Suzana Herculano-Houzel

Sweating is good for the brain


Gone are the days when exercise was only recommended to keep your heart healthy, your cholesterol low and your blood pressure under control. Nowadays, it’s also recommended for maintaining brain health: it combats the harmful effects of chronic stress, depression, anxiety, improves memory and learning, and even makes the brain produce substances that keep neurons healthy and more resistant to damage.

Regular physical exercise is now considered the closest thing to an elixir of youth: it causes the body to increase the release of two hormones, IGF-1 and growth hormone, the reduction of which over the years is associated with the normal ageing of the body and mind. With age and less and less of these hormones, the body accumulates fat, loses muscle mass, cardiac power and elasticity of the arteries, and even loses neurons in the brain, especially if stress is a constant in life.

All this is inevitable for those who lead a sedentary life – but it changes dramatically when you start sweating regularly. Every time you run, jump, play ball or walk fast enough to sweat, your body secretes growth hormone and IGF-1 into your bloodstream. Both are largely responsible for the health benefits of exercise: muscle mass increases, the body fat index decreases, bones and the heart become stronger, and even the skin’s collagen production increases, which helps to maintain a youthful appearance.

And the benefits don’t stop there. IGF-1 from the blood enters the brain and increases the production of a growth factor that keeps neurons healthy, causes more new neurons to be born in the structure responsible for new memories, and protects neurons from insults such as ischemia and strokes. As a result, memory improves, stress responses become healthier and anxiety decreases. Exercise also activates the reward system, generating pleasure and well-being, and increases the production of prolactin, a hormone that brings a sense of calm.

We weren’t made to sit on the sofa. The comforts of modern life are great, but a sedentary lifestyle may be largely responsible for the downside of ageing. You can’t stop time, but reversing its undesirable effects on body and brain is within everyone’s reach. All you have to do is break a sweat.

Originally published in Folha de São Paulo on July 12th, 2006.

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