NASM PES Chapter 4: Flexibility Training Concepts

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Chapter Goals:

• Explain the effects that imbalances in muscles will have on the kinetic chain.
• Be able to explain the scientific rationale for the use of an integrated flexibility program. 
• Be able to find the flexibility techniques based on the needs of the athlete. 

Introduction

The general purposes that we have for implementing a program for flexibility are going to be:

• Correct muscle imbalances
• Increase the joint range of motion
• Decrease the muscle hypotonicity
• Relieve stress on joints
• Improve the extensibility of the musculotendinous junction
• Maintain the normal functioning length of all the muscles. 

Flexibility is defined as the soft tissues’ normal extensibility that allows for the full range of motion and optimal neuromuscular efficiency throughout functional activities. 

Many sports professionals lack the understanding of the main concepts of flexibility training, which can be seen in some poor training programs for this variable of sports performance. 

The benefits of flexibility training are:

• Decreases in the chance of injury
• Preventing the development of muscular imbalances
• Correcting existing muscle imbalances and joint dysfunctions
• Improving the posture and correcting distortions of postures
• Enhancing the strength, joint range of motion, and the power

The Purposes of Integrated Flexibility Training

Optimal alignment and function of the human movement system is a cornerstone of sports performance training programs.

When one segment is not in the proper alignment or functioning, a predictable pattern of dysfunction begins, which starts the cumulative injury cycle. 

The cumulative injury cycle is a cycle where an injury will induce inflammation, muscle spasms, adhesions, altered neuromuscular control, and muscle imbalances. 

All components must be working properly and interdependently. These are the muscular, articular, and neural systems.

Causes of Muscle Imbalances

Muscle imbalances can be caused by problems like possible stress to decrease recovery and regeneration. 

These imbalances result in altered reciprocal inhibition, synergistic dominance, and arthrokinetic dysfunction.

Altered reciprocal inhibition is the concept of muscle inhibition that is caused by tight agonists, and this causes a decrease in the neural drive of the agonistic muscle. This may also result in altered force-couple relationships and synergistic dominance and lead to faulty movement patterns and poor control of the neuromuscular system.

Synergistic dominance is a phenomenon that occurs in the muscular system where the synergist muscle will take over for a prime mover that is weakened or inhibited in some way. This causes faulty movement patterns and may lead to tissue overload, decreases in neuromuscular efficiency, and injuries.

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Arthrokinetic dysfunction is a biomechanical dysfunction in some two partners in articulation and it leads to abnormal movement of the joints and proprioception.

The causes of muscle imbalances are possibly one of these:

• Pattern overload
• Poor technical skill
• Aging
• Decreases in recovery and regeneration after any activity
• Repetitive movements
• Lack of core strength in some way
• Immobilization
• Cumulative trauma
• Lack of neuromuscular control
• Postural stress

Muscle Tissue Structure Function

The structure of the muscle tissues needs to be fully understood before you can grasp the idea of how a muscle lengthens.

The details of the subcellular structure of skeletal muscles and the basic physiology of contractions are past the scope of the chapter, but you should refer to the section before chapter one on anatomy and physiology or simply a textbook in the field. 

Muscles are made up of fascicles, which are strands of tissues. 

Each fascicle is made up of fasciculate, which is the name for bundles of muscle fibers. 

Thousands of myofibrils make up muscle fibers.

The sarcomere is the muscle’s functional unit with the contractile parts within. 

Each sarcomere has myofilaments in it, which are thick and thin contractile proteins. These proteins will mainly be actin and myosin, along with the regulatory proteins of troponin and tropomyosin. 

The process of contracting muscles happens when a neural impulse is sent from the brain to the motor neuron and the impulse causes all of these filaments and their cross bridges to pull and essentially contract the muscles. 

When a fiber has been stimulated for contraction, it will completely contract in what is known as the all or none principle. 

Connective Tissue

Connective tissue is going to have multiple functional categories to be put in:

• Enclose and separate the different tissues
• Connect the tissues that are not similar
• Support and movement for the body and other tissues
• Storage of energies
• Cushioning and insulating the body
• Transportation
• Protection

Connective tissues make up the covering around most of the tissues, like the muscle fibers. We will have fibers like collagen and elastic fibers. 

Our main ones will be the endomysium, perimysium, and epimysium. These are in order of their size. 

The endomysium is the innermost fascial layer that cases in the individual fibers.

The perimysium is the sheath that binds groups of muscle fibers into the fasciculi.

The epimysium is the bigger connective tissue in relation to muscle tissues and is the outermost layer of the fibers. 

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Neurodynamics

All neural tissue needs to adapt to the constant changes in joint angles and alterations in the positions of the adjacent tissues. 

Neuropathophysiology

The integrity of the neural tissues can be compromised when you have an acute injury, chronic injury, muscle imbalance, joint dysfunction, and poor posture. 

Factors Limiting Flexibility

Effects of aging

The body has the ability to remain flexible, but this is reduced significantly as we age. 

Physical age will highly affect muscular and neural atrophy, the hypertrophy of connective tissues, increases in the stiffness of tissues, and dehydration of tissues. 

Effects of Immobilization

Immobilization has many effects on the tissues. 

Some of the biggest effects will be in alterations of the length tensions relationships, force coupe relationships, arthrokinematics, neuromuscular control, degeneration of cartilage, and the loss of ground substance. 

The loss of ground substance specifically will affect the body by decreasing the connective tissue lubrification, connective tissue inter-fiber distances, nutrient diffusion, and mechanical barriers against bacteria. 

Soft Tissue Biomechanics

Soft tissue will have many unique properties to it. 

Among these, the most important properties of this type of tissue are elasticity, viscosity, and plasticity. 

Viscoelasticity 

This is fluid like property of connective tissues that allows for an imperfect recovery after some deforming force is removed. 

One thing to remember is these tips:

• Elasticity is like a spring, you can compress or stretch it, and it will return to the original resting length. 
• Viscoelasticity is like the foam pad; you can apply slow pressure, and deformation will occur. 
• Plasticity is like pulling on a soft plastic, you can pull it apart and it might not break, but it will not return to the shape it originally had.

Plasticity

When soft tissue has been deformed permanently in response to a load, it is said to have undergone plastic deformation. 

There is no tendency for elastic recoil or recovery here. 

The nature of remodeling soft tissue will follow that of Davis’s Law. This law states that soft tissue will model along the line of stress that it is exposed to. 

Neurophysiological Principles of Flexibility Training

Muscle stretching or elongation will begin with the sarcomere acting as the contractile unit of the muscle. 

In the contraction, we have the actin pulled over the thick myosin through the cross bridges; the sarcomere shortens. 

When the sarcomere is less than the optimal length, the actin filaments overlap, producing some tension when stimulated due to the lessened shortening capacity. 

With stretching, the overlap in the sarcomere decreases, allowing the fibers to get closer to the optimal length and peak tension production. 

Recruitment is an impulse we have transmitted over increasing nerve fibers, which pulls more muscle fibers for the task. 

The Golgi tendon organ is a receptor that is located in the musculotendinous junction that is sensitive to tension and the rate of change in tension. 

Muscle spindles are a major organ for the sensory system and are made up of microscopic intrafusal fibers lying parallel to the extrafusal muscle fibers. These will be sensitive to changes in length and the rate of length change. 

Joint receptors are in the joints and they are throughout the fibrous capsule and ligaments. They signal the information regarding the joint position, movement, and pressure change to the body.

The Stretch Reflex

This basic reflex has a sufficient stimulus applied to the ending receptor and creates an impulse. His impulse will travel to the spinal cord and excite a motor neuron. The nerve impulse is conducted to the muscle’s effector site, and a motor response will be returned. The reaction will match and be proportional to the stimulus that it is given.

Integrated Flexibility Continuum

Sports performance professionals should have a firm understanding of the different types of flexibility training so they can prescribe the right program for the goals and needs of their clients. 

We have three categories of flexibility programs: corrective, active, and functional. 

Corrective flexibility is designed to correct common posture, muscle, or joint dysfunctions. This will feature the techniques of self-myofascial release, static stretching, and neuromuscular stretching. 

Active flexibility programs are made for working on the extensibility of soft tissues in all planes of motion by employing the neurophysiological principle of reciprocal inhibition. We do this through the use of self-myofascial release, active isolated stretching, and neuromuscular stretching. 

Functional flexibility improves the multiplanar soft tissue extensibility and provides optimal neuromuscular control through the entire range of motion while doing functional movements that use the body’s muscles to control the speed, direction, and intensity of the stretch. This makes use of self-myofascial release and dynamic stretching to achieve its goals. 

Self-myofascial release is a flexibility technique that focuses on neural and fascial systems within the body. 

The concentration for SMR is on alleviating myofascial trigger points and the areas they have with hyperirritability in the bands of muscle. 

Static stretching combines the low force and long time movements with the utilization of neurophysiological principles of autogenic inhibition to improve the extensibility of the soft tissues. This all allows for relaxation and concomitant elongation of the muscle. 

Active isolated stretching uses agonists and synergists for dynamic joint movement through the whole range of motion.

Neuromuscular stretching is based on the influence of neurophysiological mechanisms of autogenic inhibition and reciprocal inhibition. This involves the professional passive movement of the limb until the first resistance barrier is found. Then the use of relaxation and contraction is implemented. 

Dynamic stretching uses the muscle’s force production and the body’s momentum to take a joint through the full range of motion.