Pushups are an exercise that can help you to build upper-body muscle mass using only your own body weight as resistance. It's convenient because you don't need any equipment. It is possible, however, to do too many pushups. It's generally best not to do strength-training exercises every day, to avoid injuring yourself and to aid in proper muscle development.
The American College of Sports Medicine recommends you get at least 30 minutes of cardiovascular activity five times a week. Suitable activities include walking, jogging, running and cycling. You also need at least 20 minutes of strength training twice a week to stay in good health and shape. You can exceed these minimum amounts and still see positive effects, but exercising every day, particularly strength training, can make building muscle more difficult.
The pushup itself is a simple exercise but it requires absolute proper form to accomplish correctly and for the most benefit. Done right, a pushup works your chest, arms, abdominals and shoulders all at once. This is called a compound exercise because it works more than one joint at once. Muscles need time to recover from strength-training exercises like pushups, and doing them every day could damage your muscles. If you nevertheless want to work out every day, do not work the same muscle groups two days in a row. Instead, do pushups and other upper-body exercises on alternating days; in between do leg-strengthening workouts.
Whenever you perform a strength-training exercise like a pushup, the muscles strain and tear slightly at the microscopic level. This isn't a problem if you give your body time to heal. While healing, your body creates new muscle tissue to fill in where it previously tore; this is how you build muscle mass. If you don't rest properly between pushup sessions, however, the tissue doesn't have time to heal, meaning you just repeatedly injure the muscle and don't get added bulk to show for it.
How many pushups you do per exercise session is largely determined by your current fitness level and your fitness goals. However, if you push yourself at each workout to the point where you can't do another pushup without breaking proper form, you must rest. In fact, the American College of Sports Medicine advises you wait at least 48 hours before doing more pushups. This can help prevent injury and allow you to see results in the form of increased muscle mass.