Does Current Research Support The Use of Dynamic Stretch During Warm-up

by: Carol J.M. Clein, MBA, MS, CSCS
Boyd H. Anderson High School, Lauderdale Lakes, Florida
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Traditionally, preparation for football practices or games includes warm-up and static stretching, with no particular preference for what order they are performed in. Dynamic stretch is becoming more and more popular; however, it has yet to have a major presence in football. This article reviews research on dynamic stretch to see if it is appropriate as part of the warm-up for football.

On almost every football field in America at some point before practices and games, the teams line-up and static stretch. Football teams have always done it, so what is the problem? The problem is that if anyone responsible for those football teams was asked why they are static stretching, they will probably not be able to offer you a reason that is supported by current research. More importantly, is there a better activity to include in the warm-up?

Ideally, warm-up for a sport should include activities that prepare the body for the sport, improve performance – or at the very least, not negatively impact performance - and reduce the risk of injury. Of course, every football coach would like a warm-up that turns their team into a dominant and aggressive football machine, but the first set of objectives will have to do for now. The sport of football involves explosive movements of power and speed that are repeated with active rest intervals. Since research has not been specifically performed on dynamic stretch for football, the purpose of this article is to review current research on the effects of dynamic stretch on explosive power and speed, and whether there is sufficient research evidence to support the inclusion of dynamic stretch in a warm-up for football. As a by-product, any activities that would be contraindicated, based upon the stated warm-up goals, will also be identified.

What is Dynamic Stretch?

Dynamic stretch can generally be defined as controlled, steady movements through the range of motion that would be achieved by each joint during the activity (4). For the purposes of this article, “dynamic stretch” will be very loosely defined to include all definitions of dynamic stretch used in the research studies presented. Ballistic stretch, though sometimes confused with dynamic stretch, is actually repeated bouncing or jerky movements that use momentum to rapidly and repeatedly stretch the muscles. Ballistic stretch has been linked to muscle soreness and damage.

Prepare the Body for Sport Performance

Preparing the body for sport performance involves the raising of core body temperature and increasing the blood flow to, as well as the temperature of, the muscles to be used during the sport. The increased temperature increases the speed of the chemical reactions involved in energy utilization, and assists in the transition from resting to exercise.

In 2001, Church et al. studied the effects of different pre-performance activities on vertical jump performance (2). The 40 volunteer female participants were NCAA Division 1 athletes age 18 to 22 years. Treatment 1 was a 10 exercise body weight circuit that they were familiar with, that totaled to a 5 minute general warm-up. Treatment 2 was the same general warm-up followed by a static stretching routine that focused on the large muscle groups of the thigh. Treatment 3 was again the Treatment 1 general warm-up, except followed by proprioceptor neuromuscular facilitation (PNF) of the large muscle groups of the legs. The study found that Treatment 1 resulted in the best vertical jump performance, followed by treatment 2, then Treatment 3. Only Treatment 3 exhibited a statistically significant decrease in vertical jump performance when all results were compared. In practical application, the author’s believed that easy movements increasing in intensity and covering a range of motion applicable for the activity to be performed was the most appropriate preparation for powerful activities. They also recommended that stretching should be performed after these activities, but not before.

The warm-up activities described as appropriate by the authors are a basic description of dynamic stretch. These results can be interpreted as an endorsement for dynamic stretch during warm-up for football. In another study, it was found that even when the stretching was performed between warm-up activities, dynamic stretch was more effective as preparation for high-speed sport performances. Little and Williams performed their research on eighteen professional soccer players. The subjects performed 4 minutes of warm-up exercises followed by a stretch protocol, followed by 4 more minutes of warm-up exercises, prior to performing the tests. The stretch protocols were either static stretch, dynamic stretch or no stretch (1 minute of rest). The tests consisted of vertical jump, 10 meter acceleration, flying 20 meter maximal speed, and zig-zag agility. The dynamic stretch yielded the same or better results in all tests, particularly the zig-zag agility test in which the dynamic stretch subjects performed significantly better than both the static stretch and the no stretch groups. This finding is very relevant to this article, as change of direction is such a critical part of football performance.

Improve Performance

Commonly used measures of football potential, such as those tested at a football combine, are not always direct indicators of football performance. This fact is evident every year after the NFL draft, when some of the fastest and strongest athletes are quickly without a job, and some of the un-drafted individuals with sub-standard speed and strength have lengthy, successful football careers. The strength and speed tests are used as indicators of one element of performance; therefore improved speed and strength performance is desirable for football. Specific isolation of only the effects of static and dynamic stretch on leg power was researched in 2005 by Yamaguchi and Ishii. The author’s specifically set out to perform a realistic amount of static and dynamic stretch prior to testing leg extension power, because they determined that the static stretching performed in previous research was too lengthy to be considered applicable to a real sport situation. Eleven healthy college aged male subjects each performed the leg press test after all three conditions on separate days. Condition 1 was no stretching. Condition 2 was assisted static stretching of the legs held for 30 seconds on each leg. Condition 3 was dynamic performance of the same stretches with increasing speed. The subjects were tested before and after the Condition was performed. The study found that only Condition 3 improved performance over pre-condition results. There was a slight decrement in performance after Condition 1 and Condition 2, and the performance difference between Condition 1 and Condition 3 was statistically significant.

The author’s concluded that static stretching for 30 seconds during a warm-up for an activity that requires strength and power is not recommended. Important to this review, they also noted that the subjects with greater pre-condition power experienced larger decreases in power after static stretching. Variation on the effects of warm-up protocols on various muscle density or muscle types, would be a significant finding well beyond applicability to football.

The limitations of the study must be noted. Unlike what would be expected in football, no warm-up of any kind was performed, unless you consider the pre-condition leg extension test a warm-up. The subjects were only recreationally active and were not considered to be athletes. These points bring to question the direct applicability of this study to football.

The effects of static stretching on peak torque were studied in 2004 by Cramer et al. This study utilized a 5-minute moderately paced warm-up on a stationary bike before the pretest, stretching treatment and post test. Fourteen college aged women who were recreationally active but not formally trained, were evaluated using a dynamometer. The static stretching consisted of four repetitions of 30 seconds each of four static stretches performed on each leg, resulting in a total stretch and rest time of about 16 minutes.

The study found that peak torque decreased following static stretching. The authors advised strength and conditioning professionals to consider these results when establishing a warm-up routine for their athletes, since this study and other studies conclude that static stretching has a negative impact on maximal force production. Although this study was performed on women, and most football players are not women, there is no indication that the results would not be applicable to both genders. Other studies have concluded that static stretching reduces power. Knudson and Noffal determined the varying effect of the duration of the stretch on strength. The 57 subjects (33 male, 24 female) performed a one minute warm-up prior to performing 10 three-second maximal grip strength tests. During the one minute interval between tests, some of the subjects performed a 10-second static stretch of the wrist flexors. While both the stretch and non-stretch groups experienced a decrement in strength with each performance, the stretching groups performance decrement was statistically significantly different from the non-stretch group after 40 seconds of static stretching. The author’s question the applicability of these results to other muscle groups, however this study does give an indication that effects of static stretching on strength performance may change from “no affect” to “detrimental” after a stretch is held for 20-40 seconds.

Zakas et al. performed a similar study on leg extension peak torque in fourteen young semiprofessional male soccer players (about 18 years old). This study included a five-minute warm-up on a stationary bike followed by a pretest, one of three static stretch protocols and a post test. Peak torque was unchanged in the shortest static stretching protocol, in which one stretch was held for 30 seconds. Statistically significant decreases were noted in the protocols in which 10 stretches were held for 30 seconds, and 16 stretches were held for 30 seconds. Both this study and the prior study suggest that total volume of static stretch affects the potential decrement to performance.

Another important and frequently measured component of athletic ability needed for football is speed. In 2004, Fletcher and Jones looked at the effects of different stretch protocols on 20 meter sprint times (4). Ninety-seven male rugby players were divided into four groups, each performing a different stretch protocol. All groups performed a 10-minute jog warm-up, after which they performed two 20 meter pretests, a stretch protocol, and two 20 meter post tests. The four stretching protocols were identified as passive static stretch (PSS), active dynamic stretch (ADS), active static stretch (ASST), and static dynamic stretch (SDS). PSS and ADS are more or less self explanatory. ASST was the same as PSS, except that the agonist muscle of each stretch was contracted during the stretch. The author’s indicated that the SDS performed the same stretches as the ADS group but in a stationary position, and very little additional information was provided. Sprint times were found to be significantly faster when ADS was performed, and significantly slower with any of the other three protocols. The authors stated that coaches and athletes should consider how passive and active static stretching could negatively affect performance, and how specific movement rehearsal prior to performance could positively affect performance.

Details about the stretching used were not well described by the authors, and a control group that performed no stretching may have strengthened these research findings. However, the results are still valuable for this review because the sport of rugby and the attributes of rugby players are not completely dissimilar from football. The findings that dynamic stretch benefited short distance speed performance, and static stretch negatively affected speed performance in these athletes is a relevant finding.

Another study performed in 2005 found that no stretch yielded better 20 meter sprint times than three different 30-second static stretch protocols. Eleven male and five female NCAA Division 1 track athletes from a nationally ranked team were recruited during their competitive outdoor season to participate in the study. Each athlete performed one of the four protocols on four consecutive Mondays, in random order. Prior to each stretch (or no stretch) protocol and the three 20 meter sprints, each athlete performed their regular warm-up, which included an 800 meter jog, 120 meters of forward skips, 120 meters of side shuffles, and 120 meters of backwards skips. If performed correctly, this would appear to be controlled activities taken through the full range of motion used in the activity about to be performed; essentially, a dynamic stretch.

The authors stated that repetitive performance of a skill requiring high power output would be negatively affected by passive muscle stretching prior to performance of the skill. They also noted that the athletes performed better even though they were uncomfortable performing the sprints without their traditional passive stretch warm-up. Though they felt more prepared psychologically to sprint after passive stretching, they were physiological hampered.

In these last two studies, short distance speed performance of athletes was improved after dynamic stretch (or the rough equivalent) and degraded after static stretch. These studies would seem to be applicable to football players.

Reduce the Risk of Injury

There is a common belief that stretching prior to exercise is required to prevent injury. As previously stated, the authors of the passive stretching noted that the athletes were uncomfortable performing without passive stretching, even though they had performed a thorough warm-up (8). Perhaps because of this universal belief about the prophylactic effect of stretching, few studies have been performed that directly address this issue.

One such study was performed in 2000 by Pope et al. In this study, 1538 male Australian army recruits were studied for a 12 week training period. All recruits performed an active warm-up. The 735 member stretch group then performed a series of 20 second one repetition lower body static stretches prior to every physical training session. Injuries were tracked throughout the training period and no statistical difference in injury rates between the stretch group and the no stretch group were found. These findings are significant because of the size of the subject group. The authors had performed similar studies on smaller groups and felt that these results further support their findings that injury rates are completely unaffected by pre-exercise stretching protocols. The authors did note that fitness level and age were strongly correlated with risk of injury, however this study was not designed to explore those relationships in depth.

A review of the literature on stretching and sports injury was performed in 2004 by Thacker et al. The author’s concluded that research to date was insufficient to support or discourage pre-exercise stretching as a means of reducing injury. Flexibility was clearly enhanced by stretching but it was not clear what affect flexibility had on risk of injury.

In 2000, the President’s Council on Physical Fitness and Sports stated that there is little evidence to support current common stretch practices as a way of reducing muscle injury (5). In this same document, stretching is recommended after vigorous exercise, during cool down to prevent injuries caused by stretching. Interestingly, there is also a warning: “Stretching in the warm-up prior to physical activity may weaken muscles and decrease performance.” Maybe the government does actually have a valid point from time to time.

Based on these studies, there is no correlation between static stretching before exercise and reduced risk of injury. As of this review, research regarding dynamic stretch and injury was not available.

Final Analysis

Based on the research reviewed here, and in consideration of the purposes of the warm-up previously stated, dynamic stretch may be appropriate as part of the warm-up for football. Dynamic stretch increases blood flow and body and muscle temperature because it is an active form of stretch. Studies consistently demonstrate an increase in power and speed when compared to non-stretch, static stretch, and other stretch protocols. At this time, no studies regarding dynamic stretch and injury could be found. It may be logical to assume that the same injury reducing benefits expected from warm-up could be seen from dynamic stretch, however the affects of the actual range of motion movements on risk of injury requires additional research.

More assuredly, we can conclude that the effect of static stretching on power and speed performance ranges from no effect to significantly negative effects, depending on the length of the static stretch. Some evidence supports an increase in the likelihood of injury. The very nature of static stretch leads to no appreciable “warm-up” effect, such as increased core temperature, muscle temperature or blood flow to the muscle groups the athlete is preparing for performance.

This appears to be a research area requiring great attention. Young and Behm came to nearly the same conclusion in their article from 2002 entitled “Should Static Stretching Be Used During a Warm-Up for Strength and Power Activities?” The most recent research has only laid a foundation for critical research. The findings of research on the best warm-up activities for individuals of differing skill levels and performance objectives could have far reaching beneficial effects, if the results are put into practice. It is certainly possible that the “traditional warm-up” that has been universally accepted as helpful may be directly contributing to reduced performance and increased injury. It is only fair to disclose that the football teams coached by the author perform a brief “warm-up” activity followed by dynamic stretch, then sport-specific movements of increasing intensity, prior to any practice or game. Any static stretching is performed when football activities are completed (end of practice, end of game). The same basic methodology is used during off-season conditioning. Though the author’s experience is limited to five seasons with this type of pre-exercise routine and observation has been unscientific, there appears to have been a reduction in non-contact injuries. Research does not conclusively support these warm-up choices for football, however, the author has a reason for every warm-up activity included and excluded, and none of the reasons include the words “tradition”, “all the other teams”, or “always done it”.

Brief Author Bio

Carol J.M. Clein has her Master of Science, Exercise Physiology from Florida Atlantic University (2006). She has coached football for eight seasons and is currently the Associate Head Coach, Strength and Conditioning Coach, and Defensive Line Coach at Boyd H. Anderson High School. She is also an Adjunct Professor in the Department of Physical Sciences and Wellness at Broward Community College.

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