Because only uninjured fibers or those with adequate glycogen function properly, vigorous exercise demands the same work from fewer fibers, increasing the likelihood of injury. Exercisers who work out daily should stress different parts of the body. Only swimmers can tolerate an intense and an easy workout each day. Presumably, the buoyancy of the water helps protect their muscles and joints. Bones can be weakened by osteoporosis.
Joints are more likely to be damaged if supporting muscles and ligaments are weak.
Running on banked tracks or crowned roads places greater stress on the hip of the leg that strikes higher ground, increasing the risk of pain or injury at this site. Pronation helps prevent injury by distributing the force of impact with the ground. A cavus foot has a very high arch. Many people who appear to have a cavus foot have normal arches but rigid ankles, so they pronate very little. Their feet usually are poor shock absorbers, increasing the risk of stress fracture in the bones of the feet and legs.