[potato24]

I actually put my feet under the couch and do sit-ups.

If you are a big guy like me and can't do push ups, then you can do Knee push-ups or alternatively you can also stand between two walls at angle and push yourself away from the other wall. For heavier guys like me This is the equivalent of pushing about 20Kg. In general the higher the incline the less of your body weight you lift.

If you don't have any dumbbells at home you can also fill up multiple water bottles and put them in a rather strong bag(like the eco friendly ones you buy at the store). After all 1L of water is about 1Kg.

Don't forget, you must not rush the exercise. Slow make sure you keep a good form.

Also if this is your first day exercising. Don't do more than 5-10 minutes. You can increase the time you exercise the next time.