Make little derogatory comments like, �You look like you have arthritis the way you�re hobbling around.� And then if he complains vocally just add, �Go home then!�.
Comment on his age if you can. Something like, �Well aren�t you a bit old to be doing things like this anyway? You should�ve got your bike test out of the way years ago when you were fit and capable.�
If you can�t get away with saying it with a straight face, then make it sound like you�re trying to be funny instead.