NASM CES Chapter 4: Lengthening Techniques

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Chapter Goals:

• Define muscle length, extensibility, and flexibility. 
• Describe the function of lengthening techniques in a corrective exercise program. 
• Discuss the guidelines for applying stretching techniques. 

Introduction

This is the second phase of the corrective exercise continuum, following the previous inhibiting phase.

Lengthening refers to elongating the connective tissues to increase the range of motion at the tissue and the joint.

The most common static, dynamic, and neuromuscular stretching methods will be focused on in this chapter.

The goals of stretching in all three will be improving the range of motion available, increasing the extensibility of the tissues, decreasing muscle and tendon injuries, and enhancing neuromuscular efficiency. 

Flexibility is defined as the range of motion available to a joint or a group of joints. 

Stretching is an active process trying to elongate the muscles and the connective tissues to increase the state of flexibility. 

Types of Stretching Techniques

Stretching is the technique to lengthen muscles and tendons and has been the subject of debate for several decades, thus leading to a lot of research on the effects, duration, and methodologies for stretching.

It might be the most widely studied topic in all of human performance. 

Static Stretching

This has been the most common stretching technique for health and fitness professionals. Three things characterize it:

• The elongation of myofascial tissue to an end-range and statistically holding that position for a period of time.
• Max control of structural alignment.
• Minimal acceleration into and out of the stretched position. 

This form of flexibility training is associated with a lower risk of injury in a stretching routine and is deemed the safest because people can do them on their own and with slow or no motions. 

Mechanical Adaptations

It is believed that static stretching produces adaptations that lead to a greater range of motion in the joints stretched. 

Neurological Adaptations

Static stretching to the end range of motion is seen to decrease the excitability of motor neurons.

With passive stretches, we see the muscle extending slowly or moderately into an elongated position and held for some time.

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The muscle spindles in the muscle are used for detecting the changes in length and the rate of said changes.

The nuclear chain fibers inside the muscle spindles will respond to changes in elongation and the nuclear bag fibers are for the elongation rate and the stretch’s extent.

Muscle relaxation occurs as a response to the amount and rate of lengthening. 

Other mechanisms affecting the stretch include the Golgi tendon organs and the Renshaw cells.

The Golgi tendon organ is activated by tension exerted on the muscle tendon, contributing to reflex inhibition.

The Renshaw cells contribute to the relaxation or inhibition of muscles with large amplitude stretches. 

Psycho-physiological Adaptations

One of these responses would be the increased stretch tolerance that occurs from stretching chronically.

This is seen as one of the greatest contributors to increasing the range of motion. 

Chronic Adaptations to Static Stretching

All of these previous ones may occur acutely with a single session, but long term stretching will cause chronic changes that affect many factors.

Changes in muscle and tendon stiffness are known to occur long term.

Tissue creep may occur over the long term.

This is where the muscles and tendons do not return to their original length following prolonged stretching. 

Neuromuscular Stretching

This is also going to be called proprioceptive neuromuscular facilitation.

It has received a lot more attention as of late and is an optimal way to lengthen myofascial tissues.

This stretching involves a process of isometrically contracting a specific muscle in a lengthened position to induce a relaxation response in the muscle and then allow it to elongate further.

Many researchers believe that this is a combination of static and active stretching. 

Four stages characterize neuromuscular stretching:

• Hold the muscle to the end range of motion for 10 seconds.
• Actively contract the muscle that will be stretched for 5 – 10 seconds. 
• Passively elongate the muscle to the new end range of motion. 
• Statically hold this new position for 20 – 30 seconds and repeat these steps three times. 

You might see some variations done for this process, like the contract-relax technique or the contract relax, agonist contract method. 

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An advantage of neuromuscular stretching over static stretching is that the contraction of the stretched muscles places more mechanical stress on the tendon than during the passive stretches. 

Since the muscle is already elongated, the next contraction will emphasize the elongated tendon, providing an additional mechanical factor.

One usual weakness of neuromuscular stretching is that it usually requires the assistance of another person or at least the use of a band to replace that person. 

Mechanisms of Neuromuscular Stretching

The reflex inhibition techniques are seen to have a part in neuromuscular stretching likely.

A similar increase is seen in the tolerance to stretching, just like we had with static stretching. 

Dynamic Stretching

This has also become popular lately, like neuromuscular stretching.

It has been seen as a great addition to the warmup routines of clients.

Dynamic stretching uses controlled movements in their whole range of motion in the active joints. 

It is similar, but also very different, to ballistic stretching.

Ballistic stretching emphasizes high velocity movements and bouncing actions at the end range of motion, making it a tad more dangerous.

Static stretching is used for inhibiting the nervous system, while dynamic stretching is used for activating and exciting the nervous system.

Dynamic stretching has more advantages for use before sports performance or more demanding exercise.

Muscle contractions also work to increase the activity of the metabolism and this elevates the temperature of the muscles. 

Improving Range of Motion

Stretching exercises are used mainly to increase the available joint range of motion.

This is truer if tight tissues limit the range at the joint.

Stretching is needed to be done both acutely and chronically.

It is not conclusively stated that one type of stretching is better than another.

Some researchers have found that the ability to change the range of motion is possibly different with the use of different stretching methods at different joints.

Some respond better than others to stretching types.

Fitness professionals should work to evaluate movement and decide what is best for the desired outcomes.

Impacts on Athletic Performance

There is a common misconception that stretching will reduce someone’s athletic performance, and thus, it should not be done before athletic activity. This is not necessarily true.

Dynamic stretching, for example, is very beneficial before sporting events and should actually be implemented for optimal performance.

Some studies have found that static stretching in the warm up, at least to a great degree, has some negative effects on performance potentially. 

Warm up components based on the type of stretching

For myofascial rolling, 5 – 10 minutes of time will help.

For static stretching, less than 60 seconds per muscle group is ideal, and you should not have discomfort or pain.

For dynamic stretching, we see a need for less than 90 seconds per muscle group and moderate speeds for the exercises.

And task specific or specific warmup, we should have a total of 5 – 15 minutes. 

Obviously, we will not do all four types for a warmup; this is if you only choose to do one of these. 

Effects of Stretching on Improving the Resistance to Injury

Many health professionals and athletes perform their stretching before activity as a part of their warmup, which started the idea of preventing injury.

The studies show that pre-event static stretching does not actually affect injury risks.

On the other hand, long term stretching protocols have been found to decrease the injury rate in the muscles and the tendons. 

Application Guidelines for Lengthening Techniques

Precautions for Stretching:

• Special populations
• Seniors
• Hypertensive patients
• Neuromuscular disorders
• Joint replacements
• Fibromyalgia
• Marfan syndrome

Contraindications for Stretching:

• Acute injuries or muscle strains or tears in the muscle to be stretched
• Recent musculoskeletal surgeries or treatments
• Acute rheumatoid arthritis within the affected joint
• Osteoporosis

Static Stretching Acute Training Variables

• The frequency should be daily or some other specified days.
• The reps should be 1 – 4 repetitions.
• The duration of the stretches is 20 – 30 seconds holds or 60 seconds for older patients. 

Neuromuscular Stretching Acute Training Variables

• These can be done daily unless told in some other order. 
• 1 – 3 reps or cycles is normal per stretch.
• The contraction time is 7 – 15 seconds, with 10 being the ideal amount. 

Dynamic Stretching Acute Training Variables

• 90 seconds or less of the dynamic stretches should be done for each muscle group. 
• The velocity needs to be under control and performed at a rate of one cycle every second.