When the neuromuscular system performs functional activities (body movements) with the least amount of energy and stress on the kinetic chain (human movement system), functional efficiency is achieved. Functional efficiency prevents over-training, injuries and lackluster performance. The kinetic chain can not have functional efficiency when postural dysfunctions are present.
When muscles are operating efficiently, they work together to reduce force, stabilize force and produce force in all 3 planes of motion.
1. Frontal Plane – imaginary bisector that divides the body into equal front and back halves. The motions primarily involve abduction and adduction (side-to-side motions). Abduction takes a limb away from the midline of the body and adduction takes the limb closer to the midline of the body. Examples include exercises performed on a hip abductor and hip adductor machines. Other frontal plane motions would be side lunges, dumbbell lateral shoulder raises and lateral spinal flexion. Quickness and agility movements made by athletes require adequate frontal plane stability, strength, power, flexibility and balance.
2. Sagittal Plane – imaginary bisector that divides the body into left and right halves. The motions involve forward-backward and up-down movements relative to the body and/or joint. Examples would be walking, running, bicep curls, leg curls and seated back rows. Traditional training techniques (such as training with machine weights) have focused on the sagittal plane of motion. This is not an effective training technique if the other planes of motion are ignored during training.
3. Transverse Plane – imaginary bisector that divides the body into top and bottom halves. The motions are primarily rotational. Obviously, this will be a dominate plane of motion for many athletes. Baseball players (swinging, turning, pivoting, etc.), football defensive backs (hip rotations, quick turns, etc.) are just two examples.
The actions of muscles during movements are as follows:
1. Agonists - These muscles are the prime movers. For example, the gluteus maximus is the prime mover for hip extension.
2. Antagonists - Muscles that act in direct opposition to the prime movers. The psoas is antagonistic to the gluteus maximus during functional movements.
3. Synergists - These muscles assist the prime movers during functional movements. The hamstrings assists the gluteus maximus during hip extension.
4. Stabilizers - These muscles stabilize the body while the prime movers and synergists perform movements. Core muscles, such as the transverse abdominis, stabilize the body while the prime movers and synergists perform functional movements.
5. Neutralizers - These muscles counteract the unwanted action of other muscles.
Postural dysfunctions are caused when the kinetic chain is out of line. When this happens, synergists often do the work that weak prime movers should be doing. Notice the following:
2. Altered Muscle Force-Couple Relationships - The central nervous system is designed to select groups (synergies) of muscles to produce movement. When this is altered, the wrong muscles produce movement at the wrong time.
3. Altered Joint Arthrokinematics - When length-tension relationships and force-couple relationships are altered, normal joint movement is also altered.
These alterations in normal relationships leads to the start of the cumulative injury cycle.
Common postural distortions are:
1. Lumbo-Pelvic-Hip Postural Distortion - This distortion causes you to have increased lumbar lordosis and an anterior pelvic tilt as shown below.
2. Upper-Extremity Postural Distortion - This distortion is seen in a person with rounded shoulders or a forward head posture as shown below.
3. Lower-Extremity Postural Distortion - A person with this distortion often has flat feet (pronation), feet pointed outward (slew-footed) and internal rotation of the knees (knock-kneed). During the squat exercise the knees will collapse and the heels will rise off the ground.
In Part 4 of this series, I will detail how to correct these postural distortions.