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Static stretching is a type of stretching exercises in which elongation of muscle with application of low force and long duration (usually 30 sec). Static stretching has a relaxation, elongation effect on muscle which increases range of motion (ROM) , decreases musculotendinous stiffness and also reduce the risk of acute muscle strain injuries.[1][2] It is a slow controlled movement with emphasis on postural awareness and body alignment. It is suitable for all patient types. Impact of Stretching on Muscle performance[edit | edit source]It is a traditional practice to perform static stretching exercises before the main exercise session or main sports events in order to improve muscle performance and minimizing risk of injury. But the recent reviews found that stretching immediately prior to exercise does not prevent injury and can lead to detrimental effect on muscle performance. Therefore performing static stretching before main exercise session or main sport events can lead to decrease in the performance in these subsequent events.[3][4] To understand how static stretching can lead to decline muscle performance we have to understand the acute effect of static stretching and the effect of regular stretching. Acute Effects of Static Stretching on Muscle:[edit | edit source]
Collectively all these acute changes in the muscle lead to decrease in force production, performance and increasing in the risk of injury . Effect of Regular Static Stretching on Muscle:[edit | edit source]Regular static stretching exercise shown that it improves force and performance in activities.it`s underlying mechanism is that regular stretching induces muscle hypertrophy. It is shown that if stretching a muscle group for 30 to 60 s/d over months results in hypertrophy[3] Summary[edit | edit source]The evidence shows that performing static stretching exercises before sports activities lead to decrease the performance and increasing the risk of injury, while in the other hand performing regular stretching exercises lead to improve in force production and performance in all activities[3] References[edit | edit source]
Stretching exercises have traditionally been included as part of a training and recovery program. Evidence shows that physical performance in terms of maximal strength, number of repetitions and total volume are all affected differently by the each form of stretching:
This 4 minute video is a good summary of stretching. The below video gives a brief description of the types of stretching ( isometric stretching here is similar to PNFS) [4] Technique[edit | edit source]Techniques of stretching include Static Stretching[edit | edit source]Static stretching (SS) is a type of stretching exercises in which elongation of muscle with application of low force and long duration (usually 30 sec).Static stretching has a relaxation, elongation effect on muscle, improving range of motion (ROM),decreasing musculotendinous stiffness and also reduces the risk of acute muscle strain injuries.[5] It is a slow controlled movement with emphasis on postural awareness and body alignment.It is suitable for all patient types.[6] Dynamic Stretching[edit | edit source]Dynamic Stretching (DS) involves the performance of a controlled movement through the available ROM. Involves progressively increasing the ROM through successive movements till the end of the range is reached in a repetitive and progressive manner. Dynamic Stretching:
Pre-Contraction Stretching: Proprioceptive Neuromuscular Facilitation Stretching (PNFS)[edit | edit source]This form of stretching involves a contraction of the muscle being stretched or its antagonist before stretching. PNF is the most common type, see below. Other types of pre-contraction stretching include “post-isometric relaxation” (PIR). This type of technique uses a much smaller amount of muscle contraction (25%) followed by a stretch. Post-facilitation stretch (PFS) is a technique developed by Dr Vladimir Janda that involves a maximal contraction of the muscle at mid-range with a rapid movement to maximal length followed by a 15-second static stretch. Multiple PNF stretching techniques exist, all of them rely on stretching a muscle to its limit.This triggers the inverse stretch reflex, a protective reflex that calms the muscle to prevent injury. Regardless of technique, PNF stretching can be used on most muscles in the body.PNFS can also be modified so you can do them alone or with a partner.[9] The types of PNF stretch techniques are: Contract Relax (CR) Contraction of the muscle through its spiral-diagonal PNF pattern,followed by stretch; Hold Relax (HR) Contraction of the muscle through the rotational component of the PNF pattern, followed by stretch; Contract-Relax Agonist Contract (CRAC) Contraction of the muscle through its spiral-diagonal PNF pattern, followed by contraction of opposite muscle to stretch target muscle. Mechanisms of Stretching[edit | edit source]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. Therefor 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.[10] 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.[11] 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.
The Stretch Reflex[edit | edit source]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[10]. The below 5 minute video gives is on the stretch mechanism Indications[edit | edit source]Indications for stretching include:
Contraindications[edit | edit source]Include:
Determinants of Stretching[edit | edit source]
Evidence[edit | edit source]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.Older 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.[2] Outcome[edit | edit source]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 [2]."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[edit | edit source]
References[edit | edit source] |