Dr. Christine Louden
Question: Dr. Louden, could you help me with muscle cramps ? I am a runner and have done a few marathons. Each time around the 19th mile I get significant leg cramps. Is there anything I can do to prevent them?
Dr. Louden: No one knows for sure what causes muscle cramping during exercise. There are three main theories- the dehydration hypothesis, the electrolyte imbalance hypothesis and the neuromuscular fatigue hypothesis.
What we do know is that some people are more prone to cramping, and it is more common in racing situations.
Dehydration and electrolyte imbalance have been the predominant theories for decades. However, research has shown there is little to no difference in dehydration or electrolyte status in athletes who cramped during a race vs. those who did not. This led researchers to come up with an alternative theory- the fatigue hypothesis.
This hypothesis may explain your muscle cramping. Pushing in a race beyond what your training has prepared you for may lead to muscle cramping. According to the fatigue theory of muscle cramping, when the muscle gets to the point of fatigue, the normal reflexes that relax the muscle are inhibited allowing the signals that contract the muscle to dominate causing a cramp. The best solution is to stop and stretch. Stretching sends a signal allowing the muscle reflexes to “rebalance” and the muscle will relax.
The good news is that cramping may not have to be your destiny in every race. As your training progresses and with modifications to future programs you may be able to delay the onset of muscle fatigue at your race pace.
But could muscle cramping be related to dehydration despite the lack of evidence? Are electrolytes unimportant? Actually hydration status and electrolytes are important for performance and muscle function. Absorption of carbohydrate fuel is impacted by hydration status and fueling during exercise is one way to delay fatigue.
Especially in longer races and in warmer conditions, blood is diverted to the skin for cooling. This means more competition for blood between the working muscles and the skin for cooling. If your muscles are not supplied with enough blood flow, nutrition delivery in slowed and waste accumulates. Blood flow to the stomach is required for absorption of fuel during racing and there is a science to how well fluids and carbohydrates are best absorbed.
The osmolality of your drink plays a critical role in fluid absorption. For more detailed information on this see this interview with sports physiologist Stacey Simms. http://sportsnutritioninsider.insidefitnessmag.com/4815/sni-interviews-stacy-sims-phd-all-t
Within the athletic community there is debate over how much to drink, what to drink and caution regarding over and under drinking during athletic events. The issue is not an either/or situation. The hydration and fueling plan needs to suit the athlete and their individual needs, the race (duration and intensity) and the environmental conditions. What an individual does leading up to an event may be as important as what she/he does on race day. Some athletes “sodium load” in the days up to a race in order to increase blood volume going into a race with a potential advantage.
To prevent future muscle cramping here are some helpful tips:
1. Train progressively. Include some race paced longer runs and above race pace intervals in the 6 weeks leading up to your next marathon. Training plans and books are a good place to start, but individual athletes often benefit from a plan tailored to their unique needs.
2. Stretch after every run and for 10-15 minutes each night.
3. Make sure calcium, magnesium, potassium and sodium levels are replete well before race day.
4. Have a fueling and hydration plan based on your unique needs.
5. Consider sodium loading prior to your next race.
6. Use salt tabs if they help you.
7. If you do cramp during a race stop and stretch.
For more in depth discussion of the various hypotheses on muscle cramping see http://www.sportsscientists.com/2007/11/muscle-cramps-part-1-theories-and.html
Dr. Louden is our own triathlete. She competes in events through the year and is our go to person for training and sport’s nutrition.
If you have questions for her please forward them to me at firstname.lastname@example.org.