To Stretch, Or Not to Stretch?

Before we get started, let's go over some basics on the muscle/tendon relationship. Our tendons are more involved in contractions than previously understood. The muscle actually doesn't move much at all, but builds up tension and has the tendon do the majority of the work. Think of the tendon as a spring; the muscle contracts or relaxes to control the tension of this ‘spring', which then facilitates joint movement.

There are ideal flexibility levels for certain types of movements. Depending on the activity you are participating in, you will want more or less flexibility or ‘stretch' in the working muscle/tendon unit (MTU). If you want to transfer power (swim, bike, run), less flexibility is better because a more elastic tendon will actually absorb energy. That means you have to generate more power to get the same result as someone with a less elastic MTU. This may be why static stretching prior to activity has been shown to compromise muscle strength 5 – 30%. In fact, as little as two minutes of static stretching can impair power performance (1).

In addition to detrimental performance effects, there is evidence that stretching does not protect against injury, and prior to exercise may actually increase the rate of muscle injury. There are several theories as to why this is the case, ranging from decreased stability from increased range of motion created by stretching, to increased pain tolerance leading to tissue damage we could otherwise avoid (4).

In place of stretching, increasing muscle temperature via submaximal exercise is a more appropriate way to warm-up for your activities, as increasing the internal temperature of your working muscles has been shown to increase resistance to muscle tear (2), with the added benefit of increasing the rate of oxygen transfer to working muscles. Studies that attempted to isolate the influence of stretching prior to activity have shown decreased performance with stretching alone versus a combination of submaximal efforts and stretching, which indicates that stretching was the culprit to the decreased performance (3).

While evidence seems to be pointing toward keeping away from pre-exercise stretching for low-intensity or limited stretch-shortening cycles (swim, bike, run), it seems that a regular stretching routine done away from your regular activity does help in injury prevention. You see, stretching results in the same hypertrophy you get from strength training! Stretching will cause minute tears (just like weight training, but not as extreme), which then have to be healed, resulting in larger, stronger muscle. Also, once you have an injury, stretching facilitates the healing process. When a muscle or tendon is injured, materials are deposited at the site to rebuild the damaged tissue. These materials are deposited in a clump, and when you stretch (or get a massage) these materials are encouraged to line up in the injury, and voila, the healing begins! This is the ‘scar tissue' you've probably heard your massage therapist mention.

In summary, the evidence seems to suggest that stretching pre-activity could decrease your performance ability, and increase your chance of injury. Stretching post-activity doesn't seem to have an impact either way, while stretching away from your other activities could be beneficial. The bottom line, as I always say, is to know your own body, and do what works for you. It is my goal to simply educate you in that process.

Tammy Metzger is a coach at Seattle's Cycle U. To find out more about Cycle U, see www.cycleu.com .

References:

1. Young WB, Behm D. Should Static Stretching be Use During a Warm-up for Strength and Power Activities? Nat'l Strength and Cond. Assoc. 24(6):33-37. 2002.
2. Knudson D. Stretching During Warm-up. Do we have enough Evidence? J. Phys. Ed. Rec. Dance. 70(7):24-27. 1999.
3. Knudson D, Bennett K, Corn R, Leick D, Smith C. Acute Effects of Stretching are not Evident in the Kinematics of the Vertical jump. J. Strength Cond. Res. 15(1):98-101. 2001.
4. Thacker, SB, Glchrist J, Stroup DF, Kimsey Jr, CD. The Impact of Stretching on Sports Injury Risk: A systematic Review of the Literature. Official Jrnl of the Amer College of Sports Med. 371-378, 2004.