Viscoelasticity of the muscle-tendon unit is returned more rapidly than range of motion after stretching.
Mizuno T, Matsumoto M, Umemura Y. Scand J Med Sci Sports. 2011 May 12. doi: 10.1111/j.1600-0838.2011.01329.x. [Epub ahead of print]
https://www.ncbi.nlm.nih.gov/pubmed/21564309
Static stretching is one of the most common injury prevention techniques used in athletics, both competitive and recreational. It has been shown to have acute benefits like increased range of motion (ROM) and decreased stiffness of the muscle-tendon unit. Chronic stretching has also been studied and found to have benefits. All of these benefits are thought to minimize stress on the joint and muscle-tendon unit and therefore decrease the risk of injury. However, the duration of these benefits following acute stretching have never been examined. Therefore, this study examined the displacement of the myotendinous junction, passive end ROM, and passive torque of the gastrocnemius medialis muscle in 11 healthy participants (average age 23 years) following an acute bout of static stretching to determine the duration of beneficial effects. These characteristics were measured before stretching as well as 0, 15, 30, 60, and 90 minutes following stretching. During the time point participants remained in a seated position. Stretching consisted of passive dorsiflexion to the end ROM which was held for 1 minute and repeated 5 times. They found that after stretching passive end ROM significantly increased at 0, 15, and 30 minutes but not at the 60 or 90 minute time point compared to pre-stetching. Passive torque at end ROM was also increased after stretching. Stiffness was found to be significantly decreased immediately after stretching however stiffness was similar to pre-stretching by 15 minutes post-stretching.
This study provides additional information to clinicians for the benefits of stretching but also raises additional questions. Static stretching is thought to decrease injuries by decreasing tissue stiffness and increasing ROM. Previously this was thought to be maintained for extended periods of time during activity. These results suggest that only ROM is sustained overtime and muscle-tendon unit stiffness is not. This raises some interesting questions clinically. Which is more important in preventing injuries: ROM or stiffness? Do these characteristics contribute to reducing injury rates at all? The sustained increase in ROM could potentially help to minimize injuries by dissipating force over a greater ROM and time. This study found that it only lasted 30 minutes however these participants remained seated during that period. Therefore, walking or running may help to further maintain the increase in ROM and stiffness. This would be a nice follow-up study. One methodology issue is that muscle-tendon stiffness was calculated by the displacement of the myoteninous junction and the torque during passive motion. However, this torque is caused by the entire ankle joint, not just the gastrocnemius. Therefore, the stiffness is not specific to the muscle-tendon unit but the whole ankle joint. As clinicians we are continually searching for validity to the treatments we used every day. This study is a nice addition to the knowledge about static stretching and how long the beneficial effect can be maintained. However, additional research is required. What are your thoughts on these results? Do you feel static stretching is an important part of injury prevention? Do you feel its joint specific?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Steve:
Thanks for the interesting post. I initially had some hesitancy about the fact the participants remained seated during the follow up period but it does offer a nice first study as you suggested (to be followed up with an active rest).
A few quick thoughts:
1. If stiffness is beneficial, and we lose that benefit in less than 15 minutes when a person is not active, then perhaps we need to be more diligent with athletes who have breaks before the game or initially start on the sideline.
2. In the clinical setting, this may be worth noting because sometimes a patient may need to wait a few minutes for the clinician after they finish stretching (here they may be sitting making the results applicable). We may want to do our manual work with them quicker or encourage them to do an active task after they stretch (again that follow-up study you suggested would be valuable).
3. It's interesting that improved ROM lingered beyond the changes in stiffness. It makes me wonder what other structures may be contributing to the improved ROM or if there may be a neuromuscular component.
4. It is worth noting that some articles area suggesting acute static stretching may have acute negative influence on function performance. Some of these authors advocate more dynamic/active stretching/warm-ups, which may not causes the impaired performance, and/or doing the static stretching at a different time than the practice/competition:
Review: https://www.ncbi.nlm.nih.gov/pubmed/21373870
Golf: https://www.ncbi.nlm.nih.gov/pubmed/21068685
Track:
https://www.ncbi.nlm.nih.gov/pubmed/20683355
(This will be an area getting more attention in the coming years as conflicting research comes out. I think we will find that static stretching has a stronger negative impact with high velocity/force activities when performed immediately before the task).
Great topic steve and my thoughts are that in this particular circumstance the obvious increase in joint ROM is with dorsiflexion. You posed a question in your post to which is more important in preventing injuries – ROM, stiffness. That all depends on the joint we are discussing. To me the only static stretching I recommend is the hip flexor and posterior capsule of the shoulder. Beyond that, to me, its more of a mobility issue rather than a flexibility issue with other commonly "stretched joints".
Our body is designed to alternate between stability and mobility joints. The ankle is designed to be a mobility based joint. The increased ROM is ideal here. At the knee or low back lets say, I much rather want to see increased stiffness in order to stabilize that area.
Mobilizing that ankle and increasing dorsiflexion is a main goal in preventing ankle injuries in order to at least allow that joint to get into a closed-pack position. We can't prevent all injuries but our MOI in ankle sprains is in a plantar flexion and inversion position. The inability to dorsiflex and have that range of motion available will increase that person's chances of injury.
Stretching is one way to get that done in dorsiflexion but don't forget to joint mob and teach that person to actively mobilize that ankle themselves!
Jeff thanks for the comment. I will try to go through each of your thoughts.
1. I think the question remains is a decrease in stiffness beneficial. If so then yes, athletes should be performing some quick stretches every 15 minutes or so to maintain the beneficial effect.
2. I completely agree. After stretching in a rehab setting there shouldn't be much down time before starting more active exercises.
3. This is a good point and an interesting finding. I often associated those two things together (increased ROM = decreased stiffness) so to see them behave in a non-linear relation is interesting. There could very well be a neuromuscular aspect to the improved ROM.
4. This is also a great point. This has been a common finding and is important as it relates to this study. When examining the duration of improvements from stretching they are suggesting that there are beneficial effect in terms of injury prevention but don't consider performance. I would suspect that there was some slight decreases in performance based on previous research. However, that brings up an interesting point. If stiffness and ROM recover within at least 30 minutes, do the decreased effects on performance also recover within that time frame. It may also be possible that the decreased stiffness is the aspect linked to a decrease in performance. Something to look into.
Tommy thanks for the post. I like your view on this topic. In terms of ankle sprains it completely makes sense. With performing joint mobilizations you bring up a good point. If ROM is the major contributor to injury prevention then we wouldn't need to perform static stretching prior to athletic events and risk having a decrease in performance. That would be an interesting study to conduct.