Wednesday Workout Tip: How much should I drink during exercise?
“How much should I drink during exercise to avoid dehydration?”
According to Tim Noakes, an exercise physiologist located in South Africa we should “drink according to the dictates of thirst. If you are thirsty, drink; if not, do not. All the rest is detail.”
Who is this Noakes fellow and how does he know so much about exercise, thirst and dehydration? Well, Noakes has conducted a number of studies to investigate the difference between dehydration and performance versus being thirsty and performance.
What’s the difference? Thirst is a protective mechanism that occurs (according to Noakes) prior to dehydration damage. According to Noakes’ “Central Governor” theory, the brain (a.k.a. the central governor) monitors signals from various parts of the body with the primary goal of reducing exercise intensity before the damaging effects of dehydration can occur. Our thirst signal could sound something like this, “Hey brain, we, the cells, are thirsty and need some H2O. If that isn’t available, could you get the body to slow down a couple of notches?”
Simply put, you won’t slow down until you feel thirsty, regardless of how much fluid you’ve actually lost. And we all have different thirst set-points. What does this mean? That there is variability in the level of water loss that individuals can withstand before the damaging effects of dehydration occur. Thus, two runners with the same water loss, but with different thirst set-points will vary in performance. If the runner with the lower thirst-set point does NOT have access to water to replenish, they will undoubtedly and unconsciously slow down.
The fastest finishers have been found to be the most dehydrated which proves Noakes theory – that dehydration doesn’t necessarily determine performance, but the feeling of thirst which, in turn, signals to the brain that the needs to slow down. And we will only feel thirsty, once we have surpassed our own thirst set-point.
Hutchinson, Alex. 2011. Which Comes First, Cardio or Weights? McClelland & Stewart: Toronto.