The Art of Running Slower Faster by Mark Stone
April 2016. In February I completely revamped my training routine as a runner, adopting Heart Rate Monitor (HRM) training for the first time. While the basic precepts of HRM are compelling, the available information on an actual training plan is complex, confusing, and often contradictory. I thought, therefore, that I'd set out how I've come to think about HRM, in the hopes that other confused runners may find this helpful.
Let me start with a bit of evolutionary speculation. Homo sapiens is a unique species with two distinct physical traits that matter to runners. First, we are the most migratory of land-based mammals. We are the only such species to have found our way across the entire Eurasian land mass as well as into and throughout the Americas. Second, we have a remarkable balance of speed and stamina when in the "fight or flight" mode of hunter versus prey. With a top speed of about 20 MPH humans can certainly be outpaced over short distances by a number of other species. But once distances reach endurance length, humans are almost unmatched for speed. This has made humans superb hunters over the millenia, with a remarkable ability to wear down and outlast their prey.
Yet biology, and hence evolution, dictates very different needs for these two different modes of movement: migration versus pursuit. The human body has two different energy reserves: fat stored in tissue, which can only be accessed and utilized slowly, and carbohydrates circulating in the form of blood sugar, which can be accessed immediately, but whose reserves are only a fraction compared to the body's fat reserves. The former is aerobic effort - we are not depleting oxygen in the blood faster than we can replenish it, and fat suffices as an energy source. The latter is anaerobic effort - oxygen intake cannot keep up with oxygen depletion, and thus we draw on limited carbohydrate reserves to sustain effort.
Nature has evolved our brains to decide which energy reserve to tap into based on a simple cost benefit analysis: based on our current activity, which reserve is most likely to yield a net gain in energy in the future?
Members of a species migrate when available food in a region has become scarce, necessitating a change in location over long distances. Attempting to sprint, or even run, to this new location would result in energy failure. We don't have enough blood sugar to propel us that far. Instead the body burns fat, gambling that we can find a new, abundant region before fat reserves are exhausted. By contrast, this slow pace would be useless in a hunt as our prey would simply elude us. Instead the brain gambles on using precious blood sugar reserves to bring a quick success and a food source that will more than replenish those reserves.
How does the brain determine whether we are in migration or in pursuit? This judgment is tied to sensory perception, and whether or not our senses have triggered a "fight or flight" response in the form of adrenalin release and increased heart rate.
In short: above a certain heart rate threshold the body is in anaerobic effort and draws primarily on blood sugar for energy reserves; below that threshold the body is in aerobic effort and draws primarily on fat for energy reserves.
For endurance runners, why does this threshold matter? If you race distances of 10K or less, it probably doesn't matter. Even up to a half marathon runners can sustain anaerobic effort for the entire distance. No, it is for marathon and ultra runners that this threshold is crucial. To quote Tim Nokes from The Lore of Running:
"The marathon is less a physical event than a spiritual encounter. In infinite wisdom, God built into us a 32-km racing limit, a limit imposed by inadequate sources of the marathoner's prime racing fuel -- carbohydrates. But we, in our human wisdom, decreed that the standard marathon be raced over 42 km. So it is in that physical no-man's-land, which begins after the 32-km mark, that the irresistible appeal of the marathon lies."
Exhausting that carbohydrate reserve somewhere around the 32-km mark is what runners refer to as "hitting the wall." But what if you could run your entire race below your aerobic threshold, and thus never hit the wall? Most runners react to this prospect by thinking that the result would be a slower pace and thus a poorer finishing time. And for runners who changed nothing about their training routine, and simply tried to run at a lower heart rate come race time, this is exactly what would happen. Thus most runners would rather gamble with the wall.
But HRM training offers a different prospect - what if we changed our entire training routine to emphasize aerobic activity? We lead such sedentary lives that our bodies are unacustomed to operating in migration mode. Being an active runner doesn't necessarily change this. I know only a couple of runners who are so naturally patient that they intuitively settle into an aerobic level of effort. Most endurance runners spend so much of their training time at anaerobic levels of exertion that they are simply signaling frequent pursuit mode to their bodies rather than signaling migration. As a result humans, even most endurance runner humans, have allowed ourselves to lapse into very poor fat burning machines.
If, instead, we runners spend the vast majority of our training time at aerobic levels of exertion, we keep our effort in fat burning mode and gradually we re-train our bodies how to become efficient at burning fat as an energy source while running. The result is that over time we become faster at the same heart rate level of exertion. For example, a pace that once required 160 bpm to maintain can be maintained at 155 bpm, and then at 150. The wall that once stood before us at 32-km has vanished. The ultra distances that once seemed unattainable are within our grasp.
That's the theory. What does this look like in practice?
First a brief word on gear. In the early days of digital fitness technology, heart rate monitoring required an awkward chest strap and a device that could only record to local storage, which would subsequently have to be plugged into a PC for a runner to output and view heart rate data. For many runners this was not an inviting prospect.
These days technology has changed dramatically. Miniaturization has made devices smaller and inobtrusive. Tiny optical sensors provide accurate heart rate data. Bluetooth enables devices to broadcast this data via an industry standard like Ant+ so that any Bluetooth-capable smart device can run apps that know how to receive and interpret that data.
In my case I am using the Scosche Rhythm+ armband. It's about the size of a wrist watch, and straps to my fore arm. I pair this with an Android phone running Runkeeper,which supports Ant+ and can thus receive the heart rate data and integrate it with the GPS and other data that Runkeeper tracks from my runs. Runkeeper visually shows my heart rate during activity, and also provides configurable audio cues to alert me about my heart rate during activity.
This combination is easy, inobstrusive, and inexpensive. There are many similar combinations that should work just as well. With a good source of data for during and post run, you can work out an approach to HRM training.
The various approaches to HRM training agree on some basics. They generally divide heart rate into five zones, where each zone might be a range that differs by 10 to 15 bpm. Zones 1, 2, and 3 are at aerobic levels of exertion, and Zones 4 and 5 are at anaerobic levels of exertion. You might think of them this way:
- Zone 5 - Maximum Anaerobic Exertion. This level of exertion is barely sustainable for even just a short period of time, and tops out at your maximum heart rate (MHR).
- Zone 4 - Anaerobic Exertion. This level of exertion starts when you cross your aerobic threshold. It can be sustained for minutes at a time, perhaps even many minutes, but not for hours at a time.
- Zone 3 - Maximum Aerobic Exertion. This level of exertion definitely requires effort, and a beginning or out of shape runner can't keep this up for very long. But by building stamina over time, this level of effort can be greatly extended.
- Zone 2 - Aerobic Exertion. This should feel like a relatively easy pace, one where you could run and maintain a conversation without shortness of breath.
- Zone 1 - Minimum Aerobic Exertion. Barely above a walking pace, this slog jog should feel unnaturally slow, particularly at the outset of training.
Contention among HRM training programs stems from how to find your heart rate zones, and how to allocate training time among zones. Unfortunately these views are often contradictory, and the science is murky.
The most direct way to determine your MHR would be the brute force method: push yourself to maximum exertion and see what your heart rate turned out to be. While the experience would be unpleasant, the result would be individual and accurate.
Most formulas for calculating MHR seem designed to help you avoid this unpleasantness. The simplest one recommends subtracting your age from 220. The problem? This method doesn't work. By this calculation my MHR should be 164, but I know from direct observation that my high intensity workouts tend to have my heart rate in the 166 - 170 range, with spikes up into the low 170s.
One common recommendation is that runners who are both reasonably fit and over 40 should use the "220 minus your age" formula, but then add 10. This would give me a MHR of 174, which seems pretty close. There are other problems, however.
The methods just described assume that everyone of the same age has the same heart rate. On this theory I have the same heart rate as my obese neighbor down the street, and the same heart rate as every former Olympic athlete in their mid-50s. That just isn't plausible.
A number of programs recommend that you re-check your heart rate and relculate your heart rate zones regularly while doing HRM training. This advice makes sense; as you get further into training your body and your heart rate will change, and your plan should reflect those changes. But if my formula is just my age modified by a number, then there's nothing individual about that calculation, and thus nothing to recalculate. I'll get the same calculation a month or three months from now as I get today. Again, this just isn't plausible.
Another suggestion is to see a doctor or go to a sports lab and get a full cardio work up. This approach may yield accurate results, but it isn't very practical. Scheduling such an appointment isn't easy, and the expense can be prohibitive for many. And again, the implication that you check one time and now you know your heart rate zones is just an implausible idea. No one other than a professional athlete is going to get a full medical / professional work up every month or so.
No, the correct approach has to be a calculation you can do on your own, but one that provides individual results. In my case I've settled on the Karvonen method. To use this method, you'll need to know your resting heart rate (RHR), your MHR, and you'll need to calculate the difference between these two numbers, known as your heart rate reserve (HRR).
RHR is easy to determine. Use your heart rate monitor during a period of sedentary activity, or while you're asleep. Use not the absolute lowest number from your measurements, but what looks like the typical low point in your heart rate. For example, I've seen my heart rate dip as low as 47 bpm on rare occaisions, but 49 bpm is a more typical minimum. So that's the number I use.
For MHR, there really is no substitue for simply pushing yourself and measuring the result. Do about 30 minutes of whatever your standard high intensity workout is. This might be wind sprints, stair climbing, whatever. After 30 minutes of working out, settle in to whatever the highest intensity part of this routine is, and then hold sustain that for as long as you can. If you're doing it right, this won't be very long; probably a few minutes at most. Then look and see what your heart rate peaked at during this workout. Use that for your MHR. Right now for me that's 174 bpm.
Now substract the RHR from the MHR. This is your HRR. I have a HRR of 125. Now with these three numbers you can applythe Karvonen formula to determine your five heart rate zones. There's a handy tool at fitdigits that calculates zones for you. If you prefer to do the calculations manually, then the formulas are as follows:
- Lower end of Zone 1 = (1/2 HRR) + RHR
- Upper end of Zone 1 = (3/5 HRR) + RHR
- Upper end of Zone 2 = (7/10 HRR) + RHR
- Upper end of Zone 3 = (4/5 HRR) + RHR
- Upper end of Zone 4 = (9/10 HRR) + RHR
- Upper end of Zone 5 = MHR
Heart rate zones should be re-calculated regularly; once a month is probably a good interval.
Now that you know your heart rate zones, what do you do? How do you turn this information into a training plan?
Again, the available information is complex, and conflicting. Some recommend that all training be within your aerobic threshold (Zones 1, 2, and 3). Others recommend some high intensity workouts. All agree that most runners spend too much time doing anaerobic workouts, and that even once a week is probably too frequent for work in Zones 4 and 5.
At the same time that I've been researching HRM training, I also read Meb Keflezighi's excellent book Meb for Mortals. Two themes from that book are relevant here. First, Meb suggests a basic training plan built around four types of runs:
- Long slow run. Builds stamina, and establishes a base distance you are comfortable with. Essential for marathon and ultra training.
- Tempo run. At or slightly above your desired race pace. Not as long as the long run, but should be a significant distance acclimating you to maintaining pace over distance.
- Intervals. A high intensity workout focused on speed. This could be repeats of winds sprints, hill climbs, a sustained run with fartleks, whatever you are comfortable with. It should be the highest intensity workout in your routine, and total distance should be shorter than your tempo run.
- Recovery run. Even slower than the long slow run, and on a day immediately following one of the other runs. Helps stretch out stiff muscles, and helps build stamina by recruiting somewhat different muscle groups than those used the day before.
Meb also notes that the ideal would be to do a recovery run the day after each of the other three runs, but that this breaks with the seven day schedule most of us follow to stay on a weekly cycle. Particularly for older runners, who benefit from more recovery time, he recommends a nine day cycle. It might look like this:
- Day 1 - Long slow run
- Day 2 - Recovery run
- Day 3 - Rest day
- Day 4 - Tempo run
- Day 5 - Recovery run
- Day 6 - Rest Day
- Day 7 - Intervals
- Day 8 - Recovery run
- Day 9 - Rest Day
I'm finding that the nine day cycle is not as awkward to maintain as I had feared. My family appreciates having some weekends where I am not consumed with getting in my long run, and between some very early mornings an occasional flexibility to work from home, I do manage to squeeze in long runs during the week when necessary.
The next piece in the puzzle is to match each type of run with the appropriate heart rate zone. That's actually quite straightforward. The key point of HRM training is to be able to race within your aerobic capacity, so tempo runs should be in Zone 3. The long slow run should be slower, so Zone 2. Recovery runs should be even slower, so Zone 1. Intervals, or whatever high intensity workout you prefer, can burst into Zones 4 and 5. By sticking to a nine day cycle, this means I am also following the guidance of doing high intensity workouts less than once a week.
Many people won't have the flexibility to follow a nine day schedule. For those training within the constraints of our seven day week, I'd recommend something like this:
- Day 1 - Long slow run, Zone 2
- Day 2 - Recovery run Zone 1
- Day 3 - Rest day
- Day 4 - Tempo run, Zone 3
- Day 5 - Rest Day
- Day 6 - Odd weeks: Intervals, Zone 4-5. Even weeks: Tempo run, Zone 3
- Day 7 - Rest Day
What should your distance goal be for a long run, and what should your distance goal for a tempo run be? That's a highly individual choice, and it depends on what even you're training for. Here's how I do it; your mileage may vary:
- Half Marathon:
- Long run - 15 miles
- Tempo run - 8 miles
- Long run - 20-22 miles
- Tempo run - 10 miles
- 50k Ultra:
- Long run - 24 miles with at least 3000' of elevation gain
- Tempo run - 10 miles with at least 1000' of elevation gain
If I'm coming off of a period of fairly casual running then my starting point for long runs is around 10 miles, and my starting point for tempo runs is around 5 miles. Plan to increase mileage by no more than 1/8 per 9 day cycle, or no more than 10% per one week cycle. Build your training calendar accordingly to ramp up at no more than these rates from your starting point to your target distances.
So you now you have your heart rate zones, a method for re-checking those zones over time, and a training plan that tells you what distances to run and types of runs to run, and what heart rates to target for those runs. What should you actually expect to experience with HRM training?
This is maybe the most important but least discussed question around HRM training. I say this because HRM takes a lot of patience, and progress can feel slow to non-existent in the early stages. If you don't know what to expect, if you don't know what "normal" is, then it's easy to become discouraged and simply give up.
First of all, it will take months for your body to transition to aerobic efficieny, even if iyou are an experienced runner. Expect it to take 12 to 18 months of dedicated HRM training before your speed results will meet or exceed what you experienced on more traditional training methods. The payoff is that once you reach that level of fitness and performance it will be more sustainable and you'll be less prone to injury.
Second, become well acquianted with the term cardiac drift. This is the experience of running at a steady pace and what you perceive to be a steady level of effort, and having your heart rate start to climb. There are lots of explanations for cardiac drift, and some controversy around the meaning of those explanations. But simply put, when your body is not at a good level of aerobic fitness, your heart rate tends to escalate towards anearobic levels to find the energy needed to sustain effort.
You'll experience cardiac drift in two forms throughout the early stages of training. When you first start HRM training, every run will feel like a struggle to stay within the target heart rate zone and you'll be in a state of near constant cardiac drift. This is natural. You're asking your body to run in a new way, and your body isn't used to it. Accept these early limitations, and slow down, to a walk if necessary, to bring your heart rate back within range.
After a while you'll have a better sense for how to ramp up your workout slowly, and how to moderate your effort to stay within a particular zone. Those first few miles, and then the first half to 2/3 of your run, will feel more natural and stay within zone more easily. That's when you'll start to notice the second form of cardiac drift.
Cardiac drift will set in towards the tail end of your run. A long run may go fine for 8 miles, and then for the last 2 miles you have to slow down more and more to keep your heart rate steady. A tempo run may go fine for the first 3 miles, and then in the last mile or so your heart rate climbs, even though you don't feel like you're working harder.
This kind of drift is natural, and it's a sign that you still haven't built up the needed base stamina. Slow down, keep your heart rate under control, and be patient. What you're experiencing is an imbalance between your body's draw on fat burning and bloog sugar burning. Because your body is not yet fully efficient at fat burning, you experience an increased dependence on blood sugar for energy as you reach your stamina limit towards the end of your run.
This balance will improve over time. Don't be afraid to continue to nudge your distance up gradually during this phase, as you continue to build base stamina. You'll still experience some cardiac drift for awhile, but what used to happen at mile 8 as you aimed for 10 miles will now happen at mile 10 as you aim for 12, for example.
I should note that there is a third form of cardiac drift to be aware of. Heart rate is part of your body's cooling system; the faster blood flows, the more easily you cool down. So significant changes in air temperature can affect your heart rate, as your body adjusts to the proper cooling rate. In particular, summer runs that start out in cool early morning temperatures but end in warmer mid morning or midday temperatures can cause cardiac drift.
At some point -- expect it to take months -- the magic happens. You're running your target distances for the race distances you have planned, and you're not experiencing any cardiac drift. Your heart rate ramps up gradually during your warm up, and remains steady throughout your run. Congratulations; you now have a strong stamina foundation on which to run.
Here's a tip about handling cardiac drift. In addition to drift, you'll experience cardiac lag. In other words, changes in heart rate lag slightly behind changes in effort. When your brain notices your legs working harder, it signals your heart to increase its rate. However, this isn't an instant process. It can take anywhere from a few seconds to 30 seconds. Similarly, when your legs ease their effort, your heart rate doesn't instantly slow down. You still experience cardiac lag.
As a result, if you run with your heart rate near the top of your target zone, cardiac drift will push you out of that zone and cardiac lag will keep you from bringing it instantly under control when you slow down. The result is you'll spend too much time above your target zone rather than in it.
The solution is to aim to keep your heart rate in the middle of your target zone, at least through the early months of training when you're still battling cardiac drift. That way slight upward drifts won't take you out of your zone before adjusting your level of effort brings your heart rate back down.
So the months have passed and you've reached your target distances while staying comfortably within your target heart rate zones. Now what? Well, you're still slow as heck, aren't you? At least compared to what you used to be, or what you expected. This is natural. The same rebalancing dynamic between carb burning and fat burning is still at work in your body.
What you'll now experience is a gradual drop in heart rate to maintain the paces you've been maintaining. In other words, you're getting faster -- you'll be able gradually increase your pace while staying within the same heart rate zone. There's no way to predict where this will take you. Everyone is different. However, you will be running within your body's natural capabilities, instead of pushing yourself to (or across) the threshold of injury with effort levels your body cannot sustain.
You've mastered the art of running slower faster.