On Christmas I love to cook a prime rib. That requires about 4 hours of time to kill and during that time I like to scroll through various Facebook groups looking for interesting content to write on and potentially do an episode of Power Athlete Radio. And there are lots of “bro science” and misconceptions get tossed around in fitness, performance and Jiujitsu circles. I stumbled upon on this one today and realized there is no greater a misconception than lactic acid.

So, let’s clear this up going into 2025 and hopefully put this to rest because lactic acid isn’t actually a real thing when it comes to exercise physiology. It has more in common with the Yeti than it does with performance. The body produces lactate, not lactic acid, and it’s not what’s causing the issues everything from burning in our muscles to an upset stomach.

When you are training hard, your muscles are working overtime to produce energy or ATP. To fuel this effort, your body relies on carbohydrates (CHO) to produce ATP, the molecule that powers muscle contractions. This process, called glycolysis, creates a byproduct called pyruvate. Pyruvate then takes one of two paths:

  1. If oxygen is available, it enters the Krebs cycle to generate more ATP.
  2. If oxygen is limited, like during intense effort, it’s converted to lactate.

Lactate isn’t your enemy—in fact, it’s a valuable fuel source. During exercise, your body transports lactate to the liver, where it’s converted back into carbohydrates and reused for energy. If it’s not immediately needed, lactate is carried through the bloodstream and broken down elsewhere. So, the burning sensation you feel in your muscles isn’t caused by lactate or the mythical “lactic acid.” While lactate levels do rise during intense training, they aren’t responsible for the burning in your muscles or the sick feeling in your gut.

What’s even more fascinating is how lactate affects the brain. Once it crosses the blood-brain barrier, lactate acts as a signaling molecule that enhances cognitive function. It promotes the production of brain-derived neurotrophic factor (BDNF), a protein critical for learning, memory, and synaptic plasticity. This makes lactate a powerful player in supporting overall brain health. Beyond its cognitive benefits, lactate also has neuroprotective properties. It helps shield neurons from damage and stimulates neurogenesis, the creation of new neurons, further emphasizing its role as a key contributor to brain function and resilience.

If you want to read more about the effects of lactate on the brain check out – The Potential Mechanism of Lactate in Mediating Exercise-enhanced cognitive function: a dual role as an energy supply substrate and a signaling molecule

Why You Feel Sick During Hard Training

When you’re pushing yourself hard, like during multiple live rounds of Jiujitsu, on intervals on the Echo bike, or during your favorite Johnnie WOD workout, your muscles demand oxygen. To keep up, your heart works overtime, pumping blood to deliver more oxygen to those working muscles. As part of this process, your body prioritizes blood flow to active muscles and redirects it away from less essential areas, like your stomach. This is a function of the fight-or-flight response, where the central nervous system narrows blood vessels through a process called vasoconstriction.

The reduced blood flow to your digestive system is why you feel nauseous and want to puke after a few intense rounds. It’s not because of “lactic acid in your stomach” – that’s just a myth that a basic physiology class can debunk.

What’s the Solution?

Conditioning needs work. Being out of shape for the intensity of the training, particularly when it comes to aerobic capacity, is the likely culprit. To improve, I’d recommend focusing on Zone 2 and Zone 4 conditioning outside of jiu-jitsu and away from the mat.

Zone 2 training (low-intensity, steady-state work) helps build your aerobic base, which improves your body’s ability to deliver oxygen and recover between rounds. Zone 4 training (high-intensity intervals) conditions your ability to sustain bursts of effort and recover quickly. Together, these approaches will help you perform better on the mat and reduce the chances of feeling sick after hard rolls.

For tracking our conditioning, I use Joel Jamieson’s Morpheus system with my pro jiu-jitsu guys. We test lactate levels during Zone 4 and 5 sessions to optimize their training. Over time, this type of targeted conditioning will dramatically improve your ability to handle high-intensity efforts without feeling like your guts are about to revolt.

Time to Bury Lactic Acid

Just so we are clear, lactate isn’t causing your discomfort. It’s actually a helpful fuel source that your body is using to keep you going. The real issue is likely a combination of poor oxygen delivery to your gut and a need for better conditioning. Dial in your training with Zone 2 and Zone 4 work, and you’ll see a big improvement in how you feel during and after hard rolls.

Merry Christmas, thanks for coming to my TED Talk and my prime rib recipe is a few articles back.