Magnesium for skeletal muscle cramps
Seven articles on PainSci cite Garrison 2020: 1. The Complete Guide to Trigger Points & Myofascial Pain 2. The Complete Guide to Muscle Strains 3. Water Fever and the Fear of Chronic Dehydration 4. Does Epsom Salt Work? 5. 35 Surprising Causes of Pain 6. Vitamins, Minerals & Supplements for Pain & Healing 7. Cramps, Spasms, Tremors & Twitches
PainSci notes on Garrison 2020:
This review of only a handful of existing studies concluded that “it is unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps.” Amazingly, the evidence for the effect of Mg on cramps caused by exertion, disease, and pregnancy is just hopelessly inadequate. You’d think someone would at least have studied exercise-induced cramping, given its importance in elite athletics. The last version of this review was in 2012, and almost nothing changed.
Common issues and characteristics relevant to this paper: ?Scientific papers have many common characteristics, flaws, and limitations, and many of these are rarely or never acknowledged in the paper itself, or even by other reviewers. I have reviewed thousands of papers, and described many of these issues literally hundreds of times. Eventually I got sick of repeating myself, and so now I just refer to a list common characteristics, especially flaws. Not every single one of them applies perfectly to every paper, but if something is listed here, it is relevant in some way. Note that in the case of reviews, the issue may apply to the science being reviewed, and not the review itself.
- Paper points to an “absence of evidence” rather than “evidence of absence,” which is just a fancy way of saying “inconclusive.”
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
BACKGROUND: Skeletal muscle cramps are common and often occur in association with pregnancy, advanced age, exercise or motor neuron disorders (such as amyotrophic lateral sclerosis). Typically, such cramps have no obvious underlying pathology, and so are termed idiopathic. Magnesium supplements are marketed for the prophylaxis of cramps but the efficacy of magnesium for this purpose remains unclear. This is an update of a Cochrane Review first published in 2012, and performed to identify and incorporate more recent studies.
OBJECTIVES: To assess the effects of magnesium supplementation compared to no treatment, placebo control or other cramp therapies in people with skeletal muscle cramps.
SEARCH METHODS: On 9 September 2019, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, LILACS, CINAHL Plus, AMED, and SPORTDiscus. We also searched WHO-ICTRP and ClinicalTrials.gov for registered trials that might be ongoing or unpublished, and ISI Web of Science for studies citing the studies included in this review.
SELECTION CRITERIA: Randomized controlled trials (RCTs) of magnesium supplementation (in any form) to prevent skeletal muscle cramps in any patient group (i.e. all clinical presentations of cramp). We considered comparisons of magnesium with no treatment, placebo control, or other therapy.
DATA COLLECTION AND ANALYSIS: Two review authors independently selected trials for inclusion and extracted data. Two review authors assessed risk of bias. We attempted to contact all study authors when questions arose and obtained participant-level data for four of the included trials, one of which was unpublished. We collected all data on adverse effects from the included RCTs.
MAIN RESULTS: [details omitted]
AUTHORS' CONCLUSIONS: It is unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps. In contrast, for those experiencing pregnancy-associated rest cramps the literature is conflicting and further research in this population is needed. We found no RCTs evaluating magnesium for exercise-associated muscle cramps or disease-state-associated muscle cramps (for example amyotrophic lateral sclerosis/motor neuron disease) other than a single small (inconclusive) study in people with liver cirrhosis, only some of whom suffered cramps.
- “Origin and Development of Muscle Cramps,” Minetto et al, Exercise & Sport Sciences Reviews, 2013.
- “Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes,” Schwellnus et al, British Journal of Sports Medicine, 2011.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
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