Dynamic Stretching: Part 1… “The Basics”

If you’re like me, you’ve been doing dynamic stretches practically forever. I grew up always performing “high-knees,” “butt kicks,” and “toy soldiers” before every practice and game. Of course, in college I actually had an idea of what I was doing, compared to when I was younger, but nobody ever told me why I was doing these. My coaches would just tell me to stretch and that it was good for me and I, as well as my teammates, accepted that. Lucky for me, I got into a profession where I can finally figure out why I am doing these sometimes-crazy-looking-stretches and how they are going to affect my performance. Let’s start off with the basics… but, beware, this is part of an in-service presentation I am giving, so it can get a little science-y.. (I left a “bottom line” portion at the end of each paragraph or so, if that helps)

What is dynamic stretching?

Dynamic stretching is a form of stretching that incorporates whole body movements in an active manner. Dynamic stretching does not involve bouncing movements that exceed comfortable ranges of motion. This type of stretching would be known as ballistic stretching and is not to be confused with dynamic stretching.1

What is the difference between dynamic and static stretching?

Static stretching is a prolonged, passive stretch that is generally held for a few seconds up to about 90 seconds. Static stretching is said to acutely depress the reflex activity of a muscle and increase muscle compliance. The increase in muscle compliance then increases the time to and decreases the force of a myofibril contraction during muscle performance. 1 In a comparison, dynamic stretching is said to help preserve this muscle-tendon unit stiffness in order to enhance muscle performance instead of stunt it. In a systematic review, static stretching of the upper body was shown to have neutral effects on power, whereas it was shown to negatively affect physiological outcomes (Ex: heart rate, vO2). 2 It is important to include static stretching in sports that require static flexibility; however, 90 seconds of static stretching has been shown to produce impairments on dynamic movements. 3

Bottom Line: Static stretching is okay to improve passive motion; however, it can impair activities that involve strength and power.

Why does it work? (#science)

One theory behind dynamic stretching is known as postactivation potentiation (PAP). PAP increases cross bridge cycling via an increase in myosin phosphorylation of the regulatory light chains. 3 In more basic terms, by performing similar muscle contractions, you are conditioning the muscle and its contractility so that it is more, in a sense, “ready” to perform more contractions. Essentially, you are progressively warming up the muscle so that it may contract more efficiently in the exercise that follows. 4 PAP is said to increase the rate and ability of a muscle to develop force; therefore, it influences and increases a muscle’s mechanical power. 4

Some other thoughts behind dynamic stretching include its ability to increase heart rate and increase core and muscle temperature. By doing so, the blood flow is increased throughout the body so that the body may move more efficiently during activity. 4 In addition, dynamic stretching is said to improve kinesthetic awareness and enhance motor unit excitability. 1

 Bottom Line: Dynamic stretching can enhance your performance in activities that follow by improving a muscle’s effectiveness and efficiency during muscle contractions. It helps get your muscles ready for the important stuff!!

How will this benefit me?

If you are performing any sort of active motion, you will want to initiate dynamic stretching instead of static stretching. While static stretching has been shown to improve static flexibility, most required functional tasks and/or exercises involve active movement, which requires dynamic stretching to improve.

Types of dynamic stretching are important to consider based on the tasks/activities performed after the warm up. 2, 4 The velocity and intensity of lower body dynamic stretching has been shown to impact and improve both vertical jump and long jump performance. 4 In a study by Chatzopoulos et al, dynamic stretching was shown to improve balance on a stability board whereas static stretching was shown to harm balance. This is attributed to the quick movements needed to maintain one’s balance.

It should be noted that if a person already has a way they like to warm up or some sort of stretching routine involving static stretching that they are not willing to change, static stretching deficits should not exceed 5% in comparison to no stretching. 6

 Bottom Line: When you move, you use your muscles differently than when you stand still. So why warm up by standing still? Get out there and MOVE to warm up! Also, just remember that some people are stubborn and won’t change their ways – they shouldn’t be negatively affected greatly by static stretching before exercise, but they will be affected (and YOU will be better than them, duh).

Does it affect the upper and lower body differently?

Currently in the literature, there are no articles to investigate the effects of dynamic stretching of the upper body and its impact on injury prevention. High-load dynamic stretching in the upper body (anything greater than 20% of maximum effort, ex: plyometrics) has been shown to improve strength and power with good evidence, flexibility, and delayed onset muscle soreness with moderate evidence . 2 In the upper body, there was also no benefit in performing low-load dynamic stretching (Ex: repetitively gripping a sponge) prior to exercise. Specifically for those who play baseball, dynamic task-specific warm-ups (swinging a bat) at the standard weight has been shown to improve swing speed more than using a heavier or lighter weighted bat. 2

One study of the upper body also demonstrated that a low-volume dynamic stretch of the pectoralis and triceps brachii muscles showed a decrease in the maximal isometic peak force during the bench press exercise. There was also no short-term effect on the time to maximal isometric force or the rate of force production following dynamic stretching. In the same study, there was a negative effect induced by static stretching when performing upper body tasks after. This must be taken with caution, again, as we do not know the proper load and duration to perform dynamic stretching. We must also consider that there are articles out there that say otherwise (that dynamic stretching improves performance). Additionally, the 2 dynamic stretches performed in this study may not have been appropriate in fully stretching or warming up the muscles in a dynamic, task-specific manner. 7

In regards to the lower body, a study by Curry et al. compared static vs. dynamic stretching in females in their mid-20s and its effect on lower body balance, force production, reaction time, and power output. In these females, who were recreational athletes, time to peak performance improved with both 10 minutes of dynamic stretching and a 5 minute bout of light cycling. These improvements were seen 5 minutes after stretching had occurred. 30 minutes after stretching had occurred, time to peak force began to increase with the basic cycling; however, it remained fairly steady in those who performed the dynamic stretching routine.

 Bottom Line: There is little to no research out there to show any evidence in dynamic stretching decreasing a risk of injury in the upper or lower body. While there is more research on the lower body, both the upper and lower body generally seem to have impairments of power and strength following static stretching while there are enhancements following dynamic stretching. Wade cautiously, though, some studies don’t have many subjects.. There definitely needs to be more research.

How long should I stretch?

For upper body dynamic stretching, there has been no research to determine proper load and duration that provides maximal effectiveness to improve strength and power. 2

In regards to lower body dynamic stretching, a study by Ryan et al. compared 3 groups who performed different warm-up activities: A-5 minute jog and 6 minutes of dynamic stretching, B-5 minute jog and 12 minutes of dynamic stretching, C-5 minute jog only. Those in group B who performed a longer duration of dynamic stretching showed a decrease in muscular endurance, attributed to a decrease in high-energy phosphates and a repeated high-intensity contraction to failure. Both groups A and B showed an increase in vertical jump height and velocity. Group C, who did not perform any dynamic stretching, had no effect on the vertical jump; however, did show an increase in flexibility. Overall, the most appropriate volume, as concluded by this study, indicates that 6 minutes of dynamic stretching after a 5 minute jog is adequate in stretching the hip and thigh musculature, improving vertical jump performance, and not affecting muscular endurance. To be noted, this study was performed with recreationally active men in their mid-20s.

 Bottom Line: Don’t stretch too little because you won’t see a great effect. Don’t stretch too long because then you’re going to have tired muscles. Simple as that. 6-10 minutes is most likely adequate; however, it will depend on how “in shape” or well-trained you are. The higher training you have, the more it will take before you fatigue.

But I’m not a young, 20 year old, competitive athlete?

This will still help you!! While most of the literature focuses on high-school aged to mid-20s recreational and competitive athletes, a study by Behm et al. recognizes the similarities and differences in dynamic stretching effects in regards to young and middle-aged men. The study mentions that dynamic stretching provides similar improvements to static flexibility as static stretching does. It also notes that static stretch-induced impairments and dynamic stretch-induced enhancements of the countermovement jump are not affected by the difference in age, meaning they respond similarly as the younger counterparts. The article also mentions previous literature that discusses that older, untrained women experienced a deficit in strength training following static stretching, similar to younger female athletes studied. While these demonstrate similar effects on middle-aged people, we must keep in mind the elderly and frail have not yet been studied in regards to effects of dynamic stretching.

Bottom Line: It doesn’t matter how young or old you are, dynamic stretching still works the same! Age is not an excuse!!

Is there anything I should be cautious about?

Caution should be taken when performing dynamic stretching prior to any activity that may have a higher risk of knee injury in regards to an improper hamstring:quadriceps ratio. 8 In a study by Costa et al, an overall decrease in hamstring:quadriceps ratio was seen, suggesting that the hamstrings may respond to this type of stretch differently than the quadriceps. The hamstrings provide a great deal of eccentric control in the last 3rd of the swing phase during running as well as assist the anterior cruciate ligament (that darn ACL everybody hears about..) in decreasing anterior tibial translation. As this study shows a decrease in peak torque of the hamstrings, caution must be taken in order to maintain a proper balance between muscles. While this is not a true contraindication and more of a precautionary measure, clinical judgment should be made before introducing dynamic stretching. As this is only one study, there should be further research to determine if there is a higher risk of injury in certain regions after performing dynamic stretches of particular muscles or if this study is merely an outlier.

Bottom Line: There is one study that says to be cautious performing dynamic stretching before activities that cause a higher risk of knee injury (basketball, soccer, etc.) HOWEVER, this is ONE study and to be conclusive to the larger population, there needs to be more standardization, subjects, and further research in general. Proceed with the same caution you would proceed with when performing any activity.. just use your noggin!!

So… now you know the basics. Stay tuned for some upcoming posts with different examples and what they are targeting, etc.

Have a great day! 🙂

-Jen

References

1Curry B, Chengkalath D, Crouch G, Romance M, Manns P. Acute effects of dynamic stretching, static stretching, and light aerobic activity on muscular performance in women.Journal Of Strength And Conditioning Research / National Strength & Conditioning Association [serial online]. September 2009;23(6):1811-1819. Available from: MEDLINE, Ipswich, MA.

2McCrary J, Ackermann B, Halaki M. A systematic review of the effects of upper body warm-up on performance and injury. British Journal Of Sports Medicine [serial online]. February 18, 2015;Available from: MEDLINE, Ipswich, MA.

3Samson M, Button D, Chaouachi A, Behm D. Effects of dynamic and static stretching within general and activity specific warm-up protocols. Journal Of Sports Science & Medicine [serial online]. June 1, 2012;11(2):279-285. Available from: MEDLINE, Ipswich, MA.

4Ryan E, Everett K, Fiddler R, et al. Acute effects of different volumes of dynamic stretching on vertical jump performance, flexibility and muscular endurance. Clinical Physiology And Functional Imaging [serial online]. November 2014;34(6):485-492. Available from: MEDLINE, Ipswich, MA.

5Chatzopoulos D, Galazoulas C, Patikas D, Kotzamanidis C. Acute effects of static and dynamic stretching on balance, agility, reaction time and movement time. Journal Of Sports Science & Medicine [serial online]. May 1, 2014;13(2):403-409. Available from: MEDLINE, Ipswich, MA.

6Behm D, Plewe S, Button D, et al. Relative static stretch-induced impairments and dynamic stretch-induced enhancements are similar in young and middle-aged men. Applied Physiology, Nutrition, And Metabolism = Physiologie Appliquée, Nutrition Et Métabolisme [serial online]. December 2011;36(6):790-797. Available from: MEDLINE, Ipswich, MA.

7Leone D, Pezarat P, Valamatos M, Fernandes O, Freitas S, Moraes A. Upper body force production after a low-volume static and dynamic stretching. European Journal Of Sport Science [serial online]. 2014;14(1):69-75. Available from: MEDLINE, Ipswich, MA.

8Costa P, Herda T, Herda A, Cramer J. Effects of dynamic stretching on strength, muscle imbalance, and muscle activation. Medicine And Science In Sports And Exercise [serial online]. March 2014;46(3):586-593. Available from: MEDLINE, Ipswich, MA.

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