In walks Jay Blahnik. Apple's director of fitness for health technologies is wearing black-and-blue Nike Frees, matching black athletic shorts and shirt, and a black-and-gray hoodie unzipped at the three-quarters mark. His movements are precise, and his smile sincere-looking but somewhat practiced in a way that makes you think he’s retired from the track to the studio. When we shake hands, I count to six before he lets go.

For more than 20 years, since shortly after graduating college, Blahnik has worked in the space where hardcore exercise science meets pop-fitness psychology and where product development bleeds into what most companies would call marketing. He’s published a bestselling book on flexibility, consulted with the biggest sports companies in the world, been named an international fitness instructor of the year, helped to create Nike’s social fitness platforms, and was a key voice on the Nike+ FuelBand, the last non-Apple wearable seen on the wrist of his current boss, CEO Tim Cook. So, in the summer of 2013, when Apple went on a Watch-related hiring spree, they brought on Blahnik to lead a cadre of exercise science experts in imagining what exactly an Apple fitness device should do.

Their answer: Silence the noise. “The team really focused on saying, ‘As fitness and activity and trends come and go, what would always be a good recommendation?’” Blahnik says. “It came down to sit less, move more, and get some exercise.” That formula became the foundation of Activity, the Watch’s all-day fitness tracker app.

The Watch itself has been a hit with consumers. Analysts estimate that Apple has sold more than 3 million watches, captured 75 percent of the smartwatch market share, and generated over $1 billion in revenue. By some measures, that’s better than the iPhone and iPad performed at launch. Even more impressive, 97 percent of owners are satisfied or delighted with the product, and 86 percent wear it daily. That makes it a standout in the wearables category. Wearables, ironically, are infrequently worn. More than half of consumers stop wearing their devices, with a third setting them aside within six months.

And yet the Watch has also met with a skeptical press, especially when it comes to its capabilities as a fitness device. Reviewers have called it “nowhere near a complete solution” and argued that “this isn’t a fitness tracker built for fitness fanatics.”

This despite evidence suggesting that the Watch is having a significant impact on wearers’ behavior. According to surveys by Wristly, a research group dedicated to helping wearables succeed (so, yeah, biased), 75 percent of Watch owners claim the device helps them stand more frequently, 59 percent say they’re making healthier choices, and 57 percent note that they’re exercising more often. In a review meets personal essay posted to the Loop, longtime Apple correspondent Jim Dalrymple reported that he lost 42.4 pounds since he started wearing the Watch.

As a Watch owner and dedicated athlete, I’m still undecided on its impact and potential. In the eight weeks I’ve owned it, I’ve come to love my Watch. But there are things—like tracking intervals or differentiating high-intensity exercise from things like brisk walking—that I wish it could do better. So it’s with some skepticism that I listen to Blahnik’s pitch.

OUTSIDE: Do you really think the Watch is capable of changing someone’s behavior in a lasting and positive way?

JAY BLAHNIK: I get that I’m different than many consumers—I work out everyday, I’m enamored with exercise, and I consider myself self-motivated—but there are some things that almost all the Watch users have in common. Like everyone, I’m addicted to closing the rings. [The Activity app displays your progress toward your daily exercise, move, and standing goals as a series of concentric rings.] I’ll find myself going for that extra walk around the block at 9 p.m. if a ring isn’t closed.

We’re also seeing that the Watch’s weekly summaries are really motivating. If someone’s been off the wagon for a couple weeks, Activity will suggest a lower Move goal, and they go, “Wait a minute! I don’t wanna drop it!” And they start being active again. In the fall, when third-party apps will run natively on the Watch and get access to its sensors, you’ll be able to see the weekly summary in the middle of the week. Force-touch the Move ring, and you’ll actually see a beautiful graph showing if you’re above or below your goal.

Isn’t that what other fitness trackers aim to do? What makes the Watch different?

Other activity trackers focus on just one thing: steps or calories. That offers a certain level of simplicity, which is very attractive, but it’s also misleading. Tell me that you’ve burned more calories during the day, and I’m going to immediately ask, “How and when did you burn them?” The Watch tracks three things: movement, standing time, and minutes of exercise. It’s about more than quantity. As I like to say, it gives you three ways to win. And it does so in a visual way.

What features of the Watch are you most excited about?

The first thing I'll say is that I think the greatest benefit of the Watch in the health and fitness space is that it's not just about tracking activity. For many people, community is what keeps them active. Seeing the leaderboard for Nike+ on my wrist or getting Cheers in My Ears during the middle of my run is just as important as knowing how fast and far I’ve gone. It can be as simple as being shown the right tweet at the right time of day, something that actually gets me motivated and prevents me from talking myself out of a run.

If social’s the next big thing in fitness, who’s furthest along in figuring it out for the Watch?

We’re already seeing some really interesting things in the Equinox app. Not only does it pull in all your workouts so that your trainer, if you use one, can see what you did outside of the club, but it’s also smart about reminders. If you’re a regular indoor cyclist and love the Spinning classes, the app will prompt you to register 25 hours in advance. And you’ll be able to book your favorite bike right from your wrist. That has nothing to do with tracking, but it may be that one thing that gets you to make a commitment to fitness.

Circumnavigating the Apple campus at Infinite Loop at a brisk walk with Blahnik takes 10 minutes and 16 seconds and burns 35 active calories. For many Americans, that’s a workout. But for an athlete, it’s just a walk. Say you fall into the latter group—do you need to pay attention to the Watch’s standing and movement reminders?

An increasingly robust body of evidence suggests that even athletes need to be worried about movement. A recent study in the journal Annals of Internal Medicine found that “prolonged sedentary time was independently associated with deleterious health outcomes regardless of physical activity.” That’s because, as Blahnik says, you “can’t exercise your way out of sedentariness.”

Surprisingly, very few fitness trackers were built with that understanding. Most simply prompt you to set a daily movement goal and help you hit it. And that’s great. But imagine you went for a morning run and, come lunchtime, you’ve already hit your daily movement goal. Your wearable isn’t going to remind you to keep moving while you spend the rest of the day parked at your desk. Not so with the Apple Watch. You can’t hit all your standing goals in the morning—the Watch prompts you to get up once every hour of the day (your goal: 12 hours with standing time). Even the Move goal, your daily calorie target, is difficult to hit without doing a substantial workout. The Watch forces athletes to stop obsessing over exercise as a panacea and to integrate health with fitness.

What can the recreational athlete learn from the Watch?

That you might be very, very fit, but if you’re also very sedentary, there are health risks associated with that. Not moving is dangerous. Regardless of how often you exercise, being active throughout the day in big and small ways is really important. I think this is how we need to look at things across the board. As a population, we’ll be healthier and live longer not because of any one single workout or minute of standing, but by how it all collectively adds up and interacts.

How does that compare to what elite athletes are learning?

We’re hearing from elite athletes who say, “I never really thought I needed an activity tracker, because I get up in the morning and do a three-hour bike ride or I run ten miles. But I found out that I’m sitting a lot.” They’re motivated by that. Or they’re learning that they’re actually burning more calories than they realized by moving throughout the day. It’s not just a beginner sort of story.

What about coaches?

Most coaching happens inside or in a controlled environment, and that training or competitive moment will always be super important. But there’s an opportunity to get a better sense of the athlete’s whole day. Those other 21 hours are potentially just as important as those three spent on the bike. I also think we’re going to see more and more people get comfortable tracking and thinking in terms of the three metrics in the Activity rings. That’s going to lead to more helpful coaching across a wide variety of things, not just what the workouts look like.

When people say the Apple Watch isn’t a fully baked fitness device, they typically mean one of two things: It brings nothing new to the table from a hardware perspective, or its software is lacking in functionality. Behind both of those concerns, there’s typically an undercurrent of dismissal. What does Apple know about fitness?

The answer to the hardware problem is straightforward: No, the Watch doesn’t bring anything radically new. But it does offer heart rate monitoring, the one thing almost all endurance athletes need, and it will be well positioned to talk with new devices as they’re created. So while sports like CrossFit present a problem—“With strength training, there’s no sensor that measures the load in your hand,” Blahnik notes—soon enough, an app may be able to pair with your dumbbells and clothing to determine the load you’re lifting and correct your form.

The software defense is more complicated. To deliver it, Blahnik takes me to an unassuming building five minutes away from Infinite Loop that serves as Apple’s fitness lab. Motivational photos dot the walls, high-end machines—ergs, treadmills, exercise bikes—ring the room, and a handful of Apple employees mill about exercising. Blahnik explains that 26 full-time nurses and 14 exercise physiologists have collected more than 33,000 hours of fitness data from Apple volunteers, testing them in one of three temperature-controlled exercise rooms, outside on bikes, on the floor of the main fitness facility, and in the adjoining yoga studio. He claims the company owns more metabolic carts—tools capable of determining exactly how hard an athlete is exercising—and has possibly collected more exercise data than any other university, sports lab, or research institution in the world.

The result: Apple was able to build its own fitness algorithms to power Activity, increasing the app's accuracy and intelligence. According to Blahnik, it’s smart enough to learn just how fit you are and how many calories you’re actually burning compared to somebody your same weight who isn’t in as good shape as you are. But while Activity app is intuitive, its real strengths aren’t yet user-facing. If you’re using a third-party app instead of Workout, the Watch’s homegrown fitness tracking app, exercise doesn’t count toward your daily goals in Activity. That will change in September with the release of Watch iOS 2. Activity will become the hub of all your workout data, regardless of where it originates, and power users will have access to full-functioned versions of the apps they’re already using to train on their phones—but with new twists.

What’s the next big thing for the Watch?

Native apps and experiences. Early on, we realized that we needed to have two apps: one for all-day tracking and something to measure those dedicated exercise moments. That led to Activity and Workout. The next step, and one of the things we’re most excited about going into the fall, is having native third-party apps and giving them access to the sensors. We’ll be keeping Activity as the centerpiece—workouts that happen in third-party apps will be aggregated and shown in the app—but we’re not expecting the hardcore cyclists to use our Workout app instead of Strava. If you’re really motivated by that app, the last thing we want to do is to tell you to leave. We feel strongly that if the activity rings can aggregate your day, we’re happy to have you use the apps you want to record the workouts you’re doing.

Specifically, what’s most exciting about the new native third-party apps?

There are a lot of sports and activities where the sum of the activity isn’t necessarily measuring what actually matters. Think about golf or tennis or baseball. If you can measure what’s happening at the wrist, you may get an opportunity to learn things that aren’t about calories or tracking but about form or injury prevention.

Going beyond the Watch itself, how else do you see third-party devices integrating with Activity and other apps?

We have the ability to bring in metrics from lots of different devices. We see more and more people buying scales to lose weight. But that same scale could work for a cyclist to get her ready for race day. Someone may be able to create a great app for that scale or a great app for the PowerTap on your bike. There’s a huge appetite from consumers to get more measurement from more devices.

How does Apple fit into that appetite for more data?

What I love about working with Apple is the desire to reach as many people as possible and the approach that everything we do is a platform. We did the best job we could with the Activity and Workout apps, and we’ll continue to evolve those experiences, but the Watch is a platform for third-party apps to do things we may not be able or want to execute.

On a personal note, what’s been the most surprising thing you’ve learned while working on the Watch?

That the human body is incredibly complex. There’s no sensor or product that will get every single measurement right every single time. You have to go beyond machines—you need to get people on real runs and bike rides. All that data shows just how much we still have to learn about fitness.

This interview has been condensed and edited for clarity.