Consideration of Selected Research: Refined Static Stretching Protocol for Fitness Professionals

by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

Static stretching has seemingly lost credibility with strength and conditioning professionals. New research has highlighted some flaws in our understanding, but the strength and conditioning community should consider refining static stretching protocols before simply replacing them with active and dynamic techniques. Our understanding of how the body adapts to static stretching is still evolving. In the following article static stretching is refined after considering the length of time a static stretch should be held, the amount of force used during a static stretch, when a muscle should be stretched, and the goal of a static stretching program.

Adaptation to a static stretch

It is important to clarify that the body adapts to a static or PNF stretch differently than the body adapts to an active or dynamic stretch. Each stretching technique has its inherent benefits, drawbacks, and best use. To understand the best use of static and PNF stretching we should consider the hypothesized adaptation to a static stretch.

Davis’ Law states that soft tissue will remodel along lines of stress1, 11. The forces created during static and dynamic postures, as well as the intentional forces applied during stretching, create a stimulus for connective tissue adaptation. The direction, duration, and amount of force applied will have an effect on that adaptation2, 5, 11. However, every force imparted on muscle and connective tissue does not result in adaptation. Muscle tonicity and stretch reflex ensure that muscle tissue protects fascia from most forces that would result in unwanted change.

It is hypothesized that static and PNF stretches reduce muscle tonicity and inhibit stretch reflex via autogenic inhibition1, 2, 5, 11. When adaptive shortening leads to tightness and restriction we can use static and PNF stretches to reduce muscle tonicity, inhibit stretch reflex1-2, and impart a force on connective tissue. A lengthening force on connective tissue will act as a stimulus for adaptation via Davis’ law1, 10.

How long?

Studies show that static stretches held for 30 seconds or more consistently result in an increase in muscle extensibility6; however, an arbitrary time limit does not ensure a “successful” static stretch. Considering Davis’ Law and autogenic inhibition, 30 seconds may simply be a guideline that allows enough time for most people to experience autogenic inhibition and the resultant force applied to connective tissue. Force applied to a muscle that does not result in inhibition is unlikely to produce a change in connective tissue length. This may be noted in individuals who resist a stretch, often termed “guarding”.

The autogenic inhibition of stretch reflex that initiates a transfer in force to connective tissue may be felt by the strength and conditioning professional as a relatively sudden decrease in muscle tension or increase in flexibility (sometimes referred to as a feeling of release by the “stretchee”). This in conjunction with practical experience would suggest that a decrease in muscle tension, or increases in length are better indicators of a “successful” static stretch than an arbitrary time limit.

How hard?

How hard we pull or push on those under our guidance should be carefully considered; if not for liability reasons, than in respect to the intention of static stretching. A muscle should be elongated to the first resistance barrier with a moderate force that induces mild discomfort or a feeling of stretch. More force is likely to increase stretch reflex intensity, decreasing the likely-hood of inhibition. Simply, the harder you push, the harder the muscle pulls back. This is evidenced by a study in which increased force applied during a stretch did not increase the gains made during a static stretching protocol4.

Further, there is a point when force on connective tissue will induce trauma rather than the adaptive elongation that is intended. An example of traumatic elongation is a muscle strain.

When?

The question of when fitness professionals should recommend static stretching is not a matter of before or after, but whether or not a muscle exhibits tightness. Studies have shown a reduction in muscular force output post static stretching, and because of these findings it has been suggested that stretching should be done after exercise3, 12. Neural inhibition, a reduction in musculotendinous rigidity, and changes in muscle length/tension relationships have been suggested when explaining the post-stretching reduction in force production3, 12. However, if a muscle is overactive and connective tissue has adaptively shortened there may be a benefit to pre-activity stretching. In the one study I could locate that selected individuals who exhibited clinical tightness before testing, stretching the tight hamstrings increased performance in a single leg hop test9. Could it be that inhibition and a change in hamstring length reduced resistance to motion and improved length tension relationships?

Further, changes in range of motion (ROM) will likely vary greatly between someone who exhibits limitations and someone who exhibits flexibility at or beyond normal. The results may be similar to the differences in gains between novice and experienced weight lifters. In a preliminary study comparing sit-and-reach protocols it was noted that those individuals who possessed excellent flexibility before the intervention gained nothing from the flexibility program9.

What is our goal?

The duration of stretching sessions cannot compete with the duration of stress as a result of static and dynamic postures in the presence of gravity. Less than optimal mechanics can alter length/tension relationships, force couplings, and muscular synergies that will have an effect on soft tissue adaptation all day. An illustration of this integrated dysfunction was seen in a study on Gaelic football players, revealing a correlation between increased lordosis and a decrease in ankle dorsi flexion8. Although general flexibility programs have their place in the health and wellness community, capable individuals should assess posture and muscle length to create a program that addresses tight structures; reinforcing optimal static and dynamic postures. The ability of static stretching to improve integrated function may be evidenced by a preliminary study that showed an increase in vastus medialis obliquus (VMO) activation after a biceps femoris stretch5. Static stretching as a means of improving posture and function may reinforce positive soft tissue adaptations and increase the chance for long term success.

Refined static stretching protocol:

1. 1. Assess posture and individual muscle length to identify short, overactive structures that may benefit from a static stretch.
2. 2. Slowly elongate the muscle until you reach a point of mild tension or discomfort and hold that position steady. Pay careful attention to the direction of force applied.
3. 3. Hold stretch until you feel a release, a reduction in tension, or an increase in muscle length.
4. 4. After the initial release you may move to the next resistance barrier and repeat (up to 3 times).
5. 5. Reassess posture, muscle length, and performance and proceed accordingly.

Bibliography:

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4. Byrd T, Corneau M, Brown L, Greenwood L, Graves M. The Effects of Two Different Stretching Forces on Viscoelastic Properties of the Hamstring Muscle Group. Med Sci Sports Exerc. 2002;34(5):S15
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11. Tippet S, Voight M. Functional Progressions for Sports Rehabilitation. Human Kinetics, Champaign, Illinois, USA 1995
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