Things Your Watch Gets Wrong

Your watch is a tool. It is not a coach, a doctor, or you. But it's easy to start treating it like the final word on how a run actually went. Here's where I think it falls short, and how I'd use it instead.

It doesn't know what "productive" means. My watch will tell me I had an unproductive run and then quietly drop my predicted 5k time. Tell me how that's possible. Most of these algorithms weight your most recent runs heavily, so one hard or "bad" effort, especially in heat, can swing your predicted time even though nothing about your actual fitness changed. One run does not undo months of training.

Workouts get judged in a vacuum. This is probably the biggest blind spot. Your watch has zero idea what's going on in your life. It doesn't know about the bad night of sleep, the stress at work, or the fact that you're running in 90 degree heat. It just sees pace, heart rate, and movement, and makes a guess from there. A high stress week or a rough night of sleep can tank your "score" with no context for why. You have all the context. That's worth more than its algorithm.

Sleep tracking has gaps. Sleep is generally the least reliable metric your watch produces. It's inferring stages from movement and heart rate, not actually monitoring your sleep directly. My husband sleeps with his watch on, and it doesn't always catch when he's up in the middle of the night with our baby because there's not enough movement to register as "awake." If you're using your watch to gauge recovery, treat it as an estimate, not a full picture of your night.

Heart rate is a big one. Wrist-based heart rate monitors can be off by 10 to 15+ beats per minute during a run, sometimes more depending on the device and how it fits. That's a big deal if you're building your training zones around that number. If zones really matter for your training, a chest strap is going to give you something far more reliable.

What it does get right: pace and distance. This is where your watch earns its keep. GPS-based pace and distance are generally pretty accurate, and useful to actually look at.

So how should you use it? As a tracker. As one more piece of helpful information. Not as the final say on how your training, your sleep, or your body is doing. Nothing on your wrist knows your body better than you do.

-Eliana