Stretching for Injury Prevention, Mobility and Performance
A regular stretching routine is an essential practice to maintain the mobility in your body, so you can do and enjoy the things you love in your life. When properly administered, stretching has not only shown to improve general mobility. Stretching also helps to lower the risk of muscle and tendon injuries and can assist in increasing athletic performance output. There are numerous studies that have examined the benefits of stretching and identified that pending intent of outcome, different approaches to stretching must be applied. The two main approaches to stretching are called static and dynamic stretching.
Static stretching is generally the most well-known type of stretching. It is defined as stretching of muscles, tendons and connective tissues crossing your joints, with sustained holds of 30 to 90 seconds at the end of available ranges. Dynamic stretching, on the other hand, increases flexibility through movement. In a dynamic stretch a person gradually and gently sinks in and out of a stretch. The end of the stretch range is generally not held for anything more than a brief pause, and the joint is taken through its full range of motion. Dynamic stretches are typically performed in activity or sports specific motions for about 10 repetitions, targeting specific muscle groups.
Stretching tendons and connective tissues, whether statically or dynamically, is different from stretching muscles. Two common constituents of connective tissue and tendons are elastin and collagen. I often compare elastin to rubber bands that get taut and spring back once you release tension. Collagen, on the other hand, is more like old putty - rigid to stretching forces, yet conforming to prolonged or repeated tension, which results in lasting flexibility. Muscles, on the other hand, can be pulled apart to a certain extent, but eventually return to a neutral state. To understand more about the effects of stretching on a muscle, let me tell you about the wondrous mechanism of a skeletal muscle.
Skeletal muscles only exert force by either shortening (concentric), holding static position (isometric) or resisting lengthening (eccentric). A skeletal muscle can not push itself apart. It needs to be pulled to lengthen again after contracting. While, physiologically speaking, there is a whole lot going on in a muscle cell, I would like to offer a simplified analogy to illustrate a muscle contraction - a centipede climbing up a rope. The microscopically small contractile element in a skeletal muscle cell is called a sarcomere. It has 2 main interacting proteins: Actin (the rope) and Myosin (the centipede). As the centipede climbs up the rope, it needs to hold tight, and the more feet can take grasp of the rope, the stronger the pull will be against gravity (the load). If the centipede wants to get back down, it has to gradually release and lower itself, as gravity (the load) pulls it down to the ground. Fascinatingly, a foot long myofibril is formed of more than 125000 consecutive sarcomeres (centipedes holding onto a rope). A muscle fiber can contain more than 2000 myofibrils. A biceps muscle, on average, has more than 240000 muscle fibers.It’s almost unimaginable how many small contractile elements are working together to provide you with a simple movement, such as bending your elbow.
Now, when imposing a static long duration stretch of more than 60 seconds on, for example, your hamstring, collagen fibers gradually release, giving you more flexibility around the hip and knee joints. However, you also cause less strength in your muscle as you stretch the small contractile elements of the muscle apart. Utilizing the prior analogy, you pull the rope away from the centipede, causing it not be able to fully latch on with all of its feet. This effectively decreases its ability to exert force. Many studies have now shown that long duration static stretching prior to exercising can lead to temporary decreased performance and now is generally recommended to be done after exercising to improve overall tissue mobility.
Dynamic stretching is generally recommended as part of a pre-exercise or pre-activity warm up. Dynamic stretches maintain the connections in the contractile elements of the muscle. The muscle never fully relaxes, yet connective tissues and tendons get stretched within the desired ranges for the intended activities, and blood circulation increases leading to overall warming of the surrounding tissues. Studies have shown greater performance output and flexibility with pre-exercise warm-up routines that include light aerobic activities and dynamic stretches. If short duration static stretches of less than 30 seconds are included in the warm-up, studies also suggest a lower risk of injuries to the muscles and tendons.
There is a lot more to say about stretching, and you can find some resources as well as references for this article below. I also recommend consulting with your personal trainer or physical therapist, if you look for guidance in how to establish a stretching program that meets your body’s needs. Every-body should stretch a little.
Move Better, Live Better!
Ideas and Examples:
Library of Movie clips for dynamic stretching:
Four-Week Dynamic Stretching Warm-up Intervention Elicits Longer-Term Performance Benefits; Herman, Sonja; Smith, Derek
Journal of Strength and Conditioning Research: July 2008 - Volume 22 - Issue 4 - p 1286-1297
Acute Effects of Static Stretching on Muscle Strength and Power: An Attempt to Clarify Previous Caveats; Helmi Chaabene, David G. Behm Yassine Negra and Urs Granacher; Front. Physiol., 29 November 2019 | https://doi.org/10.3389/fphys.2019.01468
Dynamic Stretching Has Sustained Effects on Range of Motion and Passive Stiffness of the Hamstring Muscles Masahiro Iwata, Ayano Yamamoto, Shingo Matsuo, Genki Hatano,Manabu Miyazaki, Taizan Fukaya, Mitsuhiro Fujiwara, Yuji Asai,and Shigeyuki Suzuki; J Sports Sci Med 2019 Feb 11;18(1):13-20. eCollection 2019 Mar.
Effects of Dynamic and Static Stretching Within General and Activity Specific Warm-Up Protocols; Michael Samson, Duane C. Button, Anis Chaouachi, and David G. Behml; J Sports Sci Med. 2012 Jun; 11(2): 279–285.