Staying hydrated is critical to your running performance and, more importantly, for preventing heat-related illnesses. Dehydration in athletes may lead to fatigue, headaches, decreased coordination, and muscle cramping. Other heat-related illnesses, such as heat exhaustion and heatstroke, have even more serious consequences. Runners need to pay attention to what and how much they’re drinking before, during and after exercise.
Before
Over-consumption of water in the days and hours before an event is a common mistake which, counter-intuitively, can leave you feeling parched at the start line. This is because the body senses the huge amount of liquid you’re suddenly downing and releases a diuretic hormone in an attempt to bring your fluid levels back to normal. In the short-term, this reactive offloading (your half hourly flights to the bathroom) can be over-compensatory, leaving you dehydrated at the worst possible time. The best thing to do is sip regularly before the race, if you start to get a ‘sloshing’ feeling in your stomach, you’ve drunk too much – but frequent small sips should help you avoid this.
Bear in mind that if you feel thirsty, you’re already dehydrated
The very real dangers of over-hydration have not been communicated effectively enough in the past. A recent study in the British Journal of Sports Medicine highlighted the case of a runner in the London marathon who collapsed and died, after crossing the finish line, due to exercise-associated hyponatremia (EAH) – caused by an increase in total body water leading to a low concentration of sodium in the blood. More common in cooler conditions, you’ll cut your EAH risk hugely by sipping on a sports drink containing sodium and electrolytes alongside plain water – and upping your salt intake in the days before a race (heart-health permitting) can also help.
During
The current advice about running and hydration is very simple — try to drink to thirst. Scientific evidence says that drinking when you’re thirsty can help prevent under hydrating (which can lead to dehydration ) and overhydrating, which can lead to hyponatremia (low blood salt level due to abnormal fluid retention).
If you’re looking for a general rule of thumb for fluid consumption during your runs: You should take in 113 – 170ml (equates to just over 1/3 to half of a 330 ml bottle) of fluid every 20 minutes during your runs. Runners running faster than 8-minute miles should drink 170 – 230ml (half to 2/3rds of a 330ml bottle) every 20 minutes. During longer workouts (90 minutes or more), some of your fluid intake should include a sports drink to replace lost sodium and other minerals (electrolytes). The carbohydrates and electrolytes in the sports drink also help you absorb the fluids faster.
Take full advantage of every drinks station, but don’t chug back the whole bottle, take some swigs, see how it feels on your stomach, and think about how much you’re sweating.
After
Replacing lost fluid and electrolytes immediately post-run is crucial for lessening debilitating stiffness and muscle pain – and it’ll also reduce the risk of your weakened body being struck down by illness. To help muscle atrophy, you need protein in a huge way so you’re not walking like John Wayne for the next seven days. The best ratio is three parts carbohydrates to one part protein.
Research from the University of Bangor found downing a good recovery drink immediately after exercise maintains your immune function at its pre-exercise levels. Waiting an hour or downing a carbs-only beverage, on the other hand, can leave it severely compromised.
Don’t forget to rehydrate with water or a sports drink after your run. You should drink 20 to 24 fl oz. of water for every pound lost. If your urine is dark yellow after your run, you need to keep rehydrating. It should be a light lemonade colour.