Whoop’s Strength Trainer Has Its Flaws, but Is Still Better Than Anything Its Competitors Have

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Two years ago, screenless fitness tracker Whoop took on a problem that none of its competitors have managed to solve: answering the question “how hard was your weightlifting workout?” Its initial implementation was clunky and finicky. I don’t think I managed to log a single workout correctly. But now, with improvements over the years, it’s become a much more useful feature. 

The game changer for me? Being able to connect exercises to a workout after you do the workout. This way you can’t mess up the tracking during the workout, but you still get the thing you actually care about—a Strain score accurate enough to power the app’s sleep and recovery recommendations. Read on for more about how to use the Strength Trainer, and what it can and (still) can’t do. 

What is Whoop’s Strength Trainer? 

Credit: Beth Skwarecki

The Strength Trainer is a way of tracking strength workouts, separate from the way you’d track any other workout with Whoop. It was introduced in 2023, and aims to give you a more appropriate Strain score (reflecting how hard the workout was on your body) compared to tracking it purely by heart rate. 

To use the Strength Trainer, you need to create (or choose) a workout in the app, telling Whoop exactly what exercises you plan to do, what weight you’re using, and how many sets and reps. You can either have the app follow along with your workout in real time, or connect a workout to an activity after the fact. 

Why Whoop’s Strength Trainer gives it a huge advantage over other wearables 

Normally, when you track a workout with Whoop, you simply start an activity, and it measures your heart rate during the activity. This makes perfect sense for cardio activities, like running. The higher your heart rate is, for longer, the higher Strain score you’ll get as a result. A high Strain activity is hard on your body, and requires more recovery. A lower Strain score is easier, maybe even restorative.

This approach never worked for strength training, though—and that’s a caveat that applies to tracking strength training with any heart-rate-enabled wearable. Your heart rate graph during a weightlifting session will show lots of resting time, and only brief spikes into higher territory. Those heart rate spikes don’t tell the full story of how hard your muscles were working to lift the weight. That’s why I keep saying to ignore heart rate during weight lifting sessions. 

Before Whoop introduced the Strength Trainer, my weightlifting sessions would always appear in the app as light workouts, equivalent to an easy run or brisk walk—even if I’d had a killer, heavy workout. But with the feature, strength workouts now show an appropriate amount of Strain. And since Strain scores power your recovery recommendations, that’s kind of important. The Strength Trainer turned Whoop from a wearable that only made sense for endurance athletes into one that makes sense for strength athletes, as well, and everybody in between. 

The best way to use Whoop’s Strength Trainer is after the fact

Adding the details of my strength workout brings it from a 9.2 strain (light) to 13.1 (the upper end of moderate—maybe not accurate, but definitely closer to reality). Credit: Beth Skwarecki

Below, I’ll explain how you’re supposed to use the Strength Trainer during workouts. But let me skip to my conclusion: Using it during a workout sucks. Using it after a workout is a stroke of genius by the Whoop team, and gives me everything I really need from this feature. 

All you do is this: 

1. Tap “start activity” and select the activity type as Weightlifting, Powerlifting, Functional Fitness, or Box Fitness. Do your strength workout. 

2. End the activity and wait for Whoop to process it. 

3. Tap the activity, ignoring its insultingly low Strain score, and tap the box that invites you to connect a strength workout to calculate muscular load. 

4. Choose or create a workout that matches what you did. 

5. Wait while Whoop re-processes the workout, and enjoy your new, higher Strain score.

I keep track of my workouts in a notebook while I do them, so it’s simple for me to fill in the details afterward. You could use an app if you prefer—Hevy is one of my favorites. And yes, you could follow along with the Whoop app, but that’s an experience so frustrating and error-prone that I can’t recommend it. Still, for the sake of being thorough, let’s dig in.

How to use Whoop’s Strength Trainer during a workout (and why I don’t)

Before you start using the Strength Trainer during a workout, you’ll need to set up a workout with the specific exercises you’d like to do. You’ll also want to fill in the reps and weights of each exercise, if possible. 

To start the workout, you go to the plus icon in the corner of the app’s home screen, and instead of selecting Start Workout, select Strength Trainer instead. Choose the workout you created, and hit Start Workout from that screen. The app will start a warmup timer, and you can begin your exercises by tapping Start First Set. 

Ironically, one of the things that makes the Whoop ideal for weightlifting—that you can wear it on a bicep band to keep your wrists free for wraps, straps, or kettlebell movements—is not kosher here. The app asks if you’ll be wearing your Whoop on your left or right wrist. Those are your only choices. (I wear it on my bicep anyway. I don’t know if this affects the results.)

To do the workout, you’ll need to tap a button in the app every time you start a set and every time you finish one. This is awkward if you don’t want to have your phone with you, and double awkward if you do want to use your phone for anything during the workout. For example, if I’m videoing a set, I need to start the set, switch apps, start my camera, do the set, stop my camera, switch apps, and stop the set in the Whoop app. Miss a step, and you screw up your workout tracking. 

During a workout, you can: 

• Add a set 

• Remove the last set of an exercise (but not a specific set in the middle)

• Reorder exercises

• Redo a set (if you started it by accident)

• Add an exercise

• Remove an exercise

• Change the weight of an exercise (including one you already did)

You cannot: 

• Log a set as having been done in the past (if you did it but forgot to hit the start button)

• Set a timer to alert you when a certain rest time has passed

Being able to edit the workout on the fly, or undo a set, are great additions that the Strength Trainer didn’t have when it first launched. But there is still no way to address the common problem (for me, anyway) of forgetting to start a set. When I’m filming sets, or using my phone for anything else during the workout—responding to a text, say—I can easily lose track of the Whoop app. I say, “that’s enough texting,” put down the phone, lift my weight, and then return to the phone and realize my mistake. Drives me nuts. 

It would help if the Strength Trainer could do a live activity on the lock screen, like it does when I go for a run. Unfortunately, live activities for strength training are only available on Android at the moment. (I use an iPhone.) 

Why the Strength Trainer still disappoints me

I still have such mixed feelings about the Strength Trainer. On the pro side: It does give me an appropriate Strain score for my weightlifting, and adding the workout after the fact is convenient and doesn’t mess up my workout. (I wish there were a push notification so I couldn’t forget, but as long as I remember, it’s all good.) No other wearable does anything like this; they all track the effects of strength training as if it were a type of cardio. 

But the follow-along version is high-maintenance, like babysitting a toddler during your workout. I’m always making mistakes that there isn’t an easy way to fix. It also doesn’t want me to use my bicep band (sorry, but I can’t use a wrist device for some of my exercises). There’s also no way to enter paused exercises (like a squat where you count to three before standing up) or complexes (like clean + front squat + jerk as one rep). 

These limitations seem to be tied to the Strength Trainer’s origins in Whoop’s 2021 acquisition of Push, a company that tracked strength exercises through a wrist-based velocity sensor. Whoop users were excited to see velocity-based training (VBT) come to Whoop, but that never happened. 

In a VBT workout, a coach (or app) gauges how fast you were moving—say, how fast you could stand up from a squat—and use that data to tell you whether or not to add weight for your next set. This way, you’d get customized coaching that responds to how you’re actually performing that day. If you’re tired and everything feels heavy, you’d move slower and the app would cue you to use less weight. If you’re feeling great and even heavy weights move fast, the app would have you push yourself a little harder. 

But Whoop never brought that promise to Whoop users. (If they have plans, they’re still under wraps.) Instead, they seem to have used some of the underlying technology to train their own algorithms to recognize exercises. If you do a squat while using the Strength Trainer, your Whoop device will, presumably, notice when your rep starts and ends, and record how fast you did the squat. 

What Whoop does with this data is unclear, though. The company’s materials, like the press release from the Strength Trainer’s launch, carefully avoid using the word “velocity” anywhere. Instead, they seem to use “intensity” as a substitute, which only leads to confusion. In traditional strength training, an intense (heavy, hard on your body) rep would show up in VBT as slow movement. But a Whoop spokesperson said on Reddit that they assume you’re working harder when you move a weight fast. 

Unfortunately, since Whoop is so squirreley in describing its algorithms, it’s really hard to know what it’s doing, or even what you’re missing (if anything) when you log a strength workout after the fact versus following along in the moment. I emailed back and forth with the Whoop team when the Strength Trainer first came out, trying to understand what calculations it was doing and why, but they kept sending me vague statements that explained nothing. 

There also haven’t been any validation studies that I can find, comparing the results of the Strength Trainer to, well, anything. Whoop now says it “estimat[es] maximum volume from your workout history,” but I don’t know if that’s a change from the initial implementation or not. They also say it “calculates your personal muscular load by taking the highest intensity of each exercise from your profile.” Does that mean the heaviest (using the traditional sense of intensity) or the fastest (using intensity as a euphemism for velocity)? Again, they don’t define their terms.

So, I’m disappointed on many levels. I’m disappointed that Whoop seemed to cannibalize a VBT company to provide something that doesn’t even do VBT. I’m disappointed that Whoop doesn’t tell you what the Strength Trainer is even doing in there. I’m disappointed that the Strength Trainer is so hard to use in its most full-featured version, and I’m disappointed that I don’t even know whether I’m missing out by using the more convenient Log Later function. 

Ironically, the part of the Strength Trainer I use most—logging later—probably never needed any heart rate or velocity tracking at all. Just enter your numbers, and let the algorithm see how much and how heavy you were lifting. Whoop didn’t need to acquire a company or build out a finicky follow-along feature for that. 

But here we are. If you find it convenient to follow workouts through the app, great. You are luckier than I. But even with the after-the-fact workout logging, Whoop has still managed to address the fact that strength training is harder on your body than a light cardio workout—something that other wearable companies have not figured out how to do.