What is Heat Training? And why is it making runners faster? - The Welsh Runner

Aug 13, 2025

Intro

This is a quick summary of What is Heat Training? And why is it making runners faster? from The Welsh Runner. It’s a great watch — we’re breaking it down so you can try the workout today. Be sure to watch the full video for all the details.

Key Points

Heat training (heat acclimation) is deliberately raising your core temperature during or after exercise, using either active heat (running in hot conditions, extra layers) or passive heat (sauna, hot bath).
Benefits include earlier sweating, higher plasma volume (4‑18% increase), lower heart‑rate at a given effort, improved cardiac output, and a 1‑4% increase in hemoglobin mass after 3‑5 weeks (boosting VO₂max).
It improves performance in both hot (+4‑8%) and cool (+2‑5%) conditions and builds mental toughness.
Practical tips: stay hydrated before, during, and after sessions; replace electrolytes; expect heart‑rate drift—use HR, not pace, to gauge effort; avoid immediate cold‑water cool‑down (use a natural cool‑down instead); monitor iron status if you aim for hemoglobin gains.

Workout Example

Adaptation Block (2‑week intensive, 10‑14 sessions)

Active heat on bike: 5‑10 min at high wattage to raise core temperature, then drop to Zone 2 and hold for the remainder of the session.
Post‑run sauna: after an easy run or treadmill session, immediately enter the sauna for 10‑20 min (core already elevated). Optional hot‑bath if sauna isn’t available.
Easy‑day layers: wear extra layers on easy runs to increase core temperature.
Recovery: finish with a natural cool‑down (no cold plunge) to retain the heat stress.
Frequency: 2‑3 sessions per week after the initial 2‑week block, then 2‑3 per week for maintenance.

Closing Note

Give heat training a try and tailor the durations and intensities to match your own paces using the Pacing app. You’ll likely feel stronger, cooler, and faster—so go ahead, heat up your training and watch the gains roll in! 🚀