You've got questions. Should clients stretch before and after exercise? Does stretching improve sports and fitness performance and reduce injuries? Researchers may have the answers.

Stretching has always been considered a staple of the athlete's and exerciser's preparation and training program. Strident claims that it improves performance and reduces chance of injury have been made since the fitness boom started in the 1970s. Other benefits of stretching are purported to be reducing post-competitive or post-training muscle soreness, relief of low-back pain, counteracting muscle imbalances and relieving muscle cramps.

Yet, in the past 10 years, the relevance of stretching for these purposes has been challenged by exercise scientists - especially since one bombshell study found that runners who stretched occasionally have a higher injury rate than runners who don't stretch. Another research paper got coaches' attention when it showed that overstretching is the third major cause of injury to distance runners. Nevertheless, personal trainers, athletic trainers, physical therapists and coaches continue to recommend stretching, at least for rehabilitation and warm-up purposes. So, the debate rages to this day.

What the experts say

Following are 24 summaries and conclusions from more than 20 different research papers published in respected and reputable research journals. The research on the benefits of stretching are contradictory at the very best, and many are unfavorable toward the activity. In particular, pay attention to those summarizing research against stretching - they're eye-openers.

Flexibility and injury reduction - conflicting evidence

Research/arguments in favor of stretching for injury prevention.

  • Improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance.20
  • Experts in the field of training and conditioning agree that good flexibility is essential to successful physical performance, although their ideas are based primarily on empirical, rather than experimental, evidence.20
  • Maintaining good flexibility aids in the prevention of injuries to the musculoskeletal system.20
  • Current sport research shows that improving flexibility or increasing joint range-of-motion (ROM) is significant in its contribution to movement efficiency, amplitude of movement and prevention of soft tissue injury.8
  • Athletic trainers and physical therapists feel that maintaining good flexibility is important in the prevention of injury to the musculotendinous unit.20
  • The statistical analysis indicates an association between the incorporation of a static stretching program and a decreased incidence of musculotendinous strains in Division III college football players.4

Inconclusive research for stretching and injury prevention.

  • No conclusive statements can be made about the relationship of flexibility to athletic injury.6
  • Due to the paucity, heterogeneity and poor quality of the available studies, no definitive conclusions can be drawn as to the value of stretching for reducing the risk of exercise-related injury.20
  • There is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent injury among competitive or recreational athletes. Further research is urgently needed.18
  • Static stretching decreased the incidence of muscle-related injuries, but did not prevent bone or joint injuries.1

Research against stretching for injury prevention.

  • There is no strong evidence proving that flexibility or stretching is associated with rates of strains, sprains or overuse injuries that can be applied across all sports or levels of competition.6
  • New evidence suggests that stretching immediately before exercise does not prevent overuse or acute injuries.16
  • This stretching intervention was not effective in reducing the number of running injuries.19
  • There was no significant effect of pre-exercise stretching on the all-injuries risk rate between the stretch group and the control group.9
  • A typical muscle stretching protocol performed during pre-exercise warm-ups does not produce clinically meaningful reductions in risk of exercise-related injury in Army recruits.9
  • Injured runners were more likely to have stretched before running.10
  • Although stretching to increase flexibility is widely recommended to prevent training injuries, data to support the practice are lacking. This data indicates that both the most-flexible and the least-flexible individuals are at higher risk of lower-body injuries. Subjects in the least-flexible and most-flexible groups were 2.5 and 2.2 times more likely to get injured than subjects in the middle group.12
  • The results of this review do not support the role of pre-exercise or post-exercise stretching as an intervention addressing post-exercise muscle soreness. In addition, the evidence presented in this review does not support the role of pre-exercise stretching in the reduction of lower-extremity injury risk.2

Flexibility and performance - more conflicting evidence

Research/arguments in favor of stretching for performance improvement.

  • These results show that stretching may favorably influence the force/velocity relationship of the trained muscle, as well as the shape of the torque curve during movements at a given velocity.7
  • Regular stretching improves force, jump height and speed, although there is no evidence that it improves running economy.17

Research against stretching for performance improvement.

  • Greater flexibility may impair performance in sports that do not require a high degree of flexibility such as running. Runners with less flexibility are actually more efficient at running.11
  • Intense static stretching may reduce maximum force production. The loss of voluntary strength and muscular power may last up to one hour after the static stretch.5
  • Based on these results, performing stretching before a vertical jump test would be detrimental to performance.3
  • Observations by coaches and athletes have called into question the universal prescription of stretching for the purpose of enhancing sport performance, and this skepticism is being supported by the growing body of empirical data.13

Using common sense

Certainly many of these conclusions against stretching, if true, are of concern to the personal trainer. The potential implications that a) athletes are getting injured from stretching, b) athletes who stretch seem to have a higher incidence of injury, c) stretching may actually cause loss of muscular power and force production, d) stretching does not appear to improve running economy and e) runners with increased range of motion may have impaired performance, are undesirable outcomes for exercisers, athletes and runners of any level.


Strength Suppliers

Since strength and flexibility go hand-in-hand, here is a list of suppliers of strength products for your fitness center.

What appears to be at the crux of the matter, according to researchers who venture an opinion, is that, "when the type of sports activity contains low-intensity or limited-stretch shortening cycles (e.g., running, cycling and swimming), it is not necessary to have a very compliant muscle/tendon unit."15 This is because most of its power generation is derived from active (contractile) muscle work that is directly transferred (by the tendon) to the articular system to generate forward motion. Therefore, stretching (and thus making the tendon more compliant) may not be advantageous.

Thus, it appears that much of the purported benefits of stretching and improved flexibility may depend entirely on the nature of the sport or activity. And this may well have implications for fitness and weight-training aficionados who work out several times a week. The evidence that static stretching before resistance training may affect one's ability to use explosive power (because it causes the muscles to lose energy stored in its elastic tissue) is at least enough to make one reconsider the necessity of stretching before lifting weights.

Perhaps one researcher is close to the truth with this conjecture: "While increased flexibility is important for performance in some sports that rely on extremes of motion for movement, decreased flexibility may actually increase economy of movement in sports that only use the mid portion of range of motion such as running."15

So, where does this leave the exerciser who is following a flexibility program now, or contemplating taking up a stretching program? Perhaps common sense should help dictate whether you should recommend stretching, and how much your clients should stretch. If your clients have been stretching and remain uninjured, then they should continue with the stretching program. If they've been stretching consistently and getting injured consistently, perhaps you should have them back off the stretching or reduce its intensity. If, however, your clients are contemplating starting up a stretching program, proceed with caution because it may not be the best thing for them, depending on why they're exercising.

Fitness stretching

Here are some practical tips for start-up stretchers in the fitness setting:

Avoid overstretching. There are enough studies showing that stretching may cause injuries or make people more prone to getting injured. Make sure your clients and members don't overdo it.

Warm up before stretching. Five to 10 minutes of easy aerobic activity (e.g., treadmill, cycle, elliptical trainer) will help ease exercisers into stretching. And, recent research shows that clients are better off performing some easy stretches at the end of their workout, rather than before a training session.

Stretch within the body's limits, and without straining. Do not allow clients to force a stretch to the point of pain! Straining at a painful stretch will not allow the body to relax because it activates stretch reflexes - exactly what your clients are trying to override. Perhaps this is why some studies show impaired performance and loss of muscular power from stretching.

Spread it out. It's probably not necessary for clients to stretch every day, but three to four times each week will show an improvement in range of motion. But be warned that your clients might just get what they want - increased range of motion - which may reduce running, cycling or swimming economy.

Hold the stretch. Clients should be able to hold the stretch for five to 10 minutes. (They should not actually hold the stretch for this long, but the stretch should be mild enough to hold it for that amount of time.) In light of the mentioned studies, your clients are better off performing a few easy static stretching exercises for 10 to 30 seconds each, rather than a lengthy session.

Be patient. It will take a minimum of two to eight weeks to see long-term improvements in flexibility. Clients' short-term flexibility increases after stretching will last from 90 minutes to 24 hours, according to research. But, if they stop stretching, they will start to lose their newly gained flexibility in about four weeks.

Breathe naturally. Clients should breathe calmly and relax when stretching. Encourage them to avoid comparing their flexibility to other people. Help them develop a liking and routine for stretching.

What to stretch. What regions should be stretched? The shoulders, chest and arms can all be stretched with one or two common stretches. Hip flexors and abdominals can be stretched with two common stretches. The back, gluteals and hamstrings can be stretched with a few common stretches. Clients can stretch their quadriceps and calves with separate stretches.

What not to stretch. Clients should avoid these stretches: hurdler stretch with the knee back, deep knee bends, a standing toe touch, a back arch/bridge, a standing torso twist with broomstick and the "yoga plow."

Stretching shouldn't be torture

It seems ironic that a widely practiced sports technique was used several centuries ago as a technique to make hapless victims confess to crimes (on the "rack"). Stretching may be appropriate for certain activities and sports that are performed through a wide range of motion, but fitness professionals may want to reexamine its use for repetitive and rhythmic sports that involve a shorter range of motion.

1. Amako, M., T. Oda, K. Masuoka, H. Yokoi and P. Campisi. Department of Orthopedic Surgery, Japan Self-Defense Force Beppu Hospital. Effect of static stretching on prevention of injuries for military recruits. Military Medicine 168(6): 442-446, June 2003.
2. Andersen, J.C. Stretching before and after exercise: Effect on muscle soreness and injury risk. Journal of Athletic Training 40(3): 218-220, July-September 2005.
3. Church, J.B., M.S. Wiggins, F.M. Moode and R. Crist. Effect of warm-up and flexibility treatments on vertical jump performance. Journal of Strength and Conditioning Research 15(3): 332-336, 2001.
4. Cross, K.M., and T.W. Worrell. Effects of a static stretching program on the incidence of lower extremity musculotendinous strains. Journal of Athletic Training 34(1): 11-14, January-March 1999.
5. Evetovich, T.K., N.J. Nauman, D.S. Conley and J.B. Todd. Effect of static stretching of the biceps brachii on torque, electromyography, and mechanmyography during concentric isokinetic muscle actions. Journal of Strength Conditioning Research 17(3): 484-488, August 2003.
6. Glein, G.W., and M.P. McHugh. Flexibility and its effects on sports injury and performance. Sports Medicine 24(5): 289-299, November 1997.
7. Handel, M., T. Horstmann, H. Dickhuth and R.W. Gulch. Effects of contract-relax stretching training on muscle performance in athletes. European Journal of Applied Physiology 76: 400-408, 1997.
8. Hartley-O'Brien, S.J. Six mobilization exercises for active range of hip flexion. Research Quarterly for Exercise and Sport 51(4): 625-635, 1980.
9. Herbert, R.D., and M. Gabriel. Effects of stretching before and after exercise on muscle soreness and risk of injury: systematic review. BMJ 325(7362): 468, August 2002.
10. Jacobs, S.J., and B.L. Berson. Injuries to runners: A study of entrants to a 10,000 meter race. The American Journal of Sports Medicine 14(2), 1986.
11. Jones, A.M. Running economy is negatively related to sit-and-reach test performance in international-standard distance runners. International Journal of Sports Medicine. 23(1): 40-3, January 2002.
12. Jones, B.H., D.N. Cowan, J.P. Tomlinson, J.R. Robinson, D.W. Polly and P.N. Frykman. Epidemiology of injuries associated with physical training among young men in the Army. Medicine & Science in Sports & Exercise 25(2): 197-203, 1993.
13. Neal, J.R., and W.A. Sands. Stretching for performance enhancement. Current Sports Medicine Reports 5(3): 141-146, 2006.
14. Pope, R.P., R.D. Herbert, J.D. Kirwan and B.J. Graham. A randomized trial of pre-exercise stretching for prevention of lower-limb injury. Medicine & Science in Sports & Exercise 32(2): 271-277, 2000.
15. Shellock, F.G., and W.E. Prentice. Warming-up and stretching for improved performance and prevention of sports-related injuries. Sports Medicine 2: 267-278.
16. Shrier, I., and K. Gossal. Myths and truths of stretching. The Physician and Sportsmedicine 28(8), August 2000.
le="text-indent: -20px;">17. Shrier, I. Does Stretching improve performance?: A systematic and critical review of the literature. Clinical Journal of Sports Medicine 14(5): 267-273, September 2004.
18. Thacker, S.B., J. Gilchrist, D. Stroup, C.D. Kimsey. 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.
19. van Mechelen, W., H. Hlobil, H.C. Kemper, W.J. Voorn and H.R. de Jongh. Prevention of running injuries by warm-up, cool-down, and stretching exercises. American Journal of Sport Medicine 21(5), 1993.
20. Weldon, S. The efficacy of stretching for prevention of exercise-related injury: A systematic review of the literature. Manual Therapy 8(3): 141-50, August 2003.