I previously wrote a post on the topic of acute stretching, injury, and performance and recently published a study in the same vein in the Journal of Strength and Conditioning Research. At that time, I made only a brief reference to long-term stretching. A recent article regarding a long-term static stretching intervention resulting in strength increases in the contralateral muscle from Nelson et al. 12 inspired me want to write a little more about long-term stretching.
What do we know about the effects of long-term stretching? At this time, we know we can use it to improve static range of motion (ROM)8,9, muscle strength, endurance, and power 7,8. There is also some evidence that long-term (again not acute!) stretching has a role in decreasing musculotendinous injury2. The mechanism involved in producing improvements in ROM from long term stretching is unknown at this time. Classically, the belief was that we are primarily “lengthening the muscle”. However, ROM improvements related to long-term static stretching appear to be largely related to increased stretch tolerance and not an actual changes in tissue extensibility 3,5,9, which would indicate some sort a neurological influence. The exact mechanism for the strength, endurance, power, and injury prevention benefits are also unknown, but a couple of thoughts seem to permeate. The first being that hypertrophy of skeletal muscle tissue and/or connective tissue may play a role, but this has only been demonstrated in animal studies 14. Which brings us to a neural influence. We typically think about the neural influences of stretching on the acute effects of performance, but between previous evidence3,5,9 and now Nelson et al. 12, I am hedging a bet towards long term neural adaptation being a key component in the positive outcomes of long-term stretching.
Briefly, Nelson et al. examined the cross training effect of a 10-week static stretching in an untrained population (important note) on calf strength which demonstrated a 29% increase (higher than contralateral resistance training studies!) in strength of the contralateral calf, as well as a statistically significant 1% increase in ROM for the contralateral calf12. This change in ROM may seem minimally relevant, but the fact that there was a detectable change in ROM of the contralateral limb may provide additional support for a neurological influence in this change. This is because if hypertrophy had occurred, increased tendon stiffness would likely be noted 15, which probably would have prevented a detectable change in calf ROM. Further yet, previous examinations on unilateral resistance training and its effect on the contralateral limb demonstrated strength increases in the absence of hypertrophy11 and appear to be related to neurological changes4, and there is little reason to believe the effects of stretching would be different than resistance training.
So what is the practical application of this discussion? Mechanism wise, whether hypertrophy or neural based, it doesn’t matter, both are synergistic benefits of long term training. The fact that there are physiological changes with concurrent performance improvements indicate a value in us maintaining or adding a long-term stretching regimen.
More specifically, most athletes can benefit from increasing static ROM. I state this with some caution as there definite risks with excessive flexibility, in particular at the spine. Greater flexibility of the lumbar spine is associated with disc degeneration6,17, and excess flexion and rotation are associated with disc herniation1,10.
Regarding improvements in muscle strength, power, and endurance, these benefits have only been demonstrated in the untrained population7,8,12, so it is difficult to apply to the higher level athlete because neural changes primarily are a part of early training with the influences of hypertrophy primarily playing a role in later gains. As stated by Nelson et al., there may also be a benefit in managing strength loss in an immobilized limb12.
Ultimately, the most practical application for chronic long-term stretching may lie in prevention of musculotendinous injury , although only one study has provided evidence for this proposal2. It appears that this injury reduction is the result of a training response over time, not an isolated occurrence, not in relation to pre-exercise stretching, but a long-term adaptation. As has been repeated to death at this point, no evidence for pre-exercise stretching reducing injury risk currently exists2,13,16,18, but a long-term relationship does exist, and justification for static stretching over time as a method to reduce injury risk is very plausable. There is some suggestion and guidance to the exclusive emphasis on dynamic stretching with no thought towards a post-exercise or separate static stretching sessions, and this may come at the detriment of some benefits we still do not understand. Needless to say, beyond the time commitment, unlike pre-exercise static stretching, there really is no evidence to demonstrate a negative impact of post-exercise static stretching or independent static stretching sessions.
So now it is your turn. What are your thoughts regarding keeping or adding a long-term stretching intervention? Is it worth the time it takes to keep or add it in your program?
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12. Nelson AG, Kokkonen J, Winchester JB, et al. A 10-week stretching program increases strength in the contralateral muscle. J Strength Cond Res. 2012;26(3):832-836. doi: 10.1519/JSC.0b013e3182281b41.
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17. Tanaka N, An HS, Lim TH, Fujiwara A, Jeon CH, Haughton VM. The relationship between disc degeneration and flexibility of the lumbar spine. Spine J. 2001;1(1):47-56.
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