Are Fitness Trackers & Smartwatches Really That Smart?

If you look around the gym, or even the office, it feels like everyone has a fitness tracker. Apple Watch, Fitbit, Whoop, Garmin, Oura Ring… the list is endless. In 2024, The ACSM declared it the #1 fitness trend of the year. They promise to monitor your heart rate, sleep, steps, calories burned, and more. But how trustworthy are those numbers? Can they really help someone serious about fitness or recovery, or are they just cool gadgets? Here’s what recent research tells us and how to think about using them.

 What they tend to do well:

• Heart rate monitoring during rest & moderate activity. Many devices are reasonably accurate when you're at rest or doing moderate exercise. Recent studies show error rates compared to medical/clinical gold standards, of 3–5 % in some conditions.

• Tracking steps / movement patterns. These are usually okay for getting a rough count, though the device sometimes misses steps or mis-categorizes other motions (e.g. hand movements) as steps.

• Trends over time. Even if a single reading is off, wearables tend to be more valuable in showing how things change e.g. “my resting heart rate is creeping up,” or “my average daily steps dropped last week."

• Motivation & behavior change. Multiple reviews and trials show that wearing a tracker can increase physical activity levels, just by giving feedback.

Where they struggle:

• Calories burned / energy expenditure. Estimates often deviate by 20–30% or more, especially during mixed-intensity activities.

• During very intense or irregular activity. Accuracy tends to drop during high-intensity bursts or when movement is complex and/or unsteady.

• Sleep phases, stress, variability. Devices can reasonably estimate total sleep time, but their classification of light vs deep sleep, or wake/sleep transitions, is less reliable. For stress metrics, studies have shown a very weak correlation with how people feel.

• Individual differences. Skin tone, wrist anatomy, device fit, positioning, and even motion artifacts can all affect accuracy.

• Not a medical device. Most wearables are consumer-grade. They are not a replacement for formal medical testing or professional assessments.

So: Are they useful for the “real fitness person” or for recovery?

Short answer: yes, with caution and context... For someone serious about fitness or returning from injury, wearables can be very helpful in these ways:

Tracking consistency. They help you see how much movement, heart-rate response, or effort you’re doing week to week, something that’s often forgotten.

Feedback & accountability. They can nudge you to move more, rest more, or avoid overtraining.

Monitoring changes. If your trends (resting HR, recovery heart rate, total activity) shift significantly, it may prompt you or your therapist to adjust.

Remote monitoring potential. Some clinical and research groups are using wearables to monitor patients’ cardiovascular performance or recovery between visits. But they should not be blindly trusted for every number. Use them as a guide, not gospel.

How to get the most out of a wearable:                       

Tip	Why it helps
Use the same device consistently	Switching brands or models makes trends harder to interpret
Focus on trends, not each reading	An off reading here or there is expected
Take note of conditions	(e.g. tight band, sweaty wrist, cold fingers) – these can mess up readings
Use in conjunction with subjective awareness	If your legs feel “off” or fatigued, don’t ignore that just because wearable says “normal”
Don’t overreact to calorie numbers	Use them as a rough guide, not a precise measure
Share data (if helpful) with your therapist	It can give additional context between visits
Allow for rest days and variability	The device may show dips; that may be your body telling you to recover