I want to incorporate some more cardio into my training - I mainly do weights at the moment - but I don't want to lose any of my hard-gained muscle. What do you recommend?
Sam Lloyd, Devon

Matt Hart answers: Heavy or prolonged aerobic exercise can have a catabolic effect on the body, which means it begins to break down muscle protein for fuel. Muscle protein is converted to carbohydrate which in turn is burnt off in a process called gluconeogenesis. This is likely to happen if there's not enough carbohydrate available from your diet, so sip a carbohyrdrate-rich energy drink during cardio sessions.

There's also a nutritional supplement called HMB that helps prevent muscle breakdown as well as having anabolic (bodybuilding) properties. You would need three to five grams of HMB per day.