Exercise Associated Muscle Cramps

What is EAMC?

• Painful, spasmodic and involuntary contraction of skeletal muscle occurring during or immediately after exercise
• Common especially in endurance events e.g. marathon, triathlon

What does cramp feel like?

• Muscle pain developing over a few minutes in intense, prolonged exercise
• A ‘cramp prone state’ may occur beforehand with twitching
• Spasmodic contractions and frank muscle cramping may occur if activity continues
• Usually in active muscles e.g. calf, hamstring, quadriceps
• Muscle feels hard, contracted and twitches

What causes cramp?

• Some cramps are due to medical and drug-induced causes
• Exact cause of EAMC is still unclear and continues to undergo research
  • Modifiable Risk factors
    • Increased exercise intensity
    • Increased exercise duration
    • Shorter daily stretching time
    • Irregular stretching habits
    • Heat and humidity
    • Early muscle fatigue
  • Unmodifiable Risk factors
    • Older age
    • Past history of cramps
    • Past family history

I always thought it was due to dehydration or electrolyte (salt) depletion?

• Evidence shows no difference between cramped and non-cramped athletes in:
  • Hydration status
  • Electrolyte (sodium or salt) concentrations in blood or sweat
• Generalised electrolyte imbalance only occurs with generalised muscle cramps in some medical conditions
• However, with EAMC, cramping is localised to a single muscle group

Cramp might be due to fatigue and altered nerve supply to the muscle!

• Growing evidence – muscle fatigue as possible cause for cramping
• As muscle fatigues, it contracts (shortens) in length.
• As it contracts, excitable nerve signals involuntarily cause it to contract even more
• Increasing contraction leads to cramp

What is the treatment for cramp?

• Passively stretch the affected muscle:
  • Get someone to help you stretch that cramped calf or hamstring
  • Relief in seconds but 30 minutes to stop twitching
• If you suffer from recurrent EMAC, seek help to ensure it is not due to an underlying medical condition

How can I prevent cramp?

• Address the modifiable risk factors:
  • Lower intensity and duration of activity
  • Avoid hot and humid environments
  • Train and condition yourself for the event
  • Stretch calf, hamstring and quads regularly
  • Adequate carbohydrate intake to prevent early muscle fatigue

References
Schwellnus M, Drew N, Collins M. Muscle Cramping in Athletes – Risk Factors, Clinical References Assessment, and Management. Clinics in Sports Medicine 2008; 27:183-194
Schwellnus M. Cause of Exercise Associated Muscle Cramps (EAMC) – Altered Neuromuscular Control, Dehydration or Electrolyte Depletion? British Journal of Sports Medicine 2008; Published online 3 Nov 2008