Running

Cycling really helps running, as it keeps fitness up, without impacting joints. Doesnt work the exactly same muscles though.

Running doesnt help cycling in the same way unfortunatly. So you end up running more, and just cycling to rest the joints, and for fun.

Boku truth here. I've been loving running so much I've totally neglected the bike, and am really having to work hard to get the bike legs up to speed.

Mind you, did my first 100km run at the weekend, on concrete, so planning on taking a bit of a break to let the joints recover and get the bike strength back.