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In certain circles, magnesium is sometimes referred to as the ‘muscle mineral’. And rightly so – magnesium is involved in over 325 enzymatic reactions and plays a key role in both aerobic and anaerobic energy production. More specifically, it is actually involved in the chemical signalling process that governs muscle contraction. But the average bodybuilder really wants to know if taking magnesium is going to improve their strength and/or help with muscle gain. Thankfully there are a few good studies which have explored this issue, with some encouraging findings.

Magnesium Supplements & Increased Strength

The first clues that magnesium may be important in strength training surfaced in 1992. In that year a study appeared in the Journal of the American College of Nutrition showing that magnesium supplementation resulted in superior strength gains versus placebo1. Subjects underwent a 7-week supplementation period concurrent with a strength training program. The program consisted of three sets of 10 reps of leg press and leg extension three times per week - a pretty simple strength training program by anyone’s measure. This was most likely because the young subjects (18-30 years-old) were untrained and the researchers didn’t want to make it to complex. The other issue when they do these studies is safety. This is why exercise such as squats and deadlifts are often excluded when the subjects have no experience with weight training. The last thing researchers want is one of their subjects getting an injury during their study. Finally, subjects in this study took 8mg/kg bodyweight of elemental magnesium in the form of magnesium oxide. This works out to be 640mg of elemental magnesium for an 80kg individual.

Practicalities in Magnesium Supplements

To get over 600mg of elemental magnesium from the average magnesium product, one needs to take quite a few tablets; anywhere from 3-6. Why harp on about the exact dose and form of magnesium you ask? Well, it’s common for people to quickly scan over the findings of a study like this; buy a magnesium formula and just take a couple of tablets a day. But in fact they may require 4-5 tablets to get any benefits in terms of strength gains.

Magnesium Supplements in Football Players

It took another 8 years before the next major study appeared linking magnesium supplementation with favourable strength gains and changes in anabolic hormone profiles2. This study was a bit more applicable to the average gym goer. It involved NCAA, division II varsity football players from the Western Washington University football team.

Magnesium Aspartate & Zinc Monomethionine (ZMA)

Subjects in the active arm of the study received a zinc-magnesium-B6 complex, popularly known nowadays as ‘ZMA’. More specifically, subjects took 3 capsules nightly, which amounted to 30 mg zinc monomethionine aspartate, 450 mg magnesium aspartate, and 10.5 mg of vitamin B-6. This amount of magnesium aspartate equates to 112.5mg of elemental magnesium or 1.4mg/kg bodyweight for an 80kg individual; considerably less than 8mg/kg used in the aforementioned study. However, magnesium aspartate is considered a more bioavailable form of magnesium compared with magnesium oxide; so less may be required for the same effect.

The authors of the study did not mention any details of the typical resistance training program during the supplementation period, other than to specify it was during the footballers’ ‘intensive’ spring football practice season. Compared with the controls who received a placebo, the subjects receiving ZMA showed a significant improvement in strength together with free testosterone and IGF-1 levels. This was accompanied by significant increases in plasma levels of zinc and magnesium compared with controls.

ZMA Studies

On the surface, the results of the above study are impressive but there are some credibility concerns worth highlighting. Namely, the study was funded by the company responsible for patenting ZMA. The other issue is that no detail was given as to what training program was followed during the footballers’ spring pre-season training. This lack of detail makes it hard for any other researchers to replicate the study. Indeed, another group of independent researchers did attempt to replicate the study 4 years later. This study took experienced resistance trainers who had been training for a minimum of 1 year at least three times per week. Subjects were randomly divided into two groups, one with ZMA and the other placebo. Unlike the initial ZMA study, each subject was put through the same weekly resistance workout routine. This consisted of two sessions a week of upper body exercises and two sessions a week of lower body exercises for 8-weeks. In contrast to the previous study, these researchers found that supplementation with ZMA did not result in any significant gains in strength or favourable changes in anabolic hormones like testosterone or IGF-13.

Issues in ZMA Studies

Aside from the conflicting findings for these two studies on ZMA, it’s also hard to say what results would have eventuated had only magnesium aspartate been given to the test subjects.  The other issue is that of dose. Anecdotal reports suggest that nutritionists and naturopaths’ commonly prescribe between 300m-600mg of elemental magnesium for patients at high risk of deficiency or with common symptoms of deficiency. The two ZMA studies highlighted above only used 112.5mg of elemental magnesium from magnesium aspartate, which begs the question; what effect would a higher dose have? Thankfully, a recently conducted study using only magnesium provides some clearer, less ambiguous findings. Interestingly, this study used a much higher doses of magnesium.

Higher Testosterone with Magnesium after Exercise

The study in question was published in 2011 and involved active subjects participating in tae kwon do 90-120 min/day, 5 days per week.  The subjects were split into two groups randomly, with one receiving 10mg/kg of bodyweight magnesium from magnesium sulphate. The study also included 10 sedentary subjects who received the same amount of magnesium, but did not take part in any regular tae kwon do training. In each group, the exhaustion exercise test was found to increase testosterone levels relative to resting values; however the group receiving the magnesium and undertaking regular tae kwon do had the biggest increase in testosterone4.

Magnesium & Testosterone in the Elderly

A couple of other recent studies are worth mentioning in regards to magnesium’s link with testosterone. Both studies involve prospective data collected from a study of aging individuals in Chianti, Tuscany. The first one, published in 2006, involved 1138 men (46%) and women (aged 66.7 ± 15.2) with complete data on muscle performance and serum magnesium. After adjusting for confounding variables, serum magnesium concentrations were significantly associated with indexes of muscle performance. The authors concluded that serum magnesium concentration is an independent correlate of muscle performance in older persons5. The second study published in 2011 evaluated 399 ≥65-year-old men from within the same Chianti study population. This group had complete data on testosterone, total IGF-1, sex hormone binding globulin, dehydroepiandrosterone sulphate and serum magnesium levels. After adjusting for age and other confounding factors, magnesium levels were strongly and independently associated with the anabolic hormones testosterone and IGF-16.

Magnesium Pros Outweigh Cons

Despite the conflicting studies on ZMA, the studies covered in this article provide a sound enough argument that adequate magnesium may be important in maintaining healthy testosterone levels. Moreover, supplementation with high-dose magnesium may increase testosterone above normal levels and improve muscle strength. With all the other well-known benefits of magnesium supplementation from relief of night-time calf muscle cramps to raised energy levels, magnesium is one of those supplements bodybuilders would be amiss to dismiss.

Brilla LR, Haley TF. Effect of magnesium supplementation on strength training in humans. J Am Coll Nutr. 1992;11(3):326-329.
Brilla LR, Conte V. Effects of a novel zinc-magnesium formulation on hormones and strength. JEPOnline. 2000;3(4):26-36.
Wilborn CD, Kerksick CM, Campbell BI, et al. Effects of zinc magnesium aspartate (ZMA) supplementation on training adaptations and markers of anabolism and catabolism. Journal of the International Society of Sports Nutrition. 2004;1(2):12-20.
Cinar V, Polat Y, Baltaci AK, et al. Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biol Trace Elem Res. 2011;140:18–23.
Dominguez LJ, Barbagallo M, Lauretani F, et al. Magnesium and muscle performance in older persons: the InCHIANTI study. Am J Clin Nutr. 2006;84(2):419–426.
Maggio M, Ceda GP, Lauretani F, et al. Magnesium and anabolic hormones in older men. Int J Androl. 2011;34(6 Pt 2):e594-600.
Wilborn CD, Kerksick CM, Campbell BI, et al. Effects of zinc magnesium aspartate (ZMA) supplementation on training adaptations and markers of anabolism and catabolism.

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