As a young man Darwin would have been reasonably fit. He was often away doing natural history walks of several days. Certainly, after coming back from the Beagle voyage he would have been in good condition. Although he suffered from sickness throughout his later life he was very keen on his constitutional walks around the Sandwalk (where he did a lot of his thinking). I suspect that Darwin would have liked a fitbit, where his steps and active minutes would be recorded and uploaded. He would probably have especially liked the opportunity to link with his colleagues. Although he might have found the competition side of it impinging on his time: “Emma, I just need to need to walk up and down the stairs a couple of times before I turn in. That cad Huxley is obviously out on the town wandering around London still and he might overhaul my total before midnight.” I wonder if they would have taunted each other? “Charles you’re supposed to study barnacles, not act like one!” or “Thomas you certainly are my bulldog and not a greyhound!“.