---
title: "Your heart rate is lying to you in the heat"
date: 2026-02-08
categories: ["Hydration & heat","Data & monitoring"]
url: https://www.semiprocycling.com/digest/your-heart-rate-is-lying-to-you-in-the-heat
author: Damian Ruse (SEMIPRO Cycling)
---
# Your heart rate is lying to you in the heat

![](https://www.semiprocycling.com/digest/images/3d1581ac12798002c3f1eede.webp)

Most riders assume hot, sticky weather steals their top-end. So they back off early, stare at heart rate, and then wonder why they still get dropped when the surges hit.

A new lab study tested a pretty real-world pattern: **40 minutes of steady riding**, then **5 × 6-second all-out sprints** with short recoveries. They ran it in three environments: normal, hot-dry, and hot-humid (matched for heat stress).

Here’s the twist.

**Heat pushed strain way up, but sprint output stayed the same.** Core temp rose more in the heat. Heart rate ran higher. Subjectively, it felt more expensive. Yet **peak and mean sprint power were not meaningfully different** between conditions.

So if you are doing short events, bunch rides, or anything with repeated surges, the risk is not “I won’t be able to sprint in the heat”.

The risk is **you’ll pace the lead-in badly because your heart rate looks scary**, then you arrive at the sprint already overcooked.

## The practical takeaway (use this next week)

**1) In the heat, heart rate is a cost signal, not a green light or red light.**

Expect HR to be inflated. Don’t auto-panic. Anchor decisions to **power and RPE**, then use HR to gauge how much you’re paying for the same output.

## 2) Protect the middle, not the finish.

If your sprint is usually there, your job is to stop burning matches early. In hot races, the winners are often the riders who keep the lead-in “cheap enough” to still access their top-end later.

## 3) Cooling tactics matter more than humidity stories.

Don’t get stuck debating humid vs dry. Focus on what you can control: cold fluids, shade when possible, airflow, wetting jersey, ice in bottles if you can.

## A simple coaching cue

If it’s hot and your heart rate is high earlier than usual, don’t assume you’re unfit today. Assume the **conditions are taxing**, and race with patience until the moments that matter.

## Reference

Anbalagan et al. *Medicine & Science in Sports & Exercise*. Published 1 Feb 2026

## On my mind: Older Motivation

Lately I’ve been a bit obsessed with motivation, especially for older riders.

I’ve got a video coming that shares some direct insights, but I wanted to add my own two cents.

As life goes on, motivation feels less like finding new things to chase, and more like a process of elimination. You get clearer on what you don’t want to spend your time doing. A few things become obvious. You start doing more of those.

For me, cycling always comes back to two simple truths.

First: I never regret going for a ride.

Never. Even after one of those rides where everything feels heavy and you question why you left the house. I still come home glad I went.

Second: the purest moments in my week usually happen on the bike.

Sometimes it’s that awake, almost meditative feeling on a downhill where you’re completely present. Other times it’s the opposite: pushing the intensity up until your whole world narrows and you can only repeat one line of a song in your head. No noise. No multitasking.

It’s an escape that’s hard to find in the other pockets of life these days. And it gives me a rolling kind of meditation, and a rolling kind of rumination, that nothing else I enjoy really matches.

None of that is performance-driven. Not directly.

But it’s the foundation. It’s what keeps me coming back, week after week. And from there it’s easy to add a few more hours, or get sharper, or build towards something specific, because the base is already solid.

I’m not sure what this adds to your cycling life, but here’s the small nudge: spend a minute this week thinking about what keeps you coming back. The real reason. Not the one you tell yourself, the one that actually pulls you out the door.

And if you feel like sharing, just hit reply and tell me what yours is.