Leg muscle cramps (LMC) can crop up during exercise and put a damper on your triathlon training. When leg muscle cramps hit you during a race, your PR goals and even completing the distance can be put at risk.
What Happens
Cramping typically begins with spasmodic muscle twitches that progress into a painful sustained contraction during the bike or run.
Bulging in the affected muscle is easily seen and massage seems to help. However, the normal contraction-relaxation cycle is disrupted and continuing at race pace becomes impossible.
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There are two general types of race-associated LMC. Type I cramps involve several muscles, whereas Type II is defined here as cramping confined to a single leg muscle.
Why it Happens
Considerable uncertainty exists about the etiology of race-associated LMC. While dehydration and electrolyte depletion are credible causes of Type I cramps, single muscle cramping is more likely due to localized impairment in the muscle tissue rather than a systemic problem.
An emerging theoretical explanation for Type II cramping is excessive activation of certain groups of fibers within the affected muscle. The hyperactivity of these fibers leads to their premature fatigue, failure to relax, and the onset of spasms.
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What causes this abnormal excitation remains controversial, but it may compensate for relative weakness or fatigue in adjoining groups of fibers.
The impairment probably involves residual deficits in strength and flexibility leftover from prior injury. LMC at rest or during nighttime could be a complication of Type II.
Why it Matters
The soreness that follows LMC is an indication that the cramping itself may injure muscle fibers. The pathophysiology of post-cramp soreness is unclear, but possibly similar to that of a muscle strain.
Endurance athletes commonly have a history of injury to the same muscle(s) involved in race-associated LMC. Cramping is often reported following calf or hamstring strains.
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The site of damage in muscle strain is usually where tendon elements attach to the muscle fibers. These viscoelastic muscle-tendon junctions are weak links.
In strains, the junctions tear when the muscle is overstretched by sudden or unaccustomed repetitive eccentric forces. In cramp-injury, extreme muscle fiber shortening (spasm), rather than lengthening might tear the junctions, leading to soreness comparable to strain.
What You Can Do About It
Triathletes can prevent Type II race-associated cramping by first protecting any recent muscle-tendon injury (due to strain or cramps) and allowing time for full regeneration.
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Then use stretches and strengthening exercises typically found in muscle rehabilitation programs. It might be worth trying neuromuscular re-education to address any imbalances in strength, flexibility and activation of surrounding muscles.
The goal of muscle rehab is to achieve bilateral symmetry in lower-extremity strength and flexibility.
If LMC continues to plague your training and races, it's time to seek outside expertise and consult a sports medicine clinician.
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