Tag Archives: Dynamic Stretching

To Stretch or Not To Stretch

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Stretching is regularly included in exercise regimes by athletic trainers and coaches and is often recommended to novice athletes. The chronic effects of stretching result from consistent practice and are thought to be a preventative measure to reduce risk of injury by increasing flexibility to increase overall range of motion. [1] This increased range of motion is thought to increase overall performance. However, those against stretching argue the long-term effects could lower performance by decreasing muscle strength.

Types of Stretching

Three common types of stretching include static, dynamic, and proprioceptive neuromuscular facilitation (PNF). [2] Static stretching involves lengthening a specific muscle group for a period of time without movement. This method is arguably the safest form of stretching, especially for beginners, as it minimizes the risk of tearing or straining the muscle by overstretching. [3] PNF incorporates static stretching in addition to isometric contraction and relaxation of the muscle. Unlike static and PNF methods, dynamic stretching involves active movements to increase the range of motion while raising the heart rate before an exercise.

Mechanisms to Increasing Flexibility

Several mechanisms describe how stretching can increase flexibility over time including increasing compliance and increasing stretch tolerance. Compliance relates to the elasticity of the muscle-tendon unit and is useful in generating forces as elastic energy is stored by eccentric contractions during the stretch-shortening cycle (SSC). [4] Stretching can increase the compliance of the muscle-tendon, increasing the energy potential. Increasing the stretch tolerance of a muscle is a second mechanism to increase flexibility. Long-term stretching can alter how the central nervous system receives signals from structures aiding in proprioception and regulation of muscle stiffness including nociceptors, Golgi tendon organs, and muscle spindles. [5] Altering these signals may result in greater ranges of motion with decreased resistance by the nervous system.

Stretching Reduces Injury in Some Sports

Research has shown that stretching can reduce injury by increasing flexibility, but only in some sports. For sports requiring jumping motions that involve high intensity SSCs, like soccer and football, stretching has been shown to reduce injury. [4] In these sports, the muscle-tendon system works as an elastic spring. With a compliant unit, potential injury is reduced as greater energy can be absorbed by the tendon, sparing the muscle fibers potential damage. However, if the tendon has low compliance greater forces can be transferred to the muscle, resulting in injury if the muscle is unable to support high amounts of energy.

A prospective study published in 2003 from Ghent University measured initial muscle flexibility for 146 male professional soccer players and analyzed how flexibility related to the development of muscle injuries throughout the season. Goniometers were used to measure the flexibility of the hamstring, quadriceps, adductor, and gastrocnemius muscles on both sides of the athletes. The study reported no statistical significance between players height and weight, but did not analyze other factors like age. Throughout the season, 67 players were diagnosed with a lower extremity injury. For the hamstring and quadriceps muscle, the injured group had a significantly lower initial mean flexibility. No significant difference for flexibility was found for injuries involving the adductor or gastrocnemius muscles which could be due to the low power of this analysis. Thus, this study recommends implementing a stretching program to prevent muscle injuries, although there are many limitations. This study only analyzed intrinsic muscle flexibility when muscle injury can be caused by many intrinsic and extrinsic risk factors. Also, the specific circumstances of the injuries were not incorporated in analysis. [6]

Unlike sports involving high intensity SSCs, there is insufficient evidence that stretching is effective in preventing injury in sports with lower intensity SSCs, including cycling and swimming, as well as jogging (which utilizes high intensity SSCs, but not at maximum exertion). [4,7] Rather than utilizing the ability to absorb energy, these sports utilize the conversion of metabolic energy into mechanical work by concentric contractions. [4]

Can Stretching Increase Performance?

Although long-term stretching can increase range of motion, this does not always mean an increase in performance.  A 2007 study investigated the long-term effects of PNF and static stretching on range of motion and jump performance. Twenty-three healthy male volunteers were randomly divided into 3 groups to follow a static stretching program, PNF stretching program, or a control group with no stretching. Range of motion was recorded by a goniometer. Jump performance was measured by timing a subject dropping from a box onto a contact mat and jumping as high as possible to then calculate jump height. Measurements were recorded at the beginning and end of the study. While no group had any significant change in jump performance, both stretching groups had a significant increase in joint range of motion. The authors believe measuring muscle hypertrophy could have been a better measure of performance. [8]

Does Stretching Decrease Performance?

Stretching is not always recommended for sports involving lower intensity SSCs because a muscle-tendon system that is too compliant could reduce performance. For these sports, decreased flexibility with greater stiffness can contribute to more rapid tension changes for faster responses. [4] A 2001 study investigated the effects of stretching on 16 male and 16 female college aged runners. At the beginning and end of the study VO2peak, running economy, and flexibility, measured by a sit and reach test, was evaluated. Running economy is used to evaluate running performance as a measure of VO2 and the respiratory exchange ratio. [9] The participants were randomly assigned to a stretching or non-stretching group and followed these programs for 10 weeks. The stretching group performed 15 static stretches in a 40 minute session for 3 days a week for the 10 weeks of the study. This study found an increase in flexibility in the stretching group, but no significant change in running economy for both the stretching or the non-stretching group. Stretching does not appear to increase or decrease running performance, and thus may not be harmful to incorporate in these sports. However, limitations to this study include the limited measurements of flexibility provided by the sit and reach test, as well as potential confounding factors that can affect running economy. [10]

Although acute stretching often results in decreased muscle strength, longer-term effects of stretching may actually promote muscle hypertrophy. A 2013 study analyzed the effect of stretching before a strength training workout and found that strength levels increased for both the stretching and non-stretching groups, although the group without stretching had a greater increase. [11]

To Stretch or Not To Stretch?

Overall, the long-term effects of stretching include increased flexibility which can reduce injury in sports with high intensity SSCs. Although stretching has not been found to decrease the risk of injury in sports with low intensity SSCs, it does not lower performance. The studies discussed did not find that stretching enhanced or reduced performance, but this may be due to influences to muscle hypertrophy that were not included in these studies. As long as stretching is performed utilizing proper techniques to prevent overstretching, incorporating stretching into your workout can be beneficial and help increase flexibility overtime.

Questions to Consider

  1. Do you regularly stretch? If so, do you prefer stretching before, after, or before and after your workout? In your own experiences have you noticed any effects from stretching versus not stretching?
  2. What do you think about the different methods to measure flexibility (goniometry, sit and reach test)? How might the limitations of each of these methods influence results and conclusions made by studies? If you are unfamiliar with sit and reach tests, check out this video. Is there a better way to measure flexibility?
  3. Do you think the duration of stretching for the stretching protocols in these studies is important to consider? Do you think these protocols should be standardized across studies (such as types of stretches performed or muscles that are targeted by stretching for certain sports)?

References

[1] Stone M, Ramsey MW, Kinser AM, O’Bryant HS, Ayers C, Sands WA. Stretching: acute and chronic? the potential consequences. Strength and conditioning journal. 2006;28(6):66-66. doi:10.1519/1533-4295(2006)28[66:SAACTP]2.0.CO;2.

[2] Mann D, Whedon C. Functional stretching: implementing a dynamic stretching program. Athletic therapy today. 2001;6(3):10-13. doi:10.1123/att.6.3.10

[3] Muniz Medeiros D, Martini T. Does Stretching Have Long-Term Effects on Muscle Performance? A Clinical Commentary. J Yoga Phys Ther. 2017;7(2). doi:10.4172/2157-7595.1000269

[4] Witvrouw E, Mahieu N, Danneels L, McNair P. Stretching and injury prevention : an obscure relationship. Sports Med. 2004;34(7):443-449. doi:10.2165/00007256-200434070-00003

[5] LaRoche D, Connolly D. Effects of stretching on passive muscle tension and response to eccentric exercise. The American Journal of Sports Medicine. 2006;34(6):1000-1007. doi:10.1177/0363546505284238

[6] Witvrouw E, Danneels L, Asselman P, D’Have T, Cambier D. Muscle flexibility as a risk factor for developing muscle injuries in male professional soccer players. a prospective study. The American Journal of Sports Medicine. 2003;31(1):41-46. doi:10.1177/03635465030310011801

[7] Yeung EW, Yeung SS. A systematic review of interventions to prevent lower limb soft tissue running injuries. Br J Sports Med. 2001; 25: 383-9. doi:10.1136/bjsm.35.6.383

[8] Yuktasir B, Kaya F. Investigation into the long-term effects of static and pnf stretching exercises on range of motion and jump performance. Journal of Bodywork & Movement Therapies. 2009;13(1):11-21. doi:10.1016/j.jbmt.2007.10.001

[9]Nelson AG, Kokkonen J, Eldredge C, Cornwell A, Glickman-Weiss E. Chronic stretching and running economy. Scandinavian Journal of Medicine & Science in Sports. 2001;11(5):260-265. doi:10.1034/j.1600-0838.2001.110502.x

[10] Saunders PU, Pyne DB, Telford RD, Hawley JA. Factors affecting running economy in trained distance runners. Sports Med. 2004;34(7):465–485. doi:10.2165/00007256-200434070-00005

[11] Borges Bastos CL, Miranda H, Vale RG, et al. Chronic effect of static stretching on strength performance and basal serum igf-1 levels. Journal of Strength and Conditioning Research. 2013;27(9):2465-2472. doi:10.1519/JSC.0b013e31828054b7

Holding Your Stretch is Holding You Back

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By: Juliana Gullotta and Laura Sturgill

If you’ve participated in any athletic event, you know that one of the first things you do is to start stretching before any activity takes place. Coaches and trainers emphasize that stretching should occur on a regular basic, and become part of an individual’s workout routine. These stretches are usually static stretches (holding a stretch for 20-30 seconds). The intent of prescribing stretching before exercise, is based on the assumption that by stretching you enhance performance, prevent injuries, and increase flexibility. However, several studies, including one from the Journal of Applied Physiology, Nutrition, and Metabolism, have shown that stretching before exercise can actually do more harm than good, and increase your risk of injury.

Results from study Conducted by the University of Nevada comparing the effects of static, ballistic, and no stretching (control) on muscle power. Asterisk signifies statistically significant.

While stretching before exercise does activate the muscles and increase blood flow to the areas as a “warm up”, it can be potentially very detrimental to an athlete’s workout. This conclusion is especially pertinent when the sport in question requires maximal force production. In a study conducted at the University of Nevada, researchers determined that leg muscles generate less force after static stretching than if they did not stretch at all. When muscles are subject to the strain of static stretching, they remain in a weakened state, thereby temporarily reducing the force that it can produce. The researchers evaluated two types of stretching, ballistic (bouncing) and static (control is no stretching). After stretching for 3 sets of 30 seconds, subjects performed a vertical jump on a force plate. Power values were compared for each of the conditions (Figure 1). From this graph it is clear to see a significant difference in the power values observed in the control group and static group. The decrease in power after stretching could inhibit a good muscle building workout. For sports that require maximum power (ex. football), static stretching should be limited before activity.

Static stretching intervals should last for no more than 60 seconds, or moderate reduction in maximal muscle performance may be observed. In a study conducted by Behm et. al. the effects of static stretching on power-speed and strength tasks were compared. One of the main components of this study involved investigating the relationship between time spent holding a stretch and subsequent performance in a physical activity. In order to perform these tests, two groups of healthy and active adults were randomly assigned, with one group holding their static stretch for less than 60 seconds and the other for a period of time greater than 60 seconds. On average there was a mean reduction of muscle performance for both test groups, but the group that held the stretch for a longer period of time experienced significantly higher reduction rates in performance. For the individuals that held the stretch for less than 60 seconds, a mean reduction of 1.1% was observed and categorized by the researchers as a small reduction in performance. However, a moderate reduction of 4.6% was noted in the population that held the stretch for longer than 60 seconds, indicating that there is a dose-response relationship between stretching and maximal muscle performance.

To investigate this relationship further, two types of physical activity were studied. Power-speed tasks were given to both groups and the results supported the notion that on average static stretching, especially when held at higher intervals, impaired muscle performance in the test subjects. While only a small mean reduction rate of 1.3% was observed for this type of exercise, this change could be extremely detrimental to an athlete’s performance where maximal speed is critical (i.e. sprinters). Power tasks were also completed, and the negative effects of static stretching on performance became more apparent. On average there was a 4.6% reduction in an individual’s maximum muscle performance, with a higher instance of 5.1% reduction when the activities were completed after a period of stretching lasting longer than 60 seconds. In another study also conducted by Behm et. al, these findings were not only supported by additional trials, but also expanded upon to look at the long term effects of stretching on overall performance. In his initial study that looked at power and speed tasks, maximal muscle performance was calculated minutes after the the stretching was complete. The second study, however, observed the prolonged effects that static stretching would have on an athlete, and concluded that even 2 hours after the last set of static stretching, instances of decreased performance existed.

The results from these studies suggest that time spent holding a stretch and subsequent muscle performance have an inverse relationship. For this reason more and more coaches and athletes are looking to implement a different approach to their warm up routine.

Straight leg march can be used as a dynamic stretch alternative to the static sit-and-reach stretch. Courtesy of the New York Times

Dynamic stretching (Figure 2) is simply the act of stretching your muscles while moving, and it is an effective method to get your blood flowing and increase your power, flexibility, and range of motion prior to working out. This type of stretching is unique in that the activities performed have the ability to target specific muscles necessary for the task at hand. In other words, different forms of dynamic stretching would be used for a sprinter and a volleyball player because each sport requires a different amount and variety of muscle activity. Dynamic stretching allows athletes to engage their bodies’ muscles in a way that static stretching cannot, thereby quickly earning its place as a replacement to static stretching in many pre-workout routines.

While the value of traditional static stretching before exercise may be an outdated concept, the benefit of increased flexibility in athletes should not be ignored. For this reason post workout stretching is recommended as a “cool down”. If necessary, short duration, lasting less than 30 seconds, low intensity static stretches could be implemented before activity to get blood flowing to muscles and reduce stiffness, but this does not offer the best possible results. The ideal warm-up routine for athletes to minimize risk of injury and maximize performance should include aerobic activity, dynamic stretching, and sport specific dynamic exercises.

Questions to consider:

How would the stretching routine you made for football players differ from that of a sprinter?

There is a lot of information about how bad form or technique during exercise can cause injury, should there be attention called to the potential adverse effects of stretching improperly?

References

Samuel, M. N., Holcomb, W. R., Guadagnoli, M. A., Rubley, M. D., & Wallmann, H. (January 01, 2008). Acute effects of static and ballistic stretching on measures of strength and power. Journal of Strength and Conditioning Research, 22, 5, 1422-8. 

Behm, D. G., Blazevich, A. J., Kay, A. D., & McHugh, M. (January 01, 2016). Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Applied Physiology, Nutrition, and Metabolism =, 41, 1, 1-11.

Shrier, I. (October 01, 1999). Stretching Before Exercise Does Not Reduce the Risk of Local Muscle Injury. Clinical Journal of Sport Medicine, 9, 4, 221-227.

Behm, D. G., & Chaouachi, A. (November 01, 2011). A review of the acute effects of static and dynamic stretching on performance. European Journal of Applied Physiology, 111, 11, 2633-2651.

Shrier, I. (January 01, 2000). Stretching before exercise: an evidence based approach. British Journal of Sports Medicine, 34, 5, 324-325.

Herbert, R. D., & Gabriel, M. (January 01, 2002). Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. Bmj (clinical Research Ed.), 325, 7362.)

Reynolds, Gretchen. (2008) Stretching: The Truth. The New York Times. Retrieved from: http://www.nytimes.com/2008/11/02/sports/playmagazine/112pewarm.html

Reynolds, Gretchen. (2016) The Right Way to Stretch. The New York Times. Retrieved from: https://well.blogs.nytimes.com/2016/01/21/stretching-back-to-the-past/

Nah Coach, I don’t have to stretch.

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Ever wondered if those pre- and post- workout sessions really make a difference in your daily exercise regimen? It is commonly believed that stretching prior to and following a workout will decrease the likelihood of injury, minimize post workout pain, and increase performance. However, other athletes and trainers believe that stretching has no impact on these factors and can even decrease strength and performance. But what are the facts?

Figure 1. Examples of active and passive/static and dynamic stretching.

There are several subgroups of stretching but I will focus on performance results with regards to the two most well researched types: static versus dynamic. Each stretch can be done actively or passively, where active stretching is when you contract the muscle in opposition to the one you want to stretch and passive uses an external force such as a strap, the force of your body weight, or gravity. Each type of stretching, shown above, has been shown to impact exercise in different ways. Let’s start with the most frequently used type, static stretching, where a person slowly moves muscles until they reach the brink of pain and hold that position for 20-30 seconds.

Static stretching has been compared to continuously stretching a rubber band. Immediately after stretching the rubber band, the band remains limp as it contracts slowly back into its original form, similarly to the behavior of a muscle. It seems unrealistic to expect a maximum amount of contraction and force immediately after stretching your muscle. In more physiological terms, the loss of muscular stiffness caused by static stretching results in an increase in length of sarcomeres in each muscle fiber, decreases contact between actin and myosin, and therefore decreases the force produced (Shrier, 2004; Kokhonen et al., 2004).

Figure 2. Actin and myosin movement in relaxed muscle versus contracted muscle. The less contact between actin and myosin, the less force produced.

One study by Fletcher and Jones (2004) on 97 male rugby union players showed a significant decrease in sprint times for the passive static stretch group. This could be due the mechanical impact of stretching on the muscle, kinematic differences, or neural inhibition which decreases the neural drive to muscle. Dynamic stretching focuses on moving through a range of motion repeatedly and mimics motion that will occur during exercise. Fletcher and Jones’ (2004) study showed more beneficial performance results from active dynamic stretching prior to sprinting though. The active dynamic stretch group of rugby players improved their sprint times significantly.

These results could be explained by information in a systematic review of studies on stretching and exercise by McGowan et al. (2015). This review showed that dynamic stretching increases the temperature of the muscle more than static stretching. This increase in temperature activated an increase in muscle metabolism, elevated oxygen uptake, and increased the power output of the muscle. Another study by Gray et al. (2008) showed a correlation between increased muscle temperature and faster ATP turnover, caused by an elevated rate of creatinine phosphate utilization and H+ accumulation. The elevated muscle temperature also resulted in short term (~2 minute) increase in anaerobic glycolysis and muscle glycogenolysis. These physiological responses, in theory, would result in greater power production during sprint and sustained high-intensity exercise, however high quality research results on this topic are limited.

Several literature reviews regarding this topic exist, but compiling results from hundreds of varying studies makes it difficult to normalize the results. Several reviews analyzed results that were not statistically significant, skewing the review results. By looking at the methods researchers used to gather and compile data and at the sources they cited, I was able to identify the sources where results were significant and relevant. The review also covered studies on a span of sports from swimming, to sprinting, to jumping, all which are impacted very differently by stretching, which makes the conclusions for these reviews far reaching statements. When more studies are done within each of these sports, reviews that group together specific events and exercises will provide more beneficial results.

When looking at the impact of stretching on pain, several papers used self-reported ratings of pain to measure differences. In those studies the results did not show a significant difference between ratings from groups that stretched and controls. Self-reported measurements of pain contain bias which makes them difficult to compare between groups of people. Some papers overcame bias by observing differences in delayed muscle soreness by measuring creatine kinase levels, a commonly used marker for muscle damage. One experiment by Buroker and Schwane (1989) showed no significant difference in creatine kinase levels from stretching post-exercise. Very few studies are done solely to measure the effect of post-exercise stretching on soreness and risk of injury so it is difficult to differentiate these results from the pre-exercise stretching.

Keeping these biases and knowledge gaps in mind when considering the results of these papers, it is plausible that for the majority of exercises, dynamic stretching can positively impact your performance. This is largely due to the fact that it increases the core body temperature and targets activity in specific muscles that will be used instead of just stretching them. Static stretches prior to a workout seem to have no impact or a negative impact on performance since the muscle needs time to recover and regain stiffness before use. Personally, this would convince me to do some dynamic stretches before my next run rather than static stretches. While it differs from sport to sport, dynamic stretching appears to be the ideal pre-exercise stretch to optimize performance.

Recommended Further Reading:

1. Blahnik, Jay. Full-Body Flexibility, Second Edition. Available at: http://www.humankinetics.com/excerpts/excerpts/types-of-stretches

2. Sifferlin, Alexandra. Why Stretching May Not Help Before Exercise. (April 08, 2013) Available from: http://healthland.time.com/2013/04/08/why-stretching-may-not-help-before-exercise/

3. Shrier, Ian. Sports Med (2004) 14:267-273. Available from: http://www.elitetrack.com/article_files/stretchingreview.pdf

4. Kokkonen,  J.,  Nelson,  Α.  G.,  Cornwell,  Α.  (1998). Research Quarterly for Exercise and Sport. 69 (4): 411-415. Available from: https://www.ncbi.nlm.nih.gov/pubmed/9864760

5. Fletcher, IM, Jones, B. J Strength and Condition Research. (2004) 18(4), 885-888. Available at: http://staps.nantes.free.fr/L3/entrainement/etirements/THE%20EFFECT%20OF%20DIFFERENT%20WARM-UP%20STRETCH.pdf

6. McGowan, C.J., Pyne, D.B., Thompson, K.G. et al. Sports Med (2015) 45: 1523. Available at: https://link-springer-com.udel.idm.oclc.org/article/10.1007%2Fs40279-015-0376-x

7. Gray, SR, Soderlund, K, Ferguson, RA. J Sports Sci. (2008) 26(7):701:7. Available at: https://www-ncbi-nlm-nih-gov.udel.idm.oclc.org/pubmed/18409101?dopt=Abstract

8. Buroker, KC, Schwane, JA. The Physician and Sportsmedicine (1989) 17(6): 65-83. Available from: http://www.tandfonline.com/doi/citedby/10.1080/00913847.1989.11709806?scroll=top&needAccess=true