Stretching before participation in athletic activities is typical practice for all levels of sports, competitive or recreational. Athletes, coaches, trainers, physiotherapists, and physicians recommend stretching in an effort to both prevent injury and enhance performance. Several papers have been published which has produced a significant body of evidence that stretching may not be the way to improve performance and decrease risk of injury. Recent research demonstrates that stretching prior to physical activity decreases performance. However, these stretching bouts are not representative of athletes during warm up procedures, as they are usually time consuming. The aim of the this study is to examine whether the duration of acute static stretching is responsible for losses in sprint times compared to increased/decreased flexibility. Research has shown the reduction of peak flow force when using static stretching but research has also shown the reduction of injury and the improvement of flexibility in the long term which also assists in sprinting performance. Research in this area has sometimes been vague involving the time of the static stretched used.
Bandy (1997) used 57 subjects from the age of 21 to 37 years old, 40 of these being male and 17 female with all participants having limited hamstring flexibility. These participants were randomly assigned to four groups. Three groups stretched 5 days per week for 15, 30, and 60 seconds, Group four served as a control group, and did not stretch. The test was ran over a six week period. The results showed that holding a stretch for 30 seconds was optimal as it had a greater effect on range of motion than the 15 seconds and control group and the same effect as the 60 seconds. Bandy (1997) concluded that because there was little difference between no stretching and 15 seconds coaches and athletes must raise the question of the effectivness of static stretching for periods less than 30 seconds. Although this study supports its hypothesis it is very specific to the hamstring and lower body. Muscle such as the gasrtocnemuis may show different results due to the higher percentage of fast twitch muscle fibres which performs larger, more powerful movements REF. The study did not show the acute effects of static stretching so we cannot assume these results would or would not enhance range of motion/flexibility gains prior to any sporting events. Also this study is excessively narrow in subject focus and as all participants had limited amount of range of flexibility within the hamstring, with a higher majority of subjects being men. Therefore this makes the results only valid to this population. Due to the length of the study and the uncontrolled environment I would have to question the suitability of the research design and the effectiveness of the data collection. The subjects were only tested once after the six week period, therefore subjects were subjected to outside environmental factors during the six weeks which may have affected results. Testing and monitoring constantly throughout the six weeks would improve the reliability of this study.
A more controlled study was done by Shirer (2005). This study focused on muscle performance rather than flexibility. He conducted a study using males from a university population who were pre and post tested for isometric force and surface electromyography activity. (Shirer 2005 pg 22) “tests were performed on only lower limb muscles, range of motion in seated hip flexion, prone hip extension, ankle planter and dorsi flexion, no-counter movement jump height, and ground contact time”. Male participants were tested 30, 60, 90, and one120 seconds after static stretching. The group partake in an 18 minute static stretch routine for the lower body (hamstrings, quadriceps, and planter flexors). 45 seconds was the protocol stretch time used for each muscle group and was repeated four times with a 15 second break in-between. Shirier (2005) found differences in the acute (just before exercise) and regular stretching (over a period of time). Results stated that there was no significant benefit of acute stretching on isometric force production, isokinetic torque, or jumping height. In addition, (Shirer 2005 pg 25) concluded by saying “that regular stretching after exercise may improve strength, jump height, and running speed”. As a result these findings imply that acute stretching before exercise had no positive effects on strength and power while regular stretching after training or competition improved strength and speed. Results did not relate to the acute effects of static stretching but only the acute effects of isometric force. Again this study provides significant evidence for the effects of stretching on performance, however the time frame used for the stretches in this study was 45 seconds and 30 seconds has been proven in the previous study to be the optimal time. This extended period of time could therefore affect the force production and therefore the results.
A similar study by Fowles (2000) that supports Shirer (2005) body of evidence showed the effect of stretching on muscular strength over time. (Fowles 2000 pg 1179) “Subjects performed 13 stretches of the plantar flexors, holding each stretch for 135 seconds during a time frame of 33 minutes. Maximal voluntary isometric contraction (MVIC) was assessed 6 times during the ensuing 60 minutes”. Fowles (2000) concluded that an intense extended stretch (of the plantar flexors) reduces MVIC for up to 1 hour after stretching. Although this evidence supports that of Shirier (2005) it is not relevant to sports performance as proven by Bandy (1997) the time for both holding the stretch and time spent on stretching is too long and therefore is not specific to sports performance and is not relevant.
A more sport specific study was done by (Sayers AL 2008) who performed a study using 20 female football players to determine which phase of the 30 meter sprint (acceleration and or maximum velocity) was affected by performance static stretching. Participants were assigned at random to either a stretch or no stretch condition on two non-consecutive days. The athletes in the no-stretch condition completed a standard warm-up protocol and then performed three 30-m sprints, with a 2-minute rest interval between. The athletes in the stretch condition performed the standard warm-up protocol, completed a stretching routine of the lower limbs which included calf, quadriceps, and hamstrings and then without delay performed three 30-m sprints, also with a 2-minute rest between each sprint. The groups would then reverse the next day, and indistinguishable procedures were followed. A considerable statistical difference in acceleration maximal-velocity sprint time, and overall sprint time between the stretch and no-stretch conditions was seen. (Sayers AL 2008 pg 1420) concluded by stating that “static stretching before sprinting resulted in slower times in all three performance variables”. Although this study proves that static stretching diminishes spitting performance it does not state the time held with the stretches. Again this study is gender specific and as studies has proven significant differences between male and females relating in flexibility and spots performance we cannot assume these results are relevant for both genders.
Favero (2009) took this further by relating flexibility to performance investigating the effect of stretching on sprint performance and baseline flexibility. 10 trained male subjects (age 22 to 23 yrs) were randomly designated to “Rest” and “Stretch” conditions. (Favero 2009 pg 52) “A low intensity 5 min running warm-up procedure was followed by either 12 min of inactivity (Rest) or lower-limb stretches”. No statistically significant difference in measures of sprint performance between conditions were seen, however there was a significant correlation between baseline sit-and-reach scores and mean change in mean velocity between conditions. There was an preference for stretching to a harmful affect on sprint performance in subjects with moderately high baseline flexibility. (Favero 2009 pg 54) concluded by saying “an acute bout of stretching does not exert a significant effect on sprint performance under prescribed conditions”. This research therefore disputes previous studies which state that stretching effects sprinting performance. Unlike the previous studies Favero (2009) compared the difference in flexibility compared to the sprinting performance, therefore making the results specific, reliable and valid. Unfortunately there is a lack of evidence and current data to support this conclusion.
Kistler (2008) conducted a similar study to see what would happen to these performance effects at longer distances such as those seen in competition.(Kistler 2008 pg. 2281) “This study investigated the effects of passive static stretching vs no stretching on the 60- and 100-m sprint performance of college track athletes after a dynamic warm-up”. Results discovered a considerable slowing in performance with static stretching in the second 20 (20-40) m of the sprint trials. Following the first 40 m, static stretching exhibited no added affect on performance in a 100-m sprint. However, even tho there was no further time loss, athletes never retrieved back the time that was initially lost in the first section of the trials. Therefore, in strict terms of sporting performance, it is probable that including static stretching will have a diminishing affect of sprinting performance up to 100 meters. (Kistler 2008 pg. 2283) “went on to say that the study found no additional inhibition during the final 60 m of a 100-m dash, therefore it is possible that performance in even longer events could actually benefit from static stretching”. This study supports that of previous literature and supplies solid evidence to propose that static stretching has an effect on sprinting performance at short distances; however many athletes use stretching as a method of injury prevention and increase range in motion, and this study does not provide any information about the effectiveness of static stretching in this regard.
All but 1 study found that an acute bout of stretching diminished performance tests of sprinting, or jumping performance
Even though most studies used a randomised cross-over design some studies used a pre-post design. Results were in general constant across designs. Static stretching was used in most of the studies, even tho there are many other appropriate methods used to stretch. Affects were however was observed with other forms of stretching as well. The review showed body of evidence suggesting that these affects were consistent across different types of stretching for isometric force, isokinetic torque, and jump height. Even though different types of stretching in running produced incompatible results, the main methodological difference was the duration of stretch, which was inconsistent and had no explanation for the use of the time used. As a result it was found that longer stretch produced worse results. In relation there was limited research on acute effects after stretching in relation to range of motion and flexibility.
A huge variable to consider was the subject population as most studies found similar results across age, gender and level of athletic ability. This may suggests the results are due to fundamental physiological adaptations that occur in the muscle, a hypothesis that is supported by the critical science evidence on stretch-induced muscle damage and stretch-induced hypertrophy (Morgan 1999). Possible improvements in performance may be at the expense of an increased risk of injury. Therefore the advantages and disadvantages of stretching need to be considered for individual athletes, together with but not partial to competition level, competition timing (e.g., early or late in the season). Although different forms of performance were tested in these studies, including isokinetic, isometric force, jump height, jump velocity, acceleration, and sprint speed, these do not account for all aspects of performance. In addition, stretching may be a method of relaxation for athletes, and may possibly affect performance. If this were a method to improve performance, then stretching should be compared with other methods of relaxation for quantifiable effectiveness.
In summary, the literature suggest that for athletes who take part in sports that require power, strength, and explosive movements need to consider that static stretching before activity may cause a short-term decline in sprinting performance. Conversely, frequent stretching will advance the results for all activities. This is comparable to the fact that stretching directly prior to exercise does not diminish the possibility of injury, nevertheless regular stretching may reduce the risk of injury. Therefore, athletes should stretch after exercise, or at a time not associated to exercise.
Further research is necessary to ascertain both the degree of pre-stretching necessary to cause a damaging effect, and the time-course between the preservation of the increased range of motion and the prolongation of the capacity to generate maximal power.
The focus of this study was to test the length of time taken with a stretch and compare this to the performance of both sprinting and flexibility.
30 male participants were recruited from Cheddar Football club. Subjects were required to read and complete a health questionnaire and sign an informed consent document. The appropriate institutional ethics committee approved the study. The participants were not informed of the results until the study was completed. A convenience sample was used as a high volume of participants were readily available and allowed basic data and trends to be obtained without the complications of using a randomised sample. All participants regular play football and are subjected to sprinting. This makes my sample specific and relative to athletic performance where as an ideal sample results may differ due to gender, age, and athletic ability differences. A secondary observer was used to record the results and help time the pre stretches. This ensured subject were monitored, and therefore helped ensure the test procedure was followed correctly. The 30 males partaked in both a pre sit and reach flexibility test and a 40 meter sprint. Participants were subjected to a 5 min protocol warm up prior to the pre test comprising of jogging 400 m, forward skips 2 x 60 m, side steps 4 x 20 m, backwards skips 2 x 60 m. Participants only had 1 attempt at each of the pre test. To minimise variation in climatic conditions, all sprints were performed on an indoor track using running trainers. The sprints were initiated from a standard stationary split stance with the dominant foot to the front and foot behind the starting line, with no rocking movements and were timed with (Omoron electronic timing gates). Timing gates were used to ensure the most accurate readings as the difference in times will be minimal, therefore this will ensure there is no room for human error, therefore making the results more reliable. The time would start as soon as the participant travels through the first beam and then would stop when the participant travels through the beam 40 meters from the starting line. To control for error, the laser beam was positioned so the height above the ground approximated the height of the runner’s waist. The sit and reach test was then performed 2 minutes after the 40 meter sprint. A modified sit and reach test was used to control for the variable lengths of people’s arms and legs, which is a limitation of the standard test. The equipment was set up that, the zero mark is adjusted for each individual, based on their sitting reach level. This ensured that the result would be a positive number which is necessary for a statistical analysis. An (Acuflex) modified flexibility sit and reach test box was used to record the test.
Three different stretch protocols were used, with each protocol being performed on a different day. Group 1 would hold the stretch for 30 seconds, group 2 for 15 seconds and group 3 would stretch for 5 seconds. All groups were given the same protocol warm up as the pre test. The stretching activities were ones that the athletes normally used in their daily warm-up rituals. All groups then stretch their hamstrings, quadriceps, and gastrconemuis for their given times. For each activity, the range of motion was increased until the person acknowledged a stretch-induced discomfort similar to that normally felt during their daily stretching activities. At this point, the stretch was maintained for their given times.
The first stretch was a hamstring stretch. The subjects laid down in a supine position on the floor with a leg extended. The opposing leg was flexed at the patella at 90 degrees and hip 45 degrees, with the sole of the foot planted tightly on the floor. From this pose, the extended leg was raised to an upright position. The second was a quadriceps stretch. The participant adopted a vertical position, standing on one leg with the other leg flexed with the heel pulled close to the glutes with the help of the hand. The last stretch was the glastocnemius. The participant adopted a split stance shoulder width apart with the front leg slightly bent. The body weight is transferred forward whilst keeping the heel of the back foot on the ground. All stretches were performed in the order mentioned above, in accordance of a 30 second rest interval dividing each different stretch. Once this sequence of stretches was finished, the leg was rested for a further 30 seconds and then the sequence was repeated until all muscles were equally stretched 3 times. One full cycle of stretches on one leg was performed before changing legs. Following the stretching regime, the athletes were told to relax for 3 minutes before beginning the 40 meter sprints.
The modified sit and reach test followed the 40 meter sprint. The test involved sitting on the floor with legs stretched out straight ahead. Footwear was removed. The soles of the feet were placed flat against the box. Both knees were locked and pressed to the floor with the palms facing downwards, and the hands on top of each other or side by side, the subject then reached forward along the measuring line as far as possible. The hands had to remain at the same level, not one reaching further forward than the other. The subject then reaches out and holds that position for two seconds while the distance is recorded. Groups repeated the test 1week later changing the time of the stretch. 1 week wash out time was given to ensure significant time to recover. This was again repeated the following week with the groups changing the times once again. I have used repeated measure as it ensured the experiment was more efficient and helped keep the variability low. This therefore helped to keep the validity of the results higher, while still allowing for smaller than usual subject groups. It also allowed the experiments to be completed more quickly, as only a few groups need to be used to complete the entire experiment. It is important to make sure the experiment is completed quickly as changes in participants may occur due to practice effects.
The two pre- and two post-sprint times were averaged. Data was analysed using qualitative measures. The reliability of the 40 meter times for each stretch condition was calculated using an intraclass correlation coefficient on pre test measures. A one-way analysis of variance (ANOVA) with repeated measures was used to compare the times for each stretch condition. I have used this method of testing as it will reduce the likelihood of a false positive (type 1 error). For this reason using the ANOVA will help me compare three means. In addition to the above analysis on the average 40 m sprint times, a post-hoc analysis was done on the best time for each trial. I have used these methods of testing as they have been used in many of the reviewed literature. Therefore I know these methods are applicable and will therefore allow me to easily compare my results to previous literature. To prove my hypothesis, I have used a common alpha value of 0.05 (5%).
Parametric (anova) or non Parametric