Dr. Chris:

I've been a triathlete for about 3 years now and happily I have avoided injury. I'm confused by advice I get from my teammates, as some tell me that I should stretch only before I workout, others say only after a workout. Others tell me I don't need to stretch, and still others tell me I should stretch all the time. Who's right?

- Steve (New York, NY)

Steve: I completely understand your confusion. As with many things related to the human body, we continue to learn new (and surprising) tid-bits every year. Let me start by saying every opinion you got has some truth. Then let me completely confuse you by saying that every opinion you got also erred. The key lay in understanding that different stretches affect different parts of the tendon-muscle unit.

But before I go any further, let me make two points: 1) your teammate suggesting you shouldn't ever stretch may have seen the research that indicates that static stretching seems ineffective in preventing injury. Point for him/her. However, point 2) stretching has been linked to improved performance.^{3, 4} And isn't that why we're all here, anyway?

Briefly, a muscle (rubber band-like) turns into a tendon (rope-like), which then joins the bone. When the muscle contracts (shortens), it pulls slack out of the tendon, and moves the associated bone. The tendon lengthens a little, but not much - most of the overall length change occurs exclusively in the muscle. These two structures (muscle and tendon) behave very differently, and require dissimilar types of stretching. Muscles lengthen with static stretching,^5-7 but acutely lose their maximal strength capacity.⁸ On the other hand, tendons acutely become more pliable after dynamic (or ballistic) stretching,⁵ thereby increasing the tendon's ability to withstand sudden lengthening without tearing. But static stretching has no effect on a tendon, and ballistic stretching has no effect on a muscle.⁵

The effect of lengthening a muscle right before hard eccentric loading (such as for shock-absorption with each foot-fall when running hard) by performing a static stretch has been shown to increase the probability of injury to the associated tendon.^{5, 7} Thus as a triathlete, the only time you want to avoid static stretching is right before you do hard runs (e.g., interval and tempo runs). Interestingly, this is probably the one time want to be sure you do perform dynamic stretching right before your hard runs, in order to improve the pliability of those tendons.⁷

For those under the age of 65, a 30-60 second hold is recommended for static stretches,⁹ and for those age 65 and over, a full 60 seconds (a long time).¹⁰ Warming-up does not seem to affect stretching one way or the other,⁶ regardless of the age range of the individual,^{11, 12} so anytime is really an okay time to stretch.

The effects of a single bout of stretching have a limited duration. De Weijer et al⁶ found that the acute effects of a static stretch reduce significantly across the initial 15 minutes, and essentially disappear after 24-hrs. Another study looking at the effects of stretching note that while 6 weeks of consistent stretching does improve joint range of motion, cessation of that stretching program for only 4 weeks results in a return to baseline mobility.¹³

The optimal plan to include stretching into your training regimen for performance enhancement and injury prevention:

• Daily static stretching at any time except right before hard efforts
• Dynamic stretching immediately prior to hard efforts for tendon protection
• Static stretch duration of at least 30 seconds, and 60 seconds for those 65+ years old
• Static stretching should be continued throughout the entire season

In conclusion, the only person you should ignore is the one telling you not to stretch; better yet, start stretching and you can say "I told you so" after the next race results come out.

References:

1. Herbert RD, Gabriel M. Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ. August 31, 2002 2002;325(7362):468-.

2. Thacker SB, Gilchrist J, Stroup DF, Kimsey CD, Jr. The impact of stretching on sports injury risk: a systematic review of the literature. Med Sci Sports Exerc. Mar 2004;36(3):371-378.

3. Kokkonen J, Nelson AG, Eldredge C, Winchester JB. Chronic static stretching improves exercise performance. Med Sci Sports Exerc. Oct 2007;39(10):1825-1831.

4. Herman SL, Smith DT. Four-week dynamic stretching warm-up intervention elicits longer-term performance benefits. J Strength Cond Res. Jul 2008;22(4):1286-1297.

5. Mahieu NN, McNair P, De Muynck M, et al. Effect of static and ballistic stretching on the muscle-tendon tissue properties. Med Sci Sports Exerc. Mar 2007;39(3):494-501.

6. de Weijer VC, Gorniak GC, Shamus E. The effect of static stretch and warm-up exercise on hamstring length over the course of 24 hours. J Orthop Sports Phys Ther. Dec 2003;33(12):727-733.

7. Witvrouw E, Mahieu N, Roosen P, McNair P. The role of stretching in tendon injuries. Br J Sports Med. April 1, 2007 2007;41(4):224-226.

8. Nelson AG, Kokkonen J, Arnall DA. Acute muscle stretching inhibits muscle strength endurance performance. J Strength Cond Res. May 2005;19(2):338-343.

9. Bandy WD, Irion JM. The effect of time on static stretch on the flexibility of the hamstring muscles. Phys Ther. Sep 1994;74(9):845-850; discussion 850-842.

10. Feland JB, Myrer JW, Schulthies SS, Fellingham GW, Measom GW. The effect of duration of stretching of the hamstring muscle group for increasing range of motion in people aged 65 years or older. Phys Ther. May 2001;81(5):1110-1117.

11. Zakas A, Doganis G, Zakas N, Vergou A. Acute effects of active warm-up and stretching on the flexibility of elderly women. J Sports Med Phys Fitness. Dec 2006;46(4):617-622.

12. Zakas A, Grammatikopoulou MG, Zakas N, Zahariadis P, Vamvakoudis E. The effect of active warm-up and stretching on the flexibility of adolescent soccer players. J Sports Med Phys Fitness. Mar 2006;46(1):57-61.

13. Willy RW, Kyle BA, Moore SA, Chleboun GS. Effect of cessation and resumption of static hamstring muscle stretching on joint range of motion. J Orthop Sports Phys Ther. Mar 2001;31(3):138-144.

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