The researchers got 16 male students, average age 21, to sleep 60 percent less than they needed. Half of the students drank a zero-calorie sports drink containing 25 mg magnesium and 50 mg calcium four times a day every day. The researchers do not say what forms of calcium and magnesium they used.
The subjects ingested a total of 100 mg extra magnesium daily. In developed countries most people consume less magnesium than nutritionists recommend, but consume more calcium than they need. To keep things simple we assume that the effects measured in this study are the result of magnesium supplementation and not of calcium supplementation.
The researchers got the students to cycle, against increasing resistance, both before and after the sleep deprivation period. The researchers then recorded the intensity at which the students’ muscles switched over to anaerobic respiration, whereby the body converts glucose into energy faster, but more lactic acid is released than the body can eliminate. This point is known as the anaerobic threshold. You can only keep up this intensity of exercise for a very limited amount of time.
The left-hand figure below shows that sleep deprivation slightly reduced the intensity (measured as oxygen consumption) with which the students reached the anaerobic threshold, and that this reduction was absent in the students that took extra magnesium. The right-hand figure below shows that the students reached their anaerobic threshold more quickly when deprived of sleep, but also that this was not the case in the students that had taken extra magnesium.
A shortage of sleep reduced oxygen uptake a little, and it also reduced the length of time that the students were able to perform at their maximum intensity. Once again, these effects were absent in the students that had taken extra magnesium.
A possible explanation for this is shown above. Magnesium supplementation boosted the subjects’ noradrenalin concentration. The researchers suspect that the effects would have been even more pronounced if the subjects had been given higher doses.
The research was financed by the Japanese government.
Efficacy of oral magnesium administration on decreased exercise tolerance in a state of chronic sleep deprivation.
We have previously reported that chronic sleep deprivation causes a deficiency of intracellular magnesium (Mg) and decreased exercise tolerance. The aim of this study was to clarify whether oral administration of Mg could be effective in restoring the exercise tolerance that is decreased by chronic sleep deprivation. A bicycle ergometer cardiopulmonary exercise test was performed by 16 healthy volunteers (mean age 21.9 years). They were divided into 2 groups: 8 received doses of 100 mg of Mg orally per day for 1 month (Mg group) and the remaining 8 received no Mg and served as the control group. The study conditions were designed as follows: (1) the usual state (good sleep); and (2) the sleep-deprived state (sleeping time up to 60% less than the usual state for 1 month). The ratio of intracellular Mg content of the sleep-deprived state to the usual sleep state was significantly higher in the Mg group (p<0.05) than the untreated control group. There was no difference between the sleep-deprived state and the usual state with regard to anaerobic threshold and peak oxygen uptake in the Mg group, whereas both of these decreased in the sleep-deprived state in the control group. These results indicate that decreased exercise tolerance observed in the sleep-deprived state could be improved by oral Mg administration.
PMID: 9626901 [PubMed – indexed for MEDLINE]