Stretching

Original Editor - Lucinda hampton

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Introduction

Stretching is a physical exercise that requires putting a body part in a certain position that'll serve in the lengthening and elongation of the muscle or muscle group and thus enhance its flexibility and elasticity.

Effects of Stretching

1. Improves flexibility delaying impaired mobility associated with aging
2. Improves performance in physical activities as a result of improved flexibility
3. Reduce the risk of injury and damage
4. Improves blood circulation reducing muscle soreness and time for recovery
5. Increasing the range of motion

Indications

• Improves the joint range of motion
• Improves posture by strengthening the back muscles
• Returns normal neuromuscular balance between muscle groups
• Reduce injuries, strains and damage
• Before and after exercise to reduce muscle soreness

Contraindications

• Limited movement at the joint due to the presence of a boney block
• Directly after fracture when it has not completely healed
• Acute inflammation or, infection
• Sharp pain during joint movement
• Hematoma or other soft tissue trauma
• Hypermobility

Types of stretching

Stretching exercises have traditionally been included as part of the training and recovery program. It's important to note that, maximal strength, number of repetitions and total volume is different for each type of stretching.

The three different types of stretching are:

1. Static stretch (SS)
2. Dynamic stretch (DS)
3. Pre-contraction stretching: Proprioceptive Neuromuscular Facilitation stretching (PNFS)

The following video provides a brief description about the different types of stretching.

Static Stretching

Static stretching (SS) is a slow-paced controlled physical activity which involves putting the body part in a comfortable position that elongates the muscle without causing pain with low force for a prolonged duration of time (usually 30 seconds).

There are two types of static stretching:

1. Active-static stretching involves performing static stretches without assistance.
2. Passive-static stretching involves performing the stretches passively with assistance from an external force which can be a partner, an accessory or the force of gravity.

Effects of static stretching:

1. Improves range of motion in the joint
2. Reduces stiffness and pain in muscles
3. Reduces the risk of muscle strains and other injuries
4. Improves postural awareness and body posture
5. Increases circulation which in return decreases recovery period after exercise

Frequency and Duration of Static Stretching

The duration of the hold of the stretch is irrelevant to notice improvement but rather how many times the stretch is repeated in a week. Its important to note that each muscle should be stretched only once and should be held for five minutes which is broken into five one-minute exercises or ten exercises of thirty seconds. The more we stretch in a week, the better the outcomes where according to certain studies stretching for more than three weeks served in decreasing stiffness and increasing the range of motion (two to eight-minute stretches served in increasing range of motion while ten minute stretches served in reobtaining normal range of motion).

For individuals whose main objective is general fitness, it's recommended that static stretching should be done at least twice a week and stretch held for a minimum of 15 seconds followed by dynamic stretching.

For older adults, the duration of static stretching should be longer to notice improvements. For example, a sixty-second hold stretch served in an increase by 2 degrees per week in range of motion while a thirty-second hold stretch served in an increase by 1 degree.

For children, incorporating static stretching in physical education class significantly improved the flexibility of the hamstring muscles where four sessions per week served in a 17 degree increase in range of motion while two sessions per week improved the range of motion by 9 degrees.

As a warm up, static stretches held for less than 60 seconds can have minimal negative effects on strength and performance. Hence durations < 60s can be considered for warm ups.

Dynamic Stretching

Dynamic Stretching (DS) is a controlled movement, unlike ballistic stretches that involve bouncing movements which increase the risk of injury, involving the performance of a movement progressively increasing the range of motion through successive repetitive motions till the end of the range is achieved. It can be done standing or while moving.

For individuals who perform specific sports such as swimming, dynamic stretching exercises involve mimicking the movement of the activity such as circling arms before getting in the water and is often done after static stretching.

Effects of dynamic stretching:

1. Restore physical functioning and flexibility
2. Improve neuromuscular control through repetitive movement which: enhance the nervous message conduction speed, motor control and muscle compliance
3. Elevates core body temperature
4. Accelerates energy production
5. Improves performance measures such as speed and strength

Based on a randomized controlled trial conducted on 60 participants on the efficiency of dynamic stretching on hamstring extensibility and stretch tolerance compared to static stretching, dynamic stretching was more effective at achieving an increase in hamstring extensibility and stretch tolerance one-hour post-intervention than static stretching.

Pre-Contraction Stretching: Proprioceptive Neuromuscular Facilitation Stretching (PNFS)

Pre-contraction stretching is a type of stretching that involves both the contraction and stretching of the muscle. It has been originally developed for the sole reason of relaxing muscles and increasing muscle tone.

The most common type is PNF, proprioceptive neuromuscular facilitation, which is a technique which can be performed in different ways. One of which is the contract-relax method during which the muscle is held in a stretching position by a partner and the person contracts the muscle for a minimum of 4 seconds followed by a short relaxation period of two to three seconds. The stretch should progressively be pushed further than the initial stretch and held for a longer period of time(held for a minimum of 10 seconds and relaxed for 20 seconds). Another would be hold-relax method which involves putting the muscle in a stretched position first by a partner and then the partner contracts the muscle while asking the person to prevent this contraction and afterwards passive stretch of the muscle is applied by the partner. A different method would be the contract-relax agonist contract during which the muscle is also elongated by the partner for a minimum of 4 seconds and the person is asked to contract the agonist of the muscle then activate the antagonist of the muscle followed by a relaxation period of 20 seconds.

Other types of Pre-Contraction Stretching are Post-Isometric Relaxation (PIR) and Post-Facilitation Stretch (PFS).

There are different PNF stretching techniques, all of them focus on the stretching a muscle to its limit, can be used on almost all muscles in the body and can be done alone or with assistance. The stretching of the muscle to its limit, triggers the inverse stretch reflex, a reflex that returns the muscle to its initial position to prevent injury.

Based on a study conducted on 45 healthy university students on the efficacy of static stretching and proprioceptive neuromuscular facilitation stretch on hamstrings length after a single session, results showed that the PNF group demonstrated significantly greater gains in knee extension compared to the static stretching group with the static stretching group noting an increase by 7.53° and the PNF group noting an increase by 11.80° in knee extension.

Mechanisms of Stretching

The stretching of a muscle fiber begins with the sarcomere, the basic unit of contraction in the muscle fiber. As the sarcomere contracts, the area of overlap between the thick and thin myofilaments increases. As it stretches, this area of overlap decreases, allowing the muscle fiber to elongate. Once the muscle fiber is at its maximum resting length (all the sarcomeres are fully stretched), additional stretching places force on the surrounding connective tissue. As the tension increases, the collagen fibers in the connective tissue align themselves along the same line of force as the tension. Therefore when you stretch, the muscle fiber is pulled out to its full length sarcomere by sarcomere, and then the connective tissue takes up the remaining slack. When this occurs, it helps to realign any disorganized fibers in the direction of the tension. This realignment is what helps in the rehabilitation of scarred tissue.

The initial changes that are produced by stretch training involve mechanical adaptations that are followed by neural adaptations, which contrasts with the sequence observed during strength training.

When a muscle is stretched, some of its fibers lengthen, but other fibers may remain at rest. The more fibers that are stretched, the greater the length developed by the stretched muscle.

Proprioceptors: The proprioceptors related to stretching are located in the tendons and in the muscle fibers.

1. Muscle Spindles (intrafusal fibers) lie parallel to the extrafusal fibers. Muscle spindles are the primary proprioceptors in the muscle.
2. Another proprioceptor that comes into play during stretching is located in the tendon near the end of the muscle fiber and is called the golgi tendon organ.
3. A third type of proprioceptor, called a pacinian corpuscle, is located close to the golgi tendon organ and is responsible for detecting changes in movement and pressure within the body.

The Stretch Reflex

When the muscle is stretched, so is the muscle spindle. The muscle spindle records the change in length (and how fast) and sends signals to the spine which convey this information. This triggers the stretch reflex which attempts to resist the change in muscle length by causing the stretched muscle to contract. The more sudden the change in muscle length, the stronger the muscle contractions will be (plyometric training is based on this fact). This basic function of the muscle spindle helps to maintain muscle tone and to protect the body from injury. One of the reasons for holding a stretch for a prolonged period of time is that as you hold the muscle in a stretched position, the muscle spindle habituates and reduces its signalling. Gradually, you can train your stretch receptors to allow greater lengthening of the muscles .

The below 5 minute video provides an explanation on the stretch mechanism

Determinants of Stretching

• Alignment: The position of the patient has to be comfortable and should be such that the stretch force is applied on the particular muscle.
• Stabilization: The bony segment of the muscle to be stretched, should be fixed appropriately.
• Intensity: It is the magnitude of the stretch applied.
• Duration: Total time of the stretch which is to be applied.
• Speed: The rate at which initial stretch is applied.
• Frequency: Total number of stretching sessions per day or per week.
• Mode of Stretch: This is the type of stretch. Static, ballistic or cyclic, the amount of participation of the client (active or passive) and the source of the stretch ( manual/mechanical/self)

Evidence

When it comes to contractures, stiffening of soft tissues or muscles, it is seen that there is poor evidence for stretching as a treatment for contractures. In studies conducted of short term stretching durations (4-8 weeks) and frequency of stretch, it is seen that the impact of stretch only has a beneficial effect for a few minutes.

There seems to be high quality evidence which shows that stretch doe snot have a clinically significant effect on joint mobility, in individuals with or without neurological conditions, despite the duration of stretch application each day.

Moderate to high quality evidence also exists which shows that stretch doesn't have any effect on pain or quality of life in individuals with non-neurological conditions.

Overall, a Cochrane systematic review determined that stretch is not effective for the management of contractures in individuals with or without neurological conditions, carried out in a short-term program.

However, some practices are quite different than the presented evidence. Individuals with spinal cord injuries are frequently prescribed 1 hour of stretching on a permanent basis, to prevent or treat contractures. Considering such cases, it is very possible and likely that stretching may have an effect when carried out for extended periods of time, greater than 7 months, especually when it contains a static component.

From another study conducted on the stretch response of dorsiflexors, it was fund that static stretching and proprioceptive neuromuscular facilitation (PNF), as described above, has an effect in increasing dorsiflexion range of motion.

Another view, which may be more conventional in practice is as follows:

A 2012 study on the evidence surrounding stretching techniques found that the benefits of stretching seem to be individual to the population studied. To increase ROM, all types of stretching are effective, although PNF-type stretching may be more effective for immediate gains. To avoid decrease in strength and performance that may occur in athletes due to static stretching before competition or activity, dynamic stretching is recommended for warm-up. Adults over 65 years old should incorporate static stretching into an exercise regimen. A variety of orthopedic patients can benefit from both static and pre-contraction stretching.

Outcome

Increased ROM as a result of stretching exercises can be a result of patients/athletes ability to withstand more stretching force or a real increase in muscle length ."İncreased stretch tolerance" term is used for ability to withstand more stretching force. Increased muscle length or increased extensibility terms are used for real increase in muscle length. Measurement of passive ROM is not sufficient to measure extensibility. Passive ROM should be measured with reference loads to identify increased stretch tolerance and increased extensibility.

Final Words

1. To increase joint range of motion all types of stretching are effective, PNF-type stretching may be more effective for immediate gains.
2. Dynamic stretching is recommended for warm-up for athletes before competition or activity.As static stretching will likely decrease strength and may influence performance.
3. Post exercise static stretching or Proprioceptive Neuromuscular Facilitation stretching is recommended for reducing muscle injuries and increasing joint range of motion. Although Stretching has not been shown to be effective at reducing the incidence of overall injuries.
4. Stretching is often included in Physiotherapy interventions for management of many kinds of clinical injuries. Despite positive outcomes, it is difficult to isolate the effectiveness of the stretching component of the total treatment plan because the protocols usually include strengthening and other interventions in addition to stretching.
5. Despite stretching not having strong evidence in research, it is highly sought by Physiotherapists for an effective long-term treatment modality.