Indoor exercises can also be done fairly easily. Jumping
rope is a very easy exercise to do indoors. If you can
jump rope continuously for 10 or 15 minutes you are already doing excellent; or you can do a session of say 1 minute jump rope, then recover for 2 minutes (doing say 20 squats), then 1 more minute jump rope, then recover for 2 minutes (doing say 20 push ups).