Hot Tubbing: Can soaking in hot water help you run faster?

Can you improve your endurance by sitting in a hot tub instead of doing another hard workout? We dig into a study that put elite runners through five weeks of what we affectionately call “endurance hot tubbing” to see whether heat alone could trigger the same cardiovascular adaptations as altitude training. Along the way, we explore crossover study designs, multiple testing, why significant physiological changes don’t necessarily translate into better athletic performance, and how an exploratory regression analysis ended up answering the wrong scientific question. We also discover that serious hot tub research involves surprisingly little relaxation, debate whether bubbles should count as an experimental condition, and learn why distance runners pay good money to sleep in tents with some of the oxygen sucked out.

Statistical topics

• best subsets regression
• causal inference
• crossover studies
• exploratory analyses
• mediation / mechanisms
• model specification
• multiple testing
• peer review
• sample size

• (00:15) - Introduction
• (00:44) - Can Hot Tubs Replace Exercise?
• (01:27) - Crazy Runners and Crazy Training
• (05:44) - The Amazon Delivery System Metaphor
• (12:12) - From Heat Training to Hot Tubs
• (13:33) - The Study: 10 Runners in Hot Water
• (22:31) - Results and the VO2 Max Question
• (29:26) - Statistical Sleuthing: Best Subsets Regression
• (36:50) - The Peer Review Problem
• (41:39) - Rating the Claim

Methodologic Morals

• “A model can be very good at answering the wrong question.”
•  “The label ‘peer reviewed’ does not guarantee ‘carefully reviewed’.”

References

• Jenkins EJ, Killick JA, Zerilli O, et al. Long-term passive heat acclimation enhances maximal oxygen consumption via haematological and cardiac adaptation in endurance runners. J Physiol. Published online November 20, 2025. doi:10.1113/JP289874
• Stembridge M, Jenkins E. Marathon training: Why hot baths might help you run faster. The Conversation. Published March 16, 2026. doi:10.64628/AB.6vknm9esh

Kristin and Regina’s online courses: 

Demystifying Data: A Modern Approach to Statistical Understanding  

Clinical Trials: Design, Strategy, and Analysis 

Medical Statistics Certificate Program  

Writing in the Sciences 

Epidemiology and Clinical Research Graduate Certificate Program 

Programs that we teach in:

Epidemiology and Clinical Research Graduate Certificate Program 

Find us on:

Kristin -  LinkedIn & Twitter/X

Regina - LinkedIn &ReginaNuzzo.com

• (00:15) - Introduction
• (00:44) - Can Hot Tubs Replace Exercise?
• (01:27) - Crazy Runners and Crazy Training
• (05:44) - The Amazon Delivery System Metaphor
• (12:12) - From Heat Training to Hot Tubs
• (13:33) - The Study: 10 Runners in Hot Water
• (22:31) - Results and the VO2 Max Question
• (29:26) - Statistical Sleuthing: Best Subsets Regression
• (36:50) - The Peer Review Problem
• (41:39) - Rating the Claim