WHY DO YOUR MUSCLES GET TIRED?
When your lungs are locked in a desperate struggle for oxygen, your mind tormented by pain, and your skin blanketed with sweat, the mechanisms of muscle fatigue are probably the last thing on your mind.
Scientists and athletes have always thought that your muscles tire because they reach some kind of physical limit. Either they run out of fuel, or they drown in toxic by-products.
In the past few years, researchers Tim Noakes and Alan St Clair Gibson have begun to question the standard theory. And they're convinced that fatigue simply isn't the same as a car running out of petrol.
Fatigue, they argue, is an emotional response that begins in your brain.
Read more:
http://www.thefactsaboutfitness.com/news/cent-gov.htm
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GROUP EXERCISE "BOOSTS HAPPINESS"
Those who trained alone withstood less pain - a key measure of endorphins - than those who exercised together.
Read more:
http://news.bbc.co.uk/2/hi/health/8257716.stm