Corrective Exercise: Buzz words and Intro to Basic CEx

When discussing corrective exercise several buzz words always come up. Words like overactive, underactive, length-tension relationship, synergistic dominance, altered reciprocal inhibition, altered force-couples, agonist, antagonist, synergists, and stabilizers. Great words! But what does it mean and how does it affect you?
Let’s take a quick look at the definitions and then put it all together using a squat as an example …

Agonists are the muscles primarily responsible for a specific movement, also called the prime mover. The bicep is the agonist for bicep curls.

Antagonists are the muscles that oppose or work in opposition of the agonist. The triceps are the antagonist for the biceps.

Length-tension relationship - this is the length at which a muscle can produce the greatest force. If a muscle is lengthened beyond this “optimal length”, it reduces force production. If a muscle is shortened beyond this “optimal length”, it reduces force output.

Synergistic dominance – when a synergist (helper) compensates for a prime mover to maintain force production.

Altered reciprocal inhibition - when a tight muscle causes decreased neural drive to its functional antagonist. Reciprocal inhibition is a normal occurrence. When you perform a bicep curl, the Central Nervous System (CNS) sends a message to the triceps to “relax”. This allows the bicep to contract and perform the curl. If the triceps did not relax the arm wouldn’t move. The dysfunction occurs when the bicep stays in the tight, contracted, or overactive state… this forces the triceps to remain in a lengthened/relaxed state. While in this relaxed/lengthened state, the CNS cannot properly recruit the triceps and it becomes weak. This is when synergistic dominance occurs; other muscles must start performing the work the triceps are supposed to do.

Overactive – muscles that are in constant “shortened”, tight, or contracted state.

Underactive – muscles that are in a constant “lengthened” state. The CNS can no longer properly activate these muscles to perform their function.

Force-couples – Muscles work in “groups” or together to produce movement. The CNS selects muscles to work in “synergy” to reduce, stabilize, and produce force. Muscles do not work in isolation. With every movement, there are muscles working to assist the muscle doing the activity and stabilizing the joints involved. All the muscles working together to produce movement are working as a force-couple.

Intramuscular coordination – ability of the neuromuscular system to allow optimal levels of motor unit recruitment and synchronization within a muscle.

Intermuscular coordination - ability of the neuromuscular system to allow all muscles to work together with proper activation and timing between them.

Synergists assist agonists, or prime movers, during an activity. The front of the shoulder and the triceps are synergists to the chest during bench presses.

Stabilizers work to support or stabilize the body while agonists and synergists work.

Concentric contraction is the shortening of the muscle to produce force. When you perform a bicep curl, the bicep “shortens” as the weight comes toward the shoulder.

Isometric is a contraction where the muscle neither shortens nor lengthens, but maintains its length. This is the main contraction used for stabilization.

Eccentric contraction is the lengthening of the muscle to reduce force. When you lower a bicep curl, the bicep is lengthening and reducing force, or, slowing the movement down.

A popular workout in the gym is the squat.

The agonists, or prime movers, in a squat are the gluteus maximus and the quadriceps. The synergists (helpers) are the hamstrings, adductor magnus, posterior tibialis, and the gastrocnemius/soleus. The antagonist of the gluteus maximus is the psoas (hip flexor).

In this example, we’ll assume the psoas is tight or “overactive”. This decreases the CNS’s ability to recruit the gluteus maximus – a prime mover during a squat. For simplicity of the example, I'm not going to address what's going on with the rest of the body during this dysfunction, as a weak glute and tight psoas has a domino affect on the body.

During descent, as you lower to the ground, the gluteus maximus decelerates (eccentric contraction) or “slows” down this movement.

PSOAS

Gluteus Maximus

When the psoas is tight and the gluteus maximus is weak, other muscles must be recruited (synergistic dominance) to perform this deceleration function. The quadriceps and the gastrocnemius/soleus are now required to perform more work to slow down momentum. The compressive forces on the knee and can lead to pain and injury.

During hip extension, as you stand up from the squat, the glutes, quads, hamstrings, and gastrocnemius/soleus all work in synergy to produce force and allow you to stand up. With weakened glutes, the hamstrings, quads, and gastrocnemius/soleus become synergistically dominant, picking up the slack from the weakened (underactive) glutes. This puts excessive strain on muscles that were not designed to perform this function.

It is essential to have optimum length-tension relations within the body prior to performing strength training, cardio, sports or any other functional type movement.

This is the basis of Corrective Exercise:

1. Identify the overactive (tight) muscles and bring them to their optimal length.
2. Identify the underactive (weak) muscles and strengthen them (intramuscular coordination).
3. Perform integrated exercises to retrain the CNS to recruit the proper muscle synergies (intermuscular coordination).

Let's look at the process of addressing this dysfunction. If, after an assessment, we determine the only imbalances are an underactive (weak) gluteus maximus and an overactive(tight) psoas, we could address the issue using the following:

1. Inhibit the psoas with self myofascial release (foam roll). Hold on tendor spot(s) for 30 seconds – perform 2 sets.