Now that we have had some time in the heat and humidity, this is a wise time to find your sweat rate. Sweat rate is unique to everyone and varies for each person based on several factors; such as, your level of training, the modality of workout you do and the temperature/humidity in which you exercise. Knowing your sweat rate for each discipline (swim, bike, run), in different temperatures and in different phases of training provides an understanding of what your specific hydration needs are. Knowing your unique hydration needs allows for improved hydration replacement during training and racing, resulting in better training sessions, optimal recovery and improved performance.
To start, find your sweat rate in the heat/humidity for either the bike or run. Ideally, you should find your sweat rate for each discipline (swim, bike and run) in both moderate temperatures (earlier in the season) and a hotter and more humid environment (summer), every year. This provides greater insight to your specific hydration needs. The more you know and understand your body, the better off you will be, both in and out of sport.
How to find your sweat rate:
- Pick one of your training sessions this week lasting 60-90 minutes.
- Before you exercise, empty the bladder and weigh yourself nude.
- Exercise. Record how much you drank during exercise (Do not pee during exercise, this will skew the results).
- Use a water bottle or clear cup in which you know how much it holds so you know how much you have consumed.
- After exercise, dry off your sweat and weigh yourself nude.
- Every pound of body weight lost during training equals 16 oz of sweat loss.
- Fluid consumed during the workout are sweat losses replaced, so add this back into the weight lost (you can skip this step by not consuming fluid during the exercise session; however, this is not recommended for training in a hot/humid environment).
- Divide the total amount of fluid lost by the number of hours trained to get fluid losses per hour.
- 60 minute run, moderate intensity, outside, 80 degrees, high humidity
- Weight before: 150 lbs
- Weight after: 148 lbs
- Fluid consumed: 8 ounces
- Weight loss: 150-148 = 2 lbs
- Convert to fluid loss: 2 lbs = 32 ounces
- Fluid consumed: 8 ounces
- Total fluid loss: 32 ounces lost + 8 ounces consumed = 40 ounces total
- Sweat rate/hour: 40 ounces fluid lost / 1 hour = 40 ounces / hour
It is difficult to fully replace what we lose in our training and racing, essentially impossible in long course events. Having a greater understanding of what our fluid losses are sets us up for greater success in our rehydration efforts, allowing us to lessen the gap between what we lose and what we replace. Fluid losses as little as 1% total body weight can negatively impact performance. The goal is to optimize performance in racing and make the most gains possible in training by hydrating appropriately.
Ryan, M. (2007). Sports nutrition for endurance athletes. Velopress.
Sims, S. T. (2016). Roar : how to match your food and fitness to your female physiology for optimum performance, great health, and a strong, lean body for life. Rodale.