By Dave Trendler, VeloPress
On my first run after setting my power zones using Jim Vance’s method, I noticed something puzzling: the easy run was much harder than I was expecting it to be.
My workout was an endurance run: Run 40 minutes in Zone 2 with three 1-minute walk breaks. I decided to try to run at a constant power number (the very top of Zone 2) for the whole run, which meant that I had to run up hills much slower than normal, run the flats faster than I was expecting, and then run really hard on every downhill. My pace varied wildly as I responded to the terrain.
By the time I got back home, I felt as if I’d run a zone 3 tempo run instead of a zone 2 endurance run. I’ve run the same route several times before, attacking the hills at a much faster pace than this run, but this time the workout was much harder than usual. Why? Running with power leaves nowhere to hide.
That’s when I realized how a power meter can make training so much more precise. Let’s look at a marathon training tempo run as an example of what I mean.
Pretend you’re training for a marathon and the training plan you are using says that today’s workout is a tempo run: 2 x 5 miles at goal marathon pace.
Since your training plan was developed by a coach who has a solid understanding of exercise physiology, your coach has designed this workout to cause specific changes in your body that will help you meet your marathon goal. A tempo run, for example, builds endurance at race pace and also helps you internalize your race pace so you can run at a consistent pace on race day. As the Hansons say in their best-selling high-performance training program, Hansons Marathon Method, “the intensity of a tempo run is just fast enough that the aerobic system is challenged to keep up with a high percentage of fat oxidation, but it’s slow enough that the mitochondria and supporting fibers can barely keep up.”
Now let’s throw some real life into your workout: Let’s assume it’s tough in your area to find a 10-mile training ground that’s flat and that you’ll encounter some rolling hills or varying terrain during today’s tempo run.
You start your workout on flat terrain and have no trouble maintaining your goal marathon pace. Then a hill looms ahead. You stick to your workout plan and feel your glutes and calves tighten as you maintain goal marathon pace while ascending the short hill. At the top, your body returns to normal as you stick to your goal pace. Then heading back down the hill, you start breathing easily and your heart rate falls since it’s easy to maintain your goal marathon pace as you coast down the hill.
The next few miles go similarly with smaller hills, gentle inclines, and maybe a few sections where you run on trail between road segments. This is an out-and-back run, so you hit your 5 miles and turn around to do it all again. You get home and feel great that you were able to maintain your marathon goal pace for all 10 miles.
Sounds like a typical day training for a marathon, right?
But what kind of workout did you actually do? Was it truly a tempo run?
Consider this: In maintaining your goal marathon pace while running uphill, you raised your exercise intensity much higher than intended. As the Hansons say, “the intensity of a tempo run is just fast enough that the aerobic system is challenged to keep up with a high percentage of fat oxidation, but it’s slow enough that the mitochondria and supporting fibers can barely keep up.” Since running hills is much harder than running on the flat, every uphill section of today’s workout was way off your coach’s intended workout intensity.
And what about the downhill sections? Same thing. It’s much easier to run downhill, so by maintaining your goal marathon pace on the downhill, you were running way too easy.
Doesn’t it all even out? No, it doesn’t.
It’s true that you get to keep all the fitness you gain from all the time you spend in any specific training zone. But when your workout intensity varies, the benefits you reap vary, too, and you might not earn the physical changes that you or your coach intended to gain from the workout.
Exercise physiologists tell us that the body changes in specific ways in response to the time we spend at specific exercise intensities. Each exercise intensity – or zone – causes different and specific changes in our bodies. Your coach knows this and designs your training plans to include easy days (zone 1), endurance or base run days (zone 2), tempo runs (zone 3), aerobic threshold runs or intervals (zone 4), strength runs (zone 5), hill repeats or fast intervals (zone 6), and short sprints or striders (zone 7). Smart workouts that target these zones are the most effective ways to train because they cause specific changes that prepare you for the demands of your race.
So instead of running 2 x 5 miles in zone 3, which builds endurance at race pace and challenges your aerobic system and mitochondria, you might have spent 70% of your run in the right zone and 30% of your run in other zones and causing other changes.
Let’s try this same workout with a power meter. Translating this workout from pace to power might look like this: Run 90 minutes in zone 3.
You’d put on your power meter and start your run. Since you’ve already done the power test and know your power zones, you’d know that zone 3 for you is a range between 165 watts and 177 watts (for example). All you have to do is run within that power zone for 90 minutes. It’s that simple. In order to maintain your goal power number, you’ll need to slow down while running up hills and speed up while running down them. You’ll spend all 90 minutes at exactly the correct exercise intensity. You’ll come home and know that you did the workout correctly—and your coach will be happy. Your workout was laser focused in the right zone, causing the right changes in your body that your coach wants to see.
As you’re enjoying a post-run recovery snack, you might look back on your workout and think it was harder than you’d expected, which is just what happened to me on my first-ever power-based run. Why? Because you just ran the entire 90 minutes at the same, consistent effort level.
Pace ignores terrain, so if your workout calls for running at a constant pace, then you must adjust your effort to keep your pace the same. That means your effort is all over the place, which means you might train in several zones instead of the one your coach wanted you in. If you maintain your target pace while running up a hill, you’ll be running much harder than intended. If you maintain your target pace running downhill, your effort will be much easier than your workout calls for. You won’t come even close to doing this workout the right way. This variability in effort means that pace-based workouts are full of little breaks and surges.
Power leaves nowhere to hide or rest. Power gives you the option to run at the same effort regardless of terrain.
It’s possible that your coach might even shorten future power-based workouts. Since power allows you to stay in exactly the right zone for your entire workout, it should take you less time to accumulate the time in zone that all training plans are shooting for because of their corresponding physiological changes. Training with pace, despite its reputation, is a scattershot approach unless you are committed to running on a treadmill, a track, or the same flat course.
RUN WITH POWER is the groundbreaking guide you need to tap the true potential of your running power meter like SHFT, Stryd, or RPM2. From 5K to ultramarathon, a power meter can make you faster—but only if you know how to use it. Just viewing your numbers is not enough; you can only become a faster, stronger, more efficient runner when you know what your key numbers mean for your workouts, races, and your season-long training. In Run with Power, TrainingBible coach Jim Vance offers the comprehensive guide you need to find the speed you want.
Run with Power is available now from your local bookstore, tri or running shop, and from these online retailers:
Coach Jim Vance
Limited offers: Get Run with Power FREE with purchase of a SHFT, RPM2, or Stryd power meter while supplies last.