The questions are… why do we stretch? Is flexibility important? Are there other ways to maintain flexibility without stretching? Is stretching an effective tool for reducing injury? Conflicting Opinions I asked members of the R&RT community if they stretch, and the results were interesting! Have a look below…  The vast majority of voters said YES, they stretch (119 total). A few others (84) admitted to not stretching enough and the minority (65) of voters said they don’t stretch at all. The interesting part about this poll is that somebody added the “Yes, but not sufficiently” option… and it wasn’t me! This begs the question… how much stretching is enough stretching? At least 84 runners admitted to not stretching enough… but how much is enough? Is there a preconceived notion that we have to stretch A LOT in order to be “fit”? I hope to answer this question (and many more) throughout this article. “But Paulo, why is this such an important question?” you may ask… well, let’s say you spend 15 minutes stretching every day, that’s five hours total in one month, five hours spent doing something that may not be beneficial. These five hours could be spent doing exercises that will boost your physical health, for example. Besides this, there are many conflicting opinions surrounding stretching and this causes a few arguments and misleading affirmations. I have taken some screenshots of a few comments from the poll post above. Have a look at the hugely distinct opinions of the R&RT community members.
But that’s enough of opinions – let’s understand what science has to say about this. In this article, we’re reviewing a recent paper released by James L. Nuzzo, PhD, entitled “The Case for Retiring Flexibility as a Major Component of Physical Fitness”. Nuzzo has built quite a strong case against the importance that stretching currently has and this article is causing a significant ripple effect! Please take note that Doctor Nuzzo is only debating the importance that stretching has in the fitness industry – he is not arguing that stretching is bad for you or that you should stop stretching overall! This article will follow the same logic. As you can probably guess, there are many complicated scientific terms used in the paper, along with complex study results and over 300 studies used to back up Nuzzo’s claims. Nuzzo goes into lots of detail and other subjects that aren’t related to running, so I will have to summarize a few of his words in order to keep this article running related. I will try to keep things simple, but if you want to access the full study and decipher the research you can do so here. THE CASE AGAINST STRETCHING The paper proposes flexibility should be retired as a major component of physical fitness because:
“Implications of decreased emphasis on stretching include improved training efficiency and safeguarding against negative impacts on other parts of exercise prescriptions.” Stretching vs Flexibility According to the ACSM’s Guidelines for Exercise Testing and Prescription, the primary purpose of stretching is to improve flexibility. From this statement, we can assume that stretching and flexibility are one and the same. Nuzzo defines flexibility like this: “Static flexibility refers to joint ROM (range of motion) usually in relaxed muscle. Static flexibility is subjective, as the limit ROM is determined by the tester or the patient and their stretch tolerance” Simply put, flexibility is your ability to stretch a particular muscle to a certain extent – and the extent is subjective, meaning that it differs from person to person, depending on how much ‘pain’ you can tolerate. Stretching increases your range of motion, which promotes flexibility. Whenever we see someone stretching, it’s safe to assume they are increasing their flexibility – whether that is their goal or not. This paper analyses the role of static stretching and not dynamic stretching.  Why Flexibility Isn’t a Major Component of Fitness For Runners This sounds silly but runners are… people. We’re awesome people who love grueling sports BUT, at the end of the day – we’re normal people. And all of the points I’m about to mention below are related (in one way or another) to all of us. Here’s why flexibility might not be as important as we think… Mortality “Flexibility, as measured by the sit-and-reach or standing trunk flexion, is not predictive of all-cause mortality “ Nuzzo starts his case with a bang! Most people exercise in order to be fit, healthy, and live a long and pain-free life. Well, as it turns out, stretching may not be helping you live longer. As this study points out, there was no correlation between standing trunk flexion (the touch your toes test) and decreased risk of mortality. Another study, from 2002, shows that trunk flexion is also not associated with lower risk of mortality, however, the sit-up exercise is! From this, we can understand that strength training starts to gain some advantage over stretching… Aging & Risk of Falling “Flexibility declines with age, but unlike muscle strength, flexibility does not predict falls in older adults.” Both flexibility and muscle strength decline with age, if left unattended. However, flexibility (or lack thereof) does notpredict falls in older adults, whereas lack of strength does. There is further research showing that muscle strength (and not muscle flexibility) is a powerful indicator of future performance in activities of daily living (bending over, balancing on a stool, etc). This is especially important for older adults. Injury and Pain “(…) a recent systematic review concluded there is “moderate evidence” ankle and hamstring flexibility predict musculoskeletal injury (…)” I think a vast majority of runners stretch because of the fear of becoming injured, but is this fact or fiction? If you ask any runner, he or she will say that they stretch because they are trying to stay away from injury. But try asking them WHY stretching prevents injury and you’re left sitting in silence, awaiting a response. It seems like no one really knows why stretching prevents injury. Here’s what Dr. Nuzzo found in regards to pain and injury risk… High levels of flexibility might actually increase injury risk. Professional male soccer players with hypermobile joints (high flexibility) have a tendency for higher risk of injury and have more severe injuries than players without hypermobile joints. This is not true in other sports – but we’ll discuss this further along the article. Similarly, in a military-training environment, soldiers with the highest and lowest flexibility test scores are more likely to experience injury – this shows us that we should aim for average flexibility. There is also moderate evidence that high levels of ankle and hamstring flexibility predict injury in the general population. Further studies have been made outlining the effects of stretching in running, showing that stretching is not an effective tool for reducing injury risk. Although other studies indicate that evidence in sports is mixed There are other factors in fitness that indicate risks of injury, however we are only discussing flexibility in this article.  There is a lack of correlation between flexibility and other fitness components As we’ve established in the previous section, higher flexibility test scores do not indicate lower risk of injury. However, flexibility also lacks any correlation to other fitness components such as:
High flexibility levels do not indicate good cardiovascular health or high muscle endurance (or any of the other options). Interestingly, all of the three points above correlate with each other. This tells us that high flexibility doesn’t influence other aspects of sports performance… which is interesting, because we always see stretching being recommended after every training session. And we also know that high (and low) flexibility levels indicate higher injury risk. Overall, it seems like flexibility is losing a lot of the credibility it has gained! As we explore a few more topics below and all the information starts to become confusing, keep in mind that there will be a fact round-up at the end of this article to clearly show what this study indicates. Flexibility and Sports Performance “In other athletic groups, flexibility levels (…) do not correlate with athletic performance, and do not differentiate athletes of different playing abilities.” As mentioned above, some sports and athletes actually do benefit from higher flexibility, such as swimmers, dancers and gymnasts. However, in the majority of sports, high flexibility scores do not indicate greater performance. Here’s a fascinating bit of information – flexibility scores between elite and sub-elite athletes in 100-m and 200-m sprinting are comparable (study #1 involving female athletes and #2 involving male athletes). From this we can conclude that an athlete does not need to be incredibly flexible to reach elite status, especially in a sport that pushes your muscles to their maximum capacity in such a short period of time. Further, in a study regarding longer distances, faster runners sometimes have lower flexibility levels. Yes, you read that right. Some faster runners actually have LOWER flexibility than slower runners. A recent study (2018) took thirty three female marathon runners and asked them to perform a series of different tests, like the sit-and-reach test (SAR), isometric muscle strength tests, squat jump and a few other. The results concluded that the slowest group scored the highest in SAR (sit-and-reach) tests. This was a mind-blowing discovery for me!  I have to be careful when jumping to conclusions, but this essentially means that there is further evidence that runners do not need to be highly flexible. Further studies regarding flexibility in endurance running are needed in order to make a solid decision, but the study mentioned above is definitely interesting and enlightening! It’s also worthy to note that Dr. Nuzzo dove a bit further, providing a few examples of how muscle strength and endurance and cardiovascular health and endurance are better indicators of sports performance, when compared to flexibility. RESTING THE CASE These were the main points that Dr. Nuzzo presented against the importance that stretching currently has in the fitness industry. There were many more (though mostly not related to running) but I have chosen to rule them out of this article in order to keep this article as short and enjoyable as possible. Dr. Nuzzo rests his case with the following statement: “(…) if flexibility is not a major component of fitness, then stretching is not needed in exercise prescriptions for many populations” ALTERNATIVE TO STRETCHING Instead of simply discrediting flexibility, Dr. Nuzzo took his paper further and provided an alternative to stretching that still increases flexibility and provides a few other benefits. Flexibility can be increased with resistance training. Resistance training involves the repeated action of muscle lengthening and shortening and thus simulates stretching. There are numerous studies indicating that resistance training improves flexibility by as much as 25%. Dr Nuzzo outlines 8 studies in his paper which indicate the same results. From these 8 studies, 2 of them generated results greater than 20% with only three resistance training sessions per week. In a total of 27 studies testing the efficacy of resistance training to improve flexibility and only 5 of these studies did not report improvements in flexibility. A varied strength training regime seems to be optimal for maintaining and even improving flexibility, as you are gaining strength (which will benefit your running) and you are also working on maintaining a functional level of flexibility. WHAT STRETCHING DOES This does not mean that stretching isn’t beneficial! Kokkonen et al. reported that following a stretching protocol for 10 weeks improved muscle strength and endurance by around 30% in young adults (in older adults, the effect seems to be the exact opposite, leaving the individual more prone to falling and injuring themselves). However, here is a direct quote from the same study: “It is possible that persons who are unable to participate in traditional strength training activities may be able to experience gains through stretching (…)” This statement also indicates that strength training is a preferred method of improving flexibility. On another note, stretching may also improve gait kinematics in older adults, as this study shows. Gait kinematics hold a big importance when it comes to avoiding injury, so this topic is definitely interesting and I look forward to analyzing more studies about this as they emerge!  The “Coil” Argument To finish this article, here is some food for thought. I’m a big fan of reading the research and making an educated decision on how to approach sports. The following analogy made a lot of sense to me and, because of it, I have drastically reduced my stretching for the last few years. The basic idea behind this argument is that, when running, you don’t want your muscles to be loose slinky’s but instead, you want them to be strong springs/coils! The logic here is that when running, you want your muscles to be strong enough to propel you forward as easily as possible. Stretching is directly reducing your ability to have strong, springy muscles! Instead, you end up with possibly weak and overstretched muscles which won’t have the desired ‘springy’ effect when running. The paragraphs above over-simplify this concept, but I think you get the idea. My goal here is not to build a strong case for the “coil theory” but instead, to inform you of its existence. FACT ROUND-UP (for runners) I’ve spoken about a few subjects in this article and although I did my best not to, I have strayed from the subject of running a few times. So, here are the cold hard facts about stretching/flexibility and running, according to the studies cited above.
There are so many more interesting bits of information in the study so I definitely recommend you gain access to it; you won’t regret it! Before my inbox fills up, I’d like to add the following – I’m not suggesting that you stop stretching! Stretching has been shown to increase range of motion, and it does feel nice, so you may as well do it if you like it. But let me ask you this… is increased range of motion good in running? Will it improve your running? If this all too confusing, you should remember that Dr. Nuzzo was only trying to reduce the contemporary importance of stretching. He was not arguing that stretching is not effective and should be dismissed altogether! A good, sensitive conclusion should be that stretching does have its importance, however, if we skip stretching a few times per week, we’ll definitely be alright. We’re all part of a global community with readily available information, so we must learn to interpret the information we find, take away what is important to us and apply it sensibly. That’s what I propose you do with the information in this article. Be sensible, listen to your body and… keep running. This article is going to shared in our Running and Race Training Facebook community so if you want to discuss this topic further, create a post in the group and let's talk about it! Click here to access the R&RT community.  About the Author
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