Push-ups
While the push-up primarily targets the muscles of the chest, arms, and shoulders, support required from other muscles results in a wider range of muscles integrated into the exercise.
According to some treacherously complex math, when you are doing a full-blown pushup, you are "lifting" about 56% of your body weight (the other 44% is held up by your feet). In other words, for an average 200 pound person, doing one pushup is similar to (but not exactly the same as) doing a bench rep of 112 pounds. This is a great way to tone those muscles and trim the fat.
Losing weight? Sit-ups probably not the best way.
Losing weight is all about eating high quality foods and exercising regularly to burn excess calories. You can try to lose weight just by doing sit ups, but it is not the smartest or most efficient way to lose weight, according to this dude. In order to burn 3500 calories in 2 weeks, you can do (on average) 1,000 sit ups a day or walk or jog 2.5 miles a day. So it's best to grab your mesh training shorts and hit the road.
Burpees
Grab a towel for this one. You're gonna be sweating. Bodybuilding.com says Burpee Intervals are one of the best conditioning drills. These intervals consist of Burpees and shadow boxing. For example, you will perform...
- Burpees x 30 seconds (squat to leaping position, then push-up and repeat)
- Shadow box x 30 seconds
- Continue for 2 - 3 minutes
You will begin with 30 seconds of Burpees, and immediately follow with 30 seconds of shadow boxing. Continue this pattern for a full 2 or 3-minute round. You will then rest 1 minute (or 30 seconds) between each round. Shed the pounds like mad and tighten those muscles.