---
title: "When More Sweat Means Less Cooling"
date: 2025-03-22
categories: ["Hydration & heat"]
url: https://www.semiprocycling.com/digest/when-more-sweat-means-less-cooling
author: Damian Ruse (SEMIPRO Cycling)
---
# When More Sweat Means Less Cooling

![](https://www.semiprocycling.com/digest/images/e5f886e740447cbe78109a40.webp)

You’d think sweating more helps you cool down—but in high humidity, you *sweat just as much* and *cool far less*. The study found no difference in sweat rate across humidity levels, yet performance dropped by **16% in very high humidity**. Why? The sweat didn’t evaporate—it dripped off uselessly.

**Practical Recommendations for Cyclists:**

1. **Know the Danger Point:**

- *Absolute humidity over 2.5 kPa* (e.g., 33°C & 50% RH) is the tipping point. Above this, evaporative cooling drops sharply, and performance declines begin.

2. **Pace Smarter:**

- In very high humidity, power output dropped from the *start* of the time trial. Cyclists naturally paced more conservatively to limit overheating. Plan your pacing strategy based on humidity—not just temperature.

3. **Use Environmental Data, Not Just Air Temp:**

- Monitor **absolute humidity** (or dew point) using a cycling computer or app. RH is misleading.

4. **Pre-Race Strategy:**

- **Acclimate to humid heat** with 7–14 days of training in similar conditions.
- Use **pre-cooling** methods: ice vests, cold drinks, cold showers before warmups.

5. **Mid-Ride Strategy:**

- Maintain hydration, but **don’t over-drink** just to cool off. You’ll likely lose aero advantage with more bottle grabs and won’t offset the lost sweat efficiency.
- If possible, **increase airflow** with faster riding or open roads. Even 30–44 km/h airflow didn’t improve cooling if sweat efficiency is already maxed, but it helps prevent early decline if you’re under threshold.

6. **Plan Races Accordingly:**

- Adjust your *expectations and targets* for hot-humid races. A 10–20 W drop in sustainable power may be purely environmental.

**Takeaway:**

Heat isn’t the only enemy—**humidity quietly kills your cooling capacity**. And when sweat doesn’t evaporate, *your body still pays the price*. Understand your environment like you understand your power zones.

**Source:**

Bright et al. (2025), *Scandinavian Journal of Medicine & Science in Sports*

[https://doi.org/10.1111/sms.70...](https://doi.org/10.1111/sms.70041)

## On my mind: Change Your Brain Every Day

I came across *Change Your Brain Every Day* by Dr Daniel Amen, and it’s surprisingly useful for understanding and disrupting negative thought loops—especially when energy or motivation dips.

The core idea? *It’s not the thought that causes suffering, it’s the attachment to it.*

Negative thoughts trigger chemical cascades that reinforce bad moods and behaviour. He introduces ANTs (Automatic Negative Thoughts) and shows how to counter them with **accurate thinking**, not blind positivity.

Ask yourself:

1. Is it true?

2. Can I *absolutely* know it’s true?

3. How do I feel with this thought?

4. How would I feel without it?

5. Is the *opposite* even more true?

This reframing technique rewires thought patterns—simple, but potentially game-changing.

Ref: *Change Your Brain Every Day* by Daniel G. Amen, MD.

Damian.