There are 3 phases or stages in 1 rep, and they are:

 

  1. Eccentric contraction
  2. Isometric contraction
  3. Concentric contraction

 

Notice how every phase is still considered a contraction. Even if your fibers are lengthening/stretching through the eccentric, or holding still during the isometric phase, the muscle fibers themselves on a very microscopic level are going through rapid fire contractions in order to control the weight and the load. It is important for you to understand muscle fibers are working extremely hard throughout all 3 phases during 1 rep. Learn to control the load/weight by engaging in muscle tension during each phase is what makes someone a more advanced lifter. Beginners will struggle with this at first, but if the beginner is made aware of muscle tension and at least tries to understand the rep phases, then by 4 weeks they will have improved significantly. Never let momentum take control of the weight during any phase, or you risk harming your joints, ligaments, and tendons. One rep to the next should be a controlled and smooth cycle, never releasing or disengaging muscle tension at any point until the desired rep range is achieved.

 

Each one of these terms is telling you what your muscle fibers are doing during the certain phase of the rep. For example:

 

  1. Eccentric: muscle fibers are lengthening, spreading out while under tension from the load/weight you are controlling. This is the part where muscle tension and focus is the most important, because this is where 70-80% of your muscle growth is going to come from. This is the hardest phase for your muscle fibers to go through, they go through the most microscopic damage because holding a weight while being forced to lengthen is like stretching a rope while making it hold something heavy. The rope, just like your muscles, is weakened while lengthened and therefore the force of the load is going to be extremely challenging. You want to be able to control a load through the “weakened” lengthened position, you will become a lot stronger, faster. Learn how to master the eccentric phase of the movement. Never let momentum take over during this phase, your muscles need to be the most activated while being lengthened.

 

  1. Concentric: The muscle fibers are powerfully brought together after being in a lengthened/stretched position. This phase is the one everyone focuses on for the most part, the powerful contraction contributes 20-30% towards hypertrophy. The contraction phase is what provides the explosion of neural activity to the working muscle, innervating the muscle fibers. But the most important part is to have a powerful contraction while executing the exercise properly with good form, and be able to control the eccentric phase first and foremost with muscle tension. Keep in mind just because the contraction is powerful, doesn’t mean you do not squeeze through the concentric. As you shorten the muscle fibers, squeeze them while you are lifting the load as if you are squeezing a sponge.

 

  1. 3. Isometric: Muscle fibers are holding the load/weight stagnant, in one place, the muscle fibers are being squished together. Using the sponge example, if you were trying to ring out every last drop out of the sponge, you are squeezing but the sponge cannot compress anymore. By squeezing your muscle fibers together, the isometric contraction should act as a type of “breaking system” or break pad to your exercise. You should be using muscle tension by squeezing the working muscle and never release the tension onto your joints, ligaments, or tendons. Isometric contraction is at the top and bottom of your phases, separating the eccentric from the concentric/contraction. This phase provides an opportunity to squeeze and connect with the working muscle body, squeezing the working muscle hard and then taking that squeezing feeling through the eccentric and concentric phases almost as if you are dragging something. Another example of an isometric contraction would be a wall sit, where you need to hold a squat position with your back pressed against the wall. Although your muscles are not lengthening or shortening, you will still feel your muscles working hard to keep the squat position. This is because the muscle fibers are still performing microscopic contractions in order to hold your load/body weight in that position, therefore requiring a lot of nerve innervation to your working muscles, making them fatigued.

 

Crazy right!? By completely missing say, the eccentric contraction (which most do), you are giving your muscles a break. By using momentum or releasing muscle tension during the rep, there is limited microscopic damage to the fibers, and generally are not burning as much energy or calories during your workouts, and post-workout. Rep phases can be difficult for beginners to achieve because this has a lot to do with mind to muscle connection. However, with practice and by simply THINKING about what the muscle fibers are doing while you are putting them through each set and each rep will help you master and understand the phases of a rep. You will notice a massive difference in the difficulty of your workouts when you start to incorporate rep phases into each exercise. Making sure the muscle body is constantly working and never resting ensures muscle tension is always on the muscle, and the load is displaced away from joints and ligaments. The more nerve innervation you can get to the muscle body you are working, the stronger and bigger the fibers will become. Be patient, keep practicing, you got this.