There are two schools of thought on how to perform exercises: Dynamic
All too frequently, the emphasis is placed on how quickly you can perform an exercise. Actually, as long as you maintain good form throughout the movement, it’s probably OK. But even if you’re performing an exercise with good form throughout the movement (dynamic,) you may not be engaging all the muscle fibers because momentum is actually doing most of the work.
To fully engage all the muscle fibers, you need to slow way down so that you’re barely moving, or even stationary (isometric.) In fact, some exercises can be held at the point of greatest stress or muscle contraction, i.e., at the top of a pull up, bottom of a push up, or lowest portion of a squat (not all the way down so you’re resting, but at the lowest point where your thighs are still engaged or flexed.) Wall squats are good for this, too. These then become isometric exercises.
Combining Dynamic and Isometric Exercises
Dynamic and isometric exercises can be combined so you reap the benefits of both types of exercise. For example: one of my favorite push up sequences involves assuming push up position with good form, lower my body to the bottom and holding there for a 10 count, then pushing up. That is one repetition. Try doing this 10 times, it will truly engage your pectoral muscles.
Another version involves counting to 5 on the way down and pushing up to a count of 5. An yet another version involves lowering you body down to the bottom for an extended time (30-60 seconds) then pushing up. Killer. Killer. Killer. You can do this with any of your favorite exercises. I encourage you to try. The compounding effect will truly leave you breathless.