Exercise associated muscle cramps & Delayed Onset Muscle Soreness Dr Rob Collins Sports Physician www.ilovesport.co.za
Exercise Associated Muscle Cramps
Definition Painful, spasmodic, involuntary contractions of skeletal muscle that occur during, immediately after, or within 24 hours of muscular exercise. Sudden onset Temporarily debilitating
Incidence 18% of runners in a marathon Occur in: 28% of males 44% of females Frequency at an event: Marathon: 10-22% of admissions Ultra-marathon: 29% of admissions Ironman: 55% of admissions Lifetime prevalence: Marathon runners: 39% Tri-athletes: 78% Cyclists: 60% Club Rugby: 52% (Schwellnus M, et al)
Significance No long-term medical significance Very significant to the affected person Debilitating Severe local pain Commonest condition in endurance events Usually lower limb, : calves, quads, hamstrings, gluts can affect any muscle
Other conditions Painful contraction without muscle shortening: Myositis, myalgia (trigger points) Non-painful muscle shortening: Tetanus, myotonia Other causes of cramps: Malignant hyperthermia, generalised dehydration (G/E), thyroid disease, parathyroid, medications, motorneuron disease, radiculopathy, etc NB to distinguish true cramp from cramp-like pain often referred pain
Many theories Dehydration Abnormal sweat sodium concentration Abnormal neuromuscular control Low carbohydrate intake Excessively tight muscles Environmental extremes Aetiology
Aetiology 1. Dehydration: High sweat volume plasma volume Interstitial fluid volume Hyper-excitable motor neuron axon terminals ( exposure to levels of excitatory extracellular constituents electrolytes, acetylcholine) Spontaneous discharge of nerve terminals Localized cramping
Aetiology 2. Abnormal sweat sodium concentration sodium conc in sweat (has never been shown to occur) osmolality of plasma Fluid shift from interstitial space to plasma Cramping as described before.
Aetiology 3. Abnormal Neuromuscular Control Imbalance betw excitatory & inhibitory input to alpha motor neuron Contributory factors: Exercise intensity Exercise duration Muscle energy stores Hot / humid environment Inadequate conditioning Muscle contracting in shortened position Localize muscle fatigue
Aetiology Local muscle fatigue excitatory afferent activity (muscle spindle)* & inhibitory efferent activity (Golgi tendon organ) = altered neuromuscular control alpha motor neuron activity localized cramping * baseline EMG activity with fatigue in cramp prone athletes.
Stretch Reflex
Golgi Tendon Organ
Risk factors for Cramping Male gender BMI Shorter dly stretching Irregular stretching habits Faster than usual running pace Further than accustomed running (esp >30km) Hill running number of running yrs Family history Muscle fatigue Poor race preparation
Treatment & Prevention Treatment: Passive stretch is the most effective treatment of acute EAMC. Prevention: Maintain hydration Replenish CHO stores Sufficient training (distance & intensity) Regular stretching routine Don t push too fast too early
Delayed Onset Muscle Soreness
Introduction Tender, aching muscles (with movement or palpation) starting approximately 1 day after unaccustomed exercise may last for up to 20 days. Discomfort is experienced at rest Associated with eccentric exercise Also known as muscle fever Features: - muscle soreness range of motion Loss of strength neuromuscular function ( motor control)
Aetiology Previously thought to be 2º to lactate concentration But: lactate subsides in 30-60 min lactate production in eccentric exercise Most accepted theory: Traumatic disruption of Z-bands protein degradation inflammation pressure in muscle compartments pain, swelling, range of motion, etc
More recent study: (PhD thesis not yet published) Microscopic evidence of muscle remodelling from day 2 Muscle hypertrophy from day 2-3 & 7-8 Aetiology Suggests that pain is caused by pressure effect of hypertrophy rather than inflammation. First explanation of why there is no further muscle damage if a 2 nd bout of eccentric exercise is undertaken in a pt with DOMS
Aetiology But: used muscle biopsies (superficial, induces damage, can t re-test same muscle fibre later) Major muscle damage occurs in only some of deep extensor muscles (may only be small % of fibres) Very strong evidence to support inflammation theory
What we know: Eccentric exercise Unaccustomed exercise Inflammatory markers in plasma Enzyme leak from injured muscles CHO stores in muscles after eccentric exercise (measured via MR spectroscopy) CHO levels dropped further in 1 st 24hrs following eccentric exercise Thought to be a consequence of muscle damage & subsequent repair Aetiology
Prevention & Treatment Distance or endurance training Eccentric training Small amount has long protection Weight training NSAIDs: During or after: no effect Before: some effect Continuous compression & electromagnetic sheild symptoms
Prevention & Treatment No effect: Anti-oxidant supplements Massage Ultrasound Ice Intermittent compression Acupuncture Hyperbaric O 2
Advice to Patient Warm up Concentric Approx 5min muscle temp muscle & connect tissue viscosity & higher resistance to tissue tearing Warm down Dynamic mobility exercises after warm up Avoid strenuous & eccentric activity when starting a new programme
Advice to Patient Gradually increase intensity & duration of exercise Active, non-weight bearing exercise while painful Complete bouts exercise similar to original cause within 1 6 weeks. Less intensity As pain allows Hydrotherapy