blog post 4

A Fresh Look at Intensity Zones

Anyone who has ever used a piece of cardio equipment at a public gym has some notion of exercise intensity zones. Here’s an example of a chart you might see stuck to an elliptical trainer at your local health club:

Training heart rate intensity zones example
Example of Exercise Intensity Zones

Athletes scoff at such simplistic, one-size-fits-all guidelines. For starters, they are based on the supposition that every human has a maximum heart rate equal to 220 beats per minute minus their age in years, which is very far from being true. My own maximum heart rate at age 49, for example, was 181 BPM, or 220 – 39. These charts also convey a misleading impression that individuals with any particular health or fitness goal should do all of their exercising in the zone associated with that goal, which is also untrue. I can assure you that doing 100 percent of one’s cardiovascular exercise at 60 to 70 percent of maximum heart rate is not the most efficient way to control one’s body weight. Those nice round numbers—50 to 60 percent, 60 to 70 percent, etc.—are a bit suspect as well.

A variety of more sophisticated zone scales—not all of them heart rate-based—have been developed for use by endurance athletes. Of these, Joe Friel’s is perhaps the best known and most widely used. David Warden and I created our own zone scale for athletes who wish to train by the 80/20 method. All of these intensity rating systems—or most of them, anyway—share certain characteristics that make them better than the ones you see at the gym. In particular, individual zones are linked to key physiological thresholds that vary with fitness and require testing to determine.

Athletes put a good deal of trust in the 80/20 zone scale and others, and rightly so—they work quite well. The funny thing is that very few elite endurance athletes use intensity zones of any kind. Take runners, for example. In any type of high-intensity workout, an elite runner is likely to try to hit a certain target rather than stay within a zone. For instance, a runner might do a set of 1-km repeats at critical velocity, which is the fastest pace that can be sustained for 30 minutes. Or a triathlete might do a long ride featuring alternating 10-minute blocks performed at Ironman power +10 watts and Ironman power -10 watts. Low-intensity sessions, which dominate the training schedules of all elite endurance athletes, are governed neither by zones nor targets but are done entirely by feel.

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The core of my endurance training philosophy is that athletes of all experience and ability levels should train the same way the pros do, albeit scaled to their level. But if that’s the case, then why do I prescribe intensity zones to nonelite athletes when elite athletes don’t use them? The short answer is that, precisely because any person who has ever exercised in a public gym is familiar with the concept of zones, this tool is helpful in facilitating correct workout execution for less experienced athletes. The way the pros regulate intensity is difficult to do unless you really know yourself as an athlete.

When I trained with the NAZ Elite team in 2017, Coach Ben Rosario always gave each athlete a precise pace or time to hit in each workout, and he was able to do so because he knew his athletes thoroughly. For example, one day he had Kellyn Taylor complete a 4 x 300m cutdown at the end of a workout. He asked her to complete the reps in 52, 51, 50, and 49 seconds, basing these numbers on her known one-mile race pace of 50 seconds per 300. She hit these numbers dead-on.

Chances are, you don’t know yourself well enough as an athlete to train with such precision, which is why you need zones. No problem. Because I truly believe that all athletes should train like the elites as much as possible, I try to have it both ways in the new 80/20 run plans I created earlier this year. Yes, the workouts use zones, but in many of them the workout descriptions instruct athletes to aim for a particular target within a zone.

An example is lactate intervals. This workout type (there are nine separate levels) features sets of 30-second intervals that are meant to be run at the fastest pace a runner can sustain for 15 minutes. In zone terms, it’s a Zone 4 session, but the specific pace target falls smack in the middle of this zone for the majority of runners. Less experienced runners are free to just think of the session as a Zone 4 workout and trust they will get the desired benefit regardless of where they land inside this zone, while more experienced runners can try to nail their 15-minute pace with Kellyn Taylor-like exactness and benefit that much more. With time, of course, runners can graduate from the first approach to the second, and from there they can advance to signing a running footwear endorsement contract and going to the Olympics.