As with any type of resistance training exercise, doing too many pushups can actually do more harm than good. The key to building muscle is getting adequate rest between workouts; this is the time when your muscles actually get bigger. Without enough rest between each pushup workout, your muscles constantly are getting broken down and are not allowed any time to rebuild and recover. That said, using pushups on a consistent basis with adequate rest in between sessions is an effective way to strengthen your chest, abs, shoulder and tricep muscles.
Your pushup workout intensity plays a major role in whether or not you can safely do a daily workout. Doing a light pushup workout every morning, for instance, to wake up and get the blood flowing, is something that you can probably do safely every day. However, doing pushups for the purpose of building strength and muscle size requires more intensity. In this case, a daily pushup workout would eventually cause too much stress on your muscles, leading to atrophy, or loss of muscle tissue.
The amount of muscle mass you currently have is a key factor in how fast your body recovers from each pushup workout. The more muscle you have, the more efficient your body is at recovering from the micro-trauma inflicted on your muscles and connective tissue during the previous workout. This is the reason that exceptionally fit people, such as those in the military, are able to perform daily pushup workouts without much risk of damaging muscle tissue.
Resting for one day between workouts is generally recognized as adequate for most people. However, beginners may need two or three days of rest between workouts. If your chest and/or arm muscles are sore from a previous workout, you may want to take an additional day of rest to ensure your muscle tissue repairs itself correctly between workouts. Eat a healthy diet rich in protein, carbohydrates and healthy fats to ensure speedy recovery times.
Former Navy SEAL Stew Smith has developed a 14-day pushup workout designed to significantly increase your pushup max. He specifically states, however, that you should only use this workout about once every six months because it can cause muscle damage if done beyond the 14-day workout period. This workout involves doing 200 pushups for 10 days straight using several sets throughout the day. The final three days are for resting, and on day 14, you take a max pushup test to see your progress.