Race Day Back Spasms Related to Menstruation?

author : AMSSM

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Female triathlete wonders if unprecedented back spasms are related to menstrual period.

Question: Race Day Back Spasms Related to Menstruation?

"Sorry to ask this question: I did a sprint triathlon yesterday.....my first open water tri......the swim was hard but I managed.....the bike went really well....think I PB'd my bike section. Then I started the run and after about 500 meters my back started to spasm....smack bang in middle......I lay down twice to do some stretches and had to walk the vast majority of it.....I am in the middle of my period and wondered if this may have had an effect? Could this have caused my ligaments to be lax because of hormones and lead to the spasms? I have never had back spasms in a race before and this was the only thing that seemed to be different."

Answer from Jennifer Stromberg, M.D. 
Member AMSSM

Sorry to hear about your issues during the run, but congratulations on a great bike section and your first open water triathlon!

The Menstrual Cycle and Sports

There is no question that your hormone levels do fluctuate with your menstrual cycle -- not just during your period but all month long! A typical menstrual cycle is thought to start on the first day of your period- this is actually when estrogen and progesterone levels are at their lowest. As the cycle continues estrogen levels slowly increase until ovulation. At this point there is an initial decrease in estrogen levels followed by a rise in both estrogen and progesterone. If pregnancy does not occur these levels will slowly decline until the menstrual cycle restarts again with day 1 of your period. Most cycles last about 28 days, but they can vary slightly. If you find you are not having regular periods with training this can be a sign that you have a hormone imbalance and is something you should see your doctor about as this can significantly impact health and performance.

How these hormone levels affect the female body has been a topic of study for quite some time- we know that estrogen levels can have an impact on the cardiovascular system and metabolism and that progesterone levels can affect the respiratory system and thermoregulation. We are also discovering that other hormones can fluctuate during the menstrual cycle as well and these too may have an effect on sports performance through other changes such as ligament laxity. The strongest evidence comes in the area of thermoregulation- body temperature rises during the second half of the cycle after ovulation which could potentially affect athletes competing in hot and humid conditions. There is otherwise no conclusive evidence that these changes adversely impact female athlete performance.

Exercise Associated Muscle Cramps/Spasms

So now that we know that your period probably did not contribute to your muscle spasms, let’s look at what else might have played a role. Exercise-associated cramping was first noted mainly in laborers sweating profusely and working in hot and humid conditions- this quickly led to the theory that cramping is related to dehydration and salt or electrolyte depletion. This theory has been very popular in endurance sports over the years and many athletes have tried increasing salt intake when racing in these conditions with the hope it will ward off cramps. Surprisingly, studies have shown that electrolyte levels and hydration status in athletes who cramp are not significantly different from those who do not.

With the dehydration and electrolyte imbalance theories proving to be less likely scientists began to look for new possible causes of exercise associated cramping and spasm. The current theory is that this is actually related to muscle fatigue and alterations in neuromuscular control. Studies show that exercise in hot and humid conditions can result in increased muscle fatigue regardless of hydration and electrolyte status, which may be why cramping is more common is these types of conditions. A study of Ironman triathletes showed that athletes who experienced cramping tended to race faster relative to training than athletes who did not cramp. Again, this is thought to be due to a difference in relative muscle fatigue.

We have also learned that nerves can play an important role in the development of muscle cramps or spasms during exercise. If the nerves which excite muscles are repeatedly stimulated this can cause cramping. We also know that cramping is relieved by inhibiting this stimulation by stretching. Some athletes may be genetically predisposed to this excess nerve stimulation- athletes who tend to cramp seem to have greater excitatory nerve activity at rest and a family history of cramping has been shown to be a possible risk factor.

The Bottom Line

Based on the current available evidence I would suspect that you experienced back spasms during the run because of increased fatigue after your PB on the bike. This may have caused your muscles to become over-stimulated leading to muscle spasms. Now that you know what you are capable of on the bike I would suggest matching your training a little closer to what you will do in a race to prevent early muscle fatigue, or perhaps working on core and back strengthening. You may also want to try making sure you take in carbohydrates during your race as there is some evidence that this can delay the onset of muscle cramps- probably by delaying reduction of muscle energy stores and therefore muscle fatigue. When it comes to exercise associated muscle cramps we still don’t have all the answers- but we do know world records have been broken during menstruation and Olympic gold medals have been won throughout the cycle, so don’t let your period stop you from getting out there and having a great race!

References: 

Constantini, N.W., Dubnov G., & Lebrun, C.M. (2005). The Menstrual Cycle and Sport Performance. Clin Sports Med 24 (2005) e51-e82.

Schwellnus, M.P. (2009). Cause of Exercise Associated Muscle Cramps (EAMC) – Altered Neuromuscular Control, Dehydration or Electrolyte Depletion? Br J Sports Med 43:401-408.

Author: Jennifer Stromberg, M.D. Assistant Professor, Community and Family Medicine, Duke University Student Health Services

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date: August 31, 2016