How to utilize isometric training

Before reading this article I recommend you to reading this one first.

Every dynamic movement consists of three parts as it relates to the muscles involved in the movement. We have eccentric(lengthening), isometric(static), and concentric(shortening). Training these three parts individually can be incredibly beneficial for sports performance and is often referred to as Triphasic training. Today we'll discuss the second part, isometric training.

Isometric Training

An isometric action refers to when the joint angle remains constant. It is important to note that the muscle itself does not remain constant as it is still contracting. The tissue might look static, but if we were to look in a microscope at each muscle fiber, the myosin head keeps on grabbing and releasing the actin. After all, it is called an isometric contraction.

The Physiological Effects of Isometric Training

The isometric phase has two physiological processes that need to be trained to maximize the force transfer from the eccentric phase to the concentric contraction. If a muscle needs to increase its level of force production, it has two options:

By increasing the number of motor units recruited(motor unit recruitment) as well as the rate they are firing at(rate coding), the athlete can produce more force in less time, which sport is all about.

Motor Unit Recruitment

The number one thing that dictates motor unit recruitment is the size principle, which governs the order in which motor units are activated based on the size of the motor neuron and the number of fibers it controls. This recruitment pattern typically begins with smaller motor units and progresses to larger ones. Research indicates that slow-twitch muscle fibers (Type 1) are recruited before fast-twitch muscle fibers (Type 2). However, it's the fast-twitch muscle fibers that are crucial for power production. As the force exerted on a muscle increases, larger motor neurons are recruited to aid in generating more force. When eccentric force is applied, more motor units are required to decelerate and stop the load. The exciting aspect of this process is that it's trainable. Isometric training enables athletes to promptly activate larger, high-end fast-twitch motor units in response to increased force levels. This facilitates greater energy absorption in the stretch reflex and the stretch-shortening cycle (SSC), resulting in a heightened rate of force development..

Rate Coding

When a muscle needs to build intramuscular tension quickly to overcome an external load, it increases the frequency of the signal sent to the nervous system and the alpha motor neuron of the motor unit. To clarify, if the nervous system needs to increase the force of a contraction, it increases the frequency of the signal causing numerous contractions to happen quicker. All of these "mini-contractions" together will let the muscles reach their absolute peak force. Similar to motor unit recruitment, this process can be trained, and a well-conditioned alpha motor neuron will initiate a series of mini-contractions, culminating in maximal force production by the muscle, thereby facilitating faster energy transfer.

Importance of Isometric Strength in Sport

Imagine a soccer player that wants to dribble their opponent and quickly has to change direction. The player has minimum time to produce an isometric force great enough to completely stop the energy of the eccentric contraction, loading their quads before reaccelerating concentrically and sprinting in the other direction. This action has to occur faster than their opponent if they want to run them off.

How to Apply Isometric Training

With any exercise that we want to apply isometric training to, the athlete has to bring the eccentric load to a stop instantly. The athlete who can decelerate the eccentric load faster will experience greater benefits, including an enhanced stretch reflex and increased energy absorption for utilization in the stretch-shortening cycle (SSC). Any delay between the eccentric contraction and concentric contraction will result in lost energy from the SSC. Since it is crucial to bring the eccentric load to an instant stop, always have someone spotting the athlete when performing isometric training. The main goal of isometric training is to teach the athlete physiological components to absorb energy instantly. Therefore, the athlete must perform the eccentric phase quickly. They must hit the isometric phase like a stone hitting the ground, bringing the weight to a complete stop, fast!

Here are some general parameters for isometric loading:

Load	Total Time of Eccentric(seconds)	Rep Range	Sets
85%	3-4	1-2	4-5
80%	3-4	2-3	4-5
75%	4-5	3-4	3-4
70%	4-5	4-5	3-4
65%	4-5	5-6	3-4
60%	4-5	5-6	3-4

Summary

If an athlete can produce more force, he can apply more force, simple as that. However, it is vital to notice that if you train slowly you'll become slow. Therefore, always maximize the speed during the eccentric and concentric phases. Isometric training is all about energy transfer, turning that eccentric energy into explosive concentric actions. Sport is about producing more force in less time. Strength is not what sport is about. While strength is essential, its application at high velocities is crucial for sports performance. Therefore an athlete who can transfer more force and at higher speeds will have an advantage compared to someone that can't do it as well.