Magnesium For Performance | Benefits & Deficiency Symptoms | PART 2


By Myprotein Writer | Chris Tack

Clinical Specialist Physiotherapist

This is part 2 of our two part series on magnesium (Mg).

In PART 1 we discussed the benefits of magnesium on our general health and to prevent the effects of aging. This time around, we’re discussed the effects of magnesium supplements on our athletic performance!

How Can Magnesium Influence Our Athletic Performance?

As described in part 1, magnesium has a variety of functions in our body- and in particular some of these functions can assist our physical performance in sport. These effects occur in various body tissues, including the nerves, muscles, bones and our cardiovascular system- just to name a few(1-2).

Whilst Mg deficiencies are likely to only be minor to moderate(3); the spread of deficiency in athletes is wide. Deficient groups include adolescent tennis players(4-5); male endurance athletes(6); football players(7); rugby players(8); female gymnasts(9); runners(10) and ultra-endurance athletes(11).

Muscles and Magnesium

Muscles and Magnesium

One of the more apparent influences Mg has on physical performance is from its effect on muscle tissue. The amount of magnesium circulating in the body has been shown to be an independent correlate with muscular performance(12).

In fact serum magnesium concentration is associated with improved performance in maximal grip strength, knee extension torque, ankle isometric strength, and lower leg muscle power in both men and women(12). The causes of such improved performance are suggested to include a boost provided by magnesium to energy metabolism in the muscle mitochondria; and the reduction in activity of reactive oxygen species causing oxidative damage when Mg is available

Another area Mg assists physical performance is related to lactic acid accumulation following intense exercise. The increases in lactate levels when exercising to exhaustion and pummelling the anaerobic glycolytic metabolic system, can be attenuated by the presence of sufficient Mg in the muscle and blood stream(13).  This would indicate that taking a Mg supplement, to ensure the body’s concentration of Mg is sustained; would allow you to exercise for longer before lactate levels increase to the extent where you would have to stop.

Magnesium for Athletes

Magnesium for Athletes


Various game sports (including basketball, handball and volleyball) have been examined to evaluate the effect of magnesium on performance.

One particular study(14) examined elite sports people from all three sports mentioned to understand the impact of Mg intake on their performance. For this study a group of athletes were asked to record their 7 day dietary intake prior to the tests to ascertain the current intake of Mg (which was significantly lower than the recommended daily allowance).

They were then put through a battery of physical testing procedures, which included maximal isometric trunk flexion, extension and rotation; hand grip strength; repetition maximum squat; countermovement Abalakov jump (countermovement vertical jump WITH arm swing allowed); and maximal isometric hamstring and quadriceps torque.

Their findings show that all performance parameters were directly associated with Mg levels in the athlete- meaning more Mg there is available, the better the performance. They suggest that increased Mg concentration facilitates muscular performance through improved metabolism and more efficient muscular contraction mechanics.

Another study(15) also examined professional, elite volleyball athletes. In this study a group of athletes were randomly assigned to groups for either 350mg/ day of magnesium or placebo (500mg of maltodextrin). They then took this supplement for approximately 4 weeks.

The results demonstrated significant reduction in lactate production and up to 3cm greater height in a countermovement jump test (compared to placebo where there was no change). This again supports the importance of Mg in both performance of exercise to fatigue and the subsequent performance improvements from reduced lactic acid accumulation.


Magnesium for GYM TRAINING

In a fantastic study by Lindsy Kass’s research group in 2013(17), the effects of Mg supplementation on post exercise recovery and performance were evaluated.

A group of 16 healthy, active males (approximately 21 years old) were provided either 300mg of Mg oxide per day or allocated to a control group, and were followed for a period of 2 weeks. They then measured blood pressure prior to a bout of acute exercise which involved a 30 minute maximal cycling test and an isometric bench press (3 X 5 second holds).

Their results indicated that the group supplemented with magnesium had a significant reduction in systolic blood pressure at rest (8.9mmHg) and following the exercise tests (13mmHg). They found that blood pressure remained significantly lower during the recovery period post exercise. This may indicate better cardiovascular efficiency during exercise and improved recovery capacity following a bout of intense training.

However, this is not the extent of the benefits this mineral has on strength training. A study was undertaken on a group of young men undertaking a strength training programme for 7 weeks(18). The benefits of 8mg/ kg of body weight per participant were compared to placebo.

In the group taking a magnesium supplement, 20% greater knee extension torque was seen at the conclusion of the study. This significant increase in quadriceps strength showed that 250mg per day facilitated strength gains; but these gains were even more prominent with intakes >500mg per day. It also emphasises the role magnesium can play in glycolytic metabolism.


Judo competitions are closely linked to deficits in a number of minerals and vitamins secondary to the dramatic weight changes associated with “weight cutting” for tournaments.

The modification of weight via dehydration in elite judoka was examined in a study(16) of 20 participants. This study divided the group into those who lost less than 2% of intracellular water, and those lost 2% or more- in effect larger and smaller levels of dehydration to cut weight. Then the researchers measured the amounts of Mg in blood circulation and in urine; followed by performance indicators (maximal grip strength and bench press 1RM).

Their results showed that greater losses of water  (and reductions in serum Mg) were associated with greater reductions in strength. However, in some athletes red blood cells increased their Mg concentration to compensate and attenuate performance reduction.

This would highlight the negative effect of low magnesium on physical performance, whilst also showing that the intentional loss of water weight during weight cutting procedures in martial artists may lead to both Mg deficiency and poor performance.


Magnesium dosage for performance athletes

The recommended daily allowance for magnesium ranges from 400-420mg per day in males, and 310-320mg per day in females(46).

The toelerable intake levels for supplementary magnesium are different and in children this would reduce to 65mg between ages 1-3, 110mg for ages 4-8, 350mg for ages 9-18, and 350mg for 19 years +(46).

Further supplementary dosages for specific sporting situations are as follows:

Team sports

350mg per day(14-15)


✓✗ 10mg/ kg of body weight(19)


360mg per day for 4 weeks (20)

Strength training

300mg per day(17) or 8mg/ kg of body weight, average intake of 507mg per day for 7 weeks (18)

Dosages of >5000mg/ day are associated with toxicity(21).

Magnesium Supplements | Side Effects

Toxicity of magnesium is generally prevented in healthy individuals as the kidneys eliminate excess Mg in urine (22); however dosages beyond 5000mg per day have been associated with mortality in both children (23) and older adults (24).

Normal side effects from high dose consumption is diarrhea, nausea and abdominal cramping. This is particularly evident with high doses of magnesium carbonate, chloride, oxide and gluconate (25). The laxative effect of excessive consumption is due to magnesium salts being unabsorbed in the intestine and colon, which modifies movement of fluids and stimulates gastric motility.

Symptoms of potential toxicity include hypotension, nausea, vomiting, facial flushing, urinary retention (not being able to fully empty your bladder), lethargy and muscle weakness, breathing difficulties and cardiac arrest(22).

Caution should be taken with supplementation in the presence of impaired renal function (kidney disease) due to the inability to remove excess magnesium (22).

Another consideration is the impact of magnesium supplementation when taking other medications. For example, magnesium supplementation should be separated from the use of oral biphosphonates (used to treat osteoporosis) by 2 hours to prevent dampening the effect of the medication (26).

Additionally anti-biotic medications from the tetracycline family (e.g. doxycycline) should be taken either 2 hours prior to, or 6 hours following a magnesium supplement (27). Medications such as potassium-sparing diuretics (e.g. spironolactone) will reduce frequency of urination and reduce excretion of magnesium- therefore caution should be taken to avoid toxicity.

Take Home Message

Hopefully by now you can see that magnesium is not only important for general health, but also an effective ergogenic aid if you suffer from deficiency.

Either by blood test measurement or by recording your intake over 7 days, you can find out if you are one of the many who do not have sufficient amounts of this key mineral. And if you are… Make sure you up your intake!

Many thanks,





Writer and expert