Should we stretch before exercise?

In recent years stretching has become quite a controversial topic within the endurance community with many challenging its place as part of a warm up routine. Traditionally the logic has been that stretching when used in a warm up made our muscles more pliable, and readied them for exercise making them work better and reducing injury. Some of this is logical, in the sense that movement increases heart rate as the need for oxygen increases. If we go straight into a bout of exercise from a resting heart rate our requirement for oxygen surpasses our supply as it takes the heart a while to get up to speed and for vasodilation (widening of the blood vessels) to occur, so that oxygenated blood can reach the working muscles. This results in ‘oxygen debt’ which will increase the rate of perceived exertion and likely force a reduction in effort while you recover. Anyone whose set off in a race too quickly will know what this feels like, and it’s particularly unpleasant and even panic inducing if it happens in the swim of a triathlon.

However, while the need to prepare the body for exercise is still generally agreed to be necessary, when it comes to stretching and its effect on performance and injury, this notion is being challenged as more recent studies are failing to find significant evidence to support these claims. In this blog I’m going to review an article published in January 2017, that reviews recent studies and makes its conclusions about the role of stretching in endurance runners. It’s been the subject of social media posts recently, which is why I wanted to write this blog. The first issue is that in the space of a ‘tweet’ or a social media post, often we just get presented with a ‘click bait’ headline and bold statements based on a few selected phrases from a study, which in most cases has just been reposted or the blogger has just read the abstract. Reviewing the study properly we can look at what exactly was measured and just what the implications are to athletes as well as the greater population and, if need be, what changes we need to make to our training programs.

The Study
Baxter et al. (2016) The impact of stretching on injury risk and performance of long distance runners. The full article for those that are interested is available in the reference section. The first thing we need to clear up is that this study, while acknowledging other forms of stretching, focused primarily on static stretching, applying force to an elongated muscle and holding for around 30 seconds. Acute stretching is when stretches are completed just before exercises, resulting in temporarily increased joint mobility. Chronic stretching is when stretching is performed regularly over time, which results in the increased ranges of motion being more permanent.

Elite endurance runners are often less flexible that their non-elite counter parts, yet have far greater running performance. Furthermore, there is evidence suggesting a direct link between lower flexibility and increased running economy, that is; lower energy demand for a given speed. There is also a suggestion that tightness in muscles and tendons contributes to the elastic storage of energy, and therefore reduced oxygen demand. In terms of injury prevention, while it’s possible to assume that a base range of flexibility will neither improve or inhibit chances of injury, extremes outside the norm are where the risk may lie. For example; hypermobility could reduce joint stability causing increased demand for control of joints, and increased injury through uncontrolled lateral and rotational movement when running. Also, reduced mobility could cause poor biomechanics and create a situation where the lower limb joints aren’t moving enough to produce efficient movements. Whenever a joint cannot fully perform its function in a movement another joint is usually tasked with taking up the slack. And, as is often the case when this occurs on one side of the body this creates huge asymmetry within the body which can create a domino effect of poor movement throughout the body.

One of the first things we need to consider about this study is that while it does address flexibility from a performance issue, one clear area it fails to address deeply enough is that of limited range of motion or joint imbalance and asymmetry, which is very common among amateur athletes who come to sport from other backgrounds especially from sedentary jobs and lifestyles.

Stretching & Performance
When measuring sports performance, we can look at markers such as muscular efficiency, measured as the oxygen used for a given speed. This can be affected by things like joint mechanics, muscle elasticity, which is where this study looks at how stretching can impact performance. There’s a strong argument that static stretching immediately before exercise may inhibit performance due to changes in the muscle’s ability to store elastic energy. Some studies showed that inflexibility in hip and calf muscles was associated with improved running economy because less energy was required for stabilisation. However, while showing the importance of the role of muscular tension in sports performance, this does not address the differences between highly functioning athletes with years of practice, and the regular weekend warrior who may have pre-existing injuries or imbalances and less than ideal muscular economy.

Multiple studies have shown that a submaximal graded warm up not only prepares your body for exercise by increasing heart rate and temperature, but it can also reverse reduction in performance from stretching, however this doesn’t support any improvements in performance from stretching. As a result, the authors of this study concluded that “stretching does not possess properties that warrant it a useful or effective tool in the warm-up regime of long-distance runners”. However perhaps the most glaringly obvious issue with this conclusion is that it assumes that the athlete in their pre-stretched state is in an optimal alignment and position to produce efficient movement.

In my experience as a triathlete, coach and personal trainer, very few people have perfect alignment and perfect biomechanics. Limitations in joint mobility from everyday life can translate into poor joint loading in sport. Left/right imbalances, in particular, can create poor movement efficiency and over stress joints. Even when an individual’s joint balance is good, an ammeter athlete simply won’t have the strength through range of motion of that a more experience athlete would do. What this means is that the close that person gets to the end of their joint range the less controlled they are. And it’s here we need to clarify what we actually mean when we use the term “Flexibility”.

Flexibility is the combination of mobility with stability, and it’s that last part that’s key in terms of performance. While someone might be able to bend or stretch a joint into a particular range of motion, it’s their ability to balance and stabilise that movement and in the case of athlete; be able to produce meaningful and controlled movement from that position that really determines how flexible that range is. The more force or energy we put through a joint the more control we need, and it comes as no surprise that the more lengthened a muscle, the more fragile it is, and therefore more control it requires under force. It’s common to see good movement suffer when either the load is too much, or the control is insufficient. Think of someone squatting in the gym, and when they go past a weight they can control we often see poor form; not able to go as low, knees and ankles rolling in, back curving. Or, the way those with poorer run form adapt to running off-road or on slippery surfaces. So, when recommending flexibility work with my athletes, while range of motion is implied, the key component is actually the ability to control that range of motion well.

What about Chronic Stretching, where mobility is a key tool during training even if not immediately before running? Stretching, like any element of your training program, should have purpose. Just as every run session should have purpose; target pace, heart rate, or hills or intervals to perform, we should know what our targets are for stretching. We know that hypermobility can reduce performance, so when stretching, we don’t need to go to the extremes. While doing the splits isn’t necessary, being able to touch your toes would be a good indicator of sufficient mobility through hips and hamstrings. There’s evidence to suggest that when stretching is done as part of a training routine, but not directly before running, that long term improvements in flexibility are seen, without any loss in running performance. An optimal level of flexibility should allow correct joint function and dynamic posture for running so that the athlete can achieve optimal stride length and sufficiently bend the knee during the recovery phase, but not significantly inhibit elastic energy storage.

Perhaps the biggest area that needs more study is the effect of dynamic flexibility upon performance. Because dynamic flexibility involves taking a series of joints through a progressive movement based flexibility routine, without static stretching, it’s thought to achieve improved range of motion without the reduced nervous system activation of the muscles. This is because each time a stretch position is moved into, actively, not passively, instead of being held the emphasis is then on the stretched muscle to produce the force required to return to the start position. While there could be an argument for some loss in the elastic storage potential, what is gained in proprioception and joint balance would outweigh this.

Stretching and Injury Prevention
The majority of studies investigating links between stretching and injury in long-distance runners focus on chronic conditions, and given the average age of non-competitive runners is 35-50, these groups are at a higher risk of these injuries anyway. Aside from external factors such as a slip or fall, when injury occurs from internal factors these are usually related to stress, overuse and inflammation. As such it’s not likely that stretching would reduce the chances of these injuries occurring since they did not occur as a result of poor mobility.

Before we dismiss flexibility and its links to injury prevention, there’s another area that’s not considered by the article. As mentioned in its links to performance, correct joint function is key in producing efficient movement. Poor joint movement is less efficient and can lead to compensatory injuries. The causes behind them are two-fold firstly our ability to control skillful movements or movements at extreme ranges of motion, may not be adequate and when our body detects poor stability, out of self-preservation it limits our functional range of motion. Secondly, muscles may change their length over time if adapting to their environment. Two examples of this are hip flexor tightness from spending hours a day in a seated position, and calf muscle shortening through the wearing of heals. A good flexibility routine would target movements specific to the athletes’ imbalances and requirements for sport, requiring them to mobilise and stabilise joints and movements relevant to their sport, in this case running. So using flexibility to ensure correct alignment, we improve joint function and dynamic posture and in turn the athletes ability to sustain good technique.

While acute stretching may limit performance by inhibiting muscular efficiency and elasticity, we cannot take the blanket assumption that runners should not stretch. Because good flexibility is a key component of every day health as well as sports performance, it’s prudent to consider the case for every athlete and embark of a flexibility routine that supports their requirements. Like any aspect of training, flexibility should be performed with a goal in mind and any stretches or mobility work should be the result of analysing the needs of the athletes and adding it to their program. If we use stretching to ensure correct joint alignment, then use that alignment to work on improving movement patterns like squatting, lifting and gait, these movements then become better learned patters. It’s this learned movement that will then translate into better running economy.

Coach Phil Paterson

References

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