Ray Peat on Exercise

Short answer: Ray Peat was wary of intense, exhausting exercise and positive about ordinary, coordinated activity. His test was lactic acid: work that leaves you breathless damages metabolism, and work that raises carbon dioxide supports it.

What Ray Peat wrote about exercise

He wrote that intense exercise damages cells in ways that add up. Lactic acid from glycolysis suppresses respiration, and within five minutes exercise lowers the activity of the enzymes that burn glucose. Source: Mitochondria and mortality

He drew a line between kinds of work. Concentric muscular work is described as restorative for mitochondria. Eccentric work uses less oxygen, makes less carbon dioxide and more lactic acid. Source: Mitochondria and mortality, Protective CO2 and aging

Ordinary activity of an integrated kind, he wrote, increases carbon dioxide, circulation and efficiency. The same effort can help or harm depending on how much carbon dioxide you make at rest. Source: Mitochondria and mortality

Exhaustive exercise can raise ammonia in the blood to dangerous levels. Source: Fatigue, aging, and recuperation

Strenuous exercise combined with fasting, such as running before breakfast, triggers lactate and ammonia and probably increases endotoxin absorption from the gut. Source: Lactate vs. CO2 in wounds, sickness, and aging; the other approach to cancer

He also wrote that damaged mitochondria can be replaced by healthy ones simply by doing the right kind of exercise. Source: Stem cells, cell culture, and culture: Issues in regeneration

What he suggested in practice

• Stay below the point of breathlessness.
• Prefer concentric work, the lifting phase, over eccentric loading.
• Eat first. No hard work on an empty stomach.
• Sugar and caffeine reduce fatigue by increasing the oxidation of sugar.

Where he wrote about it

This topic comes up in 41 of the articles on his site. These are the most relevant ones:

• Tryptophan, serotonin, and aging · original on raypeat.com ↗
• Mitochondria and mortality · original on raypeat.com ↗
• Adaptive substance, creative regeneration: Mainstream science, repression, and creativity · original on raypeat.com ↗
• Altitude and Mortality · original on raypeat.com ↗
• Sugar issues · original on raypeat.com ↗
• Protective CO2 and aging · original on raypeat.com ↗
• Stem cells, cell culture, and culture: Issues in regeneration · original on raypeat.com ↗
• Bleeding, clotting, cancer · original on raypeat.com ↗

My take

Long runs raise serotonin and endotoxin and break down muscle. I lift, do calisthenics and MMA, and I fuel every session with sugar before, during and after.

Quick answers

Did Ray Peat say exercise is bad?

No. He warned against intense, exhausting exercise that produces a lot of lactic acid, and wrote positively about ordinary coordinated activity and concentric muscular work.

What kind of exercise did Ray Peat recommend?

Activity that does not leave you breathless, and concentric muscular work, which he describes as restorative for mitochondria.