Stretching—Will We Ever Get it Right?

The role of stretching in athletic performance continues to be debated. Common questions about stretching include:

1. What is the best stretching method?
2. How long or hard should I stretch?
3. What does stretching actually do?
4. Should I perform muscle rolling instead of stretching?
5. Does stretching prevent injuries?
6. Does stretching inhibit or enhance performance?

I wrote this article to dispel common myths, review what we do and don’t know from the scientific evidence and provide a guide for people wishing to improve their knowledge about stretching. I will review the five topics listed above and as always, I will provide references for all the research reviewed.

1.What is the best stretching method?

The answer may not surprise you— it depends on the goal! Different stretching techniques can produce different effects. If your primary goal is to increase flexibility or range of motion, static stretching has been shown across several studies to improve this.1-3,7,11The ability of dynamic stretching to increase flexibility is considered to be smaller than what is gained through static stretching and several newer and higher quality studies support this theory.2,10,13,20There is some debate about whether PNF(proprioceptive neuromuscular facilitation) and ballistic stretching have a similar effect on flexibility and range of motion but the highest quality evidence seems to favor static stretches.20

Dynamic stretching, which can be described as a slow-moving stretch, may be a good alternative to static stretching for two reasons: when comparing the ability of static and dynamic stretching to improve flexibility, the differences are small, oftentimes negligible and some studies suggest they have a similar effect.10-12Dynamic stretching is also widely considered a better pre-activity stretch due to its favorable muscle performance effects. I will review this topic in more detail when I discuss the relationship between stretching and muscle performance (question 6 for those wishing to skip ahead).

2.How long or hard should I stretch?

Chronic static stretchinghas consistently been shown to improve range of motion more than short-term stretching.2,7,9,18An interesting fact about stretching duration—time spent stretching each week may be more important than time spent stretching within a single session.20 This is great information because it can get overwhelming to try and interpret the best stretch time. Some studies say to hold at least 30 seconds13,17while other studies show significant gains can be seen with stretch times of 15, 30, 45, 60, or 120 seconds.21-25If your goal is increasing range of motion or flexibility, focus on static stretching 5 days a week for a total of at least 5 minutes each week.20If you follow this prescription you will be practicing with a current and evidence-based method for improving muscle flexibility!

Regarding stretch intensity—the general consensus amongst clinicians and many researchers is to perform low intensity stretching for longer durations.25-26This is regarded as the safest method of stretching. You should also know that most of the evidence behind this comment focuses on manual stretching, stretch tolerance and soreness, not injuries associated with stretching. In other words, we haven’t seen strong evidence that stretching with intensity causes injuries. Interestingly, several studies show higher intensity stretching is associated with larger improvements in range of motion!14-16

3. What does stretching actually do?

This is a great topic for discussion and debate! We aren’t exactly sure. There are two main theories—the mechanical theory and the sensory theory. The mechanical theory points to a change in the muscle or tendon as an explanation for improved flexibility. These changes include fascicle length, fascicle angle, tendon stiffness, and added sarcomeres in series.7The sensory theory suggests no changes are occurring in the muscle or tendon and improved flexibility is likely due to an improved tolerance to stretch discomfort— a nervous system adaptation. Essentially, tolerating the pain more allows you to stretch further. Most of the current evidence seems to favor the sensory theory, however there is some evidence that longer stretch periods (>8 weeks) may allow some mechanical changes to occur.7

4. Should I perform muscle rolling instead of stretching?

DTR(deep tissue rolling) has gained a lot of attention over the last few years. There is evidence that DTR may be used interchangeably with traditional stretching exercises for improved flexibility.4 When comparing roller massagers to foam rollers—moderate-quality studies do support the use of roller massagers but there is limited evidence on the effectiveness of foam rolling to increase hamstrings flexibility in physically active adults.5Another interesting dilemma— neither device has been shown to be superior to static stretching for improving flexibility. Similar to other stretches, foam rolling or roller massaging appears to have short-term effects on increasingrange of motion and flexibility.6

5. Does stretching prevent injuries?

I wish I could give a clear answer here but as you’ve probably noticed, the research on stretching often produces more questions than answers. The best answer I can give you is maybe! We do know there is an association between muscle changes (tendon stiffness, altered force velocity curves, etc) that occur with training and injury risk.7,27,28The problem is the lack of data on injury reduction when stretching programs are used. It is worth mentioning that the majority of high quality trials recently reviewed show some benefit of stretching with regard to injury reduction.11 When we look at sport-specific injury risk reduction, a recent review showed that pre-activity stretching may be beneficial in sports with a sprint running component but not in endurance-based running activities.11To summarize all this information—stretching may decrease injury risk and researchers are still trying to prove it!

6. Does stretching inhibit or enhance performance?

This is probably the most common question I get from athletes, coaches and trainers. After many conversations about the relationship between stretching and muscle performance I have found a pattern of underlying assumptions and I think a good approach is to address these assumptions with the available research.

The first concern is whether chronicstretching has a negative impact on muscle performance. The way this is typically communicated is a tighter muscle has a better force/velocity relationship and that when you stretch the muscle, you decrease performance by changing this relationship. Although there is some evidence to support this notion, there is a problem—this is a misunderstanding of the short and long-term effects of stretching on the muscle tendon unit. There are studies that show a temporaryimpairment of muscle performance by altering the RFD(rate of force development). It is true that a stiffer muscle tendon unit may be able to produce force at a higher rate and that static stretching may temporarily decrease stiffness and therefore decrease the RFD. Again, this is temporary, resolving within minutes. In fact, the highest quality and most recent evidence shows chronic stretching does NOT impair muscle performance, and may actually be beneficial for SSC(stretch shortening cycles).9A SSC is essentially the ability of the muscle tendon unit to store and release energy during dynamic activity. By increasing how much a muscle is able to stretch during the lengthening phase of its contraction, you may enhance its ability to store more energy that can be released during the shortening, or explosive phase of its contraction.

Another concern is that static stretching should not be performed before sport activity. I have met a lot of athletes who prefer static stretching before their activity and this isn’t necessarily a BAD idea. There are many studies supporting and refuting the theory of stretch-related muscle performance deficits and this topic continues to be debated.If you feel better after static stretching and have your mind set on performing this before activity, here is an interesting finding you will appreciate—holding your stretches for 30 seconds doesn’t seem to influence muscle power and holding them for 60-90 seconds may.8,10 You will also want to know that performing a short bout of dynamic activity between stretching and performance may diminish the short term negative effect of static stretching.10Another important thing to keep in mind here—any evidence observing stretch-related muscle performance deficits is showing small changes. Many athletes will not note any performance deficits unless the highest level of sporting endeavors are being considered.10In other words, the higher the power (force and velocity) requirement from your sport, the more you may note the transient decreases from static stretching.

A closely related topic is the idea that dynamic stretching or warming up is the preferred method before sport activity. This idea is generally supported by the best available evidence10-12and practice methods from experienced coaches and clinicians. While there is some evidence that dynamic stretching may actually enhance performance, a recent high-quality article found about half of the studies reviewed reported enhanced performance, while the remaining studies found no effect.10 Another benefit of dynamic activity as a warm up is that you can replicate the sport activity, perform a stretch and work on muscle control simultaneously.

To wrap this up—there is quite a bit of debate, limited evidence and conflicting theories when it comes to best stretching methods. However, our science does tell us a lot of great information here! Understanding the science behind stretching as well as its limitations can help you develop your own recommendations and practice methods. The most intelligent coaches, trainers, clinicians and athletes I come in contact with rarely have a hard and fast rule when it comes to this topic. I hope this information empowers you and helps your training! Please subscribe to my blog if you want more articles about injury prevention and recovery as well as athletic training and performance. My goal is to empower you with the evidence!


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