From middle school gym class to high school sports and to group fitness classes, we have always been taught to stretch so that we can decrease our risk of injury, and improve performance.
As a physical therapist and CrossFit coach, I often have patients and clients tell me that they get injured or develop pain because they haven’t been stretching enough. The purpose of this blog post is to dive into what the research says about stretching, and to give you tools to implement into training that can help to reduce the risk of injury, and improve performance that are backed by research.
In this blog post, when we say stretching, we will be talking about static stretching specifically. The American College of Sports Medicine describes static stretching as “a slow and constant motion that is held in the final position, or point of mild discomfort, for 15–30 seconds.”
The purpose is to increase static flexibility which is defined by the National Strength and Conditioning Association as “the range of possible movement about a joint, and its surrounding muscles during a passive movement.” An example of static stretching is bending over and trying to touch your toes, and holding this for an extended period of time, for example 3 sets for 30 second holds.
So let’s dive in!
Stretching and Injury Risk
Back in 2002, around the same time most people were singing along to Avril Lavigne’s “Sk8tr boi,” Herbert et al. 2002 published a systematic review looking at stretching before and after exercise, and its effect on muscle soreness and injury risk.
They found that “stretching produced small and statistically non-significant reductions in muscle soreness;” bottom line, stretching won’t help you walk down the stairs any better after leg day. Not only that, but they also found that “stretching before exercising does not seem to confer a practically useful reduction in the risk of injury, but the generality of this finding needs testing” which is where our other research comes in.
Another flashback, to the first day of gym class in middle-school, the fresh smell of polyurethane. Remember when gym teachers would ask you to sit on the floor, and reach forward with your legs straight, and try to reach your toes as far as you could? Well a few studies used a modification of this, called a sit and reach test, which is a reliable test to assess hamstring/back extensor flexibility, to compare flexibility and risk of injury.
What did they find? Well, contrary to popular belief, they found that in NCAA female rowers, sit and reach scores did not predict future injury. Other studies have found that sit and reach scores do not predict future hamstring injuries in both soccer and Australian football players. What does this mean? In essence, it means that these researchers showed that just because you are more flexible (have a higher sit and reach score) does not mean that it protects you from future injury.
In a systematic review in 2014, Laurensen compared different exercise interventions, and their effect on injury risk. They found that interventions such as strength training and proprioception training could help reduce the risk of injuries! In contrast, for static stretching they state: “despite a few outlying studies, consistently favourable estimates were obtained for all injury prevention measures except for stretching.”
Stretching and Performance
Back in 1985, researchers decided to see if strength was affected after a bout of static stretching. So, they stretched out the plantar flexors in 12 subjects for 30 minutes, and they found a decrease in maximum voluntary contraction of those plantarflexion muscles of up to 25%! They concluded it was because of reduced activation and compromised muscle force generating capacity. After 15 minutes, the activation was relatively restored, but they found that even after an hour after the stretching intervention, the muscle force generating capacity was still reduced by 8-12% in subjects.
Are you thinking what I’m thinking? 30 minutes is a while! Phew! Kevin Power sought out to see what an acute bout of static stretching the plantar flexors, quadriceps, and hamstrings, lasting just 270 seconds per group (roughly 4.5 minutes) had for results. They found that after stretching the quadriceps, there was a significant decrease in maximal voluntary force.
HOWEVER, there was not a difference in hop testing! A proposed theory as to why force was affected is because the decrease in musculotendinous stiffness can alter the length-tension relationship of the muscle fiber’s ability to produce force following static stretching. Because of this, the authors were perplexed to find that there was no difference in hop testing.
The two preceding studies mentioned were talking about an acute bout of stretching prior to activity. What these next researchers looked at is the chronic effects of static stretching on performance. In a recent published paper titled “Chronic Effects of Static and Dynamic Stretching on Hamstrings Eccentric Strength and Functional Performance.” They found that after 10 sessions of 3×30 seconds of static stretching, the hamstrings decreased eccentric knee flexion strength, which we know from previous studies can put you at risk for hamstring injury. Additionally, it also decreased triple hop performance in healthy men! They did find that dynamic stretching did not show a decrease in performance.
Hopping or jumping is important in many sports such as basketball, and volleyball, however what about if your sport is more running based? We can check out this study published by Winchester et al. 2008 to find out more. This group of researchers determined a 3% decrease in performance in 40m dash times following a pre-event static stretching routine.
Dang! That was a lot of information, but essentially, although the results are somewhat mixed, it seems that there may be a link with static stretching and not only a decrease in strength, but a decrease in performance!
So, if stretching isn’t going to reduce injury risk or improve my performance, what will?
Timing of Stretching
Static stretching shouldn’t be completely abolished, it really depends on goals. If for example, your sport requires range of motion, or you are deficient in a range of motion following surgery, static stretching can be beneficial to increase that range of motion. If you are to stretch, try and avoid static stretching 1-2 hours before exercising. Why 1-2 hours? In a previously mentioned study, it was shown that the deleterious effects of stretching on force production were seen still two hours after static stretching.
We can never prevent injuries, but we can reduce the risk, and research does show that a few things can help!
Remember that systematic review we talked about before that showed stretching didn’t reduce the risk of injury? They also found that “Strength training reduced sports injuries to less than 1/3 and overuse injuries could be almost halved.” The same author did another review in 2018, and reported that a 10% increase in strength training volume provided at least a 4% reduction in injuries.
It has also been found that strength training reduced injury rates in elite youth soccer players. Furthermore, a recent study published in the journal of strength and conditioning, reported “relative back squat strength was significantly lower in injured athletes than uninjured athletes in both men and women.” So having a higher back squat, relative to body weight, may help to reduce the risk of injury.
Now we’re on to something!
If you are participating in a sport with pivoting, jumping, and running such as football, soccer, or basketball, the FIFA + warmup is a great choice to improve performance and reduce injury. The FIFA + is a warm up created to help reduce injury risk in soccer players. Good research thus far is out that shows it can help reduce injury risk in soccer players by 39%. Recently, more studies are coming out that it can translate well to other sports. For example, one study showed that it can reduce injury rates in elite male basketball players.
The belief that static stretching improves performance, and reduces injury risk are not supported by the research.
However, that does not mean that you should never do static stretching. It really depends on what your goal is! For example if your sport requires a large range of motion, static stretching may be indicated. Or, if you have recently had surgery and are lacking a specific range of motion, such as knee extension following ACL reconstruction, again stretching can be very beneficial to help achieve lost range of motion. But if you are stretching to reduce injury risk or to improve performance, you are better off participating in a strength training regimen, or incorporating the FIFA+ into your warm up.
In 2015, Kevin earned his undergraduate degree from the University of Delaware in Exercise Physiology, and a minor in Srength & Conditioning. He then went on to earn his Doctorate of Physical Therapy from Rutgers University in 2018 while serving as a teaching assistant in Gross Anatomy for the first year DPT students. Since, Kevin has practiced as a physical therapist in northern New Jersey, treating predominately high school, collegiate, and professional athletes. Additionally, Kevin has been a Crossfit Coach since 2016, and an adjunct professor in the Rutgers Physical Therapy program adding to his teaching and coaching repertoire. He uses his experience, education, and latest research to form individualized exercise programs to facilitate the rehab process. His goal is to promote a healthy lifestyle and to get his patients moving better and feeling better in the activities they love.
Haff, Greg,, and N. Travis Triplett. Essentials of Strength Training and Conditioning. Fourth edition. Champaign, IL: Human Kinetics, 2016. Print.
Herbert RD, Gabriel M. Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ. 2002 Aug 31;325(7362):468.
Gonzalez SL, Diaz AM, Plummer HA, Michener LA. Musculoskeletal Screening to Identify Female Collegiate Rowers at Risk for Low Back Pain. J Athl Train. 2018 Dec;53(12):1173-1180. doi: 10.4085/1062-6050-50-17. Epub 2018 Dec 7. PMID: 30525938; PMCID: PMC6365069.
Orchard J, Marsden J, Lord S, Garlick D. Preseason hamstring muscle weakness associated with hamstring muscle injury in Australian footballers. Am J Sports Med. 1997 Jan-Feb;25(1):81-5. doi: 10.1177/036354659702500116. PMID: 9006698.
Van Doormaal MC, van der Horst N, Backx FJ, Smits DW, Huisstede BM. No Relationship Between Hamstring Flexibility and Hamstring Injuries in Male Amateur Soccer Players: A Prospective Study. Am J Sports Med. 2017 Jan;45(1):121-126. doi: 10.1177/0363546516664162. Epub 2016 Oct 1. PMID: 27582278.
Lauersen JB, Bertelsen DM, Andersen LB. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. Br J Sports Med. 2014 Jun;48(11):871-7. doi: 10.1136/bjsports-2013-092538. Epub 2013 Oct 7. PMID: 24100287.
Fowles JR, Sale DG, MacDougall JD. . J Appl Physiol (1985). 2000 Sep;89(3):1179-88. doi: 10.1152/jappl.2000.89.3.1179. PMID: 10956367.
Power K, Behm D, Cahill F, Carroll M, Young W. An acute bout of static stretching: effects on force and jumping performance. Med Sci Sports Exerc. 2004 Aug;36(8):1389-96. doi: 10.1249/01.mss.0000135775.51937.53. PMID: 15292748.
Barbosa, Germanna M.1; Trajano, Gabriel S.2; Dantas, Glauko A.F.1; Silva, Bianca R.1; Vieira, Wouber H. Brito1 Chronic Effects of Static and Dynamic Stretching on Hamstrings Eccentric Strength and Functional Performance: A Randomized Controlled Trial, Journal of Strength and Conditioning Research: July 2020 – Volume 34 – Issue 7 – p 2031-2039 doi: 10.1519/JSC.0000000000003080
Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA. Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study. Br J Sports Med. 2016 Dec;50(24):1524-1535. doi: 10.1136/bjsports-2015-095362. Epub 2015 Dec 16. PMID: 26675089.
Winchester JB, Nelson AG, Landin D, Young MA, Schexnayder IC. Static stretching impairs sprint performance in collegiate track and field athletes. J Strength Cond Res. 2008 Jan;22(1):13-9. doi: 10.1519/JSC.0b013e31815ef202. PMID: 18296950.
Lauersen JB, et al. Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis. Br J Sports med. 2018;52(4).
Zoulta S, et al. Strength training reduce injury rate in elite younger soccer players during one season. The Journal of Strength and Conditioning Research. 2016;30(5).
Case M, et al. Barbell squat relative strength as an identifier for lower extremity injury in collegiate athletes. J Strength Cond Res. 2020.
Thorborg K, Krommes KK, Esteve E, Clausen MB, Bartels EM, Rathleff MS. Effect of specific exercise-based football injury prevention programmes on the overall injury rate in football: a systematic review and meta-analysis of the FIFA 11 and 11+ programmes. Br J Sports Med. 2017 Apr;51(7):562-571. doi: 10.1136/bjsports-2016-097066. Epub 2017 Jan 13. PMID: 28087568.
Longo UG, Loppini M, Berton A, Marinozzi A, Maffulli N, Denaro V. The FIFA 11+ program is effective in preventing injuries in elite male basketball players: a cluster randomized controlled trial. Am J Sports Med. 2012 May;40(5):996-1005. doi: 10.1177/0363546512438761. Epub 2012 Mar 13. PMID: 22415208.