I have always had problems with muscle cramps. As I have gotten older (40-ish) I get them more regularly. I drink water like a fish but nothing ever seems to help. I am currently taking Linum B6 on advice from a friend. This past weekend I tried to step off of my bike while on a slight slope. The strain on my hamstring caused a minor rupture. It’s happened a few times while training over the years. What can I add to my diet to ward off these cramps??
While dietary strategies are often recommended in the treatment of exercise-induced muscle cramping, there exists little supporting evidence to warrant such recommendations. Theories such as the energy depletion theory, the dehydration theory, the electrolyte theory, and the environmental theory have not held up when subjected to scientific scrutiny.
The “energy depletion theory” holds that muscles cramp when muscle glycogen (the storage form of carbohydrate in the liver and muscle) and blood glucose (i.e. sugar) run low. However, it has been estimated that it would take nearly 4.5 hours of continuous cycling, at an estimated exercise intensity of 71% VO2 Max (~82% maximum heart rate), to completely deplete carbohydrate stores. Even then, elite Ironman triathletes are still able to run at a speed of 10 mph for another two and a half hours! Therefore, it seems unlikely that glycogen depletion alone would limit performance or cause cramping – especially in the motocross athlete. It should be noted, however, that the metabolism of muscle glycogen releases as much as 2 liters (~68 ounces) of fluid during prolonged endurance activity. It is this fluid loss that has led to the development of our next theory.
The “dehydration theory” states simply that muscle cramping is due to inadequate fluid replacement during and/or after exercise. Once again, no well-conducted studies have documented a relationship between dehydration and muscle cramping in athletes. In fact, quite the opposite has been found. In a study of 1,300 marathon runners, changes in hydration status (measured by changes in body weight, plasma volume, blood volume, or red cell volume) and the development of exercise-induced muscle cramping during or immediately after a race showed no correlation. The same was true of changes in serum concentrations of sodium, potassium, total calcium, and total magnesium (i.e. the electrolytes) thus refuting our third theory – the “electrolyte theory”.
The “electrolyte theory” assumes that prolonged exercise results in a significant loss of magnesium, potassium, calcium, and sodium through sweat resulting in an “electrolyte imbalance”. This loss of electrolytes is believed to disrupt the normal bioelectric control of muscle contraction and relaxation. But, as we have just seen, even though significant losses can occur with exercise lasting longer than 3 hours, electrolyte depletion still doesn’t appear to play a significant role in muscle cramping.
Finally, the “environmental theory” postulates that extreme environmental conditions of heat or cold are indirectly responsible for muscle cramping. In other words, exercising in extreme conditions results in accelerated changes in carbohydrate, water, and/or electrolyte status. While this is certainly true, we have already seen that such changes have little impact on muscle cramping.
So, what does that leave us with?
The most recent theory suggests that muscle cramping has it’s origins in the peripheral nervous system. More specifically, cramps most likely involve hyperactivity of the nerve-muscle reflex arc – the electrical circuit made up of the muscle, the nerves carrying signals to the central nervous system (i.e. the spinal cord), and the nerves carrying signals from the spinal cord back to the muscle. In other words, muscle cramping is an electrical problem.
Normal muscular activity is a delicate balance of turning muscle fibers on and off in proper sequence. As muscles fatigue this balance between tension and inhibition is disrupted. The signal to contract becomes stronger and more frequent while the signal to relax becomes weaker and less frequent. This abnormal reflex activity ultimately results in a sustained muscular contraction – a cramp. Stretching the cramping muscles (the agonists) and/or activating the opposite muscles (the antagonists) is about the only thing that breaks this reflex arc signal and stops the cramp.
This fatigue-cramp process seems to happen most often in muscles that cross two joints such as the hamstrings. Two-joint muscles are more easily placed in a shortened position during exercise making them more susceptible to cramping. Conversely, it has been shown that experimentally-induced cramps do not occur in lengthened muscles. Therefore, it seems logical that a properly designed flexibility program can go a long way in preventing the occurrence of muscle cramps.
Indeed, it has been shown that stretching of the major muscles of the lower limbs for at least five to 10 minutes during warm-up and cool-down periods can help prevent cramps. However, I would also encourage you to incorporate a stretching routine into your overall training program as stretching only on days that you ride may not be enough. This is especially true for older athletes.
As a side note, prolonged sitting subjects the hamstrings to chronic shortening. Therefore, if you have a desk job, stretching becomes even more of a priority.
So, unless your training extends beyond the three-hour barrier, stretching should correct your problem. If you do participate in activities lasting that long then carbohydrate, fluid (16 ounces per hour, or 4 ounces every 15 minutes), and electrolyte replenishment will play a greater role in preventing the onset of muscle cramps. Understand, too, that training alone can delay the onset of fatigue thus reducing the likelihood of experiencing cramps.
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