What If ‘No Pain, No Gain’ Is Damaging Your Health? Ray Peat on CO₂, Inflammation, and Rethinking Fitness

As Friedrich Miescher, a 19th-century physiologist, once stated, “Over the oxygen supply of the body carbon dioxide spreads its protecting wings.” This article delves into Peat’s critique of conventional fitness practices and explores how his focus on oxidative metabolism and CO₂ preservation could transform our approach to exercise.

Oxidative Metabolism vs. Anaerobic Stress

At the heart of Peat’s fitness philosophy is a distinction between oxidative and anaerobic metabolism. Oxidative metabolism utilizes oxygen to produce energy efficiently, with minimal byproducts such as lactic acid. In contrast, anaerobic metabolism — triggered by intense, breathless exercise — relies on glycolysis, which produces energy quickly but leads to an accumulation of lactic acid and other stress mediators.

“Anaerobic exercise (getting out of breath) increases the release of, or activity of, a large variety of inflammatory mediators, beginning with lactic acid and interleukin-6 releases from the exercised muscle itself, and including factors released from various cells in the blood, and hormones including estrogen, prolactin, and sometimes TSH.” — Ray Peat

Peat warns that these stress responses disrupt the body’s metabolic balance. Elevated levels of lactic acid impair mitochondrial function, while inflammatory mediators and stress hormones like cortisol can lead to systemic inflammation, suppressed thyroid function, and long-term fatigue. By prioritizing oxidative metabolism, Peat advocates for an energy system that minimizes stress and preserves mitochondrial health.

The Role of CO₂ in Oxygen Utilization

Often dismissed as a mere byproduct of respiration, carbon dioxide plays a critical role in oxygen delivery and cellular health. Through the Bohr effect, CO₂ enhances oxygen release from hemoglobin, ensuring that tissues receive the oxygen necessary for efficient energy production. Peat underscores the importance of maintaining high CO₂ levels to optimize cellular respiration and metabolic function.

“The presence of carbon dioxide is an indicator of proper mitochondrial respiratory functioning.” — Ray Peat

Breathless, high-intensity exercise rapidly depletes CO₂ levels, impairing the body’s ability to oxygenate tissues effectively. As CO₂ levels drop, the body shifts into an anaerobic state, further exacerbating lactic acid buildup and inflammation. Instead, Peat emphasizes exercises that sustain CO₂ levels, such as walking, swimming, and other low-intensity activities.

Miescher’s statement — “Over the oxygen supply of the body carbon dioxide spreads its protecting wings” — aptly describes CO₂’s protective role in supporting cellular respiration and minimizing metabolic stress.

Inflammation and Hormonal Responses to Exercise

One of Peat’s most striking observations is the link between high-intensity exercise and chronic inflammation. While exercise is often promoted as a panacea for health, Peat highlights the physiological toll it can take on the body. Even elite athletes, often regarded as paragons of health, face elevated risks of inflammation and related conditions.

“Elite athletes are generally considered to have ‘good genes,’ and exercise is commonly said to promote good health, so a new orientation is needed to accommodate the fact that ‘elite’ athletes, winter or summer athletes, including participants in the Olympics, have a high incidence of asthma — roughly three times higher than the general population.” — Ray Peat

Research confirms that intense exercise induces inflammatory markers in both athletes and the general population. Anaerobic workouts increase levels of interleukin-6, estrogen, and prolactin, all of which contribute to systemic inflammation. Additionally, the rapid production of lactic acid during these workouts exacerbates the inflammatory response, leading to symptoms like fatigue, muscle soreness, and even exercise-induced asthma.

“It turns out that exercise induces the signs and symptoms of asthma, not only in ‘asthmatics,’ but in normal people too.” — Ray Peat

By shifting the focus away from intense, breathless workouts, Peat advocates for gentler exercise routines that reduce inflammation and hormonal imbalances.

Concentric Exercise: A Metabolism-Friendly Approach

Peat also emphasizes the importance of the type of exercise we choose. Concentric movements, which involve muscle contraction with load and relaxation without load, align with Peat’s metabolic principles. These exercises support circulation, preserve mitochondrial function, and avoid the stress-induced oxygen deprivation that comes with eccentric movements.

“The kind of exercise that allows regular relaxation of muscles, like walking, supports circulation and metabolism while avoiding stress-induced oxygen deprivation.” — Ray Peat

Examples of concentric exercises include cycling, swimming, and controlled strength training. These activities encourage oxidative metabolism, help maintain CO₂ levels, and minimize lactic acid production, promoting long-term metabolic health.

Rethinking Fitness: From Stress to Sustainability

Ray Peat’s insights challenge the deeply ingrained mantra “no pain, no gain,” urging us to reconsider the physiological and metabolic consequences of intense exercise. Breathless workouts may offer short-term gains, but they often come at the expense of long-term health. By depleting CO₂, triggering inflammation, and disrupting hormonal balance, these workouts erode the body’s foundational systems.

Instead, Peat advocates for a smarter, more sustainable approach to fitness — one that prioritizes oxidative metabolism, preserves CO₂ levels, and reduces systemic stress. By incorporating gentler forms of exercise such as walking, swimming, and concentric strength training, individuals can build strength and vitality without compromising their metabolic health.

“Modern exercise often emphasizes strain and stress rather than supporting the energy systems that truly sustain life and vitality.” — Ray Peat

Rather than subscribing to the “no pain, no gain” mentality, Peat encourages us to rethink exercise as a practice that nurtures rather than depletes the body. Sustainable movement, focused on maintaining CO₂ levels and optimizing oxidative metabolism, offers a path to long-term health, resilience, and energy.

As Peat has emphasized, “The presence of carbon dioxide is an indicator of proper mitochondrial respiratory functioning.” It’s time to align our fitness philosophies with the needs of our bodies and embrace approaches that promote overall well-being. In doing so, we can redefine what it means to be truly fit.

References

1. Miescher, F. (1885). Observations on the physiological role of carbon dioxide in oxygen delivery.
2. Functional Performance Systems. (2012). Carbon dioxide basics. Functional Performance Systems Blog. Retrieved from https://www.functionalps.com/blog/2012/11/07/carbon-dioxide-basics/
3. Dr. Mark Sircus. (2023). Life depends on carbon dioxide. Dr. Sircus Natural Allopathic Medicine. Retrieved from https://drsircus.com/carbon-dioxide/life-depends-on-carbon-dioxide/
4. Functional Performance Systems. (2012). Exercise-induced stress. Retrieved from https://www.functionalps.com/blog/2012/03/01/exercise-induced-stress/
5. Petersen, A. M., & Pedersen, B. K. (2005). The anti-inflammatory effect of exercise. Journal of Applied Physiology, 98(4), 1154–1162.