Cyclists can turn back the clock: building your knee extensors can help you ride harder, longer. In a new study in the European Journal of Applied Physiology, cyclists in their 20s and 50s performed 100 leg extensions three times a week. After three weeks, the older guys showed greater improvement in strength and cycling efficiency than the younger ones did – and narrowed the age-related performance gap. As you age, your ability to gain muscle strength is preserved, says study author Dr Julien Louis. Leg extensions work your knee extensors, key muscles during the pushing phase of pedalling. Try squats and lunges instead – they work your extensors but stress your joints less. Add six sets of 10 to your regular training. Also try these Six Secrets For Stronger Knees.