It is quite common to see older people exercising these days.
In principle this is a good thing.

However, there are many people running without consideration of good posture; stooped back, hunched shoulders and dropping heavily into their knees.
There are reckless cyclists charging down country pathways where a mishaps could mean broken bones and a hospital trip.
Weight lifters shorten their muscles and maintain a permanently distorted, hunched posture.

Aging cannot be avoided. But you can choose how to exercise. Not all physical pursuits are wise for the over-40's.
Choose your exercise appropriately.