Does Stretching improve Performance?

Does Stretching improve Performance? A Systematic and Critical Review of the Literature

Ian Shrier
Journal Sports Medicine, 2004


Although many clinicians and authors currently advise that stretching prevents injury, recent reviews have suggested that stretching immediately prior to exercise does not prevent injury. However, there is some weak evidence that stretching at other times may indeed prevent injury.
Although clinicians are now generally aware of the issues related to stretching and injury, many authors also recommend stretching to improve performance.

Does Pre-Exercise Stretching Improve Performance?
Force, Torque, and Jump: positive studies:
There were no studies that suggested that stretching is beneficial for these aspects of performance.

Force, Torque, and Jump: negative studies:
There were 20 studies that found that an acute stretching session diminshed performance. The measures included MVC, power, jump height, jump force, and hump velocity. One of these studies found static stretching detrimental for jumping, whereas dynamic stretching had no effect.

Running
The study showing that stretching was detrimental used static stretching, and the study showing that stretching was beneficial showed greater benefits with dynamic stretching compared with static stretching. Of note, although not statistically significant, the study that showed that stretching was beneficial for running had also showed that static stretching decreased jump height by 2,5%, which is the same magnitude found in other studies. Dynamic stretching had resulted in only a 0,5% decrease in jump height.

Does regular Stretching  improve performance?
Positive studies
There was 7 studies suggesting that regular stretching improves performance. The measures of performance inclueded MVC, contraction velocity, both eccentric and concentric contraction force, counter-movement jump height, and 50-yard dash.

Negative studies
There were no studies that suggested that regular stretching diminshes performance.

Equivocal studies
There were 2 studies suggesting neither an improvement nor a diminished performance.



A review of the clinical evidence strongly suggests that pre-exercise stretching decresases force production and velocity of contraction for at least part of the range of motion (ROM), and that running economy is improved. The effect on running speed remains to be determined, with 1 study suggesting that stretching is beneficial, 1 suggesting that stretching is detrimental, and 2 equivocal small studies. The effects of regular stretching are exactly opposite: regular stretching improves force production and velocity of contraction but has no effect on economy of motion. These results are consistent with the basic science evidence and mirror the results observed with respect to stretching and injury.

Acute Stretching
Running economy is improved with an acute bout of stretching.


This review found that running economy is improved, but force and velocity of contraction are decreased.
The overall effect on running speed is therefore likely to be dependent on the balance of these factors withing any particular individual. 1 article that found that stretching improved running speed found that dynamic stretching was superior to static stretching. Because dynamic stretching also requires the muscles to contract, other possible mechanisms include central programming of muscle contraction/coordination and decreased fatigue through increased warm-up activity.

Regular Long-Term Stretching
Although the immediate effects of stretching decrease visco-elasticity and increase stretch tolerance, the effect of stretching over 3 to 4 weeks appears to affect only stretch tolerance, with no change in visco-elasticity.
The mechanism by which regular long-term stretching improves performance is likely related to stretch-induced hypertrophy occurs event though the muscle has not been contracting.

Limitations
There are many different ways to stretch, Static stretching was used in most of the studies, but the effects were observed with PNF stretching as well. Dynamic stretching is a combination of both stretching as well. Dynamic stretching is a combination of both stretching and warm-up

A muscle that contracts immediately after a stretch (e.g., jumping up immediately agter landing from a short jump) produces more force than a muscle that was not stretched. This is an important phenomenon but unrelated to the clinical effects of pre-exercise stretching.
In summary, the evidence suggests that stretching immediately prior to exercise decreases the results on performance tests that require isolated force or power. The effect on running speed remains to be determined. On the other hand, regular stretching will improve the results for all activities. This is similar to the fact that stretching immediately prior to exercise does not reduce the risk of injury, but that regular stretching may reduce the risk of injury.


Future research should investigate the cellular and molecular mechanisms by which the effects of stretching occur, whether the added benefit of regular stretching is as effective as other types of performance enhancement exercises being promoted (e.g., plyometrics, increased weight training), and whether the same effects are seen in the presence of injury.

The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature

The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature
Stephen B. Thacker, Julie Gilchrist, Donna F. Stroup, C.Dexter Kimsey, Jr.
Epidemiology Program Office, National Center for Injury Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta

Some investigators have questioned the routine practice of stretching and contend that there is little evidence that stretching pre-or post participation prevents injury and that it might affect performance negatively.
A recent systematic review concluded that hte best available evidence indicates that stretching before or after exercise does not prevent muscle soreness or injury and that there is insufficient evidence to assess effect on performance.

 

There are several methods of stretching to increase flexibility including passive, static, isometric, ballistic, and proprioceptive neuromuscular facilitation (PNF). 

Although stretching before activity might improve performance for some sports that require an increased range of motion (e.g., gymnastics or swimming), increased flexibility might compromise muscle performance for up o 1h. 

Literature reviews and analytic studies concerning injuriy enumerate many risk factors such age, extremes in body, mass index, etc...

Close examination, of these studies, howevery finds that stretching has not been shown to prevent injury.

Stretching to improve flexibility

Alternative methods of stretching, including passive stretching, static stretching, ballistic stretching, isometric contractions, and PNF, have been compared for their effects on flexibility. 

Stretching was demonstrated to increased joint flexibility about the knee (including hamstring/quadriceps muscles), hip, trunk and shoulder and ankle joints (soleus/gastrocnemius muscles). Although there is evidence that PNF stretching is more effective in improving flexibility, this has not been demonstrated consistently.

A 15s or 30s passive stretch is more effective thar shorter duration stretches and as effective as stretches of longer duration. Passive stretching is more effective than dynamic stretching of the hamstring, although no diference was found in active versus passive stretching of the hip joint.

Adverse effects of stretching/flexibility

Recent studies of passive stretching shows significant adverse effects on jump performance and plantar flexion. Increased flexibility decreases running economy and peak performance, but these findings are not consistent and there is some evidence that increased flexibility enhances performance. 

Warm-up to prevent injury

Warm-up together with stretching increases the flexibility of the ankle, hip, and knee joints but has not been shown to prevent muscle soreness.

Several programs that combine warm-up, strenght, and balance training with stretching have demonstrated effectiveness in the prevention of knee and ankle injuries, but the independent effects of warm-up and stretching were not determined. 

A positive attitude toward warm-up was associated with a significant improvement in performance. 

Risk factors for injury

Questionnaire surveys and/or personal logs of groups of runners and other athletes have asked about stretching and have shown either no association with injury, no protective effective, or no increased injury rates. 

But in order studies, stretching before or after exercise had no effect in the prevention of postexercise pain. 

Recently, the President's Council for Physical Fitness and Sports reported that Stretching not only might not prevent injuries but also might compromise performance. 

Stronger evidence demonstrates that various approaches to conditioning that include warm-up and stretching along with other techinques, such as strenght training, plyometrics, and proprioception training both enhance performance and prevent certain kinds of injury. This suggests that strenght training, conditioning, and warm-up play an important role in injury prevention. In addition, stretching of specific muscles and joints for specific activities might enhance the effectiveness of these other preexercise activities, an approach consistent with a multifactorial model for prevention. At the same time, there might also be a risk of injury and impaired performance associated with a stretching without adequate conditioning and/or warm-up. 

Some have argued that warm-up is more important than stretching in the prevention of injuries in sports. 

Based on this review, we can recommend neither the endorsement not the discontinuation of stretching, which has been a basic tenet of preparation for athletic participation. The evidence demonstrates that stretching clearly increases flexibility and, to the degree that flexibility might benefit performance or decrease the risk of injury, stretching might be desirable. It is also evident that strenght training conditioning, and warm-up have an important role in injury prevention, and we suggest that when stretching is done, it should be conducted in the context of adequate conditioning and appropriate warm-up. 

In conclusion, there is not sufficient evidence to endorse or discontinue routine pre-or postevent stretching to prevent injury among competitive or recreational athletes. Better research is needed to determine the proper role of stretching in sports, especially as there are increasing numbers of athletes and growing recognition that all people need to increase their physical activity to improve their health and quality of life.