Stretching the truth: it is no bargain! (General Training).

AT VARIOUS TIMES in our history, we have believed that the world is flat, diseases are caused by evil spirits, and warm-up stretching prevents injuries and enhances performance.

All of these premises are wrong, although the scientific literature is just beginning to question the validity of stretching as a warm-up. The research indicates that pre-game stretching can predispose the athlete to injury and reduced power and speed (R-1).

(Note: All of the notations at the end of the paragraphs--R1, R2, R-3, etc. refer to the references enumerated at the end of the article.)

In further summarizing the literature on basic physiology and anatomy (R-2), we find that:

1. Stretching doesn't increase the compliance (effective action) of a muscle during eccentric contractions--the lengthening sort of contractions most often associated with muscle and tendon injuries.

2. Stretching can produce damage at the cellular level of muscles and tendons.

3. Stretching seems to mask muscular pain--how the stretching of an injured muscle and or tendon may make it feel better while it is creating additional damage.

4. Stretching before an exercise will have no positive effect on a muscle that doesn't require elongation during the activity, such as jogging or walking. Studies of jogging and slow running indicate that stretching can cause injuries.

A number of other studies indicate that:

1. The muscles function poorly after stretching because the "stiffness" required for maximal force is reduced by the stretching.

2. Muscle power is reduced 2% to 8%.

3. Muscle and connective tissue injuries are generally higher among athletes who stretch.

4. Since most muscle injuries occur in the normal range of motion, not in a lengthened state, the stretching will not reduce the causative factors.

Stretching tends to increase the injury rate:

An Australian study of military recruits during the 12 weeks of training, with half doing stretching and half not doing them, found that "a typical muscle stretching protocol performed during pre-exercise warm-ups does not produce clinically meaningful reductions in exercise-related injuries among army recruits." Fitness may be an important, modifiable risk factor (R-3).

One thing we know is that we are all individuals with our own potential for problems related to our muscles and connective tissues. A few of us may function better after arm stretching, but most of us will not.

As has been indicated earlier, the research on stretching has not answered all, or even most, of our questions on whether to stretch or how to stretch.

Is stretching a poor warm-up for a distance runner, but essential for a high jumper or dancer? We don't know. Distance runners are studied more often than other athletes in terms of stretching. So far the results indicate that stretching is not effective as an injury preventive for most distance runners. And since leg power is essential to dancers and jumpers, the potential reduction in power could be a highly negative outcome for them.

The first study that made us question the effectiveness of stretching during warm-ups was done in 1983. A survey of 500 runners found that those who warmed up had more injuries than those who did not (87.7% vs 66%) and that the frequency of injuries increased with the length of the warm-up (R-4).

A few years later a survey of 10K runners in a national championship revealed that those who had stretched had incurred more injuries. But it is not known how many of them had stretched as a means of protection for an injury they already had (R-5).

In a study of recreational distance runners over a year, it was found that those who had stretched periodically sustained more injuries than those who had always stretched or never stretched. But those who had never stretched incurred fewer newer injuries than those who had stretched (R-6).

While the above studies cast doubt on the effectiveness of stretching for distance runners, it would appear that more and better research is required.

Stretching reduces power and strength:

Now that stretching is actually being investigated as a warm-up activity, the studies consistently reveal that stretching during warm-up decreases the athlete's power by 2% to 8%.

Why is this happening?

Researchers like Dr. Arnold Nelson at LSU believe that it's because the tendons are being stretched and thus becoming more slack.

The contracting muscle must take up the slack of the stretched tendon before it can tighten the tendon sufficiently to move the joint.

Others believe that the problem lies in the sarcomere, the small muscle cell that holds the contractile elements. It is thought that if the contractile elements-actin and myosin--are pulled farther apart by the stretching when the muscle fibers are later contracted, they must make up for that separation before the contraction can begin to be effective (R-7).

A third possibility that may reduce the athlete's power after stretching is that it will relax the muscles by reducing the firing patterns of the muscles (R-8).

Reduction of speed and power:

A number of studies have shown that stretching reduces the athlete's speed and power by at least 4%. One of the most recent studies was done in Australia (R-9). It disclosed an increase in the maximum power out- put for people who did not stretch.

The study involved four groups of subjects. Each did five minutes of jogging first. Then one group did the traditional "static" stretching (calf muscles, gluteals, and quadriceps), where the person stretches slowly to the maximum extent.

The second group did proprioceptive neuromuscular facilitated stretching (PNF) in which an assistant helped the participant stretch one muscle while forcibly contracting the opposite muscle. (If the participant is stretching the hamstrings in back of the thigh, he contracts the quadriceps in front of the thigh, while the assistant helps increase the stretch.)

The third group contracted each of the three muscle groups forcefully, but did not stretch.

The fourth, or control, group only jogged.

The test was to see how high a person could jump from a resting position, then how far he could jump in a plyometric drop jump--which would be more like running. (In a drop jump, the person jumps down from a box, then immediately rebounds as high as possible. This is more like running, where you land on your foot, absorb the shock, and immediately push off the ground.)

The results showed that the control group did the best, the group that contracted the muscles but did not stretch was second, the PNF group (which involved stretching and muscular contraction) was third, and the typical static stretching was last.

For the box jump, the non-stretchers showed a 7% increase in power.

Static stretching reduced IRM in both knee flexion and knee extension (R-10).

Since some people thought that ballistic stretching might not have the same effect, two of the authors repeated the study using ballistic stretching rather than static stretching. The results were about the same, with power being reduced about 7.5% (R-11).

In a study of 40 high school athletes in a bench press of 85% of their 1RM, it was found that after all warmed up, with some adding static stretching and others not stretching, the non-stretchers exhibited significantly more power and greater lifting velocity. This was significant to the 0.0001 level, an unbelievably high level of significance (R-12).

With this newer research in mind, we can say that stretching before a workout or competition may be a problem. "The evidence suggests that athletes should eliminate the stretching before exercise and increase the warm-up." (R-13).

If you stretch after your workout, when the connective tissues are warmer, you should be able to increase your flexibility effectively, as long as the stretching is not hard enough to set you up for an injury on your next training day.

A study measuring the vertical jump velocity after a warm-up--with and without stretching--showed that 55% of the participants had a lower velocity after stretching (7.5% lower), 10% of the subjects had no change in their jumping velocity, and 35% had higher jump velocities (an average of 2.4%).

The authors' assumption was that the lower velocities were due to neuromuscular factors rather than a reduction in muscle stiffness. This may be interpreted to mean that since a stretched muscle is more relaxed (lower firing patterns) it cannot be activated as quickly.

The muscle stiffness in this sense means the tightness of the crossbridge between the myosin and the actin (the contracting elements in the sarcomere) makes the muscle resistant to stretching (R-14).

A German study that measured the muscle reflexes and force development of the calf muscles after stretching, running 10 minutes, or with no prior warm-up indicated that the force development was about the same for the running warm-up and no warm-up and was considerably less (about 5%) after stretching.

There was, however, a great deal of difference between the 50 subjects in how each reacted to the various types of warm-ups (R-15).

This may indicate that some people have to be stretched in their warm-up, but most people do not. A Japanese study, using only five women as part of a larger study, found that the warm-up reduced the amount of muscle damage due to eccentric contractions (R-46).

Stretching and muscle soreness:

Some people stretch because they believe that it will reduce the soreness that can follow exercise. A Swedish study investigated whether stretching would decrease the onset of muscle soreness (DOMS) in women doing eccentric exercise--the type of exercise most likely to increase muscle soreness.

No advantages for stretching were found. The amount of soreness and tenderness was not reduced (R-47).

A number of other studies indicate that stretching also doesn't seem to reduce the effects of delayed onset muscle soreness (DOMS). This is the residual pain often found in beginning exercisers. It can last up to a week (R-18, R-19, R-20).

Increasing the range of motion before activity:

This doesn't seem to work, either (R-21). You can stretch too long or too far in your warm-up. Anyone entering a sprint race on the track or in the pool would want his muscle fibers to be tighter and "stiffer." Too much stretch can slow him down.

This is also true of jumpers (high jump or long jump), swimmers, and weight-lifters. But if you're getting ready for a tennis match, a long run, or a leisurely afternoon of skiing, light stretching might not pose a problem (R-22).

More research is now being done on the effectiveness of warm-up stretching for various types of other activities.

With this newer research in mind, we can say that stretching before a strength-training workout should not pose a problem. Before a weight-lifting competition, however, stretching might reduce the lifter's strength by as much as 8% If he will wait until after his workout, when his connective tissues are warmer, to stretch, he should be able to increase his flexibility effectively.

This article has been adapted and condensed from the book, Complete Conditioning for the Female Athlete, by O'Connor, Fasting, Daum, and Wells, Wish Publishing, 2001.

REFERENCES

(1.) G.W. Gleim, & M.P. McHugh: Flexibility and its Effects on Sports Injury and Performance, Spts. Med., New Zealand, Nov. 1997

(2.) I. Schrier: Stretching Before Exercise Does Not Reduce the Risk of Local Muscle Injury: A Critical Review of the Clinical and Basic Science Literature, Clinical 3. of Spts. Med., Oct. 1999

(3.) R.P. Pope; R.D. Herbert; J.D. Kirwin; & B.J. Graham: A Randomized Trial of Pre-Exercise Stretching for Prevention of Lower-Limb Injury, Med. Sci. Spts. Exer. Feb. 2000

(4.) J.A. Kerner & J.C.D'Amico: A Statistical Analysis of a Group of Runners, J. of Amer. Podiatry Assn., 1983

(5.) S.J. Jacobs & B.L. Berson: Injuries to Runners, a Study of Entrants to a 10,000 Meter Race, Amer. J. of Spts. Med., 1986

(6.) S.D. Walter, et al: The Ontario Cohort Study of Running-Related Injuries, Archives of Internal Med., 1989

(7.) Conferences of AAHPERD, Cincinnati, OH, Apr. 28-29, 2001. See also K. Weiman, & A. Klee: Die Bedeutung von Dehnen and Stretching in der aufwaermphase vor Hoechstleistungen, Leistungssports, Muenster, July 2000

(8.) K.J. Mohr; M.M. Pink; C. Elsner; & R.S. Kvotne: Electromyographic Investigation of Stretching: The Effects of Warm-Up, Clin. J. of Spts. Med., July 8

(9.) W. Young & S. Elliott: Acute Effects of Static Stretching, Proprioceptive Neuromuscular Facilitation Stretching, and Maximum Voluntary Contractions on Explosive Force Production and Jumping Performance, Red. Qtly. For Exer. and Spts. Sept. 2001

(10.) J. Kokkonen; A.G. Nelson; & A. Cornwell; Acute Muscle Stretching Inhibits Maximal Strength Performance, Res. Quart., 1998

(11.) A.G,. Nelson & J, Kokkonen: Ballistic Stretching Inhibits Maximal Strength Performance, Res Quart., Dec. 2001

(12.) E.W. McLellan: The Effect of Static Stretching on Peak Power and Peak Velocity, Unpublished Master's Thesis, U. of Memphis, 2000

(13.) I. Schrier & K. Gossal: Myths and Truths About Strtching, Phys. & Spts. Med., Aug. 2000

(14.) D. Knudsen, et at: Acute Effects of Stretching Are Not Evident in the Kinematics of the Vertical Jump, J. Stren. & Cond, Res., Feb. 2001

(15.) D. Rosenbaum & E.M. Hennig: The Influences of Stretching and Warm-Up Exercises on Achilles Tendon Reflex Activity, J. Spts. Sci., Dec. 1995

(16.) K. Mosaka & P.M. Clarkson: Influence of Previous Concentric Exercise-Induced Muscle Damage, J. Spts. Sci., Oct. 1997

(17.) P.H. Johansson; L. Lindstroml G. Sundedelin; & B. Lindtrom: The Effects of Pre-exercise Stretching on Muscular Soreness, Tenderness, and Force Loss Following Heavy Eccentric Exercise, Scand. J. Med. Sci. Spts., Aug. 1999

(18.) D.T. Gullick: Effects of Various Treatment Techniques of the Signs and Symptoms of Delayed Onset Muscle Soreness, Res. Quar. Ex. Spt., Dec. 1989. PhD Thesis from Temple U., 1995

(19.) J. Rodenburg, et al: Warm-up, Stretching, and Massage Diminish Harmful Effects of Eccentric Exercise, Intl., J. Spt. Med., Oct. 1994

(20.) D. High & E. Howley: The Effects of Static Stretching and Warm-Up on Prevention of Delayed Onset Muscle Soreness, Res. Quar. Ex. Spt., Dec, 1989

(21.) W.L. Cornelius & M.R. Hands: The Effects of a Warm-Up on Acute Hip Joint Flexibility Using a Modified PNF Stretching Technique, J. Ath. Train. Sum., 1992

(22.) G. Wilson: Applied Resistance Training: A Scientific Approach, Unpublished manuscript, Southern Cross U., NSW Australia, 1998