2 April 2026 · Aira Cheah

Many fitness tracking apps colour a run by heart-rate zone as if the runner were in a cool hall. On a Penang morning the same easy loop can sit a zone higher simply because the air is wet and the night was short. Coaches who treat that colour as disobedience end up arguing with athletes who did exactly what was asked.

We ask for two extras when a club wants a review of heart-rate traces. First, a note of start time. Dawn loops and 7 p.m. loops are different days in this climate. Second, whether the strap or the wrist reading is the source. Wrist readings after a humid climb up Penang Hill wander; we would rather read fewer sessions with a chest strap than a colourful month of guesswork.

The written reading then talks about effort in the language the club already uses — conversational pace, the hill repeat, the last kilometre home — and only then mentions the zone the app painted. If the paint and the conversation disagree, we do not automatically trust the paint.

This is not a campaign against heart-rate. It is a reminder that a tracking app stores a number that was true for a sensor, in a body, in a particular morning. The analytics worth keeping are the ones a coach can still recognise when they stand at the meeting point and look at faces.