How The Myotatic/Stretch Reflex Affects Jumping Force Production

How The Myotatic/Stretch Reflex Affects Jumping Force Production

Written by Vitruve Team

25 February, 2022


Every significant body action involves a proper collaboration between the brain and the body. This collaboration starts with the brain transmitting nerve impulses that travel through the spine towards the intended receiver. And once the task is carried out, this impulse must travel back to the brain through a reverse pathway to tell the brain about the task completion.

Nonetheless, not all processes in the body require a thought process. Examples of automatic functions are heart function, metabolic processes, breathing, disease-fighting, and several other processes that do not require mental consciousness. Many of these actions are controlled through body signals. For instance, a rising level of carbon dioxide in the body triggers an automatic nervous response that calls for an increased respiratory rate.

Another type of automatic response generated by the nervous system is the reflex. This response makes the body act in a predetermined way. This action may be a pre-programmed response by the body. One of such responses is the stretch or myotatic reflex.

What is the Stretch Reflex?

A stretch reflex is a pre-programmed body response triggered by a stretch stimulus in the muscle. A stretch in the muscle spindle releases an impulse that travels to the spinal cord to get a response signal that causes the muscle to contract. It is a very quick impulse since it doesn’t have to go all the way to the brain to get the intended nervous response.

The basic function of the stretch reflex is to prevent tear injuries and strain to the muscles and tendons. Any excitement in the muscle spindle causes an impulse to travel to the spinal cord and bring back the instructions for muscle contraction. This way, the muscle remains protected from being stretched beyond its limit.

The stretch reflex also causes the synergetic muscles to innervate. These are the muscles that produce the same movement. As a result, those muscles contract and remain safe from injury. At the same time, a stretch reflex can help control muscles that serve as antagonists in a movement. Instead of triggering a signal to contract, a stretch reflex brings a signal to relax the antagonist muscles.

Examples of the Stretch Reflex

Your body posture benefits a lot from the stretch reflex. When you lean your hip and legs, the muscles in the side angling out get stretched. This stretch gets countered by the stretch reflex promptly. If you notice, the stretch reflex is always at play as the body has to endure a consistent push and pull.

The knee-jerk test performed by the doctors is another example of a stretch reflex. When they tap the patellar tendon with a small hammer, a slight stretch occurs in the tendon and the quadriceps muscles. The resultant contraction in the quadriceps muscles causes a kicking motion.

A Bit about the Stretch Reflex’s Anatomy

Inside the belly of a muscle are muscle spindles, the stretch receptors consisting of nerve endings and spiral threads called intrafusal fibers. These spindles detect a stretching motion very quickly when there is an unusual stretching in the muscle. As a result, the stretch reflex is activated, causing the strained muscle to contract.

How The Myotatic/Stretch Reflex Affects Jumping Force Production

Factors that Activate the Stretch Reflex

As mentioned above, a stretch in the muscle spindle is what activates the stretch reflex. The primary stimulus in this entire scenario is the stretch impulse, which activates the motor neuron. The activation of this neuron accompanies contraction of the stretched and supported muscles and inhibition of the antagonist muscles.

Both external and internal forces can cause the stretch reflex to activate. An external force refers to a load placed on the muscle, while an internal force is usually generated from the stimulation of motor neurons. The external force can be when you stand while holding a tray or get into a position to jump up. An example of the internal force is the activation of motor neurons in response to the muscles stretching caused by shivering in the cold.

Stretch Reflex and Sports

Stretch or myotatic reflex can contribute a lot during fitness training. In fact, there are some exercises in which you can train your myotatic reflexes. However, doing so makes these exercises significantly tougher. This technique typically involves including a quarter rep between the first and second parts of the usual rep. This technique is referred to as a myotatic rep.

However, the above technique is not a way to induce flexibility in your muscles. Rather, this technique will help you build muscle mass faster as it teaches your muscle fibers to work in a lengthened position. As a result, you will have a burning sensation in the muscles, and fatigue will take over your body pretty fast.

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Does Static Stretching Make Your Muscles Permanently Stretched?

No, your muscles won’t remain in a stretched position after a static stretching exercise even if you engage in this workout for a long time. Such exercises only instigate a war between your conscious and subconscious brain. You convince your conscious brain to keep pulling your foot up at your backside. On the other hand, your subconscious brain – stretch reflex in this scenario – tries to keep you from over-stretching and injuring yourself.

The fact of the matter is static stretching may even cause a drop in your strength and athletic performance.

Now, you may ask yourself: “Why do I feel good when I stretch my body?”

The first possible reason for that pleasant feeling after a continuous stretching exercise is that it can make your stretch reflex less active. As a result, your muscles may remain in a stretch position for a short duration only. After an hour or two, those muscles will regain their previous form. However, performing such exercises regularly can reduce muscle spindles’ functionality, affecting your power, strength, and joint stability.

The second possible reason is that regular stretching can make you tolerate the sensation of your pulling your muscles. Again, this sensation is not permanent.

How Does The Stretch Reflex Help With Jumping Force Production?

What would you do if you were told to jump as high as possible? Your very first move would not be an upward jump. Before you could jump up, you would have to flex your knees and hip to lower your body. This action stores the potential in your legs and upper body to jump. This entire process benefits mainly from the stretch reflex. Below are the three points that describe this mechanism.

  • Loading the muscle spindle: An activated muscle spindle creates tension in a stretched muscle to prevent further stretching. Hence, an immediate stretch of the muscle before its contraction stores enough force in it.
  • The stretch-shortening cycle: A skeletal muscle is much like a rubber band that wants to get back in its original state when stretched. This stretch is known as the stretch-shortening cycle. This phenomenon stores a significant amount of elastic energy in the muscle.

Achieving optimal contraction length: A muscle tends to generate force when it is stretched up to 1.2x of its original length. This new length creates a good amount of tension in the muscle without damaging it. However, a strength length of more than 1.2x can cause damage to the muscle.

How The Myotatic/Stretch Reflex Affects Jumping Force Production

Bottom Line

The stretch reflex is the subconscious system that keeps you from over-stretching your muscles. It is also the system that contains all the potential to help you with your routine tasks and fitness training. Hence, it is not a mechanism to temper. You can rather use it to gain a significant fitness advantage.

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Sports Science Degree. Crossfit trainer, in love with weightlifting and digital marketing




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