Your easy runs are too hard: heart rate for runners over 40

Here is the pattern I see most in runners over 40. Every run sits at the same effort: not easy, not hard, just work. Nothing is easy enough to recover from. Nothing is hard enough to force adaptation. Weeks of training, no change.

The fix is blunt: put a ceiling on your easy runs and stay under it.

Where the ceiling comes from

I use 180 minus age, adjusted for training history, as a conservative first estimate. It is not a lab-measured threshold and I never pretend it is. Then I correct it from your actual running: breathing, heart-rate drift, pace at the same heart rate, terrain, heat, and how repeatable the effort turns out to be. If you can speak full sentences and your heart rate holds steady deep into a long run, the cap is close to right.

Why a cap beats pace targets

• Heat, hills, fatigue and poor sleep all raise the cost of a pace. Heart rate sees that; a pace target doesn't.
• It removes negotiation. The watch says 128, you slow down. No debate with yourself at mile four.
• It makes drift visible. If the same easy pace costs more heart rate week after week, something needs attention: fuelling, sleep, or too much load.

The part nobody likes

The first weeks under a cap feel insulting. You will walk hills. Runners you used to drop will drop you. Hold the line anyway, because the adaptation you are buying, a bigger engine at low cost, is the one that carries you through hour six of an ultra.

Most world-class endurance athletes do the large majority of their running at low intensity. They are not being cautious. They are being precise about what each run is for.

What I watch

With my athletes I go through the watch data every week:

• Time spent above the prescribed easy range.
• Heart-rate drift across each run.
• Pace at the same heart rate, week on week.
• What the heat and the terrain were doing that day.
• Whether the athlete keeps absorbing the work, or starts carrying it.

Crossing the cap by a beat doesn't mean the run changed category. It means back it off. This isn't about punishing anyone. The discipline of the easy days is what makes the hard days possible, and I'd rather adjust the cap than watch you argue with it.

Evidence level: low-intensity-dominant training is well supported in elite observation; the 180-minus-age formula is a heuristic with wide individual error, which is why it gets corrected against field data.