Your smartwatch is collecting data you've never looked at. Here's what it means, and what to do with it.

The average person wearing a smartwatch looks at their step count and their heart rate during workouts. That's it. The same device is simultaneously tracking sleep stages, heart rate variability, blood oxygen, skin temperature trends, and resting heart rate — none of which most people ever open.

This guide covers the metrics that actually matter and, more importantly, what to do with them.

The metrics worth your attention

Resting heart rate (RHR)

Your resting heart rate is one of the most reliable indicators of cardiovascular fitness over time. A lower RHR generally means a stronger, more efficient heart. More importantly: watch the trend. If your RHR rises by 5+ beats per minute over a week, something is off — you might be getting ill, underrecovering from training, or under significant stress. Your body knows before you do. The watch catches it.

Most people's RHR sits between 60–80bpm. Athletes often see 40–55bpm. Don't compare yourself to population averages — compare yourself to your own baseline.

Heart rate variability (HRV)

HRV measures the variation in time between your heartbeats. Counter-intuitively, higher variability is better — it means your nervous system is flexible and responsive rather than in a state of chronic stress.

HRV is the metric most sensitive to lifestyle factors: sleep quality, alcohol, stress, training load, nutrition. A sudden drop in your HRV score is one of the most reliable signals that your body is not ready to train hard. Most serious athletes use HRV to guide their training intensity day-to-day rather than following a fixed programme regardless of readiness.

"The best training plan is the one that responds to how your body is actually doing — not how you planned for it to be doing."

Sleep stages

Deep sleep and REM sleep are the two stages where the majority of physical recovery and memory consolidation happen respectively. Your watch estimates these using heart rate and movement data — it's not perfect, but the trends are meaningful.

What to look for: are you consistently getting at least 1.5–2 hours of combined deep + REM sleep? If not, that's the problem to solve before optimising anything else. No training programme, nutrition plan, or supplement stack compensates for chronically poor sleep quality.

Training load and recovery

Garmin's Body Battery, Whoop's Recovery Score, and Apple's Fitness+ Trends are all different implementations of the same concept: a composite score that estimates how ready your body is to perform. These are imperfect — they can't account for everything — but they're genuinely useful as a gut-check.

The athletes who overtrain most often are the ones who schedule hard sessions regardless of what their body is telling them. If your recovery score is consistently low, you're either not sleeping enough, training too hard, or not eating enough. Usually all three.

A simple weekly check-in routine

You don't need to spend hours analysing data. Five minutes on Monday morning tells you everything you need to know for the week:

  1. Check your 7-day RHR trend. Up, down, or flat? Up by more than 3–4bpm warrants caution.
  2. Check your average HRV. How does this week compare to your 30-day average? Significantly lower means your system is under load.
  3. Look at your sleep quality. Were you getting enough deep and REM sleep? If not, why — late nights, alcohol, stress?
  4. Note your current recovery score. High = you can train hard this week. Low = prioritise quality over intensity.

The most common mistake: Treating a low recovery score as something to push through. Your watch isn't telling you that you're unfit. It's telling you that your body is busy doing something — recovering from illness, adapting to training, handling stress. Respecting that signal is how you make consistent progress without breakdown.

Getting more from your specific device

Apple Watch: The Health app's Summary view gives you trends. Enable notifications for irregular rhythm detection. Use the Mindfulness app's Reflect feature — it's underrated for stress management.

Garmin: Dig into the Garmin Connect app's Performance Stats section. Training Readiness is the single most useful metric in the ecosystem. Enable Morning Report for a daily digest before you get out of bed.

Whoop: The Journal feature is the most powerful thing Whoop does — tag your behaviours (alcohol, late eating, stress) and Whoop will show you correlations with your recovery over time. This is genuinely hard to get elsewhere.

The bottom line

Your wearable is only useful if you do something with what it tells you. That doesn't mean obsessing over every data point — it means checking in regularly and making small adjustments: go to bed 30 minutes earlier, reduce training intensity when your body signals it needs recovery, notice what's consistently tanking your HRV and address it.

The technology exists to make you healthier. Most people are just too busy looking at their step count to notice.