How to stay hydrated during exercise?

glass of water

Leading in to some warmer weather the issue of hydration is definitely worth discussing, particularly for those of us who exercise regularly. Just last week I was chatting to someone I train about a triathlon she participated in on the weekend prior. We got on to the topic of heat and hydration which reminded her of an article she had recently read. I asked her to send it through and it prompted me immediately to write about hydration. The article tells the story of someone who ran a 10km event dehydrated in warm weather. In short, he collapsed and fell in to a coma. Fortunately he was revived but unfortunately he lost a leg. His body had overheated to the point that the muscles in the leg were 'cooked' beyond recovery. I have outlined some easy hydration guidelines in this article that will not only help you maintain your training performance in warmer weather but also avoid the dangerous consequences of over heating.

Water is lost during exercise by sweating - this is the body's cooling system. As sweat evaporates off the skin heat is lost from the body, and the body is cooled down (more about sweating here: Overcoming your fear of exercise (part 1): sweating & smelling). A number of factors influence the amount of sweat lost during exercise, these include:





sweating during exercise


• The intensity of exercise - as exercise intensity increases so does sweating.
• Ambient temperature and humidity - sweating increases as temperature and humidity increase.
• Body size - sweating typically increases as body size increases.
• Level of fitness - fitter people tend to start sweating earlier in exercise.
• Gender - men tend to sweat more then women.
• Genetics - some people just tend to sweat more then others.

If the fluid lost during exercise is not replaced dehydration will occur. Dehydration causes dramatic decreases in training and sports performance and if untreated can result in overheating, loss of consciousness and death. Some pre, during and post exercise general hydration guidelines are outlined below. The large variability between individuals makes it impossible to prescribe a 'one size fits all' hydration plan but these guidelines should be appropriate to get you started.

Pre-exercise hydration:

• Aim to start exercise well hydrated. Urine that is pale yellow in colour is a good indicator of this.
• Drink fluids frequently during the day, drink approximately 400-600ml of fluid in the 2-3 hours leading up to exercise and approximately 200-300ml of fluid in the 15-30min immediately before exercise.
• Weighing yourself before exercise will give you a good indicator of what your weight should return to following exercise to ensure adequate re-hydration.
• There is no performance benefit of being over hydrated before exercise. Being over-hydrated may even interfere with performance by causing bloating, gastrointestinal discomfort and toilet breaks.

During exercise hydration:

• Aim to replace as much lost fluid as possible during exercise. Find a rate that is comfortable for you, this will differ for everyone. Drinking too much too quickly could result in decreased performance  by causing bloating and gastrointestinal discomfort.
• Begin replacing fluid early in exercise. Thirst is not a good indicator of hydration, a significant amount of fluid will have already been lost by the time you start feeling thirsty.
• Drink approximately 200-300ml of fluid every 15mins during exercise, most people can tolerate this.
• Take every opportunity to drink during exercise, such as between exercise rounds, while transitioning between exercises and at set drink breaks.

Post-exercise hydration:

• Aim to replace all fluid lost during exercise. Sweating continues after exercise has ceased so this needs to be accounted for.
• Continue to drink approximately 200-300ml of fluid every 15mins following exercise until you are well hydrated, this can take 2-6 hours depending on the intensity and duration of exercise performed. Urine that is pale yellow in colour is a good indicator of being well re-hydrated. Returning to pre-exercise weight is also a good indicator.

Mizone sports drink

Water is suitable for low intensity and short duration bouts of exercise. Fluids containing electrolytes and carbohydrates such as sports drinks are ideally suited to high intensity and longer duration exercise sessions. Sports drinks provide faster hydration and replenishment of muscle glycogen stores. This can increase training and sport performance but also be counter productive for weight loss training programs. To help with weight control choose water as your main fluid unless you are participating in endurance or very high intensity sessions where sports drinks may be necessary to maintain hydration during exercise or rehydrate quickly after.

If you participate in endurance (60min or longer) bouts of exercise regularly I would recommend getting to know your approximate sweat rate during exercise and total fluid deficit after exercise. This can be used for more individualised fluid replacement planning.

Keep these hydration guidelines in mind as we head into the warmer months of the year. Staying well hydrated will ensure you continue to get the most out of your training sessions and avoid the health consequences of dehydration. More information about preventing dehydration here: 10 easy hydration tips.

Related articles: 10 easy hydration tips | Overcoming your fear of exercise (part 1): sweating & smelling | What should I eat after training?