Garage gym

Working out in my attached garage thank God the doors are insulated. Any suggestions for heating it up that won’t asphyxiatio me or run up the electric? Today first time doing 303 tempo squats in a while…now that heated it up

I usually chuck on a thermal hat and a jumper if I’m cold. Usually end up taking the hat off early doors. Other options are space heaters or electric but I find them overkill.