So, how’d your workout go? Did you get hot? How did you perform? Did you get thirsty?
During exercise, your body will dispel heat five different ways: radiation, conduction, convection, evaporation, and excretion. Evaporation is the transfer of heat when liquids change physical states, becoming a gas, a process that requires energy to vaporize the liquid.
Sweating can occur in the first 3 minutes of exercise (and plateaus within the first half hour). Thirst is triggered when you are just 1% dehydrated. At 2%, your performance will be negatively impacted, since muscles are comprised of 85% water (fat only 15%). Dehydration is affected by body size, gender, environment, exercise intensity and your conditioning status.
If you get too hot, you could experience heat stress and be at risk for heat cramps, exhaustion, syncope, and even stroke.
This relates to the other important physiological change during physical exertion: the redistribution of your blood supply. For example, at rest your muscles will get approximately 15-20% of available blood supply, while during exercise they get 70-85%. Where does the blood come from? Interestingly, blood supply comes from other areas of your body, including the brain where blood supply goes from 14-15% to 3-4%.
How much should you drink, what, and when? Here are some guidelines:
- 24 hours prior to exercise/event: consume water in an obligatory approach
- 2-3 hours prior to exercise/event: consume 17-20 ounces of water
- 10-20 minutes prior to exercise/even: consume 7-10 ounces of glucose-electrolyte solution (only during the warm up phase; 4-8% carbohydrate solution is ideal).
- During exercise:
- Events lasting < 60 minutes = water
- Events lasting 60-90 minutes = low carb ratio solution (i.e. Propel 1.3%)
- Events lasting 90-120 minutes = 4% to 8% carb ratio solution (i.e. Gatorade 5.9%)
- Events lasting > 2 Hours = add BCAA’s (branch-chain amino acids)
Post exercise/event, replenish those precious fluids that you have lost!
Post exercise/event, replenish those precious fluids that you have lost! Water is not an effective hydrator, but glucose-electrolyte solutions are. Plus, they quench your thirst. So, replace lost fluids at 100-125% of body weight lost.
On your mark, get set, go!