Fitbit Air: DesignAs someone who’s worn a Whoop for years, I’ve never really liked the design. The wearable itself is, of course, excellent, but the whole system around it has always felt unnecessarily complicated and overly fiddly. Whenever I want to swap bands, I have to unclip and rethread the sensor and the way you charge the Whoop is just as head-scratching, requiring you to slide a battery pack onto the device while still wearing it. Totally clunky – it always takes me a minute for me to get it on.So I was absolutely thrilled when I unboxed the Fitbit Air and saw how ruddy simple it was. It’s so easy to wear and looks so minimal on your wrist. The tracker itself is just a tiny pebble that slots into the included Velcro fabric band. You tighten it on your wrist and pull the strap over the top to secure it in place. You don’t need to wrestle with an annoying metal clasp, like you do with the Whoop.And it’s tiny. The Fitbit Air is just 17mm wide and 8.3mm thick, making it one of the smallest fitness trackers I’ve worn. Over the past couple of weeks, I’ve actually forgotten I was wearing it. The ultra-lightweight design makes it especially ideal for sleep tracking. For context, the Whoop 5.0 is roughly 7mm wider and 2.3mm thicker. The performance band itself is soft and comfortable and never irritated my skin. Because the tracker sits so flush against your skin, it almost disappears. You can get the performance loop band in one of four different colours – obsidian, fog, lavender and berry, and Google also sells separate active bands in silicone for sweatier, swim-ready workouts. There are also more fashion-focused leather bands as well. There’s even a Stephen Curry special edition band that comes in orange. The Whoop is a lot chunkier and bulkier than the Fitbit Air (Alex Lee/The Independent )I think Whoop still has the edge in terms of sheer customisation, with everything from leather and knit bands to bicep straps and Whoop Body clothing, so you’ve got more ways to wear the tracker, but that’ll surely improve as the Fitbit Air ages. Fitbit Air: Setup Setting up the Fitbit Air is a doddle, and it’s actually quite unlike anything I’ve tested before. After popping the tiny pebble-shaped tracker into the band and putting it on charge, you just pair it with the Google Health app and you’re essentially good to go. Being screen-free, you don’t have to configure any apps or watchfaces.But the reason why it’s so unique is because of the revamped Google Health app, which turns the usual setup process into a chat. Instead of manually entering lots of information, Google wants you to have a conversation with its new AI coach to build out your profile.I was first asked about my goals and what I wanted to achieve. I told it I wanted to reduce my body fat percentage and lower my stress levels. The coach immediately linked the two together and initially suggested increasing my daily step count and adding more intentional walks as a low-stress way to improve both. But interestingly, once I mentioned I regularly attend CrossFit sessions, it became even more personal. Instead, it said I could ditch the walking and work on training consistency, recovery and workout intensity instead.I've never experienced such a personalised setup (Alex Lee/The Independent )From there, it started asking follow-up questions. How often do I train? What does my weekly CrossFit schedule look like? Do I have any limitations? Would I rather have it automatically build a plan for me, or work through one together?Because CrossFit can be demanding, it recommended creating the plan collaboratively. It then proposed tracking four CrossFit sessions per week and monitoring my recovery and heart rate zones during workouts to make sure I was recovering properly between sessions.What was fascinating, however, was that it even adapted to things I told it. When I mentioned I was heading to Japan for a work trip so that training wouldn’t be possible this week, the coach suggested pivoting away from CrossFit goals to a more travel-friendly step target, just for this one week. And so I did. It really does feel more like talking to someone than doing the boring task of setting up a new fitness tracker.It isn’t perfect, however. Like a lot of AI, it struggled with dates and timelines. After adjusting my plan around the Japan trip, it still got confused about what day I was leaving, how long the trip was and how long I’d be away for. It’s a classic generative AI issue that still seems to plague the tech, and occasionally made setup frustrating as I had to tell it that, no, today was not Friday, and the week-long trip did not end in two days’ time. In fact, it occasionally still thinks I’m in Japan, just because it gets confused with timescales. Fitbit Air: Features and performance The Fitbit Air tracks all the basics you’d expect, including 24/7 heart rate, sleep stages, resting heart rate, blood oxygen, heart rate variability, respiratory rate and skin temperature and irregular rhythm notifications for atrial fibrillation.It also tracks workouts, steps and has a new weekly cardio load target metric, which is effectively its answer to Whoop’s strain. It measures how much cardiovascular stress exercise places on your body.You also get a daily readiness score, which looks at your heart rate variability, sleep and resting heart rate, so you know how ready you are to work out. One feature I really like is the smart alarm clock – it can wake you up at the optimal time before your chosen wake time, by gently vibrating against your wrist. It’ll snooze automatically if you don’t firmly double tap the top of the Air. That said, as a fairly deep sleeper, I wouldn’t always rely on it, I sometimes still managed to sleep through the haptics. You can also check battery life by double tapping the device. The alarm is a neat feature that Whoop doesn’t have. Most of this works without a subscription to Google Health Premium, which costs £7.99 per month after the included free trial. While the tracker works without it, many of the AI insights, contextual recommendations and coaching tools I’m talking about here are locked behind the subscription. You don’t need it to use the Fitbit Air (a benefit over the Whoop), but you’ll definitely get the most out of the device if you do take out a subscription.Daily readiness can take a week to calibrate (Alex Lee/The Independent )It’s also worth noting that, much like Whoop, some of the advanced insights take time to calibrate. It took about a week before my daily readiness score became available, with Google Health gradually learning my sleep, recovery and activity patterns to build a baseline. The coaching also became noticeably more personalised. Early recommendations focused a lot on steps and movement, but as it learnt my CrossFit schedule, travel plans and recovery patterns, the guidance became much more tailored.Sleep tracking was excellent, particularly while travelling around Japan and battling severe jetlag. It didn’t merely track my sleep stages, but also gave context around it, noticing I was sleeping badly due to the change of location. One night, after getting just 2 hours and 21 minutes of sleep and going to bed at 3:12am, my sleep score crashed to 49. The following day, my readiness score fell to 25, with Google warning me that my recent sleep trend was worse than my 28-day average.What really impressed me was the detail. Rather than just telling me to sleep more, Google Health spotted that it had taken me 39 minutes to reach sound sleep and linked my suppressed REM sleep to travel stress and recovery. And because Google Health can access my location, coaching also became more specific. At the airport, it reminded me that my time in Heathrow was a nice way to get in steps. During the trip, it recognised I no longer had access to CrossFit sessions and temporarily moved me over to movement targets instead. Once I landed back in the UK (it knew I was back based on my location), it welcomed me home and pivoted back to my original training goals, with a new weekly programme inside the app. So far, the Fitbit Air has seemed just as accurate as my Whoop, with both tracking similar data and identifying the same patterns. Both trackers showed recovery tanking during travel and sleep disruption becoming immediately obvious.Read more: I’ve tested the best fitness trackers on the market – these are my favourite optionsThe Fitbit Air noticed my heart rate variability had dropped to 12ms, while resting heart rate climbed from my usual 53bpm baseline to 65bpm, which was a pretty clear sign my body wasn’t enjoying the time-zone shift. Fitness tracking is decent – after workouts, I could view my cardio load, total energy burned and estimate VO2 max, which measures aerobic fitness and endurance, basically telling you how efficiently your body uses oxygen during exercise.Missing from the Fitbit Air, however, is dedicated stress tracking, which is one of Whoop’s best features. Another area I think the Fitbit Air needs work on is its auto-workout detection. The Fitbit Air automatically detected activities such as walking and cycling during testing. It can also detect running, cycling, hiking, elliptical workouts, aerobics and general sports, but it really struggled with CrossFit, Olympic lifting and functional fitness sessions. I had to add them manually.The Whoop, however, has recognised pretty much every workout I’ve thrown at it over the years, from CrossFit WODs and Hyrox-style sessions to general strength training. It does feel more athlete-focused than the Fitbit Air. That said, the Fitbit Air still did a good job of recognising effort through Cardio Load. One particularly brutal CrossFit session contributed 52 points alone, helping push my weekly cardio load score to 88 against a target of 75.The app told me I was officially ready to get back to CrossFit after my trip abroad (Alex Lee/The Independent )In terms of other features? Inside the app, you can log nutrition and hydration, either manually, via barcode scanning, meal photos or conversational AI prompts. You can even sync the app with third-party services like MyFitnessPal if you already track your meals elsewhere.And if you’re like me and love competing with your friends as it keeps you motivated and accountable, there are some new social features as well. You can now compete with others on shared leaderboards based on steps and cardio load, giving Fitbit something akin to Apple Watch’s competitions.Those in the US can also sync their medical records with Google Health. Google says this feature will arrive in the UK in the future. One neat addition with Google Health Premium is its recommended workouts feature – based on your goals, it can recommend specific workouts. It told me to start with some stretching, including cat and cow, bird dog, followed by squats, planks, before finally moving to the active session of rowing, walking lunges and high plank. That, it said, would help get me back into a routine after my trip away.There’s also a huge library of video workouts to watch and follow – it’s very similar to Fitness+ on Apple Health. Right now, I think the Whoop still feels better for those serious about fitness. Recovery, sleep debt and strain feel like they’re tied together a bit more and it feels more granular in terms of data, especially for CrossFitters. But Google Health feels slightly smarter and more aware of everything happening in my life, with easier to follow guidance and coaching. Fitbit Air: Charging and battery life I much prefer Fitbit’s charging system compared to Whoop’s. While you can’t charge it on the move, like you can with a Whoop, I’m not someone who tended to do this anyway, and sliding the power pack on has always been a pain. You recharge the Fitbit Air using an included magnetic charger. It simply clicks onto the front side of the tracker. It’s dead easy. The Fitbit Air is tiny and charges magnetically (Alex Lee/The Independent )Because of its dinky size, you do only get a week charge out of the device – that’s obviously way more than an Apple Watch or regular smartwatch, but while wearing both the Whoop 5.0 and Fitbit Air, I’ve had to take the Air off once to charge, while my Whoop has kept going, and it still hasn’t died. What I would say though is that it does charge super-fast. It takes five minutes for a day’s use, and a full charge takes 90 minutes. The Whoop can take up to 2.5 hours to charge, which is frankly ridiculous.Key specifications Weight: 12g (with band)Size: 34.9 x 17 x 8.3mmBattery life: Up to 7 daysCharging time: 5 minutes (1 day’s use); 90 minutes (full charge)Colours: Obsidian, fog, lavender, berryHealth tracking: 24/7 heart rate, HRV, SpO2, skin temperature, resting heart rate, respiratory rate, sleep stages, readiness score, Cardio Load, VO2 max, smart wake alarm, automatic workout detection and irregular heart rhythm notifications (Afib)