Often sports injuries are not a result of strength, flexibility or endurance. More often than not, sprains and strains have to do with balance. Proprioception, to be exact. The term proprioception refers to a sense of joint position or, according to Dictionary.com, as "awareness of the position of one's body." Proprioception training is common in rehabilitation of injured athletes. It can also be used to prevent injury. Even a strong ankle can sprain when running on uneven ground if the runner has not trained the neuromuscular system to react appropriately. Another excellent site regarding proprioception and function training.