Among magnesium’s many roles as a regulator of physiological function is its prominent role in muscle contraction and relaxation. Put simply, calcium is responsible for muscle contraction, while magnesium is responsible for muscle relaxation. In relaxed muscles, troponin and myosin sites are fully saturated with magnesium. (1) Here are a few of the roles magnesium plays in our muscle contraction cycle:
- Magnesium reduces the rate of calcium binding to troponin and myosin.
- Magnesium promotes calcium transport in and out of the sarcoplasmic reticulum (calcium must be pumped back in for muscles to relax).
- Magnesium prevents actin (part of the muscle contraction system) from denaturing before forming cross-bridges between thick and thin filaments.
What is the link between magnesium and muscle cramps and spasms?
In a state of low magnesium, less calcium is required to displace magnesium and initiate a contraction, causing our muscles to be hypercontractile. Hypercontractile muscles are more likely to spasm. In addition, when we don’t have enough magnesium to aid in relaxing muscle, we experience cramping.
Magnesium supplementation and cramp relief
In a 1995 study magnesium supplementation decreased leg cramp distress in women with pregnancy-related leg cramps, as compared with those taking a placebo. (2)
Another study (3) looked at the impacts of magnesium supplementation on chronic leg cramps. Participants supplemented with 300 mg magnesium or a placebo for 4 weeks, followed by a 2-week washout period. Then the groups switched treatments.
- Overall, 78% of participants reported an improvement in their leg cramp symptoms.
- The median number of nights disturbed by leg cramps per month decreased from 16 to 4, three months after completion of the trial.
- At the 3-month follow up, 67% percent of respondents reported fewer cramps.
Although there are a limited number of trials looking at the impacts of magnesium supplementation as a potential way to alleviate muscle cramps, it is a promising area for future research.
We know the role that magnesium plays in regulating muscle contraction, and we know that the general population is not getting enough magnesium. So, consider assessing and optimizing your magnesium status to ensure that your entire musculoskeletal system is working optimally.
- Potter, J. D., et al. 1981. Magnesium and the regulation of muscle contraction. Federation Proceedings 40(12):2653–2656.
- Dahle, L. O., et al. 1995. The effect of oral magnesium substitution on pregnancy-induced leg cramps. American Journal of Obstetrics & Gynecology 173(1):175–180. Doi:10.1016/0002-9378(95)90186-8.
- Roffe, C., et al. 2002. Randomised, cross-over, placebo controlled trial of magnesium citrate in the treatment of chronic persistent leg cramps. Medical Science Monitor 8(5):CR326-330.