You can check the activity here: https://www.strava.com/activities/14968168468

sweat testing for endurance athletes

As a biking enthusiast and fitness aficionado, I am always trying to learn more to fine-tune training, nutrition, and hydration.

Knowing how much you sweat and how much sodium I lose can dramatically impact my performance: think fewer cramps, longer rides, and faster recovery.

As someone who suffers from hard cramping, I want to learn as much as possible to improve my physical capabilities.

Recently, I ran a sweat test using two methods: a basic manual weigh-in and the Gatorade Gx Sweat Patch. Here’s how I did it and what I learned.

What Is a Sweat Test?

Sweat tests estimate:

  • Sweat rate: how much fluid you lose per hour
  • Sodium concentration: how salty your sweat is

With this info, I can now personalize my hydration, avoid under- or over-drinking, and replace electrolytes more effectively.

While lab tests exist, options like the Gx Patch and scale-based methods make this insight accessible.

My Approach

I conducted the test during a 45-minute indoor bike ride at 19°C (66°F) using two methods:

  1. Manual Method

    • Pre-ride weight: 71.6 kg; post-ride: unchanged.
    • Drank 750 ml of water during the ride.
    • No weight change = estimated 750 ml sweat loss.

  2. Gatorade Gx Sweat Patch

    • Recorded 26 oz (∼770 ml) of sweat loss—a near match.
    • Sodium concentration: 14–27 mg/oz → low sodium loss.

Results Table

Metric Value Interpretation
Duration 45 minutes Moderate indoor session
Sweat loss 770 ml (26 oz) Confirmed by both methods
Fluid intake 750 ml On point with sweat loss
Sweat rate 975–1,094 ml/hr High → requires regular intake
Sodium concentration 14–27 mg/oz Low → minimal electrolyte replacement for short rides
Sodium loss per hour 462–999 mg/hr Moderate → consider 400–600 mg/h for long/hot conditions

Key Takeaways

Given my high sweat rate, hydration during extended or hot rides is critical. But with low sodium concentration, high-sodium drinks are unnecessary unless conditions are extreme.

For longer races or hot weather, I’ll aim for:

  • 750–1,000 ml of fluid/hour
  • 400–600 mg of sodium/hour

In shorter or cooler sessions, water or lightly salted drinks suffice.

Final Thoughts

This test boosted my confidence in my current hydration habits and refined my strategy for longer races. The Gx Patch was easy to use and aligned closely with the manual method, offering reliable and actionable data.

If you’re serious about endurance sports, consider doing a sweat test—even a simple one. It might be the missing link to better performance and faster recovery.

I’m Xavier, helping people learn what matters—faster. Reach me here: xaviermorera.com/contact