Drinking water during cardio raises your growth hormone level
Strength athletes who train with sufficient water in their body will have lower muscle-busting cortisol and higher anabolic hormone levels. A piece of French research done a decade ago suggests that water has a potentially anabolic effect in endurance and cardio training as well.
In 2001 researchers at the Centre d'Exploration et de Readaptation des Anomalies du Metabolisme Musculaire published an article about a study in which they performed experiments with seven healthy males in their twenties. The subjects had to cycle twice for 40 minutes at a constant speed. The men started by warming up for 10 minutes until they were producing 150 watts, and then cycled for 30 minutes maintaining that intensity.
The researchers measured the concentration of growth hormone in the subjects' blood, and worked out from the men's bodyweight how much fluid they had lost. The amount was 568 ml. Thatís quite a bit, but the temperature in the laboratory was 25 degrees Celsius.
On another occasion the men cycled again, but the researchers replenished the fluid that they knew the subjects would lose. When they measured the growth hormone concentration in the men's blood they got the figure shown below.
The first figure shows what happens to the growth hormone level during the session. The figure below that shows the total amount of growth hormone produced during the session. In the bottom figure the striped bar represents the first session, when the subjects did not drink, and the white bar represents the second, during which they were given half a litre of water.
According to the researchers there is therefore a relationship between the fluid and growth hormone levels. They suggest that there are receptors in the bloodstream that stimulate growth hormone production when the fluid level rises. They do not go into further detail about how this mechanism might work.
Nevertheless, the study as its stands is of interest to athletes: it would seem to suggest that if you keep your fluid levels up during cardio sessions you'll burn a little more fat and lose a little less muscle.
Eur J Endocrinol. 2001 Oct;145(4):445-50.
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