I am 53 and have been a keen club runner most of my adult life. Over the past few years to avoid injury - mostly calf and Achilles strains, I have reduced the amount of running and increased cross training e.g. brisk walking, swimming and cycling.What I have found is that so long as the alternative exercise is taken at the same effort as the running, then my ability to run fast has actually improved.Most races have an over-50 category which attracts men who like me still enjoy competing but can't keep up with youngsters in their 20's.There was a program on TV yesterday about the benefits of exercise e.g. reduced anxiety, improved sleep, less likelihood of diabetes,... etc. If it were a drug, it would be described as miraculous.