Flexibility Training Concepts

Table 7.1 outlines multiplanar flexibility, identifying muscles and their movements in different planes.
- Gastrocnemius:
  - Sagittal plane: ankle dorsi and plantar flexion.
  - Frontal plane: calcaneus inversion and eversion.
  - Transverse plane: femur internal and external rotation.

Postural distortion patterns are imbalances that lead to decreased neuromuscular efficiency and tissue overload.
They result from a lack of structural integrity due to decreased functioning of components within the Human Movement System (HMS).
This lack of integrity leads to:
- Altered length-tension relationships (muscle lengths).
- Altered force-couple relationships (muscle activation).
- Altered arthrokinematics (joint motion).
The goal of the HMS is to maintain homeostasis or dynamic postural equilibrium.

Poor flexibility can cause relative flexibility (altered movement patterns).
The HMS seeks the path of least resistance during functional movement patterns.
- Example 1: Squatting with externally rotated feet due to tight calf muscles, decreasing required dorsiflexion at the ankle.
- Example 2: Overhead shoulder press with excessive lumbar extension because of a tight latissimus dorsi, compensating for limited shoulder flexion.

Muscle imbalances involve alterations in muscle lengths around a joint where some muscles are overactive.
Some muscles are underactive, leading to compensations.
Causes of muscle imbalance:
- Postural stress.
- Emotional duress.
- Repetitive movement.
- Cumulative trauma.
- Poor training technique.
- Lack of core strength.
- Lack of neuromuscular efficiency.

Muscle imbalances may cause or result in:
- Altered reciprocal inhibition.
- Synergistic dominance.
- Arthrokinetic dysfunction.
- Overall decreased neuromuscular control.

Reciprocal inhibition: Simultaneous contraction of one muscle and relaxation of its antagonist.
Altered reciprocal inhibition: A tight agonist muscle decreases the neural drive to its functional antagonist.
- Example: A tight psoas (hip flexor) decreases neural drive of the gluteus maximus (hip extensor).
Altered reciprocal inhibition leads to:
- Altered force-couple relationships.
- Synergistic dominance.
- Faulty movement patterns.
- Poor neuromuscular control.
- Arthrokinetic (joint) dysfunction.

When synergists take over function for a weak or inhibited prime mover.
- Example: A tight psoas leads to altered reciprocal inhibition of the gluteus maximus, resulting in increased force output of synergists for hip extension (hamstring complex, adductor magnus).
Results:
- Faulty movement patterns.
- Arthrokinetic dysfunction.
- Eventual injury (e.g., hamstring strains).

Arthrokinematics: Motion of the joints.
Arthrokinetic dysfunction: Biomechanical and neuromuscular dysfunction leading to altered joint motion.
Causes:
- Altered length-tension relationships.
- Altered force-couple relationships.
These factors impact the joint and cause poor movement efficiency.
Example: Squatting with excessively externally rotated feet forces the tibia and femur to rotate externally; this alters the length-tension relationships, placing the gluteus maximus in a shortened position, and the biceps femoris and piriformis become synergistically dominant. This increases stress on the knees and low back.
Over time, stress associated with arthrokinetic dysfunction can lead to pain, further altering muscle recruitment and joint mechanics.

The ability of the neuromuscular system to properly:
- Recruit muscles to produce force (concentrically).
- Reduce force (eccentrically).
- Dynamically stabilize (isometrically) the kinetic chain in all three planes of motion.
Mechanoreceptors (sensory receptors) in muscles and tendons help determine muscle balance or imbalance.
Mechanoreceptors include muscle spindles and Golgi tendon organs.

Major sensory organ of the muscle, composed of microscopic fibers parallel to muscle fibers.
Sensitive to change in muscle length and rate of length change.
Function: Prevent muscles from stretching too far or too fast.
When a muscle on one side of a joint is lengthened (due to a shortened muscle on the opposite side), the spindles of the lengthened muscle are stretched. This information is transmitted to the brain and spinal cord, exciting the muscle spindle and causing the muscle fibers of the lengthened muscle to contract, often resulting in micro muscle spasms or a feeling of tightness.
Example: With anterior pelvic rotation, the hamstring complex is lengthened, which triggers muscle spindles, causing the hamstring complex to contract.