Focusing solely on training the concentric portion of your movement is not the most effective way to build strength, speed, and explosiveness. However, you must first develop and activate the underlying mechanisms eccentrically and isometrically to maximize the concentric result.

What is a Rep

A rep comprises an eccentric, isometric, and concentric motion. For example, let’s look at the squat.

The lowering down to the floor is eccentric.

The bottom of the squat is isometric.

And the upward phase back to the standing position is concentric.

The eccentric lowering phase is called the lengthening phase. This phase is where a muscle stretches, absorbs energy and transfers it to the isometric phase. This process will determine how much concentric power will be created.

The isometric phase is the deceleration, absorption, and redirection stage. The isometric phase will absorb the eccentric energy you create.

Visualize it Like This.

If you think of it in terms of a basketball bouncing off the court, you can understand better how a rep works.

Just simply dropping the ball, the ball falling onto the court, is an eccentric motion. The court is the isometric phase, where the ball absorbs force and redirects motion. And the ball bouncing off the court is concentric. This analogy describes how a rep works.

Now, let’s delve deeper. Suppose you slam the basketball (eccentrically) on the court. It will generate a tremendous amount of eccentric force and propel the ball high into the air. The bounce height of the ball (concentric) depends on your isometric ability and strength (the court) to absorb the eccentric energy from the slam.

Suppose you replace the isometric phase with something like sand. The ball will not bounce when slammed onto the surface due to the lack of isometric capability and strength. Consequently, the concentric phase will be less effective, and the ball will not bounce high or at all.

One important thing about the lack of eccentric and isometric strength is more injuries occur than they do from concentric motion. So, when you try to run or sprint faster, your muscles cannot absorb higher amounts of force.

Training Tips for Your Motions

Slow Eccentric Training

When trying to be faster and more explosive, it is often thought that slow movements slow you down. Partly true. However, performing slow eccentric training for a few weeks will dramatically boost your strength and speed.

Slow eccentric training is only done for a few weeks. It is crucial to teach and train your muscles to absorb and adapt to force, not dissipate it, during this time frame.

The slow eccentric motion increases the time your muscles are under tension when lowering the weight slowly. Tension, along with time, produces adaptations for two important proprioceptors – Golgi tendon organs and muscle spindles. These two proprioceptors must coordinate to absorb and enhance their force production capabilities.

And when they are not coordinated, the force gets dissipated.

Muscles dissipate force to prevent injury. Dissipation causes a slower muscle reaction and response, resulting in a loss of speed and strength. For example, you can hop up and down very quickly to transfer motion up and down fast.

However, if you jump off a table, your muscles cannot transfer the force to jump up fast concentrically. The force gets dissipated to protect your muscles from injury because they are not strong enough to absorb the increased energy.

When you do slow eccentric training, focus on lowering the weight for about 5-8 seconds. Then, slightly pause isometrically for 2 seconds and go fast concentrically.

Isometric Training

By developing your Isometric phase, you will enhance your stretch reflex capabilities. This is very important to be explosive.

For example, the stretch reflex happens when a heavy or fast eccentric motion is performed. When the movement is slow, the stretch reflex switches on instantly in the eccentric phase. And when it is fast, it occurs in the isometric phase.

For instance, when you do a slow, heavy deadlift, the stretch reflex stiffens your hamstrings as they lengthen eccentrically. The stiffening and time under tension teach the hamstrings to absorb the force and coordinate the proprioceptors.

And when performing a fast rapid movement, such as a kettlebell swing, the stretch reflex causes the hamstrings to stiffen to decelerate the eccentric force in the isometric phase to transfer the motion concentrically. This is known as the Stretch Shortening Cycle.

And so, by training your eccentric and isometric phase slowly, you will boost your strength and enhance your speed by developing your proprioceptors and the stretch reflex.

The body and brain function based on a feedback loop. If you cannot do it slowly and correctly, doing it incorrectly fast will set you up for strain or injury. And so slow develops the force mechanism for speed.

You can and should train each phase of movement separately and slowly first with time under tension. This way, your muscles will learn to absorb and not dissipate force. When your muscles can absorb force, you can train explosively!