Because the symptoms of mild dehydration are subtle – often imperceptible – athletes are suffering the consequences of mild dehydration without knowing it.

Consequences of Dehydration

ARE YOU AT YOUR BEST?

Studies show that up to 87% of endurance athletes are physically impaired during their workouts and competitions due to dehydration, despite ample access to fluids. Dehydration causes the following physiological phenomena:

  • Decreased blood pressure
  • Increased heart rate
  • Increased respiratory rate
  • Decreased blood flow to extremities

These physiological changes can lead to cardio-respiratory stress, impaired thermoregulation, and fatigue – all of which have a significant impact on athletic performance.

Because the symptoms of mild dehydration are subtle – often imperceptible – athletes suffer the consequences without always knowing it.

FINISH STRONG OR STRUGGLE?

Proper hydration is central to feeling energized and motivated. Fatigue and physiological strain manifest at dehydration levels as low as 2%, making a workout feel sluggish and heavy-legged. This not only leads to an athlete feeling flat and listless, but also compromises the quality of the workout and training potential.

Studies show a significant drop in performance at mild dehydration levels as low as 2-3%. This impairment manifests itself in multiple ways.

 

  • Endurance

    For endurance athletes, dehydration causes the heart to work harder and decreases an athletes VO2max —the maximum oxygen uptake. This causes oxygen depletion in the muscles and, therefore, suboptimal endurance.

  • Strength

    Electrolyte depletion often occurs with dehydration. Electrolytes such as calcium, chloride, magnesium, phosphorous, potassium and sodium carry an ionic charge and support muscle function. When electrolytes are depleted, it results in muscle weakness and potentially contributes to cramping.

  • Cognitive

    Low body water and electrolyte levels compromise the transmission of nerve impulses in the brain, and between the brain and the muscles. Impaired neuromuscular signaling leads to delayed response times, poor judgment, mental confusion, and fatigue.

*Sources: Armstrong 1985; Pinchan 1988; Maughn 1991; Sawka 1990; Sawka 1985; Sawka 1992; Del Coso et al, 2013

Performance Impairments

How does dehydration affect your marathon?

FINISH

Fully Hydrated 4:30

MILE 26

1% Dehydrated 4:34

MILE 25

2% Dehydrated 4:43

MILE 24

MILE 23

3% Dehydrated 5:09

MILE 23

4% Dehydrated 5:10
“Calculations are based on being fully hydrated for the first half of a marathon and incurring the impairment during the second half. If you were 2% dehydrated for the the second half of a marathon, you would run the equivalent of an additional 1.3 miles. If you were 3% dehydrated for the the second half of a marathon, you would run the equivalent of an additional 3.2 miles.”