HoldsUp

Martin Gibala

McMaster University

Martin Gibala is a muscle physiologist and professor of kinesiology at McMaster University. His research focuses on the physiological impacts of high-intensity interval training, sprint interval training, and brief intermittent physical activity referred to as exercise snacks. His published work investigates cardiorespiratory fitness, exercise training frequency, myofibrillar protein synthesis, and glycemic management in populations with obesity and type 2 diabetes.

77 claims checked on air: 2 context 2 contradicted 3 overstated 62 supported 8 unverified

What they said on air - contradicted

9 citing their own research

1:09:29contradictedhighDr. Martin Gibala: The Science of Vigorous Exercise — From V

Lactate released by active skeletal muscle during exercise is taken up and used as a fuel substrate by other organs, including the heart, liver, and brain.

"and certainly during more intensive exercise where we produce lactate inside the muscles, it can be released from active skeletal muscle, it can circulate to other places like the heart, like the liver, like the brain. But certainly the heart—the heart can be a big consumer of lactate, so it takes up that lactate, can convert it back to glucose and then utilize it during exercise." (said at 1:09:29)

The speaker's statement bundles two claims: (1) lactate released by active skeletal muscle during exercise is shuttled to other organs—including the heart, brain, and liver—as an energy and gluconeogenic substrate, which is well-established and supported by human tracer studies; and (2) the heart converts lactate back to glucose before utilizing it. The second assertion is biologically incorrect and contradicted by established human cardiac biochemistry. The myocardium does not perform gluconeogenesis (which takes place primarily in the liver and kidney cortex via the Cori cycle); instead, the heart directly converts lactate into pyruvate via lactate dehydrogenase (LDH) and oxidizes it via the mitochondrial Krebs cycle and respiratory chain for immediate ATP generation.

1:22:40contradictedhighDr. Martin Gibala: The Science of Vigorous Exercise — From V

Lactic acid rapidly dissociates into lactate and hydrogen ions at physiological pH, and the resulting proton accumulation alters pH, interfering with muscle contractile processes and enzymatic function.

"lactic acid is produced at physiological pH, it rapidly dissociates into the lactate ion and the proton, the hydrogen ion. And it's the changes in pH associated with the changes in protons that we know can interfere with contractile processes and enzymes and things like that." (said at 1:22:40)

The speaker's statement reflects a classic physiological misconception that has been biochemically and experimentally refuted. In human intermediary metabolism, glycolysis does not produce undissociated lactic acid that subsequently dissociates into lactate and a proton; rather, lactate dehydrogenase converts pyruvate, NADH, and a proton (H+) into lactate and NAD+, actually consuming a proton and retarding acidosis. The accumulation of protons (acidosis) during high-intensity exercise is primarily driven by non-mitochondrial ATP hydrolysis (ATP breakdown to ADP, Pi, and H+). Furthermore, muscle physiology research demonstrates that at physiological mammalian temperatures, intracellular acidosis per se has little direct inhibitory effect on muscle contractile function, with inorganic phosphate accumulation playing the primary role in contractile fatigue.

Fact-checked episodes

Publications