The tempo of an exercise is the speed, or time it takes, to move through each of the four phases of the movement. The tempo of an exercise is typically represented based upon time, in seconds, and can be classified using a four number system, i.e. 2010. The first number refers to the time taken during the eccentric phase of the movement. The second number represents the transition time between the eccentric and concentric phases. The third number is the time taken to complete the concentric phase. The last number represents the transition time between the concentric phase and the eccentric phase.
The eccentric portion of an exercise is when the targeted muscles of a given movement are lengthening under load. In general, you can think of the eccentric phase as the lowering phase for most exercises. In the case of a squat, when begin lowering from a standing position you have initiated the eccentric portion of the movement.
The concentric portion of an exercise is the phase of the movement when the targeted muscles are able to overcome the load and shorten. In general, you can think of the concentric phase as the lifting part of most exercises. In the squat, from the bottom position, once you begin standing, you have begun the concentric portion of the movement.
The two phases between the eccentric and concentric portions of the lifts are the pauses before transitioning from concentric to eccentric and vice versa.
If your goal is to maximize hypertrophy, or muscle growth, you would typically want to increase the time of the eccentric phase of an exercise, depending on the other variables. The eccentric portion would typically be four to five seconds in a hypertrophy program, as this creates more damage to the muscle tissue, which upon recovery results in bigger, stronger muscles. However, if your goal is to generate more power, a shorter eccentric phase, 0 to 2 seconds, would be typical as you are trying to generate as much elastic response from your muscles as possible.
The two phases of a lift between the eccentric and concentric portions are the transition pauses, and are equally as important as the tempo for the movement phases, and must not be overlooked. Going back to the individual training to increase power, a minimal pause, a fraction of a second, is important to use the elastic energy stored in the muscle during the eccentric phase, and will therefore result in more power development. The more time spent between the eccentric and concentric phases, the pause, the more the elastic energy will dissipate, and therefore the more forcefully your muscles must contract to overcome the load. In some cases, this can be desired, and therefore strategically incorporated into your program. Another important consideration for programming the pauses, is the amount of stabilization your body is required to do in its end ranges of motion. Using prolonged pauses, 2-10 seconds, will require the body’s deep stabilizer muscles to work under load to maintain proper positioning. This can be extremely beneficial for joint function and overall health and performance.
By understanding this four phased system for the tempo of an exercise you can greatly enhance the results you achieve with your programming. By modifying the time spent in each phase, depending on your goal, you can accentuate the stress placed upon your body in different portions of the exercise, greatly magnifying the results.