NASM Study Guide Chapter 7 – Flexibility Training Concepts

Chapter 7 Flexibility Training Concepts:

Know all definitions throughout the chapter

  • Figure 7.10 Integrated flexibility Continuum
  • Table 7.2 Examples of stretching within the Flexibility Continuum
  • Myofascial Release
  • Table 7.3 Static Stretching Summary
  • Table 7.4 Active-Isolated Stretching summary
  • Table 7.5 Dynamic Stretching summary

Mechanoreceptors = a Golgi tendon organ (GTO) and muscle spindle fibers

GTO Muscle Spindle Fibers
Senses muscle tension Senses muscle lengthening
Relaxes the muscle in response Contracts the muscle in response
Normal reaction to avoid injury Normal reaction to avoid injury

There is a lot of useful information page 183 of the NASM Essentials of Personal Fitness Training and it will take some time to remember all of that information.  There are various strategies you can try as you attempt to retain that information.  One is to make your studying interactive by asking friends and family members to volunteer for the Overhead Squat Assessment and practice trying to locate compensations.  Another way to learn the probable overactive and probable underactive muscles is by creating flash cards.

You can also look at each overactive muscle and refer back to Appendix D (pages 575-596).  Look at each muscle’s “Isolated Function”.  Some muscles will over-do their “Isolated Function”.  Other muscles tend to be “victims of association”.  This means that they may become synergistically dominant because a muscle nearby becomes underactive/lengthened/weak.

In addition, by having a general idea of what each muscle’s “Isolated Function” is, you will be able to figure out exercises that directly work those muscles.

Think of muscles in terms of antagonistic (one is an agonist while the other is an antagonist) actions. When an agonist contracts, the antagonist will relax. Also keep in mind that several muscles may have similar actions and that the exact movement of a bone will be the result of a coordinated effort involving many muscles (force couples).  Muscles function in integrated groups to allow for neuromuscular control during movement.  A muscle’s integrated muscle function is the action it naturally tends to perform when it works in conjunction with other muscles.  By isolating each muscle on the other hand, and tracing them from their point of origin to their insertion, one can gain a better understanding of that muscle’s main function. A muscle’s isolated function is what that individual muscle is meant to do, alone, and isolated from all other muscles.

An advanced knowledge in anatomy is required to identify muscle functions such as agonists, antagonists, synergists, and stabilizers. For example, most stabilizers are proximal to the joint they stabilize, but it is dependent on the movement that is occurring. Stabilizers are generally smaller in size, made up of type I muscle fibers (slow twitch), and they are prone to weakness.

Some examples of stabilizers include (1) rotator cuff – shoulder (2) core inner unit – multifidus, transverse abdominus, pelvic floor muscles, internal oblique – stabilize pelvis and spine (3) knee- VMO, popliteus – knee. For the exam you only need an understanding of this concept to the degree the textbook discusses. If you want to learn more, then the CES does a good job explaining these concepts in more detail.

Current Concepts in Flexibility Training

  • Flexibility – Normal extensibility of all soft tissues that allows the full range of motion of a joint.
  • Extensibility – Capability to be elongated or stretched. 
  • Dynamic range of motion – Combination of flexibility and the nervous sytem’s ability to control this range of motion efficiently. 
  • Neuromuscular efficiency – Ability of neuromuscular system to allow agonists, antagonists, and stabilizers to work synergistically to produce, reduce, and dynamically stabilize the entire kinetic chain in all three planes of motion. Ability of nervous system to recruit correct muscles(agonists, antagonists, synergists, stabilizers) to produce force, reduce force, and dynamically stabilize body’s structure in all three planes of motion. When performing cable pulldown, latissimus dorsi(agonist) must concentrically accelerate shoulder extension, adduction, and internal rotation while middle and lower trapezius and rhomboids(synergists) perform downward rotation of the scapulae. Same time rotator cuff musculature(stabilizers) must dynamically stabilize the glenohumeral(shoulder) joint throughout the motion.
  • To allow for optimal neuromuscular efficiency, individuals must have proper flexibility in all three planes of motion.

Review of Human Movement System

  • Postural distortion pattern – Predictable patterns of muscle imbalances.
  • Relative Flexibility – The tendency of the body to seek the path of least resistance during functional movement patterns. Prime examlpe are people who squat with feet externally rotated, because of tight calf muscles they lack proper dorsiflexion at the ankle to perform squat with proper mechanics. Another example is overhead press with excessive lumbar extension(arched lower back). Individuals who possess tight latissimus dorsi will have decreased sagittal-plane shoulder flexion (inability to lift arms directly overhead), and as a result they compensate for this lack of ROM at shoulder in lumbar spine to allow them to press load completely overhead.

Muscle Imbalance

  • Muscle imbalances – Alteration of muscle length surrounding a joint. 
  • Muscle imbalances can be caused by – postural stress, emotional duress, repetitive movement, cumulative trauma, poor training technique, lack of core strength, lack of neuromuscular efficiency
  • Reciprocal Inhibition – simultaneous relaxation of one muscle and the contraction of its antagonist to allow movement to take place. To perform elbow flexion during biceps curl, biceps brachii actively contracts while triceps brachii(antagonist) relaxes to allow the movement to occur.
  • Altered reciprocal inhibition – Concept of muscle inhibition, caused by tight agonist, which inhibits its functional antagonist. Example tight psoas(hip flexor) would decrease neural drive of the gluteus maximus (hip extensor). Altered reciprocal inhibition alters force-couple relationships, produces synergistic dominance, and leads to the development of faulty movement patterns, poor neuromuscular control, and arthrokinetic (joint) dysfunction.
  • Synergistic Dominance – Neuromuscular phenomenon that occurs when inappropriate muscles take over the function of a weak or inhibited prime mover. Example if psoas(hip flexor) is tight, leads to reciprocal inhibition of gluteus maximus, which in turn results in increased force output of synergists for hip extension (hamstring complex, adductor magnus) to compensate for weakened glutes. The result of synergistic dominance is faulty movement patterns, leading to arthrokinetic dysfunction and eventual injury(such as hamstring strains).
  • Arthrokinematics – Motion of joints in the body. 
  • Arthrokinematic dysfunction – Altered forces at the joint that result in abnormal muscular activity and impaired neuromuscular communication at the joint. Altered joint motion can be caused by altered length-tension relationships and force-couple relationships, which affect joint and cause poor movement efficiency. Example, squatting with externally rotated feet(outward) forces tibia(shin bone) and femur(thigh bone) to also rotate externally. This posture alters length-tension relationships of muscles at the knee and hips, putting glutes in a shortened position and decreasing its ability to generate force. Further, biceps femoris(hamstring muscle) and piriformis(outer hip muscle) become synergistcally dominant, altering the force-couple relationships and ideal joint motion, increasing the stress on the knees and low back. With time, stress associated with arthrokinematic dysfunction can lead to pain, which can further alter muscle recruitment and joint mechanics.

Neuromuscular Efficiency

  • Neuromuscular efficiency, ability of neuromuscular system to properly recruit muscles to produce force(concentric), reduce force(eccentric), and dynamically stabilize(isometric) the entire kinetic chain in all three planes of motion. Because nervous system is controlling factor behind this principle, it is important to mention that mechanoreceptors(sensory receptors) located in the muscles and tendons help to determine muscle balance or imbalance. Mechanoreceptors include muscle spindles and Golgi tendon organs.

Muscle Spindles

  • Muscle spindles are the major sensory organ of the muscle and are composed of microscopic fibers that lie parallel to the muscle fiber. Muscle spindles are sensitive to change in muscle length and rate of length change. Muscle spindle’s job is to help prevent muscles from stretching too far or too fast. 
  • When a muscle on one side of a joint is lengthened(because of a shortened muscle on the opposite side), the spindles of the lengthened muscle are stretched. This information is transmitted to brain and spinal cord, exciting the muscle spindle and causing the muscle fibers of the lengthened muscle to contract. This often results in microspasms or feelings of tightness.
  • Hamstring complex is prime example when pelvis is rotated anteriorly, meaning the anterior superior iliac spines(front of the pelvis) move downward(inferiorly) and the ischium(bottom posterior portion of pelvis, where the hamstrings originate) moves upward(superiorly). If attachment of hamstring complex is moved superiorly, it increases the distance between the two attachment sites and lengthens the hamstring complex. When a lengthened muscle is stretched, it increases the excitement of the muscle spindles and further creates a contraction(spasm) response. With this scenario, the shortened hip flexors are helping to create the anterior pelvic rotation that is causing the lengthening of the hamstring complex. Instead, hip flexors need to be stretched.
  • Another example is individual whose knees adduct and internally rotate(knock-knees) during a squat. The underactive muscle is the gluteus medius(hip abductor and external rotator), and the overactive muscles include adductors(inner thighs) and tensor fascia latae(hip flexor and hip internal rotator). Thus, one would not need to stretch the gluteus medius, but instead stretch the adductor complex and tensor fascia latae which in this case are overactive, pulling the femur into excessive adduction and internal rotation.

Golgi Tendon Organs

  • Autogenic Inhibition – Process by which neural impulses that sense tension are greater than the impulses that cause muscles to contract, providing an inhibitory effect to the muscle spindles. 
  • Golgi Tendon Organs are located within musculotendinous junction(point where muscle and tendon meet) and are sensitive to changes in muscular tension and rate of tension change. When excited, Golgi tendon organ causes the muscle to relax, which prevents muscle from being placed under excessive stress, which could result in injury. Prolonged Golgi tendon organ stimulation provides an inhibitory action to muscle spindles(located within same muscle). This neuromuscular phenomenon is called autogenic inhibition. Occurs when neural impulses sensing tension are greater than impulses causing contraction. This phenomenon is termed autogenic, inhibited by its own receptors.

Scientific Rationale for Flexibility Training

  • Flexibility training is key component of all training programs, used for variety of reasons including – correcting muscle imbalances, increasing joint range of motion, decreasing the excessive tension of muscles, relieving joint stress, improving extensibility of musculotendinous junction, improving neuromuscular efficiency, improving function
  • Pattern Overload – Consistently repeating same pattern of motion, which may place abnormal stresses on the body. Pattern overload is consistently repeating same pattern, such as baseball pitching, long-distance running, and cycling, with time places abnormal stresses on the body.

Cumulative Injury Cycle

  • Poor posture and repetitive movements create dysfunction within the connective tissue of the body. This dysfunction is treated by body as another injury, and as a result, body will initiate repair process termed cumulative injury cycle.
  • Any trauma to tissue of the body creates inflammation. Inflammation, in turn, activates body’s pain receptors and initiates protective mechanism, increasing muscle tension or causing muscle spasm. Heightened activity of muscle spindles in particular areas of muscle create a microspasm, and as result of spasm, adhesions(or knots) being to form in the soft tissue. These adhesions form a weak, inelastic matrix(inability to stretch) that decreases normal elasticity of the soft tissue, resulting in altered lenght-tension relationships(leading to altered reciprocal inhibition), altered force-couple relationships, and arthrokinetic dysfunction(leading to altered joint motion). Left untreated adhesions can begin to form permanent structural changes in soft tissue that is evident in Davis’s law.
  • Davis’s Law – Soft tissue models along the lines of stress. Soft tissue is remodeled (or rebuilt) with inelastic collagen matrix that forms in a random fashion, usually it does not run in same direction as the muscle fibers. If muscle fibers are lengthened, these inelastic connective tissue fibers act as roadblocks, preventing muscle from moving properly which creates alterations in normal tissue extensibility and causes relative flexibility.
  • If a muscle is in a constant shortened state(such as hip flexor musculature when sitting for prolonged periods every day), it will demonstrate poor neuromuscular efficiency(as a result of altered length-tension and force-couple relationships). In turn this will affect joint motion(ankle, knee, hip, and lumbar spine) and alter movement patterns(leading to synergistic dominance). Inelastic collagen matrix will form along the same lines of stress created by the altered muscle movements. Because the muscle is consistently short and moves in a pattern different from its intended function, the newly formed inelastic connective tissue forms along this altered pattern, reducing the ability of the muscle to extend and move in its proper manner. This is why it is imperative that an integrated flexibility training program be used to restore the normal extensibility of the entire soft tissue complex.

The Flexibility Continuum

  • Three types of flexibility continuum, corrective, active, and functional.

Corrective flexibility

  • Corrective flexibility is designed to increase joint ROM, improve muscle imbalances, and correct altered joint motion. Corrective flexibility includes self-myofascial release(foam roll) techniques and static stretching. Self-myofascial release uses the principle of autogenic inhibition to cause muscle relaxation, whereas static stretching can use either autogenic inhibition or reciprocal inhibition to increase muscle length depending on how the stretch is performed. Corrective flexibility is appropriate at the stabilization level (phase I) of the OPT model.

Active Flexibility

  • Active flexibility uses self-myofascial release and active-isolated stretching techniques. Active-isolated stretching is designed to improve the extensibility of soft tissue and increase neuromuscular efficiency by using reciprocal inhibition. Active-isolated stretching allows for agonists and synergists muscles to move a limb through a full range of motion while functional antagonists are being stretched. For example, supine straight-leg raise uses hip flexors and quads to raise leg and hold it unsupported, whiel antagonist hamstring complex is stretched. Active flexibility appropriate at strength levels(phase 2,3, and 4) of OPT model.

Functional Flexibility

  • Functional flexibility uses self-myofascial release techniques and dynamic stretching. Dynamic stretching requires integrated, multiplanar soft tissue extensibility, with optimal neuromuscular control, through the full range of motion, or essentially movement without compensations. Therefore, if clients are compensating when performing dynamic stretches during training, then they need to be regressed to active or corrective flexibility. Appropriate at power leve(level 5). 

NASM Figure 7.10

Stretching Techniques

Myofascial Release

  • Self-myofascial release is stretching technique that focuses on the neural system and fascial system in the body. By applying gentle force to an adhesion or “knot,” the elastic muscle fibers are altered from a bundled position(which causes the adhesion) into a straighter alignment with the direction of the muscle or fascia. The gentle pressure will stimulate the Golgi tendon organ and create autogenic inhibition, decreasing muscle spindle excitation and releasing the hypertronicity(tension) of the underlying musculature. Gentle pressure(similar to massage) breaks up knots within muscle and helps to release unwanted muscular tension.
  • When person finds tender spot(indicates presence of muscle hypertonicity) and sustain pressure on that spot for minimum of 30 seconds. This will cause Golgi tendon organ activity and decrease muscle spindle activity, thus triggering autogenic inhibitory response. It may take longer, depending on client’s ability to consciously relax. Process will help restore body back to its optimal level of function by resetting proprioceptive mechanisms of soft tissue. Self-myofascial release is suggested before stretching because breaking up fascial adhesions(knots) may potentially improve tissue’s ability to lengthen through stretching techniques.

NASM Table 7.2


Static Stretching

  • Static Stretching – Process of passively taking a muscle to the point of tension and holding the stretch for a minimum of 30 seconds.
  • By holding muscle in stretched position for prolonged period, Golgi Tendon organ is stimulated and produces inhibitory effect on muscle spindle(autogenic inhibition). This allows muscle to relax and provides for better elongation of the muscle. In addition, contracting the antagonistic musculature while holding the stretch can reciprocally inhibit the muscle being stretched, allowing it to relax and enhancing the stretch.
  • Static stretching should be used to decrease muscle spindle activity of a tight muscle before and after activity.

NASM Table 7.3


Active-Isolated Stretching

  • Active-Isolated Stretch – Process of using agonists and synergists to dynamically move the joint into a range of motion.
  • Increases motorneuron excitability, creating reciprocal inhibition of muscles being stretched. Active supine biceps femoris stretch is good example of active-isolated stretching. Quads extends the knee, this enhances the stretch in two ways. First, increases the length of biceps femoris, second contraction of the quadriceps causes reciprocal inhibition(decreased neural drive and muscle spindle excitation) of hamstring complex, which allows it to elongate.
  • Active-isolated stretches are suggested for preactivity warm-up(before sports competition or high-intensity exercise), as long as no postural distortions are present. 5-10 reps of each stretch are performed and held for 1-2 seconds each.

NASM Table 7.4


Dynamic Stretching

  • Dynamic Stretching - Uses force production and momentum to move the joint through the full available range of motion.
  • Uses the concept of reciprocal inhibition to improve soft tissue extensibility. One can perform one set of 10 reps using 3 ot 10 dynamic stretches. Hip swings, medicine ball rotations, and walking lunges are good examples of dynamic stretching.

NASM Table 7.5