Competitive cycling embraces biochemistry

Performance-boosting poison

Elite road cyclists are becoming chemistry experts. Lightweighting their equipment with sophisticated materials such as carbon nanofibers has helped ease these athletes over many hills. They’ve recently been leaning into manipulating their biochemistry—and not without controversy.

Professional cyclists’ latest wheeze is to dose their lungs with the odorless but poisonous gas carbon monoxide using a device known as a carbon monoxide rebreather. Its use requires the person to inhale a small, precise amount of CO. The approach lets team doctors monitor a cyclist’s level of hemoglobin, the red blood protein responsible for delivering oxygen to tissue. CO binds to hemoglobin more effectively than oxygen and thus prevents oxygen from reaching tissues, muscles, or organs.

The idea is that this test will indicate how prepared a cyclist is for long and high-altitude races like the Giro d’Italia—events that require participants to summit mountains above 2,000 m, where each breath brings in fewer oxygen molecules because of lower atmospheric pressure. Two of the leading professional cycling teams, UAE Team Emirates and Visma–Lease a Bike, say they have used carbon monoxide rebreathers.

But the method is open to abuse. Repeatedly sucking in higher levels of CO in a training session doesn’t just provide test results but acclimates the body to using less oxygen, which can artificially enhance a cyclist’s performance. “Regularly inhaling low doses of carbon monoxide . . . leads to a significant increase in the performance,” two-time Tour de France winner Jonas Vingegaard told the French newspaper Le Monde in January.

There’s also a health risk. Repeated inhalation of CO “can result in acute and chronic health problems, for example headaches, lethargy, nausea, dizziness, and confusion,” the worldwide cycling body Union Cycliste Internationale (UCI) said in a press release in February. “Such symptoms can worsen at any time and develop into problems with heart rhythm, seizures, paralysis, and loss of consciousness.”

Vingegaard said the practice should be banned by the World Anti-Doping Agency (WADA).

On Feb. 10, the UCI introduced a ban on CO training regimens but not on CO rebreathing for testing purposes. WADA has yet to ban CO rebreathing to enhance performance in any sport.

Cycling’s lactic acid myth

On July 5, elite cyclists from around the globe will begin one of the world’s most grueling sporting events: the Tour de France. This year’s race will be over 3,320 km and feature 51.5 km of vertical gain; it ends July 27 and includes 2 rest days. The elite teams have dedicated scientists, doctors, and nutritionists. The sport even has its own annual scientific symposium, the Science & Cycling Conference.

A key conundrum for this growing peloton of scientists is how they can help their riders avoid debilitating muscle fatigue caused by the by-products of glycolysis, the process by which carbohydrates stored in the body as glycogen are metabolized into sugars for muscles. It is a myth that two of these by-products of glycolysis—lactic acid and its ionized form, lactate—cause this problem.

Aware of some of but obviously not all the science around lactic acid, cycling fans have begun painting the chemical structure of lactic acid on roads when races are on. But it turns out that muscle fatigue is caused by another glycolysis by-product—hydrogen ions. To be accurate, fans should be daubing the roads with “H+.”

Oxidizing lactate consumes hydrogen ions. This process requires strongly functioning mitochondria, the chemical powerhouses of cells. Their performance can be enhanced through rider-specific training, food, and hydration.

A rider’s ability to clear lactate is an indicator of how they can manage glycolysis by-products. Reigning Tour de France champion Tadej Pogačar appears to excel in this area. Iñigo San Millán, director of performance for Pogačar’s team, UAE Team Emirates, and assistant professor of medicine at the University of Colorado, told the cycling blog Rouleur that while it might take some riders 20 min for their lactate levels to return to normal, “with Tadej it might take 2 or 3 min.” This may be why Pogačar is able to repeatedly and rapidly leave many of his rivals in his dust.

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