Heart Rate Zones Explained: How to Train Smarter With Your Garmin Sports Watch

The most common mistake in endurance running is running easy days too hard and hard days too easy. You head out, settle into a pace that feels "comfortably brisk", and finish every run moderately tired. Weeks later, your easy pace and your race pace have drifted towards the same number.

Heart rate zones are a simple fix. Here is what each zone is for, how to set them properly on a Garmin, and how to use them on the run.

Photo: SportPlus.sg

The Five Zones at a Glance

Garmin's watches use five heart rate zones, calculated by default as percentages of your maximum heart rate. This is how the Garmin Forerunner 265 manual describes them:

Why Your Easy Runs Should Feel Easy

A 2010 review by Stephen Seiler of how top endurance athletes train found they converge on about 80% of sessions at low intensity, with about 20% dominated by high-intensity work such as intervals at around 90% of VO2 max. The review also found no convincing evidence that adding more high-intensity work gives well-trained athletes long-term gains.

The Middle Ground

Many coaches call Zone 3 the grey zone. It feels productive because you are working and sweating, but it is too hard to be truly easy and not hard enough to be a real quality session. If most of your runs land there, you can end up too tired to run your hard days properly.

Photo: SportPlus.sg

Slow down on easy days so you can go hard on hard days.

Setting Your Zones on a Garmin

Check Your Maximum Heart Rate

Garmin's default maximum heart rate is 220 minus your age. A 2001 study pooling 351 studies and 18,712 people found 208 minus 0.7 times age a better fit, and that the old formula underestimates maximum heart rate in older adults. If your maximum is set too low, every zone is too low, and an easy run can read as Zone 3.

Garmin's watches can also detect your maximum heart rate as you run, and you can enter it yourself. Garmin notes that some gyms and health centres offer a test that measures it.

Choose How Your Zones Are Calculated

• % of Maximum Heart Rate: The default. Simple, but only as good as your maximum.
• % of Heart Rate Reserve: Uses your maximum heart rate minus your resting heart rate, so a falling resting heart rate shifts your zones.
• % of Lactate Threshold Heart Rate: Anchors your zones to your threshold. Garmin's lactate threshold feature needs a chest heart rate monitor, and you can turn on Auto Detection to record it during a run.

Where Your Threshold Sits

Garmin describes lactate threshold as the intensity at which lactate starts to accumulate in the bloodstream. For experienced runners, it says, this is around 90% of maximum heart rate and between 10km and half-marathon race pace. For average runners it is often well below 90%. For zones built from your own blood, FORGED by ReFormd's Lactate Threshold Test is bookable on ATHLO+.

Using Your Zones on the Run

• Add the Heart Rate Gauge: Garmin's data fields include a colour gauge showing your current heart rate zone, so you can check your effort at a glance.
• Set a Heart Rate Alert: Garmin's range alerts notify you each time you go above or below a set range. Set one at the top of Zone 2 for easy days.
• Expect Drift in the Heat: On long runs, heart rate tends to creep up at the same pace. A 2001 review describes this cardiovascular drift as a progressive decline in stroke volume after 10 to 20 minutes of exercise, mainly due to the rising heart rate as body temperature goes up. In Singapore, slow down to stay in your zone rather than chasing pace.

Photo: SportPlus.sg

Train by Heart Rate with Garmin on ATHLO+

Browse the Garmin range on ATHLO+, including the Forerunner 265. If you want your zones measured rather than estimated, book the Lactate Threshold Test or the VO2max Test with FORGED by ReFormd.

Ready to see what training load tells you? Read Training Load and Recovery Time next.