Changes

The Stanford study started with runners in their 50s. It is reasonable to assume that a good proportion of those runners had been running for some years, which would tend to self select the healthiest, injury free people. Running can build up joint strength, but cannot compensate for previous traumatic injury. Exercise stress needs to be gradually applied; going from sedentary to trying to run a marathon without training is likely to result in injury. Likewise, starting [[Starting to run ]] while significantly overweight can stress joints beyond their ability to cope.