No matter your fitness level (in most cases), you can do some form of push-up. What you might not know, however, is that there are a lot of push-up exercises that will work many muscle groups. Just by tweaking your stance, width, and angle, you can get a killer workout, or just an easier workout if you need. Check out this graphic by GymFreeFit.com showing 100 different variations:
100 Push-Up Variations You Can Do Almost Anywhere [Infographic]
The push-up might be the ultimate muscle-building workout for anyone at any age. In fact, many think push-ups are overall better than the bench press.