Many people will look back on tree-climbing as a simple childhood pleasure and a natural test of human strength, stamina and agility. But these days, it has turned 1 a more serious activity and is 2 of the fastest-growing adventure sports in the country. 3 the invention of expensive gyms with indoor climbing walls, tree-climbing was a cheap and simple way to get a similar type of exercise. These days, if you want to 4 part in an organised tree-climbing activity, you 5 to wear a helmet and attach yourself to ropes in 6 you should lose your footing. But otherwise, tree-climbing is a very eco-friendly sport, involving minimum damage to trees or the environment. Getting off the ground is perhaps the most challenging part of a climb. 7 that, it’s about using your legs, 8 are much stronger than your arms, to drive yourself up the tree. Reaching the top and then abseiling down again is a source of great satisfaction.