I run by using heart rate, not by using pace. I’m a trail runner. The terrain I run on continuously changes, so heart rate works for me. But should I change this? Should I run with a power meter?
I’ve seen Stryd passing by a few times on Instagram. I’ve seen some stories about their power meter online. I admit, I am curious to try it out. It’s a gadget. Boys like toys. Yet, I am a minimalist as well. I think this world could do with a bit less buying, so I don’t have a Stryd yet.
Running on power
Yesterday evening ProRun, a Dutch website for runners, organised a webinar about running on power. They sell the Stryd Power meter, so of course Koen de Jong – a runner, cyclist and author of the book Lopen op Vermogen (Running on Power) – was positive about this new way of training. But am I?
Before I tell you, let’s look at what it is, and why you should do it, according to De Jong. When we run we use energy. This energy we can measure if we have the right tool. Well, Stryd is that tool. It measures the energy it costs you to move forward and expresses that in watt.
If you are a cycling fan, you’ve probably heard of watts. Even commentators now talk after a race about how many watts a cyclist was producing during either a sprint or a climb. The only thing they have to do is look at the data of that cyclist on Strava. That is, if the cyclist is sharing it.
Stryd now makes it possible for runners to focus on watts as well. The benefit is simple; if we run a race we want to distribute our energy evenly. Often we start to fast and end up without anything left in the tank at the end of the race. Sometimes it’s the other way around; we start too conservatively and discover we could have run faster when the finish is in sight.
By performing 3 all-out tests (critical power tests), roughly 1, 5 and 10 kilometers, Stryd gets to know you and can predict your race time. To run a personal record, it will tell you the amount of watts you have to run.
Evenly energy consumption
Of course, you can do it yourself, by picking a pace. If I want to run 5 kilometers in 20 minutes I can set my Garmin to 4 minutes per kilometer and keep that pace throughout the race. However, there is a big disadvantage when your run is focused on pace. For your body it works best if you keep your energy consumption evenly throughout a race. Running 4 minutes per kilometer looks evenly, but it isn’t.
Why not? Because not every kilometer we run is the same. If we run a loop, which most races are, there are parts we have a tailwind and parts we have a headwind. Some parts of the course might be ascending or descending. To run 4 minutes/kilometer with a headwind and/or on an ascending course we have to work harder. In other words we use more energy.
The Stryd power meter has an altitude sensor, wind sensor, speed sensor, temperature sensor and a ground contact sensor. No matter the wind, no matter the temperature and no matter the road, it will keep the recommended power the same. That means our pace may vary, but our energy consumption does not.
Power versus heart rate
I use heart rate, instead of pace. I’m a trail runner. Pace doesn’t work in the mountains, nor on muddy trails. As long as I keep my heart rate under 140 beats per minute (zone 2 for me) for the first 30 kilometers I am fine running a trail marathon. When I run uphill, my heart reacts, so I slow down.
De Jong has 2 objections. If you do a lactate threshold test to get to know your heart rate zones, that’s a snapshot. Heart rate zones keep on changing, the fitter you become. Which means you have to do multiple tests. For a precise test you have to go to a lab. That’s costly.
I agree on the costs, if you go to a lab, but you don’t have to. If you train you get better, so yes, you have to do multiple tests. However, most wearables let you do a lactate threshold test. Okay, it’s not 100% precise, but it gives you a good indication. Besides that, there are field tests (like the one in this blog post) you can do that can predict your lactate threshold pretty accurately. You don’t have to go to a lab. It doesn’t come down to a few heart beats more or less.
With a Stryd you have to keep doing your critical power tests as well, as your stamina is growing and your pace improving. So I don’t see the difference. Which brings us to the second argument of De Jong to use Stryd instead of heart race; intervals. If you speed up, your heart doesn’t instantly react. So heart rate isn’t a good tool for intervals.
I agree with this one. That’s why I use pace for my intervals. Okay, it’s harder to run against the wind, than with a tailwind, so using power would be more precise. But I don’t run intervals during a race. I do them in training, around my house. I can easily select where I do my intervals. In my case, on a sheltered cycling path in the forest. Problem solved.
But what about the road ascending or descending when you do interval training? I am Dutch. It’s all flat here. And if I end up running 1 or 2 seconds slower during an interval because I run uphill, it’s not going to make a big difference. It’s about training our legs, about getting stronger, not about seconds. Believe me, if you run against the wind or uphill you’ll get stronger. Even if your interval is 5 seconds to slow.
Powerless on trails
Okay, it isn’t flat when I run trails abroad. So would Stryd be a good help on the trails? Not according to Stryd, if you read in between the lines: ‘If you run on trails that are hard-packed with undulations, you can use Stryd as you would on the road. Keep your effort the same on the flat, uphills and downhills. Drop your power on steep descents and ignore completely on steep, technical descents. … On steep trails, you end up walking. .. The power hiking target cannot be derived from critical power. … You will have to determine a good power target yourself for various types of terrain: uphill running, uphill hiking, flat but technical etc.’
So if the surface isn’t hard-packed, Stryd isn’t working. Most trails aren’t hard-packed. They are muddy, sandy, grassy and soft of all the fallen leaves. That’s why they are trails. On the hills Stryd can’t tell me which power to focus on. I have to work that out myself. And every terrain requires me to come up with another useful power output. So every time I run up a hill I have to look at the gradient and how technical it is, to work out which power I should use. Does that mean I should bring a notebook with gradients and the best power on it?
To summarize; for me as a trail runner, who isn’t bothered about speed or breaking personal records, a power meter could be a fun gadget, but is not going to add anything to my training or running.