• Research articles that were preferably not paid for or administered by supplement companies.

Data Availability

• The initial round of research indicates that data availability surrounding credible academic resources that demonstrate that supplemental magnesium is effective for muscle relaxation is low [unavailable] in the public domain.
• Rather than providing nothing, we have provided four research studies that show the opposite. While that was not asked for, we had no choice as studies showing conclusive proof that it does help do not exist.

Magnesium for Muscle Cramps

•  Published on September 21st, 2020

•  Cochrane is an "international network with headquarters in the UK." Cochrane’s members and supporters "come from more than 220 countries, worldwide. They are researchers, health professionals, patients, carers, and people passionate about improving health outcomes for everyone, everywhere."
• The study can be accessed here. 
•  Verbatim conclusion: "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."
•  This research cites this study as well.
• Additionally, this source states this: "the Cochrane Review study (first published in 2012), published on 21 September 2020 by Cochrane Neuromuscular Group, is likely the most thorough literature review performed to evaluate the effect of magnesium in preventing muscle cramps."

Effect of Magnesium Therapy on Nocturnal Leg Cramps

•  Published on November 26th, 2013

• The study can be viewed here. 

•  Verbatim conclusion: "Magnesium therapy does not appear to be effective in the treatment of NLC in the general population, but may have a small effect in pregnant women. Further research using better designed RCTs is necessary."

A Higher Concentration of Dialysate Magnesium to Reduce the Frequency of Muscle Cramps: A Narrative Review

•  Published on October 22nd, 2020.

• The study can be viewed here. 
•  Verbatim conclusion: "In summary, the physiology of muscle cramping remains poorly understood, and there are no proven prevention or treatment strategies. Hypomagnesemia appears to be a potential risk factor for cramping, although several other factors may play a role and/or interact. Causes of hypomagnesemia in patients receiving hemodialysis include poor diet, use of medications that inhibit magnesium absorption (eg, proton pump inhibitors) or increase magnesium excretion (eg, high-dose loop diuretics), and a low dialysate magnesium concentration. Many patients who dialyze at concentrations ≤0.5 mmol/L will experience a decrease in their serum magnesium concentration over time. Evidence from observational and interventional studies suggests that increasing the concentration of dialysate magnesium can raise patients’ serum magnesium concentrations and this may reduce the frequency and severity of muscle cramping; however, the methodological quality of studies conducted to date is poor and the assessment of cramping is highly variable. Few interventional studies have been conducted and most used a nonrandomized, pre-post study design. In patients without kidney disease, there is inconsistent limited evidence that magnesium-based therapy provides a clinically meaningful protective effect against muscle cramps."

Oral Magnesium Supplementation for Leg Cramps in Pregnancy - An Observational Controlled Trial

•  Published on January 20th, 2020.
• The study can be viewed here.
•  Verbatim conclusion: "Oral magnesium supplementation during pregnancy did not reduce the occurrence and frequency of episodes of leg cramps."

Summary

• Our initial hour of research focused on executing detailed x-ray boolean string searches to try to find recent, credible academic resources/studies that point to the conclusion that supplemental magnesium is effective for muscle relaxation. As explained in the data availability statement, this was not possible as they do not publicly exist. We are alway disappointed when this happens, but we provide what we discover.
• We do want to point out that some studies appeared to say that there might be some benefits for pregnant women.
• We are not recommending further research for this exact question based on these facts.
• However, we are suggesting a tangential scoping path that might be useful.