The Hydration Debate

Robert W. Kenefick, PhD, FACSM, and Kurt Sollanek, PhD, CISSN, describe the current research on hydration strategies and provide practical applications for each method.
May 20, 2019

Hydration strategies used during exercise, training and competition seek to prevent over-/under-hydration and preserve performance, but it isn’t as simple as drinking throughout exercise.

Losing more than 2% of body mass through sweat is a sign of significant dehydration, and dehydration can increase the risk of heat illness and decrease performance by affecting muscle and cognitive function.1 The goal is to minimize dehydration and preserve performance.

Main Hydration Strategies

  • Programmed drinking: Pre-established drinking plan based on an individual’s sweat rate and sweat electrolyte content
  • Drink to thirst: Using the sensation of thirst as the only stimulus to drink

Key Takeaways

  • Fluid intake should approximate sweat loss to prevent significant dehydration (>2% body mass loss) or overhydration (body mass gain) during exercise
  • ~30-60gm carbohydrate per hour of exercise = ~0.5 – 1.0L per hour of a 6-8% carbohydrate solution.2,3,4

Practical Application

Programmed drinking is best for:

  • Longer duration activities greater than 90 min, particularly in the heat
  • Higher intensity exercise
  • Individuals with high sweat rates
  • Exercise where performance is a concern

Drink to thirst is best for:

  • Short duration activities less than 90 min
  • Exercise in cooler conditions
  • Lower intensity exercise

Determine sweat rate under conditions (exercise intensity, pace) and environments similar to anticipated competition environments. Tailor the programmed drinking plan to prevent greater than 2% body mass losses in athletes with high sweat rates or those concerned with exercise performance.

  1. Joint Position Statement: Nutrition and Athletic Performance. (2016). Medicine & Science in Sports & Exercise. 48:543-68.
  2. American College of Sports Medicine Position Stand. Exercise and Fluid Replacement. (2007). Medicine & Science in Sports & Exercise. 39(2):377-90.
  3. National Athletic Trainers’ Association Position Statement: Fluid Replacement for the Physically Active. (2017). Journal of Athletic Training. 52(9):877-95.
  4. Casa, Douglas. Proper Hydration for Distance Running Identifying Individual Fluid Needs, A USA Track & Field Advisory. (2004).