Story by Ian McMahan | Photo by Jeff Glaspy

It’s long been believed that muscle cramping during training and racing is brought about by either dehydration or electrolyte deficiency. However, while depletion of some electrolytes – primarily sodium – have been linked to a less common form of muscle cramping called heat cramps, the majority of scientific evidence points to a different cause – muscular fatigue.

Simply put, when muscles get very tired, they often respond by cramping. The problem is, as any triathlete knows, fatigue is the inescapable by-product of hard exercise and is difficult to avoid. So how do you prevent muscle fatigue from boiling over into muscle cramps? Well, research on the subject shows that many modifiable factors are associated with cramping in long distance endurance athletes, offering the possibility that mindful preparation and racing can reduce the chance of cramping during or after the race.

Despite the evidence that hydration and electrolyte balance do not influence susceptibility to the majority of fatigue-related muscle cramping, it is still important to stay hydrated and in electrolyte balance. When electrolytes are the problem, sodium related cramping is the more common variety and is all the more likely in “salty sweaters” – you might be one if your jersey/shirt is caked with salt after a workout.

Avoiding Muscle Fatigue Cramping

  • Occurs in working/fatigued muscles and is usually one-sided
  • Use a pre-race taper – cramping was more common in those athletes that did not use a taper
  • Don’t train hard right up until race day – more training equals less recovery, leaving muscles tired for race day
  • Start slow – going too hard early in the race leads to greater fatigue
  • Stay healthy – cramping is more common in those that suffered an injury right before the race
  • Race your pace – trying to compete at a pace that is faster than normal will get muscles tired at the end of a race
  • Be short – inexplicably, in one study of Ironman distance triathletes, taller athletes were more likely to cramp
  • Alternate positions on the bike to make slight changes in muscle use
  • Usually can be relieved by stretching the affected muscle

Avoiding Low Sodium Cramping/Heat Cramps

  • Can occur in any muscle, even those that haven’t been actively working
  • Usually preceded by muscle twitching
  • At the first indication of heat cramps, a prompt high-salt mixture (e.g., 0.5 L of a carbohydrate-electrolyte drink, with 3.0 g of salt added and thoroughly mixed, consumed all at once or over 5-10 min) has been a proven effective strategy
  • Cannot be relieved by stretching
  • Potassium-rich supplements, foods or other mineral supplements will not offer any protection against exertional heat cramping
  • Even though staying hydrated may not protect against cramping, triathletes should attempt to minimize dehydration and limit body weight losses through sweating to 2–3% of body weight
  • To avoid hyponatremia during longer races make sure fluids are replaced with a mixture of water and electrolyte replacement
  • Calculate your sweat rate
  1. Measure body weight before a one-hour moderate intensity bike or run.
  2. After the workout is completed record the amount of liquid consumed and again re-measure body weight.
  3. Determine the amount of weight change, adding in the amount of liquid consumed during the workout (e.g. pre-workout 170 lb. – post-workout 168 lb. = 2 lb. + 16 oz./1lb. of fluid consumed during workout = 3 lbs. total weight loss)
  4. Every pound lost during your workout is equal to 16 oz. of fluid.

No injury prevention plan is infallible but with a well thought out racing and nutritional plan, muscle cramps can be avoided.

Ian McMahan is a San Francisco based athletic trainer and freelance writer with a Master’s Degree in Exercise Physiology. For a more in-depth look at racing in the heat and avoiding cramping, check out Ian McMahan’s article in the October/November 2014 issue of LAVA Magazine.