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Nail your swimming hydration strategy


How do triathletes determine how much hydration to take in during indoor workouts? While it’s easy to go by feel, not all indoor training is the same. Riding or running gives you a better sense of whether you’re dehydrated than swimming does.

Many triathletes aren’t aware of their hydration levels in the water. Pools are hot and humid and a full-body workout like swimming easily causes sweating. Swimmers often forget to bring a water bottle to the pool because unlike in cycling and running, sometimes it’s hard to tell if you’re sweating or dehydrated. This winter, as you build up your base training in the water, follow these hydration tips to make sure you can perform at your best.

Triathlete Sheri Lehmer swims underwater in pool at Juniper Swim and Fitness Center in Bend, Oregon

How does does dehydration affect swimming?

As with all sports, dehydration causes your performance to suffer. Muscles weaken, fatigue sets it and breathing rate increases. Proper hydration during training and racing is important not only for safety, but for fast recovery so that you can stay on track and reach your goals.

When should you hydrate?

Proper hydration begins before the workout. Triathletes should start drinking water two hours prior to their swim to avoid going into a session already dehydrated. Caffeine and high-protein foods can lead to dehydration. If you swim mid-day, be aware of what you’ve already consumed so you can go into your workout properly hydrated.

How much hydration is enough?

The amount of water you need to consume on a daily basis without physical activity is roughly half your bodyweight, in ounces (for example, a 150-pound person should be consuming around 75 ounces of water). This amount increases depending on your level of activity. In general, swimmers should consume around eight ounces of fluids every 20 minutes of their workout.

The numbers

For those who like numbers, did you know that there’s a sweat rate to calculate how much to drink while training indoors?

Here’s the formula: (A + B) / C = Sweat Rate.

– A equals how much weight you lost, in ounces, during a workout (1lbs = 16oz)

– B is how much fluid you consumed during the workout, in ounces (1 cup = 8oz)

– C is how long the workout lasted, in hours.

For example, if you did a 1.5 hour swim, and drank 700 ml of water (700 ml = 23.7oz). Your pre-swim weight was 152lbs and post-swim it was 151.6lbs (.4lbs lost = 6.4oz lost), this is the formula: (6.4 + 23.7) / 1.5 hrs = 20.1 oz of sweat lost per hour during your workout. In this example, you should drink 20.1 oz of water per hour during your workout.

This formula is helpful for all workouts, but even more so when swimming because the temperature and environment is consistent.