Good news for couch potatoes - acording to psychology professor Ian Robertson of Trinity College, Dublin, just thinking about strenuous activity can make you fit. In his book Mind Sculpture, he describes how volunteers were asked to imagine they were constantly flexing and tensing one finger of their left hand. After four weeks of daily training, the finger strength of the 'virtual muscle builders' increased by an average of 22 per cent. It's an important piece of research for athletes too, because the mental gym never closes - injured, sick or stuck in a 16-hour flight ? Take some exercise in your head.

Professor Robertson also argues that you can make yourself more intelligent by using your body. One clear-cut example comes when children learn a musical instrument. 'The left brain', says Professor Robertson, 'is bigger in musicians than in non-musicians.' It's also the part that processes the words, and verbal memory, so young musicians literally have a head-start over their unmusical friends. Brainscans show students with best developed minds aren't necessarily the best musicians, but the ones who begin to learn earliest.

Andrew Weil, an American natural health guru, believes the simplest exercises can heal our brains. Dr. Fulford, Weils' mentoroften instructs patients to stimulate thier own healing powers by crawling like babies. This sends simultaneous signals to both sides of the brain-first the right hand and left knee move, then the right knee and left hand . "This cross-patterned type of movement," says Dr Weil, in his book sponatneous healing,'generates electrical activity in the brain that has a harmonising influence on the central nervous system. "Since it's difficult in most social situations for an adult to crawl without embarassing explanations, Dr Weil suggests a less eccentric form of excercise- when you walk, swing your left arm as your right leg steps out, then mirror the movement.

Others are coming to the same conclusions as Robertson and Weil. Dr. Rune Timerdal of Sweden put 909 people into three different groups. One group did aerobic work-outs, the nexts did weights and muscle building, and the ast did nothing. Brain scans, done before and after six-month programmes to test 16 types of mental function, revealed that different exercise booted different brain skills. Jogging, Cycling, skipping, and aerobics had a substantial impact on left brain activity, such as ability in mathematics, logic and language, while body building activated the right side of the brain, associated with more intuitive, abstract and even psychic skills. What you might call Mind-Blowing results.