In 2016, Stephen Seiler of the University of Agder in Norway created an infographic that he named Seiler’s Hierarchy of Endurance Training Needs. Loosely based on Abraham Maslow’s famous hierarchy of human psychological needs, the graphic consisted of an eight-tier pyramid that ranked various endurance training methods based on their relative impact on fitness and performance. The stronger the impact of a given method, the lower appeared on the pyramid.
Occupying the bottom tier was “Total Frequency/Volume of Training.” What this means is that, according to Seiler, the single most impactful thing an endurance athlete can do to improve his or her fitness and performance is train a lot. Plenty of other things matter too, but nothing matters more than running frequently.
The best evidence that frequency/volume is indeed the most important factor in endurance training comes from observational research, where comparisons are made among athletes following their normal routines without interference from scientists. For example, in a 2016 study published in BMC Sport Science, Medicine & Rehabilitation, Andrew Vickers and Emily Vertosick of the Sloan Kettering Cancer Center analyzed the training characteristics and race times of more than 2,300 recreational runners. They found a very strong correlation (p = 0.004 for those of you who remember your college statistics) between weekly running mileage and race times at distances ranging from 5K to the marathon. The more miles these runners ran, the faster they raced.
Other compelling evidence in support of the idea that frequency/volume is the most impactful factor in endurance training comes from elite athletes. Top performers in all major endurance sports train at very high volume and frequency. But they didn’t always. In a 2004 study, Stephen Seiler collaborated with Åke Fiskerstrand of the Norwegian Rowing Federation to gather data on the training methods of elite rowers between 1971 and 2000. Over this 30-year time period, they discovered, average training volume increased by 20 percent. And over this same span, elite rowers’ VO2max scores increased by 12 percent and their average power output in a six-minute rowing ergometer test grew by 10 percent.
The same evolutionary pattern played out in running. When Englishman Jim Peters set the last of his four marathon world records in 1954, clocking 2:17:39 at the Polytechnic Marathon in London, he did so on about 100 miles per week of training. When Eliud Kipchoge set the existing marathon world record on 2:01:40 in Berlin in 2018, he did so on about 120 miles per week of training—20 percent more than Peters did. Elite training practices have certainly evolved in other ways since the 1950’s, but greater frequency and volume is the biggest change.
Even among today’s elite runners, those who run more tend to run better. A 2019 study by British and Spanish researchers correlated various training characteristics with race performances in a group of 85 elite male runners over a period of seven years. They found that the amount of easy running (more on the easy part below) that individual runners did was the single strongest predictor of how well they performed in competition.
The specific benefits of running a lot include greater aerobic capacity, better running economy, and increased fatigue resistance. The exact amount of running that maximizes these benefits differs between individuals, but in my coaching experience, most recreational runners do substantially less than the amount that will maximize their fitness and performance. In other words, most recreational runners could get fitter and faster by running more.
Here are some simple guidelines for increasing your run frequency.
Add More Runs
There are two ways to run more. One is to make your existing runs longer. The other is to add runs to your current routine. Of these two options, the second is somewhat gentler on the body. This is precisely why elite runners get their 120 weekly miles from two moderate-length runs per day rather than one long one.
It’s important to understand that, although running more often is an effective way to boost running performance, the returns diminish rapidly. Going from four runs per week to five, for example, will yield a lot more benefit than going from seven runs per week to eight. Abrupt increases in run frequency also carry significant injury risk. For both of these reasons, you should proceed gradually in increasing your run frequency.
Consider every-other-day running (i.e., three to four runs per week) a baseline. Even novice runners can handle this frequency. From there, add one run to your weekly routine per training cycle until you’re running as often as your schedule or body can handle. So, if you’re running five times per week now, try six as you prepare for your next big race. If that goes well, try seven runs per week in the next cycle. When that becomes routine, consider going to doubles one or two times per week.
Research by Stephen Seiler and others indicates that runners of all ability and experience levels improve most when they spend about 80 percent of their weekly running time at low intensity (specifically, below the ventilatory threshold, which for most runners falls just below the more familiar lactate threshold) and the remaining 20 percent at moderate to high intensity. The average runner actually spends about half of his or her training time at moderate intensity.
Even if you have no intention of running more, you will probably experience a significant boost in fitness if you simply dial back the pace of your easy runs so that your overall training intensity balance falls in line with Seiler’s 80/20 rule. But what you may also find is that you feel fresher and more energetic, and suddenly the notion of running more frequently doesn’t seem so daunting.
The downside of running more frequently is that it exposes the body to more impact forces. For some runners, this translates to greater risk for overuse injuries. If you are an injury-prone runner, you can get the benefit of increased aerobic workout frequency without additional injury risk by adding nonimpact cross-training sessions to your weekly routine instead of runs.
Research proves this is an effective way to boost running performance. In 1998, Mick Flynn and colleagues at Purdue University added either three extra runs or three stationary bike workouts to the training programs of 20 runners for a period of six weeks. All of the runners completed a 5K time trial before this period of modified training and again afterward. Both the running-only group and the cross-training program improved their times by an average of 2.5 percent.
One of the great things about running is that you tend to get out of it what you put into it. There’s no simpler or more effective way to put more into your running than to put more runs into your week. Just be sure to go about it sensibly and respect your limits.