Exercise Associated Muscle Cramps

With so much reading material and research available on various parts of an athlete’s performance, often times it’s the little things that are forgotten. Below is an article which makes exercise-associated muscle cramps a priority. Great read and it sheds some insight on home remedies as well as various other supplement style “fixes” for those cramps we all hate so much.

– Coach Cottle – USAT L1

Exercise Associated Muscle Cramps

Although exercise-associated muscle cramping is a common complaint among athletes, it remains poorly understood and there is a lack of good quality scientific evidence to guide management. This article presents the current understanding of this complex condition.

Exercise-associated muscle cramping (EAMC) is a common condition that requires medical attention during sporting events. It is common among athletes who participate in long-distance endurance events, such as triathlon and marathon or ultra-marathon distance running, and it is documented in many other sports, including basketball, the various football codes, tennis, cricket and cycling.1 The prevalence of EAMC has been reported for triathletes (67%),2 marathon runners (between 30% and 50%),2 rugby players (52%)1 and cyclists (60%).1 Despite the high prevalence of EAMC, its risk factors, pathophysiology, treatment and prevention are not completely understood.

Muscle cramping can occur as a symptom of a variety of medical conditions. These include genetic causes, muscular disease, endocrine and metabolic diseases, hydroelectrolyte disorders, and toxic and pharmacological agents.3 This article focuses on EAMC, and excludes muscle cramping in smooth muscle, cramping at rest and cramping associated with any underlying disease or drug.

WHAT IS EXERCISE-ASSOCIATED MUSCLE CRAMPING?

EAMC is defined as a syndrome of involuntary painful skeletal muscle spasms that occur during or immediately after physical exercise.4 It presents as localized muscle cramping that occurs spasmodically in different exercising muscle groups, usually the calf, hamstring or quadriceps muscles. The calf muscles are the most commonly affected.

RISK FACTORS

eamc-fig-2_med

The risk factors for EAMC are not well documented. However, factors associated with EAMC in running have been examined in a cross-sectional survey of 1300 marathon runners and found to include older age, a longer history of running, higher BMI, shorter daily stretching time, irregular stretching habits and a positive family history of cramping. Specific sporting conditions associated with EAMC included high-intensity running, long distance running (>30km), subjective muscle fatigue and hill running.5 In a prospective study of Ironman triathletes, the only independent risk factors for EAMC were a past history of the condition and competing at a higher than usual exercise intensity.6 Importantly, the available data suggest that EAMC is associated with running conditions that can lead to premature muscle fatigue in runners who have a history of the condition.7

PATHOPHYSIOLOGY

EAMC may be caused by a combination of factors, but muscle fatigue is likely to be the principle factor. As muscle fatigue develops, there is an association with increased excitatory and decreased inhibitory signals to the alpha motor neurons; if muscle contraction continues then muscle cramping results. Effective immediate treatment is to increase inhibitory input to the muscle, either by stretching or by electrical stimulation of the tendon.8 However, science has not emphatically disproven earlier theories that EAMC is related to abnormal serum electrolyte concentrations, dehydration or environmental stress, and there is a paucity of rigorous scientific research and addressing these theories. The aetiology is most likely multifactorial, and some athletes are more susceptible to EAMC than others, given their genetic endowment and physiological response to exercise.

Different theories for the aetiology of EAMC are discussed in the box below.4,9-24

TREATMENT

There are many interventions available for the prevention or treatment of muscle cramps — most notably, stretching of an acute cramp. Much of the available scientific data for treatment is aimed at nighttime calf cramps. However, no drug therapy has demonstrated adequate efficacy for nocturnal cramping.

eamc-fig-1_med

Quinine has been used to treat cramps of all causes. A Cochrane review of 23 clinical trials has concluded that there is moderate quality evidence that quinine reduces cramp frequency, intensity and cramp days, but not duration, compared with placebo, and there there is a significantly greater risk of minor adverse events for quinine compared with placebo.25 In 2004, the TGA withdrew approval of quinine for nocturnal muscle cramps because of the risk of thrombocytopenia.26

The most commonly reported treatment used to prevent recurrent cramping is magnesium supplementation.27 However, most users report these supplements to be of little or no help. The efficacy of magnesium for muscle cramps has never been evaluated by systemic review.

Salt tablets are widely used in the athletic population to treat EAMC because they are thought to target abnormal serum electrolytes and dehydration. However, the scientific evidence suggests that salt tablets do not target the principal cause of cramps and are therefore not beneficial.

There is one case report and anecdotal evidence (level 4 evidence-based medicine) for use of pickle juice to treat EAMC. The ingestion of a small volume of this highly salty and acidic brine (30 to 60 mL) is claimed to relieve cramp within 35 seconds.28 It is unlikely that the effects of pickle juice on muscle cramp duration are due to changes in plasma electrolytes of body fluid chemistry, and the rapidity with which pickle juice relieves electrically induced muscle cramps cannot be attributed to spontaneous cramp cessation, weakness of the the induced muscle cramps, a placebo effect, or lack of fluid and electrolyte losses. It is speculated that pickle juice triggers a reflex, probably in the oropharyngeal region, that acts to increase inhibitory neurotransmitter activity in cramping muscles.28 The proposed ingredient that elicits the decrease in cramp duration is acetic acid.

PREVENTION

The pathophysiology causing EAMC is most likely multifactorial and complex and, in turn, prevention of EAMC will need a multifactorial approach. It has been found that athletes who are returning to competition or beginning the functional return to sport phase of rehabilitation after injury are particularly susceptible to EAMC. These athletes are likely to experience early muscle fatigue, to be less acclimatized to a hot environment and to have diminished sweating efficiency, thereby increasing the potential to develop EAMC.29 From the aforementioned review of the available literature, it is muscle fatigue that is the most likely principal cause. Proper progression during rehabilitation will prevent over stressing the athlete while ensuring adequate sport specific conditioning before the return to competition.

Unfortunately, there are no proven strategies for the prevention of EAMC. However, regular muscle stretching using post-isometric relaxation techniques, correction of muscle imbalance and posture, adequate conditioning for the activity, mental preparation for competition and avoidance of provocative drugs may be beneficial. Other strategies, such as including plyometric or eccentric muscle strengthening in training programs, maintaining adequate carbohydrate reserves during competition or treating myofascial trigger points, are speculative and require investigation.30

OTHER MANAGEMENT STRATEGIES

At the present time, level 1 evidence-based medicine does not exist for the treatment or prevention of EAMC. We surveyed 30 Sports and Exercise Medicine physicians currently practicing in Australia and New Zealand for their opinions (unpublished data). Muscular fatigue was thought to be most likely risk factor and cause EAMC. Survey respondents believed that useful treatments for EAMC, in addition to those discussed above, may include:

– withdrawal from athletic activity after the onset of first cramp, as this is a sign of fatigue

– active and passive stretching

– active contraction of the antagonist muscle (e.g. dorsiflexors of the ankle for calf cramp)

– heat packs in cold weather

– massage therapy

Preventive measures identified by the Sports and Exercise Medicine physicians include identifying at-risk athletes and biomechanical and/or gait disturbances pr technique errors. Other preventive measures included:

– massage therapy before and during competition (a strategy particularly used in AFL football)

– compression garments

– neural stretching

– sport-specific training

– adequate warm up

– heat acclimatization

– optimization of footwear and/or orthotics

Readers should note that the treatments and preventative measures in this section are not evidence-based.

CONCLUDING COMMENTS

Unfortunately, EAMC remains poorly understood and there is a lack of high level evidence-based medicine to guide management. The pathophysiology is most likely multifactorial, but muscle fatigue and altered neuromuscular control are thought to be central to better understanding, treatment and prevention of this complex condition.

Sophie Armstrong MB ChB, MSc(SEM)

Tom Cross MB BS, FACSP, DCH

eamc-refrences_med