As you get older, experts advise increasing strength training to help burn calories and keep your metabolism firing. But if you want stronger arms and perkier pecs, there are some non-negotiable workout rules you need to follow that will deliver the best results, says Harry Bullmore B uilding muscle is no longer a niche fitness goal for ardent gym-goers. Studies have cemented building lean muscle as the key to longevity, and strength training has since been adopted by the masses. Given its