THE CLINIC: Cramps: Overload, Fluid Imbalance, Fatigue- or Nerve Compression

Fri, 5 Oct. 2012 - 2:45 a.m. MT
Credit: ARA Staff - American Running Association

QUESTION:My wife, who is 48, is a distance runner. She has run nine marathons and five half-marathons. Last March at the Atlanta Marathon she experienced calf cramps that made it impossible to run, though she was able to walk. The cramps hit her at 20 miles. This Feb. at another marathon the calf cramps hit her at 17 miles; she was able to walk the other nine miles. A month later the cramps started at the finish of the local Half-marathon. Both marathons were very warm, in the 80- to 90-degree range. She was well-hydrated, however, especially in the second marathon. She runs 25 to 30 miles per week and has been in perimenopause for two to three years. Calf cramps never hit her until she was 47. Any ideas? What do you think of performing blood tests for minerals or electrolytes? 


Steven Taylor

Rome, Georgia


ANSWER;I feel there are several things that may be causing your wife's cramps. Perhaps she is having electrolyte difficulties but I am not so sure that this is the real issue. Being perimenopausal could be contributing to this but I am not familiar with a specific link between the two.


More likely, the cause is muscle fatigue for one of two reasons, or even both.

First, in slower runners there is a tendency to overload the calf muscles eccentrically (while her foot is planted and she is moving her body  over her foot). This causes the fatigue, and cramp. Second, if she has any compression of nerve roots from her back she may be reducing the available power supply to her legs and causing the fatigue to happen sooner than it normally would. Compression would happen in people with a disc

protrusion (new or old), spinal arthritis, or both. Does she have any history of back problems? Even if she doesn't, sometimes this phenomena can be silent as far as the back is concerned. Because running is a high demand activity, the problem may be mild enough that it only shows up when there is high demand placed on the nerve. 


So, what I would suggest is that she see a sports medicine physician who is capable with the problem I outlined above. You might also check in with physicians in your area familiar with athletes who cramp due to excessive sweating and electrolyte



John Cianca, MD

Houston, TX



ANSWER:Cramps can happen for a number of reasons, including dehydration, Over-hydration, electrolyte abnormalities, and muscle fatigue. You didn't mention any problems on her long training runs so we need to look at what is different on race day. If she is running at a faster pace than on her training runs, fatigue is a problem. She should perform runs at her planned marathon pace during training; too often, pace is faster than this on short

runs and slower on long runs. She should gradually increase runs at marathon

pace from 8 miles to 15 miles.


Sweat rates are variable from person to person and will change with acclimatization and weather conditions. Your wife should weigh herself nude prior to a long run and again following the run. Each pound that she lost is a 16 ounce fluid deficit; she needs to add the amount of fluid that she consumed during her run to this to estimate her sweat rate. Repeating this in various weather conditions can provide a good range in sweat rate. A

runner who is a little under- or over-hydrated should not experience problems. It is possible to consume too much fluid while running, causing blood sodium levels to drop. This can cause swelling, cramping, nausea, vomiting, seizures, and worse. Salty snacks or supplements may help prevent this, but avoiding over-hydration is the key factor.


The fact that your wife can continue walking without a problem when she starts cramping leads me to believe that fatigue may be the more significant factor. Incorporating strength training may also be helpful. To work on calf strength, raises should be performed at the edge of a step, dropping the heels down below the step and then rising onto her toes.


Cathy Fieseler, MD

Tyler, TX

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(RUNNING & FITNEWS® September/October  2008• Volume 26, Number 5)

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