When the Apple Watch was first released, no one really knew what it was. Was it a computer for your wrist? A fashion piece? A fitness tracker? Or something else? To be fair, the smartwatch market was—and still is—in its infancy, so it’s understandable that there would be some growing pains. But in the time since they first announced the Watch, Apple has been forced to refine their approach and decide what exactly the device is for and who it should be marketed to. One of those key demographics: athletes.

I wouldn’t consider myself athletic by any means. I played football for one season in junior high school and absolutely hated it; that was the extent of my sports career. But after I graduated from college, I took up running as a way of staying active and quickly found that I love it. The feeling of the wind against me, the soreness in my muscles after a good workout, and the sense of achievement I gain from constantly pushing myself to improve are just a few of the things I enjoy most about running. Not to mention that I simply look and feel better when I’m saying active.

When I first bought my Apple Watch, I didn’t take its fitness tracking features too seriously. Sure, it was cool that I could get a snapshot of my heart rate and an estimate of the number of calories I burned each run, but it seemed more like a gimmick than anything else. But as the Watch became more and more a part of my everyday life and I heard message after message from Apple about what a great fitness tracker the device was supposed to be, I started to pay more attention, and I wasn’t entirely impressed with what I found. Comparing the data provided by my Watch with other sources (especially workout machines and my own experience while running) led to me to a startling conclusion: Even though I’m not a particularly good runner, I’m pushing the Apple Watch to (and sometimes even past) its limit when it comes to fitness tracking.

I’ve found the Watch to be limited in its fitness tracking capabilities in two key areas: distance and heart rate. The first is more forgivable. I tend to run on a treadmill rather than on the street, which means the Watch has to depend on its accelerometer rather than GPS to measure how far I run. Basically, the Watch acts as a pedometer, estimating my distance by the back-and-forth movements made by my arms as I run. Maybe the Watch just doesn’t like my stride or pace, but it consistently measures my running distance well below the measurement I get from the treadmill, which I assume to be more accurate. This is frustrating because I use the Health app to keep a record of my exercise, and this limitation leaves me with underestimated statistics.

But even more frustrating is the heart rate problem. Independent research has concluded that the Apple Watch has the most accurate heart rate monitor of all wearable technologies on the consumer market, and the sensor has proven able to detect health issues in people wearing the Watch long before other symptoms arise. At least on paper, the heart rate monitor in the Apple Watch seems pretty incredible.

Why is it, then, that every time I go for a run, the heart monitor freaks out intermittently and simply stops working? I keep the Watch attached tightly to my wrist throughout my exercise routine, sometimes even adjusting it to fit more snugly if it starts to slip due to sweat. And yet, it seems that every time I work out, the heart rate indicator on the little screen goes dark for at least a few minutes, and I have no idea how this is affecting the results that the Watch reports at the end of each run.

I can’t be sure, but it is my suspicion that the Watch's heart rate monitor can only measure up to a certain level before it gets overwhelmed and starts losing count. It seems that if I go past 170 BPM (heartbeats per minute), the Watch just sort of gives up and stops counting until the rate comes back down. This seems like a pretty low bar, considering the fact that athletes can push themselves well past 170 BPM during training, so if Apple is serious about making the Watch the go-to wearable for athletes, they should probably upgrade the heart sensor's capabilities.

Apple seems to be aware of these issues and is working to rectify them. At this year’s Worldwide Developer Conference, CEO Tim Cook announced a new set of software tools called GymKit that will allow workout machine makers to make their machines sync with Apple Watches via near-field communications to ensure that each device is measuring and sharing the data it is best suited for. But it is unclear if these features will be available on existing machines or will roll out slowly as gyms buy new models. I’m keeping my fingers crossed. GymKit is certainly a step in the right direction, and it indicates Apple’s commitment to making the Watch the perfect wearable for athletes, but it remains to be seen if these changes will be enough.

I don’t mean to be hyper-critical. The Apple Watch is a great device, and it is certainly the best wearable on the market right now. For most people and most use cases, its activity tracking capabilities are more than adequate. But Apple wants the Watch to be for athletes, and they are the power users of wearable technology, the ones who push their devices to the limit. The Watch is going to have to step it up in order to keep up with runners like me.