Andy Galpin — Professor of kinesiology at Cal State Fullerton with a PhD in human bioenergetics. He coaches elite athletes (UFC fighters, world-champion boxers, pro athletes) and studies muscle physiology and metabolism.
The gist
Huberman and Galpin expand 'endurance' beyond long-distance cardio into multiple distinct adaptations: muscular endurance, anaerobic capacity, maximal aerobic capacity, and long-duration endurance. Galpin frames everything as two problems: producing energy and managing waste, both governed by moving carbon in and out of the body. A long metabolism walkthrough explains why you literally exhale fat as CO2, why burning fat in a workout is not the same as losing body fat, and why fasted training and 'fat-adapted' claims are widely misunderstood. The pair then lay out concrete, time-efficient protocols for each endurance type, including 'exercise snacks,' roughly five to six minutes a week of all-out intervals, and steady-state work, totaling about two hours per week.
Big reveals
- Galpin confirms you really do lose fat by exhaling more carbon than you ingest – 'carbon in, carbon out' is the true version of calories in/out.
- Claims for fat loss the macronutrient split barely matters; total carbon intake versus expenditure is what drives results.
- States training fasted is not required for fat loss or fat adaptation – it sounds logical but is a 'gross misunderstanding of metabolism.'
- Burning fat during exercise does NOT equal losing body fat; the two are routinely conflated.
- The marathon 'bonk' and collapse is liver glycogen depletion, not mental weakness – the liver will shut you down to protect the brain.
- Flatly debunks turning fat into muscle (or muscle into fat) – 'they are not the same structures.'
- Lactate is not the cause of fatigue – it is an acid buffer and a strongly preferred fuel for muscle, heart, and brain.
- Cites Gibala's research that ~6 minutes of all-out work weekly can match VO2 max gains from ~180 minutes.
Things worth remembering
- 'Exercise snacks' – a 20-second all-out stair sprint every few hours – improved VO2 max and cognition in office workers.
- Cardiac output equals heart rate times stroke volume and self-adjusts; resting heart rate drops with fitness because stroke volume rises.
- At rest the highest fat-fuel percentage is about 60-70%; you are never 100% fat-fueled, even while sleeping.
- Muscle glycogen is rarely truly depleted – most people quit around 50%, while elite skiers reach ~95% in the deltoid.
- Adding a pound of muscle likely raises basal metabolic rate only ~6-10 calories/day, far less than the old 50-calorie estimate.
- A 20-minute bout of exercise before an exam can raise test scores, partly via elevated lactate fueling cognition.
- Fuel analogy: phosphocreatine is a match (5-20 sec), carbohydrate is newspaper (minutes), fat is firewood (hours/unlimited), protein is metal (poor fuel).
- Galpin uses Brian McKenzie's breathing 'gear system' – nasal cadence to mouth-only – instead of heart-rate zones.
- Out-of-the-blue panic attacks can show up as rising blood CO2 up to 45 minutes before the event.
- A near-complete endurance program totals roughly two hours per week across all four endurance types.