Intensity Balance – 80/20 Endurance

It’s been nearly a decade since I coined the term “moderate-intensity rut” in reference to the widespread habit among recreational endurance athletes of doing a plurality of their training at moderate intensity. At that time, very few athletes were even aware of the existence of the problem. But much has changed since then. The books 80/20 Running and 80/20 Triathlon, through which I endeavor to save athletes from the rut, have sold a combined 90,000 copies, and online versions of the books’ training plans have sold close to 70,000 copies. And these numbers only hint at the ripple effect of broadening awareness of the moderate-intensity rut.

But one thing hasn’t changed, and it’s this: The vast majority of recreational endurance athletes are still doing a plurality of their training at moderate intensity. The latest bad-news report from this front comes in the form of a study led by João Henrique Falk Neto and published in the journal Sports. Nine recreational triathletes kept detailed training logs during the final six weeks before an Olympic-distance triathlon and for two weeks afterward. They also completed questionnaires intended to assess their health and well-being, including the Training Distress Questionnaire and the Training Stress Recovery questionnaire.

The main purpose of the study was not to identify the training intensity distribution of these athletes but rather, as the authors put it, to “assess how their preparation for a triathlon influences their health and their levels of fatigue.” I’m not sure what Neto’s team’s hypothesis was, or if they even had one, but if they hoped to find that the subjects’ health or well-being suffered during the eight-week observation period, he was disappointed. No significant changes were seen in any of the relevant measures.

Personally, I’m happy about that, but I’m less happy about the way these athletes trained. The most surprising finding was that their training loads fluctuated drastically from week to week. One would expect some variation in training stress, of course, but these folks took it to an extreme, with all nine subjects literally doubling their training load from one week to the next at least once. What’s more, Neto’s team was unable to identify any coherent logic or pattern to these fluctuations. They had every appearance of utter arbitrariness. My own best guess as to why training loads were so erratic in this group is that they trained too much in their “up” weeks and had to compensate by scaling way back in the weeks that followed.

As the 80/20 guy, I was most interested in how these athletes balanced their training intensities. If Neto and company’s findings regarding training loads were surprising and head-scratching, their findings on intensity balance were predictable and dismaying. Perhaps I was naïve to hope that the 80/20 message had achieved statistically meaningful penetration in this population, but it clearly hasn’t.

As most studies of this kind do these days, intensity was divided into three zones. Zone 1 is considered low intensity, and is bounded on the upper end by the first ventilatory threshold, which corresponds to 77-81 percent of maximum heart rate. Zone 2 is moderate intensity, and has an upper limit marked by the second ventilatory threshold, which corresponds to 91-93 percent of maximum heart rate. And Zone 3, high intensity, is everything above the second ventilatory threshold. On average, the subjects were found to have completed just 47 percent of their combined swimming, cycling, and running in Zone 1, and in only two weeks of the eight for which data were collected did they spend more than half of their training time at low intensity.

I should mention that these findings are skewed somewhat by the fact that they were based on session RPE ratings rather than on heart rate data. Subjects were asked to assign an intensity rating of 1 to 10 for each session as a whole, and so, for example, a 50-minute workout containing 25 minutes of work in Zone 3 would be considered a 50-minute session in Zone 3 if the athlete assigned it a session RPE of 7 or higher. Even accounting for this rather sloppy approach to measuring intensity distribution, though, we can be certain the athletes in this study were doing nowhere near 80 percent of their training at low intensity.

I feel two ways about this study. On the one hand, I’m sad that so many recreational endurance athletes are training in a self-sabotaging manner. On the other hand, as a cheerleader for athletes in the 80/20 Endurance community, I see this widespread self-sabotage as a competitive advantage for “my people.” Competition does not begin when the starting horn blares; it begins on the first day of training. If you exhibit the judgment to find and use the most effective training methods and your competition doesn’t, so be it. Exploit your advantage to the fullest possible extent, and in the meantime I’ll continue to work on trying to reach the lost sheep.

There are two kinds of endurance athlete: Those who don’t know what heart rate variability (HRV) is and those who are about to find out.

For as long as hearts have existed, these vital organs have contracted at a slightly erratic tempo, and it is this slight play in rhythm that we measure as HRV. A much newer phenomenon is the active monitoring of HRV by endurance athletes, which is done because heart rate variability itself is variable in individuals, and these changes contain information about health, fitness, stress, and recovery.

So, that’s your primer on HRV. If you’re interested in learning more about the basics of heart rate variability, just Google the term—there’s plenty of good (and some bad) information online. The purpose of this article is to tell you about a new HRV-related study that grabbed my attention. Conducted by an international research team that included Marco Altini of HRV4 fame, the study was actually a single-subject validation test of a new functionality incorporated into the HRV Logger app.

In a previous study, Bruce Rogers of the University of Central Florida, who was also involved in the study under discussion, identified a specific HRV correlate of the aerobic threshold (aka first ventilatory threshold, or VT₁) as determined through laboratory testing. The mathematics involved are highly advanced and far beyond my depth, but I’m confident that others who are good with numbers will test the validity of Rogers’s calculations. In the meantime, what he and Altini have done with them is pretty cool. As you may know, the aerobic threshold represents the dividing line between low and moderate intensity. So, the new functionality that’s been built into HRV Logger enables the app to pinpoint an athlete’s current HRV and track intensity distribution in real time. Specifically, a prior validation study linked the aerobic threshold to a DFA-alpha1 measurement of 0.75.

There are multiple advantages to this functionality. One is that the measurement involved is a better representation of global physiological demand than heart rate (or just about any other measurement that can be taken during exercise in the field). Another is that it obviates the need for formal testing outside the context of normal training. A third advantage is that the app’s aerobic threshold estimates track day-to-day and even within-session changes in your aerobic threshold. A lot of athletes don’t recognize that the physiological events such as VT₁ to which we fix our training zones are themselves not fixed, but tend to float. Zones based on testing don’t float, but HRV Logger’s estimates do. Also, these estimates are impervious to cardiac drift and other factors that warp the linkage between heart rate and true physiological intensity. And finally, DFA-alpha1 estimates of aerobic threshold are transferrable to any aerobic exercise modality. Whether you’re cycling, running, or cross-country skiing, your VT₁ is 0.75.

Anyway, the validation protocol—which was completed by a 41-year-old male former professional triathlete—consisted of three sessions. The first was a standard graded cycling test to exhaustion. This was followed by a non-exhaustive stage test in which the subject completed four, six-minute stages at incrementally increasing power outputs spanning from below to above the aerobic threshold. The final session was an hourlong easy ride. The results obtained by the HRV Logger app were compared against an analysis of the raw HRV data using Kubios HRV premium software and also against the results of a laboratory VT₁ test. When the numbers were crunched, Altini and his collaborators found a “reasonable clinical agreement between conventional retrospective calculation of the HRVT derived through Kubios HRV software to that of a real-time app” and a high level of agreement between the app’s estimate of the subject’s aerobic threshold and the VT₁ power and HR values of 220 watts and 148 bpm obtained through laboratory testing.

As the 80/20 guy, I’m most excited about DFA-alpha1’s potential use in enforcing a prescribed intensity balance. With habitual use, athletes can track accumulated time and percentages of weekly training time at and above low intensity. This information will be especially helpful to athletes in special situations, such as off-road triathlon specialists who have no hope of staying at low intensity during long rides on hilly trails and want to incorporate them in a way that doesn’t skew their overall intensity balance.

I know this article reads like an infomercial for the HRV Logger app, but I assure you it’s not. Although I have corresponded a bit with Marco Altini in the past, I have no relationship with his company and nothing personal to gain from promoting his app. What I do have is a long history of promoting products I come across that, in my opinion, meet unmet needs for athletes. Speaking of which, have y’all shelled out for an ElliptiGO yet?

Every once in a while an athlete asks me if the training plans offered in one of my older books such as Braining Training for Runners or Triathlete Magazine’s Essential Week-by-Week Training Guide are still relevant or have been rendered obsolete by the 80/20 training plans I peddle today. My stock answer to this question is that my overall training philosophy has never changed; it just has a name now. In other words, my older training plans are 80/20 plans in all but name.

Let’s not forget how the whole thing came about. In the early 2000’s, exercise physiologist Stephen Seiler set out to quantify the training practices of elite endurance athletes in various disciplines and geographical locations. His main finding was that, across the board, these athletes do about 80 percent of their training at low intensity and 20 percent at moderate to high intensity. But it’s not as if they only started training this way the day before Seiler showed up with his calculator. As I point out in 80/20 Running, four-time Boston Marathon and New York City Marathon winner Bill Rodgers did about 80 percent of his training at low intensity in the 1970s, as did 800m and 1500m Olympic gold medalist Peter Snell in the 1960s. As a high school runner in the 1980s, I was trained by coaches influenced by Snell’s coach, the legendary Arthur Lydiard, who pioneered the high-volume, mostly low-intensity approach to endurance training we call 80/20 today. I’ve never known any other way.

So, the only thing that’s really new is the phenomenon of nonelite endurance athletes consciously trying to adhere to an 80/20 intensity balance in training. Predictably, some of these athletes have become somewhat obsessive about the 80/20 Rule, going to great lengths to make sure they don’t deviate from it and fretting about the potential consequences of straying accidentally. Online 80/20 forums are rife with questions from athletes who seem to invest these numbers with an almost totemic authority. “Just tell me what to do, oh mighty 80/20 Rule!”

Okay, I’m exaggerating a bit, but I do see a fair number of athletes overthinking the whole 80/20 thing, and it concerns me. Here’s something I would like these athletes to know: Today’s elite athletes still don’t consciously adhere to an 80/20 intensity balance. Just as Bill Rodgers and company did 40-plus years ago, the champions of our time practice the 80/20 method by default, using other rules of intensity balance that, in practice, result in 80 percent of training being done at low intensity. As a nonelite athlete, you can employ the same rules to make 80/20 training easier, or to rescue yourself from the rabbit hole of overthinking intensity balancing.

First Rule

The first rule is this: Be sure you’re actually at low intensity when you intend to be. Elite athletes never fail in this regard. Their easy swims, rides, and runs are truly easy, by which I mean that they are performed entirely below the first ventilatory threshold, which falls between 77 and 81 percent of maximum heart rate in most athletes. In contrast to this, most recreational endurance athletes do most of their easy training slightly above the VT₁, which is technically moderate intensity, and creates a significantly greater fatigue burden.

Second Rule

Rule number two is this: Devote roughly one out of every three training sessions you do to moderate or high intensity. Again, this is how elite endurance athletes and their coaches balance training intensities. The typical elite runner, for example, runs 13 times per week and three of those runs are set aside for focused work at moderate to high intensity. By planning at the level of session types in this manner, elite endurance athletes end up spending very close to 80 percent of their training time at low intensity without ever actually thinking about time-based intensity distribution. If you train less frequently—say, six or seven times per week, as a plurality of recreational endurance athletes do—applying the same rule yields two moderate/high-intensity sessions per week. Pretty basic.

You can fine-tune intensity balance within this framework by adjusting the duration of individual sessions. Bigger tempo and interval workouts will make a bigger contribution to the moderate/high-intensity side of the ledger, while smaller ones will make a smaller contribution. There’s no need to get overly fussy in adjusting the size of your “quality” sessions for the explicit sake of nailing an 80/20 intensity balance for the week. Instead you can simply plan workouts that make sense in the overall context of your training, trusting that by doing so you’ll end up close to 80/20.

If you are the type of athlete who tends to lose the forest of training principles for the trees of quantitative minutiae, consider zooming out in the manner I’ve just suggested. Forget about 80/20 per se and concentrate instead on planning out your weeks by session type and on ensuring that you remain consistently at low intensity when you intend to be. If this approach seems rather inexact to you, well, this just means that exactitude is overrated!

First Rule

Second Rule

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