For a stronger tomorrow.

Because it tells the truth. A push up asks the whole body to hold one line while the arms do their work, and it shows at once where you are strong, where you are not, and whether you are moving well. Few measures of fitness are as old, as honest or as portable.

And because anyone can begin. It needs no equipment, no membership and no more room than the floor you are standing on. The first lesson is done on your knees. The last, for now, is one in which your hands leave the ground. Everything between them is a step you can see.

Three chapters, in the order we suggest you study them. The stars beside each push up say which chapter it belongs to.

• Foundations. Begin here. Alignment, control and the strength for a full push up.
• Intermediate. Shift the load. Each variation asks more of one part of the push.
• Advanced. Power, and one arm at a time. Best after a clean regular push up.

Every lesson follows the same form: what it works, how to perform it, the mental models that make it click and the common mistakes to watch for. Each one points to the lesson after it and to others like it, so you always know where to go next. The Glossary explains the words we use.

Form before numbers. A clean rep teaches you something; a sloppy one teaches you to be sloppy. We would rather you did five well than twenty badly, and every lesson is written with that in mind.

Progress is a direction, not a pace. Some people move through the Index in a month. Others take a year over the first chapter. Both are doing it right. The Institute is free, with no account and nothing to unlock, so you can come back as often as you need.

The Institute is the open half of Push Up Hero, an app for iPhone and iPad. The Index is where you learn the movement. The app is where you keep count, see your consistency build and watch push ups being logged around the world.