between consumption of a carbohydrate-electrolyte drink and plain water.
- It is recommended inclusion of sodium (0.5-0.7 g per liter of water) in the rehydration solution taken during exercise lasting more than 1 hour. This can be useful for improve palatability, promote fluid retention, and possibly prevent hyponatremia in certain individuals who drink excessive amounts of fluids.
Subudhi et al. point out that “the simplest insurance against dehydration is to consume fluids before and during physical activity or heat exposure to compensate for water loss“.
While it is true that the amount of fluid required to achieve a favorable hydration status varies among individuals, the ideal is always to drink frequently, even in the absence of thirst. “Excessive fluid intake is rarely a problem“, the experts note.
water is not everything
As we can see, water isn’t everything when it comes to hydration. But we must also take into account the use of mineral salts and electrolytes. Sodium or potassium is essential.
A 2015 study conducted by Maughan et al. aims to evaluate the potential of different beverages in a state of hydration. To do this, the study examined the effects of 13 different commonly consumed beverages on urine output and fluid balance when consumed in a euhydrated state (“normal” body water content) to establish a beverage hydration index in compared to still water.
The study found that the drinks with the highest hydration index were a solution of oral rehydration (Dioralyte)whole and skimmed milk. They also found a “moderate effect” in orange juice.
In addition, the researchers looked at electrolyte balance, finding that several drinks had a higher sodium or potassium balance than still water 2 hours after consumption. Casually, “beverages with a positive sodium or potassium balance tend to be those with the highest hydration index“.
While oral rehydration solution has a positive sodium balance, orange juice and whole and skim milk have a positive potassium balance.
What about caffeine?
For a long time there has been a debate about the diuretic effects of caffeine: causes the kidneys to produce more urine, helping the body to eliminate excess fluid and salt, and can cause dehydration.
However, Maughan’s study notes that no effect of moderate caffeine intake (96-212 mg) on net fluid balance was observedwhich may mean that within these ranges caffeine is safe in terms of dehydration.