Stress fractures are perhaps the most feared of all distance running injuries; despite their small, seemingly innocuous nature, they have the potential to ruin a training cycle and spoil the mere notion of a new personal best. There is no convenient time to get a stress fracture, as they almost always require extensive recovery and rehabilitation – so the best course of action is to not get one at all. As a result, runners tend to invest in preventative measures aimed at offsetting overuse or biomechanical imbalance, which can range from high-level stretches and dietary changes to strengthening exercises.
However, one variable is less cut-and-dry in terms of its potential impact on stress fracture development: running speed. This much-discussed factor is emblematic of distance running’s subjectivity; everyone is different in terms of their training requirements and recovery demands, but can broad speed-based changes influence a runner’s risk of becoming stress fractured? Naturally, the answer to this longstanding question is more layered than a simple yes or no.
An Ongoing Debate
Most medical practitioners define stress fractures as byproducts of repetitive orthopedic trauma, which tends to clash with the drawn-out, high-impact nature of distance running. According to Marathon Handbook, a runner takes roughly between 900 and 2000 steps in a single mile of running, and for decades, studies have debated how speed factors into the biomechanical safety of this taxing process.
The general idea has been that running too fast or hard puts athletes at a higher risk for stress fractures, as the increase in repetition and impact intensity creates an overwhelming load for vulnerable bones like the tibia or metatarsals. This notion is central to many distance running regimens, with athletes reserving quicker, higher-cadence running for just a handful of weekly efforts (usually workouts, races, and certain long runs).
Given what we know of stress fractures – namely, their cataclysmic effect on training – it makes sense for runners to err on the side of caution. That said, according to a 2019 study published in Medicine & Science in Sports & Exercise, speed may be irrelevant in this regard. The study observed 43 individuals running on a 50-meter indoor track, analyzing their shins’ impact load via track-embedded force plates. Researchers concluded that fast running did not increase the runners’ cumulative tibial load more than slower running, but, as the study’s author noted to Runner’s World: “It’s too early to make recommendations for how runners can use this information to improve their training habits … hopefully our results combined with future research on cumulative load will provide greater insight.”
Though conversations on the link between running speed and stress fractures remain a bit nebulous, the best rule is for a runner to listen to their body and take an “everything in moderation” approach. Pace is one of several interconnected contributors to healthy training; it has a symbiosis of sorts with nutrition, terrain, mileage, and a spectrum of other factors contingent upon a runner’s self-awareness and overall fitness threshold. Runners should find what works for their unique biomechanical needs, favoring gradual adjustments over abrupt spikes in intensity or volume.
Fast running and slow running have their place; the key is to establish that balance without overcommitting to one over the other. This approach remains the gold standard for mitigating injury and bringing dedicated training cycles to fruition.