In the swim with Bamorganic Ambassador Molly Renshaw
Molly is a professional swimmer, currently living and training in Loughborough at the National Centre run by British Swimming. Molly’s […]
Hydrating for endurance exercise
Although it isn’t a lab-developed, glossy-packaged sports supplement, good old H2O is nevertheless critical for performance. Water is used in digestion (gastric secretions), waste disposal (urine), heat dissipation (sweat) and nutrient transportation to and from cells (blood). Without sufficient levels of water, the everyday functions of your body will be compromised, fatigue will begin to develop, and performance will ultimately decline .
Although this summer may not have been the it’s-coming-home heatwave of last year, if you’ve exercised outside over the summer months you have probably noticed an increase in the amount you’ve sweated. The average person can lose 0.8-1.4L of fluid per hour of exercise through sweat (and even more lost as water vapour in your breath). Dehydration in exercise is commonly defined as losing >2% of your bodyweight in fluids (e.g. an 80kg person losing over 1.6L) without replacement of those fluids . Your sweat rate is also greatly affected by other factors such as clothing, temperature, humidity, body mass, wind and peripheral blood flow . The best starting point to prevent the onset of dehydration is to ensure that you are well hydrated before you even begin a workout.
The maximum gastric-emptying rate of your stomach is around 1000-1300ml/hour . In simple terms, this is how much fluid your stomach can effectively deal with per hour. Exceeding this will result in excess fluid sloshing around in your stomach and can lead to gastrointestinal discomfort. You should be able to handle workouts of up to an hour without a strict hydration strategy, providing you are well hydrated to begin with. For workouts lasting beyond the sixty-minute mark, consider implementing a hydration routine to prevent premature fatigue. A meta-analysis by Holland et al (2017) concluded that for moderate continuous exercise lasting 1-2hrs, aiming to consume 0.15-0.2ml/kg body mass/minute can see performance improvements of 2% . If you are liable to forgetting when to drink you should consider setting alarms on your watch or designating landmarks along the route as “drink points”. Temperature will affect how often you will need to drink too. You will find yourself drinking more on hot days and less on cold ones. Listen to your body, if you feel thirsty then take a drink – simple!
Everyone is different, and it is worth experimenting with what hydration strategy works best for you. Just ensure you are replacing lost electrolytes during workouts longer than 60 minutes to offset premature fatigue.