Getting fit playing chess

 Alan Turing once invented a version of chess called 'Round the House Chess'. After you moved you had to run around the outside of the house, and if you returned before your opponent had moved, you had another move (and another run). A good way to keep fit, but apparently not the only one.

Someone has invented a version of chess called "Chesst". Every time you capture an opponents piece, you have to do a set number of push-ups, based on the 'point value' of each piece. (Pawn = 1, Rook = 5 etc).  Possible modifications include making your opponent do the push-ups as punishment for having pieces captured, and adding a pushup penalty for being in check. An even crueller version would be to replace push-ups with burpees.

Of course you can go the other way, and simply play chess while getting fit. Blindfold chess while cycling as a pair, or in a group is one such possibility. Another variant is while one player is thinking, the other is doing sit-ups (or even rowing), and swapping over when a move is played. For this I would certainly recommend using a chess clock, although this may lead to a trade off between losing on time and wearing your opponent out.