-Melanie Battaglia, MS, RDN, LDN

Athletes at all levels are typically looking for ways to improve performance. For endurance athletes, one of the most common culprits of fatigue is dehydration. Everyone has different hydration needs, which depend on the type/intensity/duration of exercise, environment, opportunities to drink, and the athlete’s sweat rate. However, for all endurance athletes, it is recommended to minimize dehydration to less than 2 – 3% of your body weight to prevent dehydration related fatigue.

Maintaining hydration during exercise impacts performance:

  • Decreased thirst sensation
  • Reduced cardiovascular and thermal stress
  • Lower perceived exertion
  • Improved blood flow to muscles
  • Reduced lactate accumulation

A recent meta-analysis in the Journal of Sports Medicine explored different rates of hydration during endurance cycling performance. This article discussed how much to drink depending on the length of cycling exercise. According to this article, fluid intake during 1 hour of high-intensity cycling reduced power output by 2.5%, which indicated decreased performance. One explanation for this decreased performance could be gastrointestinal distress from drinking fluids too fast. This was an interesting result; however, it is important to note that further research is needed to explain this result and fluid intake during 1 hour of cycling may not be detrimental to all athletes.

Fluid intake during 1-2 hours and 2-3+ hours of moderate-intensity cycling had performance improvements of 2-3% and hydration needs were maintained.

Below are the hydration recommendations (ounces/ hour) for cycling performance based on this study.

Ounces of fluid needed during moderate-intensity cycling 1 – 2 hours: 0.30 – 0.40 oz per kg body mass per hour (multiply 0.30 or 0.40 x kg body weight x hours)

Ounces of fluid needed during moderate-intensity cycling 2 – 3+ hours: 0.30 – 0.50 oz per kg body mass per hour (multiply 0.30 or 0.50 x kg body weight x hours)

So for example, if you weigh 68 kg, the formula would be : 0.4 oz x 68 kg x 2 hrs = 57.4 ounces over 2 hours

Having a hydration plan during workouts is a way to improve performance. Practicing this plan throughout the season will prepare you for race day. When creating your hydration plan, don’t forget that you do sweat while swimming, although you may not notice it! In order to create a hydration plan, first calculate your sweat rate. To find out your sweat rate, use the calculations or provided sweat rate calculator below:

During exercise measure:

  • Starting weight (lbs)
  • Ending weight (lbs)
  • Exercise duration (hrs)
  • Fluid consumed (oz)


  1. Fluid consumed (oz per hr) = Fluid ounces consumed/ Exercise duration
  2. Sweat rate (oz per hour) = ((Starting weight – Ending weight) x 16) + Fluid ounces consumed / Exercise duration)
  3. Sweat rate (L per hour) = Sweat rate x 29.574/1000
  4. % Body weight lost = (Ending weight – Starting weight)/ Starting weight


  1. Holland JJ, Skinner TL, Irwin CG, Leveritt MD, Goulet EDB. The influence of drinking fluid on endurance cycling performance: A meta-analysis.Sports Med. 2017;47(11):2269-2284.
  2. Sawka MN, Noakes TD. Does dehydration impair exercise performance?Med Sci Sports Exerc. 2007;39(8):1209-1217.
  3. Jeukendrup AE. Nutrition for endurance sports: Marathon, triathlon, and road cycling. J Sports Sci. 2011;29 Suppl 1:S91-9.

**Melanie is a Registered Dietitian Nutritionist and a member of the Well-Fit Elite Program.