Of course the vending machine thing was a joke (of sorts), but it does make sense to me anyway for Mark to keep fit, especially while on tour. I feel it would make for more energy on stage. The other guys do it down the gym, even Dylan keeps fit with his boxing which is well known to be very energetic.
I realise that Mark has had back issues in recent years but there are types of exercise he can still do. I think pilates are okay and could even help him, but I'm certainly no expert!
P.S. I think Guy said he gave up playing tennis (certainly while on tour anyway).