Commissioned Corps E-Bulletin

Submitted by LCDR Scott McGrew
As you prepare for fitness testing, don’t forget that flexibility training is an important part of your exercise program. Stretching provides increased joint range of motion and improved joint mechanics necessary for maximum performance. There is, however, some controversy about when and how to stretch (Quinn, 2010).

Most adults were trained in school to do prolonged stretching just prior to athletic events. However, some recent research actually points to decreased performance and increased risk of injury when stretching prior to exercise. Current studies indicate that doing a brisk warm-up that includes mild dynamic stretching decreases the risk of injury. So if injury prevention is the primary objective, the evidence suggests that athletes should limit stretching before exercise and increase warm up time

Studies do support that range of motion can be increased by a single 15-30 second stretch for each muscle group per day. However, some people require a longer duration or more repetitions. Research also supports the idea that the optimal duration and frequency for stretching may vary by muscle group (ACSM, 2006).

The long-term effects of stretching on range of motion show that after 6 weeks, those who stretch for 30 seconds per muscle each day increased their range of motion much more than those who stretched 15 seconds per muscle each day. Another 6-week study found that one hamstring stretch of 30 seconds each day produced the same results as three stretches of 30 seconds. These studies support the use of 30-second stretches as part of general conditioning to improve range of motion.

There are several types of stretches one may incorporate into their fitness training. The following information provides an overview of stretching variations that you can read more about in the resources and references noted at the end of this article:
  • Static stretching is probably the most commonly used flexibility technique and is very safe and effective. A muscle or muscle group is gradually stretched to the point of limitation (a mild, even tension) and then typically held in that position for 15-30 seconds (Kravitz, 2009).

  • Dynamic stretching incorporates active range-of-motion (ROM) movements that tend to resemble sport or movement-specific actions. For instance, a volleyball player might do some shoulder flexion and extension actions prior to a game. The rhythmic nature of a controlled dynamic stretch has a functional application owing to its similarity to the primary movement task. Dynamic stretching is often incorporated in the “active” phase of warm-ups (Kravitz, 2009).

  • Ballistic stretching involves a bouncy approach to reach the target muscle’s motion endpoint. A concern, however, with ballistic stretching is that it is often performed in a jerky, bobbing fashion that may produce undesirable tension or trauma to the stretched muscle and associated connective tissues. It may produce a potent stretch reflex that will oppose the muscle lengthening (Kravitz, 2009).

  • Passive stretching is usually performed with a partner who applies a sustained stretch to another person’s relaxed joint. The person who is stretching their muscles is not actively involved in the stretch, but is manipulated into the stretch by his or her partner. Passive stretching, therefore, requires close communication between the two individuals, along with a slow application of the stretch in order to prevent a forceful manipulation of the body segment and possible injury (Kravitz, 2009).

  • Contract-Relax and Proprioceptive Neuromuscular Facilitation (PNF) stretching involves initially contracting the target muscle, then relaxing and stretching it with an assist from a partner or an applied force (i.e., towel or rope). A variation (contract-relax agonist-contract method) involves performing a contraction of the opposing muscle during the stretching phase to take the target muscle to a new, farther motion endpoint (Sharman, Cresswell & Riek 2006).

  • Resistance Stretching has gained much attention and interest. It focuses on contracting the target muscles as they are lengthened. Some of these stretching moves can be done alone and others with a partner. In the first phase, the target muscles are placed in the shortened position. Then the person who is stretching his or her muscles contracts the target muscle(s). While contracted, the muscles are taken through a full ROM (lengthened), either by the person alone or with assistance from his or her partner. So, Resistance Stretching incorporates a strengthening component through the entire ROM. In essence, it is a carefully performed eccentric contraction (Kravitz, 2009).
Stretching Suggestions

Stretching should be done after you are done exercising while your muscles are still warm. Hold a given stretch until you feel a moderate pulling in the muscle, but no pain. As you hold the stretch, the muscle will relax. As you feel less tension you can increase the stretch again until you feel the same moderate pull. Hold your stretch for 30 seconds. If you do not seem to gain any range of motion using the above technique, you may consider holding the stretch longer (up to 60 seconds) (Quinn, 2010).

What Stretch is Best?

In general, research indicates that PNF stretching results in greater increases in range of motion compared with static or ballistic stretching. Static stretches are a bit easier to do and appear to have good results. Studies indicate that continuous stretching without rest may be better than cyclic stretching - applying a stretch, relaxing, and reapplying the stretch; however some research shows no difference.

Most experts believe ballistic, or bouncing during a stretch, is dangerous because the muscle may reflexively contract when re-stretched quickly following a short relaxation period. Such eccentric contractions are believed to increase the risk of injury (Quinn, 2010).

For more information on stretching, check out the following sites:

ACSM. 2006. ACSM’s Guidelines for Exercise Testing and Prescription (7th ed.). Philadelphia: Lippincott Williams & Wilkins.
Andersen, J.C. 2006. Flexibility in performance: Foundational concepts and practical issues. Athletic Therapy Today, 11 (3), 9–12.
Kravitz, Len. “Stretching--A Research Retrospective.” Fitness Journal. November 2009. Web. 28 Dec. 2010
Quinn, Elizabeth. “When to Stretch – Why Experts Recommend Athletes Stretch After Exercise.” About.Com. June 04, 2010. Web. 29 Dec 2010
Sharman, M. J., Cresswell, A. G. and Riek, S. (2006) Proprioceptive neuromuscular facilitation stretching - Mechanisms and clinical implications. Sports Medicine, 36 11: 929-939.
Thacker, Stephen B. et al. "The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature." Medicine & Science in Sports & Exercise. 36(3):371-378, March 2004.
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