How slow can YOU go?

Although the mantra of “running slow to go fast” is repeated ad nauseam by coaches, many runners still ignore this advice for various reasons. They may think that only hard workouts contribute to their fitness, they may feel embarrassed by running slower than their peers, or they may not even know what “slow” means in terms of pace. After analyzing the data of thousands of race preparations by our users, we have clear indications that slow running boosts our race pace. And, as a bonus, we can also show you how slow you really should go for the most significant benefit.

In past blogs, we looked into factors influencing our race performance, such as the number of weekly training hours or whether we followed a taper phase before the event. But as we’ve seen in these articles, there can still be big differences in results between two runners doing the same amount of training. According to famous sports scientist Stephen Seiler, doing the bulk of our training at the right intensity can be decisive in our race performance. In the following analysis, we’ll examine how much of this difference in race results can be explained by how easily we take our easy workouts.

What does "slow" mean?

When talking about “slow” running, we must first define what it means. A slow run for a casual runner preparing for a 1h 10k differs from a slow run of Eliud Kipchoge. Because slowness is a relative concept, we needed to compare each runner’s training paces to their best-effort pace during a race. To do that, we took the runner’s pace measurements from 16 weeks before the race and analyzed their distributions. These show the (relative) time spent training at different paces.

Let’s look at two runners who competed in a half marathon and spent +/- 4 hours per week training for the event. Runner A ran half of their training time at a pace of 5:45 or slower (we call this pace the median training pace). Most workouts are done at a narrow range of paces between 5:20 and 6:20.

For runner B, their median training pace is slightly faster, at 5:20. But notice the huge difference in pace variation: the majority of workouts are done at paces between 4:30 and 6:30, which is more than twice the range of runner A. And there are visible chunks of high-speed work at 3:30 or faster and walking intermezzos at 9:00 and slower.

While runner A did their race in 1h55, runner B finished in 1h18! Runner A spent the slowest half of their training time at 94% of their race pace, while runner B took it considerably easier at 69%. Of course, this difference between two individuals could have many causes, such as talent, weight, sex, etc. To limit the influence of these other factors, let’s look at all runners who prepared for a half marathon and trained approximately 4 hours per week.

How slow do we go?

For every runner who participated in a half marathon, we analyzed their training pace distribution as mentioned above. We determined their median training pace as a fraction of their observed race pace. We can see now that the “average” runner has a median training pace of approximately 85% of their race pace. For example, for someone who finished a half marathon in 2 hours at a pace of 5:40, the median training pace at 85% of that would be 6:40. We can also see where our extreme examples of runners A and B are in this distribution.

How are all these runners performing in a race? How slow are these runners training compared to their race pace? For this analysis, we zoom in on the group of runners who trained around four hours per week to rule out differences caused by different amounts of training.

In this chart, every dot represents a runner’s race. The size of the dots represents the variation in training pace, as we explained above with the examples of runners A and B. We can clearly see that the fastest runners train at relatively easier paces and with higher pace variations than the slowest. This same pattern exists for the general population, regardless of the amount of training or race distance. As you can imagine, the latter is hard to visualize, so left out of this article.

As to the question of how slowly we can do our easy runs or recovery blocks between intervals, the fastest runners spend half of their training time at paces lower than 80% of their (expected) race pace and can be up to 20 minutes faster than their peers who train at above 90% of their race pace.

Does training slower cause racing faster?

What if the results above are caused by mere talent or baseline fitness before the training period instead of running at the right intensity? In that case, we must have seen several examples of fast runners who train very close to their race pace or with a low variety. However, there is only one such case (see Runner X). Going slow or having a more varied range of training paces seems to be a deliberate choice not caused by some physiological (dis-)advantage. As a pace of 8:00 can still be technically running, there’s plenty of room for slowing down, even for the slowest runners in this cohort.

What if a lower ambition causes lower-than-average performances? This seems to contradict (subjective) findings from exchanges with some of our customers, who several times indicated having a high ambition and feeling unable to run slower than a 6:00 pace. In follow-ups to this analysis, we could incorporate the runners’ subjective RPE scores and heart rate measurements to better indicate their levels of ambition.

The long-term effect of training at the correct intensities is also essential. This analysis only examined the last 16 weeks before a race. However, our results should not be interpreted as concluding that someone can improve their half-marathon time by 20 minutes in just 16 weeks. The results reflect training practices that may have lasted for years for some individuals.

Finally, to estimate the actual causal effect of slow training on race performance, we should consider that age or sex directly influences fitness. Still, it may also cause differences in training behavior, such as intensity and variation. We may investigate this causal effect in another follow-up.

How Vortza can help

All our training plans aim to provide you with a well-balanced mix of training intensities for your chosen goal. In addition, we recently introduced a new achievement called “Go slow to go fast” that rewards you when your easy - and recovery paces are really as easy as intended. If you haven’t already, you’re most welcome to download our app and try out our Pro features for free for 14 days!