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Humans were born to sweat – and sweating makes us stronger.
In Hotwired, bestselling co-author of Outlive and science editor Bill Gifford explores how heat can improve our performance and our health.
Combining cutting-edge science, personal discovery and practical insights, Gifford reveals how humans evolved to excel in hot conditions – and how we’ve lost touch with this ancient advantage. He plunges into the steamy world of Finnish saunas, serves as a test subject in heat labs and tackles a 100-mile bike ride under the blazing Texas sun to show how exposing ourselves to discomfort can expand our physical and mental limits. He even explores how infrared sauna therapy and cold plunging could fight depression more effectively than medication. And he examines how, in cities around the globe, social saunas are reviving communal wellness.
Whether you want to perform better, extend your lifespan or adapt to a warming planet, Gifford shows you the incredible benefits of reawakening your body’s natural adaptability to heat and cold. Hotwired is a thrilling call to reimagine heat – not as a threat, but as a tool for strength, resilience and longevity.

'This book moves beyond anecdotal claims…and provides a critical synthesis of the evidence demonstrating how hyperthermia can enhance endurance, improve metabolic health and generate the protective physiological changes necessary for extending healthspan.'
— Peter Attia, #1 New York Times bestselling author of Outlive

© Bill Gifford 2026 (P) Penguin Audio 2026