Stretching, flexibility, hamstrings and injury

The truth about stretching and why the Kenyan athletes always do it after their workouts are over.

Can stretching really help you improve your flexibility, lower your risk of injury, and improve your performances, as many stretching advocates claim? If so, should you stretch before or after your workouts? Which of the many types of stretching is best for you?

New research makes it clear that - in terms of improving your flexibility - it's probably best to stretch during or after your workout, not before. In a study carried out at James Madison University in Virginia, 12 healthy subjects tried out four different hamstring- stretching protocols: ( I ) after running at a fast-enough speed so that heart rate stayed above 70 per cent of heart-rate reserve for four minutes or more (heart-rate reserve is simply max heart rate minus resting heart rate), (2) after running at just 60 per cent of heart-rate reserve for three or more minutes, (3) after warming up the hamstring muscles with heating pads, (4) with the muscles in a 'cold' state - after no warm-up running or heat-pad application.

Stretching the hamstrings after vigorous running (at 70 per cent of heart-rate reserve or above) proved to be far superior to the other three methods at promoting hamstring flexibility. In fact, the range of motion at the hip was 5 per cent higher when stretches were carried out after vigorous running, compared to either light running or the application of heating pads. In addition, flexibility was nearly 10 per cent greater after strenuous running, compared with stretching muscles in the 'cold' condition.

The stretches carried out by the James Madison athletes were the 'PNF' (proprioceptive neuromuscular facilitation) type, meaning that stretches of the hamstrings were alternated with contractions of the same muscles. Both the stretch and contraction period lasted for about 10 seconds, and each stretch and contraction of the hamstrings was repeated three times. The stretch- contractions were carried out one, five, 10 and 15 minutes after exercise or the application of heat pads, but no additional gains in flexibility were made beyond the one-minute period (adding stretches at five-minute intervals after the workout didn't help unkink the muscles; the key was to carry out the PNF stretching right after the exertion ended).
Stretching before doesn't help flexibility
Interestingly enough, stretching the muscles in the cold condition didn't help improve flexibility at all, yet countless numbers of athletes stretch their sinews before their training sessions. In addition to the promotion of greater flexibility, another advantage associated with stretching AFTER working out, not before, is that it may speed recovery. A large number of studies carried out in the medical field have shown that stretching stimulates the passage of amino acids into muscle cells, accelerates protein synthesis inside the cells, and inhibits protein degradation. Thus, post-workout stretching should help muscle cells repair themselves and synthesise energy-producing enzymes and structures which enhance overall fitness.

The James Madison study is supported by another piece of research carried out at Auburn University with 51 students. In that investigation, in which subjects stretched their muscles either before or after their jogging sessions, it was determined that jogging BEFORE stretching - not after - was a superior way to improve the flexibility of chronically tight Achilles tendons and calf muscles. However, the Auburn study did support the idea of stretching out lower back muscles before running; unkinking the lower back prior to workouts seemed to alleviate lower back stiffness more effectively, compared to post-workout stretches.

The improvement in flexibility and potential augmentation of recovery which are noted when stretching occurs after a vigorous workout may help to explain the findings of David A. Lally, Ph.D., an exercise physiologist at the University of Hawaii-Manoa who carefully studied 1543 participants in the Honolulu Marathon. Lally found that runners who stretched after their workouts had relatively low rates of injury, compared to runners who didn't stretch, while runners who stretched BEFORE training sessions had HIGHER rates of injury.

Although this study seems shocking at first glance, since its results suggest that the conventional practice of stretching before workouts may be doing more harm than good, the research is not so surprising when examined carefully. First, remember that one goal of stretching is to improve flexibility, and we've already seen (from the James Madison study) that stretching muscles before a workout, when they are 'cold,' doesn't always improve flexibility, while stretching the sinews after a workout makes them more like elastic rubber bands. Second, bear in mind that although it's popular to position stretching before the beginning of a workout, there's actually very little resemblance between the act of stretching out a muscle and the rapid shortenings (contractions) which muscles undergo during a typical workout. In other words, stretching doesn't represent specific preparation for an actual training session. During a stretch, a muscle is elongated and then held in a static position; in a workout, a muscle shortens repeatedly.

On the other hand, muscles are often fairly tight - and in some cases close to going into a spasm - after a very strenuous workout ends. At that point, stretching is a fine way to transform a hypercontracted muscle into a relaxed collection of fibres which can comfortably adapt to the more passive activities which usually follow a training session. As mentioned, post-workout stretching may also be a fine way to help muscles recover in time for a subsequent quality- workout.
What kind of stretching works best?
Many different stretching techniques are available to athletes, but research carried out at the University of North Texas supports the idea that PNF stretching (the type used in the James Madison study) is superior to regular passive stretches at unkinking muscles and expanding joint flexibility (Research Quarterly for Exercise and Sport, vol. 63(3), pp. 311-314,1992).

In the Texas study, 120 college students were randomly assigned to receive one of four different stretching treatments, all of which were designed to lengthen the hamstring muscles in the posterior, upper portion of the leg. The treatments involved:
( I ) Regular passive stretching, in which the investigators manually flexed the legs of the students at their hip joints until tension or discomfort was felt behind the knee
(2) A passive stretch of the hamstrings (as above) followed by an 'active' stretch of the hamstrings which was the result of a strong contraction of the quadriceps muscles in the front of the thigh. After the active stretch, there was another passive stretch of the hamstrings.

(3) A passive stretch of the hamstrings, followed by a three-second isometric contraction of the hamstrings, an active contraction of the quadriceps muscles, and then a passive stretch of the hamstrings.

(4) The same as no. 3, except that the three-second isometric contraction involved the quadriceps, not the hamstrings.

Treatments 2-4 all can be classified as PNF stretches, because relaxation of the hamstrings is 'facilitated' by various nerve-muscle reflexes which are activated by muscle contractions (in this case by contractions of the hamstrings or quadriceps). For example, when the quadriceps contract, reflexes automatically 'tell' the hamstrings to relax so that the quadriceps can carry out their task of flexing the leg at the hip without too much resistance from the hamstrings . Also, when the hamstrings themselves contract vigorously (as in the isometric contraction of treatment no. 3), other reflexes signal the hamstrings to relax and loosen up a little.

Some studies have indicated that chilling a muscle can actually expand its stretchiness by blocking a 'stretch reflex' which normally keeps muscles from elongating too much, so half of the subjects also received 10 minutes of cold application to the hamstrings immediately prior to stretching. Since all subjects had less than 18 per cent body fat, the cold (applied by means of ice in a plastic bag) could penetrate fairly quickly through the subcutaneous tissues into the actual muscles.

However, cold application had no significant effect on untightening the hamstrings, indicating that this time- consuming procedure is unnecessary. On the other hand, the three PNF techniques (nos. 2-4) provided about 10- 15 per cent greater hamstring flexibility than routine passive stretching (no. 1). There were no significant differences between the three PNF methods. Most athletes tend to use conventional passive stretching rather than PNF, but since PNF enhances joint flexibility and works more effectively than routine, passive stretching, sports-active people would be wise to include PNF techniques in their stretching routines.

The North Texas study is supported by research carried out at the famed Karolinska Institute in Stockholm, Sweden. There, scientists were able to to improve the muscle flexibility of 47 athletes (runners, orienteers, soccer players, and ice-hockey participants) by about 6 to 10 per cent by using 'contract-relax' (PNF) stretching for the calf, thigh, and hamstring muscles. The PNF stretches were carried out quite easily: individual muscles were stretched for about eight seconds, contracted for eight seconds, and then stretched again for eight seconds. This sequence was repeated five times per training session per muscle group, with great results.

Fortunately, PNF is easy to carry out. If you want to use PNF on your calf muscles, for example, you can simply stretch your calves passively for a while, contract your ankle flexors (the muscles in the front of the lower part of the leg) and then passively elongate your calf muscles again (as in technique no. 2 from the North Texas study described above). Or, you can stretch your calves, isometrically contract your calves, work your ankle flexors, and then stretch your calf muscles again (as in North-Texas treatment no. 3). If you do this systematically - especially in areas of your body with excess muscle tightness - you should notice a marked improvement in your flexibility.
Before a workout?
So what should you do before your workout begins? Instead of stretching, try other, more specific preparatory activities. Walking, jogging slowly, skipping, hopping, walking on toes (with toes pointed to the inside, straight ahead, and to the outside), walking on heels (ditto), and carrying out the active-mobility exercises described in issue 53 of PEAK PERFORMANCE will in most cases prepare you more specifically for your workout than sitting on your rump while passively trying to unkink your cold muscles. These alternative activities bring hot blood to your muscles and wake up your cardiovascular muscular, and nervous systems, so that you're really ready to train in a high-quality way.

But don't throw away stretching altogether. You can complete your PNF stretching routine when your workout is over. After all, it's easy ! Just remember to stretch each important muscle group for eight to 10 seconds, contract it for about the same amount of time, and then stretch it for eight to 10 more seconds. Do this three to five times for each muscle group after a workout, and in short order you'll be much more flexible. This improved flexibility should allow your muscles to contract more powerfully - and promote higher performances !

Jim Bledsoe

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stretching, flexibility, injury, hamstrings

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