Essentially what rndmguy said, but I am going to add on. Can you swim? I imagine that it would be a fairly low intensity exercise, but still be enough to get you fit. Also, try squats while you are in the water to strength train. Aqua-aerobics are often prescribed to those who normally have issues like that.
Goku - Dragon Ball Z (Otakon 2015, revamp and/or DB Super)
Zoro - One Piece (Eventually)
Ippo - Hajime no Ippo (Eventually)
Free - Soul Eater (Otakon 2013, Completed)
Goku - Dragon Ball Z (Otakon 2014, Completed)
My Facebook cosplay group - Southern Maryland Cosplay
(Anyone can join)
Author of the "Getting Fit for Cosplay" Katsucon panel.