Do Runners Really Need to be Flexible?

When you picture an old-school runner, it’s hard not to think of a leather-skinned veteran stooped over a park bench, aggressively doing the classic “runner’s stretch.”

Popular opinion in recent years has moved towards a consensus that stretching, at least before going for a run, is unnecessary. Plenty of great athletes can’t touch their toes—is flexibility really that important for a distance runner?

As we always do at Runners Connect, we are going to look into the science behind these claims to leave you feeling confident, and comfortable with your future flexibility.

Does Stretching Help or Hinder Runners?

The single biggest factor that turned the running community against stretching was  the “Stretching Study”  commissioned by United States Track and Field, or USATF.¹ Between 2007 and 2009, over two thousand runners enrolled in the study.

These runners were split into two groups: a pre-run stretching group and a no pre-run stretching group.  The first group received a short pre-run stretching routine to conduct before every run; the second group was forbidden from stretching before their runs. Both groups were followed for three months, and the subjects reported any injuries.

After reviewing the data, the researchers concluded there was no statistically significant effect of the pre-run stretch: injury rates were by and large the same between groups. It get’s better: Some interesting trends developed when looking at small clusters of data.

Runners who switched from stretching to not stretching experienced a higher rate of injury, as did runners who switched from not stretching to stretching.

Despite this, the overall conclusion was, as the authors wrote, that “stretching neither prevented nor induced injury when compared to not stretching before running.”

Does this One Study Really Prove Stretching Before Running is Bad?

This led to a lot of headlines trumpeting the end of the pre-run stretch. Later research showing that rigorous stretching routines appear to decrease explosive strength and reduce running economy further damaged the reputation of stretching and flexibility for runners.²

There are, however, some significant flaws with the USATF study that need to be considered. First, the entire study was conducted online via USATF’s website; there was no in-person monitoring or tracking of the subjects. Because of this, the dropout rate was very high.

Only about half the people who enrolled in the study actually completed it. It get’s worse: As the authors noted, subjects who didn’t like the group they were assigned could easily drop out, and potentially re-enroll by signing up again on the website to try to get into the other group!

Additionally, the study only tracked pre-run stretching, not stretching in general. It could be very hard to separate the benefits of stretching by itself from stretching before a run in particular. USATF’s stretching routine was not very comprehensive, either.

It only lasted three to five minutes—probably not long enough to stretch out all of the major muscles of the lower body. Likely because of these reasons, the results of the study were never actually published in a peer-reviewed scientific journal.

This significantly hurts the credibility of the study, since one of the cornerstones of the scientific process is the ability of other scientists to review, comment on, and critique a paper before it’s published. Interestingly:

Moreover, a large body of peer-reviewed science suggests the opposite conclusion: flexibility (though not necessarily pre-run stretching per se) has a significant protective effect when it comes to a number of different injuries.

Does Flexibility have an Affect on Injury Rates?

A study published in the American Journal of Sports Medicine by Erik Witvrouw and other researchers in Belgium followed almost three hundred university students enrolled in physical education classes over a two-year period.³

At the study’s outset, Witvrouw et al. measured a number of parameters related to flexibility, strength, and muscular power.  Over the course of the study, the authors tracked the students who developed patellofemoral pain syndrome.

Through statistical analysis, Witvrouw et al. demonstrated that the people who developed knee pain like runner’s knee had, among other things, worse quadriceps flexibility at the study’s outset. A study published a year later by the same group focused on patellar tendonitis, and it had similar findings—poor quad and hamstring flexibility were found to increase the risk of patellar tendon injury.⁴

The scientific evidence on flexibility extends to other injuries too. One of the mainline treatments of plantar fasciitis is rigorous calf stretching—by decreasing tension in the calves, strain on your arch is reduced.⁵ More recent research even suggests that hamstring tightness can increase strain on your plantar fascia.^{5, 6}

Conclusion

In summary, flexibility is important for runners. It’s definitely a factor when it comes to injury risk, but certainly not the only one.

Focus on keeping the major muscles of your lower body flexible: your calves, your hamstrings, your quads, and your hip flexors.  Improving your stretching and flexibility is a long-term project.

In injury rehab programs, it can take several weeks for a stretching protocol to make a difference, so it’s only natural to expect the preventative effects to take at least as long to show up, too.