You can do this exercise either at the gym or at home. If you prefer to do them at home, you can either purchase free weights or use item like water bottles or soup cans.

Since you'll be on the ground, you may be more comfortable performing this exercise on a yoga mat, towel or any other soft surface you can put between you and the floor.c 

This exercise works your pectoralis major, commonly called pecs, which are your chest muscles.c 

1. Lie flat on the ground with your feet together and your arms out to the side, perpendicular to your body.
2. Holding a weight in each hand, raise your arms up in front of your chest until they touch directly in front of you.
3. Lower back to the starting position without touching the floor for one rep.
4. Do three or four sets of 15-20 reps.

Tip: Make sure that as you are performing this exercise, that your arms stay even with your shoulders and don't fall towards your head.

Variation: As your bring your arms together over your chest, lift both legs up so that they are perpendicular to the ground. Lower you arms and your legs to complete one rep.