Exercise induced muscle cramps are and unwelcome consequence of summer running for many athletes.While there are many anecdotal 
treatments for skeletal muscle cramps, research has been inconclusive until recently. Dr. Rob Amrine of Missoula recently referenced a 2013 British Journal of Sports Medicine article investigating the role of dehydration in skeletal muscle cramping. The article included a study in which athletes were intentionally dehydrated during exercise. The conclusion was that dehydration (3-5% body mass loss) is not responsible for muscle cramping provided fatigue and exercise intensity are controlled.i
While dehydration and over-exertion in hot weather can lead to serious medical conditions such as heat exhaustion or heat stroke, it seems muscle cramp prevention may be more complex. The reason for the complexity is the fact that the issue likely lies in the neuromuscular junction which is driven by our nervous system (aka our brain and its connections).ii In short, muscle fibers receive the electrical input required for muscle contraction via the peripheral nervous system. “Motor units” represent this muscle-nerve team. The peripheral nervous system includes the nerves traveling outside of our spinal cord into our extremities. Input from the brain (both involuntary and voluntary messages) further influence the firing of motor units in our leg musculature. Disturbances in the firing of our motor units can occur through inefficient posture, tight muscles, sustained high intensity exercise, and body asymmetries.iii
While adequate hydration is necessary for the body to function properly, effectively preventing muscle cramps may lie in physical, mental, and fueling sources. If cramping occurs while racing, it is likely that either you are not training with the intensity required to race at your race pace, or mental preparation prior to a race is often underestimated. Anxiety, fear, adrenaline, and nausea prior to and during a race negatively impacts our skeletal muscle motor units leading to cramping. The brain requires glucose to function. When blood sugar levels fall during exercise, it becomes increasingly difficulty to focus on the trail or road, but also to fuel muscle function. Regular nutritional intake during prolonged training runs and races over two hours is a necessity to maximize performance while minimizing cramping risk.
Finally, muscle cramping risk increases in the presence of body asymmetries. Postural imbalance, strength imbalance, compensatory running gait due to injury or prior injury, and poor running technique all contribute greatly to muscle cramping risk. Have a physical therapist trained in evaluating running gait mechanics, functional strength, and running-related injuries assess your symmetry and running technique. While some anecdotal methods may be hard habits to relinquish, knowing you are physically and mentally prepared is your best defense in preventing muscle cramps.
John Fiore, PT
john@sapphirept.com
www.sapphirept.com
i British J Sports Med. 2013 Jul;47(11):710-4. ii Sports Med. 1996 Jun;21(6):409-20. iii Sports Med. 1996 Jun;21(6):409-20.
