Stretching part two

This is the second installment that I lifted from Biomechfit.com .  I just wanted to add that stretching is beneficial but it is most beneficial when the tissue you intend to stretch is warm.  I can't count the number of patients I have that I can increase their hamstring flexibility and lumbar AROM simply by having them perform light exercises involving those muscles.  For example, I had a patient the other day whose straight leg raise went from 50 to 80 degrees in the course of about 45 minutes.  This is not a change in tissue length or stretch tolerance.  It is a change in tissue temperature and plyability due to increased blood flow.  Here is the lifted post.

Stretching Science Part 3: Effects on Performance

December 19, 2012 | Category: Movement Quality | 7 comments

Whether you want to run faster, jump higher, throw farther or play harder, you will need to move through an optimal range of motion to meet your performance objective. Flexibility is therefore an important factor in displays of physical performance along with strength, endurance, balance, agility and other fitness qualities. Static stretching may not be able to prevent injury or muscle soreness, but there’s no doubt about its usefulness when it comes to enhancing flexibility. Having said that, there are no universal requirements for flexibility, so the potential value of stretching must be evaluated in terms of individual needs and goals as well as any inherent limitations of stretching itself.

In that light, it’s worth examining the available evidence to determine if static stretching has any potentially negative effects on performance before engaging or continuing in a dedicated stretching program. Specifically, there are a few issues to consider: 1) the immediate short-term effects of stretching, 2) the long-term effects of chronic stretching and 3) the effectiveness of stretching as a warm up.

Acute, short-term effects of static stretching

An increasing number of studies are showing that static stretching, when immediately preceding physical activity, can actually have a negative effect on maximal performance. In a 2012 research review of the acute effects of static stretching, force output in strength, power and speed-dependent tasks was significantly reduced when the duration of stretch surpassed 60 seconds (Kay et al.) A previous review from 2004 came to a similar conclusion, finding that static stretching immediately before exercise is detrimental to performance in speed and power-related tasks (Shrier.) Performance losses have not been demonstrated, however, when stretching is limited to less than 45 seconds per muscle group.

Can shorter duration stretching provide much benefit? Well, one study showed that after a 6-week hamstring stretching program, the greatest increase in hamstring extensibility was gained when the duration of stretch was 30 seconds, with only a minimal increase in range of motion achieved by extending that stretch to 60 seconds (Bandy & Irion.) If your sport requires a maximal strength, power or speed component, then you can conceivably hold each stretch for 30 seconds to gain an increase in extensibility while avoiding any decrement in performance. Please note that the study referenced here used subjects who were classified as having “below average” flexibility, in which case you could indeed expect a relatively shorter duration of stretch to produce the desired effect. At some point, 30 seconds of stretching will stop producing gains and a longer duration will be needed for further progress.

Stretching routines should match flexibility requirements, which vary according to sport and sometimes even position within a sport

So, what about performing multiple stretches of 30 seconds as opposed to increasing the duration of a single stretch? Interestingly, another study revealed that repeated 30-second static stretches (alternated with 30-second periods of rest) may have a detrimental effect on short-distance sprinting times (Nelson et al.) There are no definitive explanations for why stretching might negatively affect performance, but a couple theories have been suggested. For example, it’s possible that stretching causes a plastic decrease in musculotendinous stiffness, which reduces the amount of elastic energy that can be stored and released, although not all studies have demonstrated a permanent loss of stiffness. Another potential effect of sustained stretching is reflex (or autogenic) inhibition, the process by which the Golgi tendon organ relaxes the musculotendinous unit in response to applied tension. This means that static stretching may be priming your muscles to relax instead of preparing them to contract more forcefully.

Many stretching regimens for team and individual sports do not exceed 30 seconds per stretch and should not interfere with subsequent performance. However, restricting the length of any stretch to a single set of 30 to 45 seconds will probably not produce maximal flexibility either. What if you need greater flexibility than can be achieved with a conservative stretching protocol? This issue may be resolved by engaging in lengthy stretching sessions only on days or at times which do not coincide with challenging training modules or competitions, or perhaps by placing stretching at the end of any workouts or events. However, identifying an ideal time to stretch by no means implies that more stretching is always better and some caution is in order before pursuing an intensified flexibility program.

Long-term effects of chronic stretching

Stretching is commonly performed with the intention of lengthening the musculotendinous unit, but an often ignored detail is the effect that stretching may have on other structural components of the joint capsule like ligaments and cartilage. Athletes who overemphasize flexibility may end up with hypermobile joints by increasing ligament laxity, and excessive stretching can even lead to degeneration in the articulating surfaces of a joint. This will place more of a demand on the musculature to actively stabilize the joints, which may not present a problem during slower, more controlled movements, even against a significant load as may be experienced in weight training. However, muscle cannot respond as quickly as ligaments against large, rapidly applied loads, especially with the torsional component present in many high-performance sports (Siff.) You should therefore consider your priorities carefully and identify the actual requirements of your sport. Do you really need more flexibility, or would the development of another aspect of physical performance like strength, stability, power or speed be a more productive use of your time?

Get ready for extreme stretching: if you fall, you die

As the late Dr. Mel Siff explains in Supertraining, “static stretching is insufficient to develop the strength, power, mobility and stability required in sport.” Passive stretching can improve passive flexibility but can only moderately enhance active joint mobility, which is a much more important quality for sports performance. On its own, passive flexibility offers no performance benefit and an increase in “range of motion is useless if not under precise nervous system control” (Sands.) The endless pursuit of an arbitrary goal of flexibility, just for the sake of being more flexible, makes little sense without having a practical application for it. Of course, flexibility requirements vary considerably depending upon the activity and sometimes change according to the role of a position within a sport. For instance, gymnastics demands greater flexibility than any ice hockey player needs, yet a hockey goalie will need to be more flexible than other teammates, especially in the hips. In other words, flexibility is specific.

So, if you need to do a full split in order to participate in your sport, then you’re probably going to spend a considerable amount of time stretching. As it turns out though, most sports only require average levels of flexibility. As an example, the popular sport of running doesn’t challenge the limits on range of motion in any way. In fact, good running economy actually depends upon sufficient stiffness of the tendons to store and release energy from each ground contact. Why would you want to potentially reduce this stiffness by means of static stretching? Contrary to popular belief, even deep squatting doesn’t require exceptional flexibility, but it does require good motor control. Enhancing motor control through a variety of dynamic movements involving all joints in the body will go a long way toward resolving limitations in mobility without much need for stretching. It’s true that stretches can provide some movement variety but stretching is not the only way to accomplish this, nor is it the most efficient.

Static stretching vs. dynamic stretching as an effective warm up

Stretching may be done without the explicit goal of a permanent increase in flexibility, and a common objective is to simply “loosen up tight joints and muscles”. For this reason, some may be reluctant to omit stretching from their pre-activity routine for fear of not properly warming up. If that is your concern, then be assured that aside from introducing an external heat source, the only way to literally warm up is by raising your metabolic rate and increasing blood flow, which static stretching cannot accomplish. A further limitation of static stretching is that you can only stretch in one plane of motion at a time, while sports typically require movement in all planes. Preparing your joints for all available multi-planar movement by means of static stretching is essentially impossible, like trying to heat every room in your house with a blow dryer. Before you can finish, you’ll have to start over.

Dynamic flexibility is much more important than static range of motion for performance in sport

Dynamic stretching, on the other hand, can provide an effective warm up by quickly raising your metabolic rate and moving your joints through all degrees of motion. This is a superior method for sports preparation because it more closely resembles what takes place in actual sporting performance. Athletes typically demonstrate a greater range of motion during the dynamic movements of their sport than with statically held positions, and some “studies have indicated that dynamic stretching can produce equal or greater results in dynamic and static range of motion tests” (Samson et al.)

Warming up for physical activity involves more than muscle extensibility, joint range of motion or blood circulation. Those are all key factors, but stimulation and potentiation of the nervous system is much more important. You can’t do anything without involving the nervous system anyway, so why not acknowledge its existence? Dynamic warm ups target the nervous system by enhancing “motor unit recruitment and firing frequency”, resulting in “an increased rate of force development”. As mentioned earlier, static stretching may actually reduce force output, which in actuality is also a product of the nervous system. In fact, whether we are discussing static or dynamic stretching, there’s compelling reason to dispense with the oversimplified concept of “stretching the muscles” to warm up. Think of engaging the nervous systeminstead, which ultimately has full control over muscle contraction and relaxation, cardiorespiration and metabolism, etc.

Practical application of the available stretching evidence

A 2008 study examined the effects of a dynamic warm up including exercises for balance, stability, strength, proprioception, and neuromuscular control for young female soccer players (Soligard et al.) This structured program not only provided an efficient warm up, but resulted in a very significant reduction in injury risk and did not include any static stretching. The study utilized the FIFA 11+ warm up program, as detailed in a full-length manual as well as in a nifty slideshow which I have linked to from the image below. While this routine was designed specifically for soccer players, it may easily be applied to other sports and adapted as necessary. Simply follow the pattern of starting with general full-body movements before moving on to more sport-specific drills:

Click this pic to view the FIFA 11+ Warm-up Program slideshow

In conclusion, the goal of attaining maximal flexibility is appropriate for some, but not all individuals. Remember, flexibility is specific. Even though some activities like gymnastics obviously demand high levels of flexibility, most sports and modes of exercise only require moderate amounts. Furthermore, passive flexibility does not necessarily transfer to dynamic flexibility, and athletes are typically more flexible dynamically than statically. If you currently possess the range of motion required for your training or sport, then you may not need to stretch at all. So weigh your needs carefully.

The currently available evidence provides some practical guidelines for stretching. Static stretching may be detrimental to the subsequent performance of maximal strength, power or speed-related tasks but this can be avoided if stretches do not exceed 45 seconds. Persistent, chronic stretching over the long-term presents the potential trade-off of gaining more flexibility at the expense of less joint stability. Finally, static stretching is ineffective as a warm up and a dynamic warm up should be performed instead. Don’t worry, your muscles won’t shorten if you don’t perform regular static stretching. Part 4 of this series will examine the effect of stretching on muscle length…

Sources

1. W.D. Bandy, J.M. Irion. The Effect of Time of Static Stretch on the Flexibility of the Hamstring Muscles. Phys Ther 1994; 74:845-85.
2. A.D. Kay, A.J. Blazevich. Effect of Acute Static Stretch on Maximal Muscle Performance: A Systematic Review. Medicine & Science in Sports & Exercise, 2012; 44(1):154-164. DOI: 10.1249/MSS.0b013e318225cb27
3. A.G. Nelson, N.M. Driscoll, D.K. Landin, M.A. Young, I.C. Schexnayder. Acute effects of passive muscle stretching on sprint performance. Journal of Sports Sciences, May 2005; 23(5): 449-454.
4. M. Samson, D.C. Button, A. Chaouachi, D.G. Behm. Effects of static and dynamic stretching within general and activity specific warm-up protocols. Journal of Sports Science and Medicine2012; 11:279-285.
5. W.A. Sands. Flexibility. In M. Cardinale, R. Newton, K. Nosaka (Eds.) Strength and Conditioning: Biological Principles and Practical Applications. Wiley-Blackwell, 2011.
6. I. Shrier. Does Stretching Improve Performance? A Systematic and Critical Review of the Literature. Clin J Sport Med 2004; 14:267–273.
7. Mel C. Siff. Supertraining Sixth Edition. 2003.
8. T. Soligard, G. Myklebust, K. Steffen, I. Holme, H. Silvers, M. Bizzini, A. Junge, J. Dvorak, R. Bahr, T. E. Andersen. Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial. British Medical Journal. BMJ 2008;337:a2469.doi: 10.1136/bmj.a2469

Image Credits: Xavier Wallach, Brittany Wouts, Eric Lon, Cheryl Albaine