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If you're in your mid-forties and exercise every day, then you probably make as much rejuvenating growth hormone as someone in their mid -twenties. Exercising this way delays the process of aging, according to researchers at the University of Parma.
Growth hormone stimulates recovery of body tissues, such as muscle fibre, bone, skin and joints. What's more, growth hormone also stimulates fat burning. The older you get, the less growth hormone the pituitary gland in your brain secretes. Researchers think that this slowing down sparks off a series of aging processes, such as osteoporosis and weakening of the joints and muscles. Synthetic hormones are still a very popular way of slowing down the aging process, but studies have shown that they have drawbacks. That's why the Italians are searching for a natural way of maintaining the body's production of growth hormone later in life.
Athletes produce more growth hormone after physical exertion. You also make more growth hormone while you sleep, but in adults this peak is nowhere near as high as the growth hormone peak after exercise. So do older athletes, because of regular exercise, maintain youthful levels of growth hormone production? That's the question the Italians set out to answer.
The researchers got 40 women to cycle for 20 minutes. The researchers gradually increased the resistance of the bike, and the women had to continue cycling until they were no longer able to turn the pedals. The researchers measured the level of growth hormone in the women's blood during the experiment.
Ten of the women were aged between 26 and 30 and did no regular sport [in the figure below: the black squares]. Ten other women were also aged between 26 and 30, but ran about 25 km a week [white squares]. Another ten of the women were aged between 42 and 46 and did not exercise [black circles]. And the last ten were aged between 42 and 46 but had been running about 25 km a week for the last 8 years [white circles].
If you're younger than 30, then training doesn't influence your growth hormone production, the researchers conclude. After a training session the subjects' growth hormone level rises by a factor of 7.5 – whether they take regular exercise or not.
Fifteen years later, however, it's a different story. By that age a difference has arisen between the athletes and the non-athletes. For the subjects in their forties with a sedentary lifestyle, the growth hormone level after training goes up by a maximum of a factor 4.4. But the growth hormone level of the subjects in their forties who take regular exercise reacts the same as the subjects in their twenties.
The researchers think that as you age you produce more growth-hormone inhibiting hormones such as somatostatin. Regular physical training could inhibit the production of these hormones, they think. This way you could halt growth-hormone related aging processes.