Smartwatches have transformed fitness tracking. Heart rate, steps, sleep, energy expenditure, activity. For everyday health and cardiovascular exercise, that is incredibly useful.
Resistance training presents a different measurement problem, because many of the variables that define a lifting session aren’t happening on your wrist. They’re happening between you and the equipment.
A wrist sensor sees movement. It doesn’t directly measure the weight.
A smartwatch uses sensors such as accelerometers and gyroscopes to detect movement. That’s powerful.
But imagine a bench press. Your wrist moves. Your arm moves. The bar moves. Your muscles produce force. And the plates are carrying a specific amount of weight.
A sensor on your wrist can observe the movement of the watch. It does not directly measure the 185 lb on the bar. Those are two different measurement problems.
A wearable can infer what you’re doing from movement. But inferring resistance is different from measuring resistance.
Wearables can count reps, but performance varies
This is important: smartwatches aren’t incapable of tracking strength training. Research shows that wearable sensors can recognize exercises and count repetitions, particularly under controlled conditions.
In a 2021 study examining an Apple Watch during barbell back squats, bench presses, and deadlifts, the correct exercise was identified in 88.4% of performed sets.
But the results varied by exercise. Repetition counting performed well for squats and deadlifts, while bench-press repetition counting performed poorly. Attempts to predict one-repetition maximum were successful in only 8.9% of attempts.
That’s a useful distinction. The question isn’t whether a wearable can count reps. It’s how reliably it can measure the specific exercise, movement, and performance variable you actually care about.
The weight room is full of edge cases
Resistance training isn’t one repetitive movement. It’s thousands of variations.
Barbell curl, cable curl, preacher curl, hammer curl
Machine row, cable row, single-arm row
Partial reps, paused reps, slow eccentrics
Supersets, drop sets, warm-up sets
The same wrist movement can appear in very different exercises. And research on wearable exercise recognition shows that similarity between exercises can reduce classification accuracy.
That’s one reason measuring resistance training from a wrist-mounted sensor can become difficult as the workout gets more complex.
Heart rate is useful. It’s just not the whole workout.
This doesn’t make heart-rate tracking useless. Quite the opposite.
Research comparing wrist wearables with chest-strap references during resistance exercise shows that devices can provide useful heart-rate measurements, although accuracy and agreement vary by exercise and intensity.
But heart rate still can’t answer some of the fundamental questions of strength training:
Did you lift 70 or 80 lb?
Did you complete 8 or 12 reps?
Did you perform three sets or four?
Did your performance improve over the last month?
Those questions require different measurements.
The missing layer is the interaction with the equipment
A smartwatch sits on you. But resistance training happens between you and the equipment. The machine has a resistance. The bar has a load. The cable has a stack. The exercise has repetitions and sets.
That’s why purpose-built resistance-training technology can approach the problem differently. Rather than trying to infer every training variable from wrist movement, the measurement can happen closer to the actual source of the exercise.
The future isn’t replacing your smartwatch
We don’t think resistance-training technology needs to replace the devices you already use.
Your smartwatch can track broader health and recovery. Your phone can manage your workouts, history, and programming. A dedicated resistance-training tracker can focus on the thing those devices aren’t primarily built to measure: what actually happens when you lift.
Because your workout isn’t just 47 minutes of activity. It’s a bench press at 185 lb, for 8 reps, across 3 sets.
And the really useful question comes next: how does that compare with last month?
That’s the difference between tracking exercise and tracking training.
