Not too long ago, Doctors were of the mind that we should slow things down as we get older; to allow HIIT and impact sports to gather layers of grey dust in the attic and resign themselves to glacial jogs around the park or a gentle round of golf. To be fair to them, exercise physiology weighed in on their side. By the age of 40 for example, a man's metabolism would have slowed by 4% since they officially became an adult, meaning that they can't burn calories at the rate they