Tadej Pogacar’s stage 15 victory at the 2024 Giro d’Italia will go down in folklore. The 25-year-old Slovenian sat three minutes behind stage leader Nairo Quintana with 14km to go. With the Colombian off the GC radar, it wasn’t a problem. Let him go Tadej, let him go. You’re already three minutes-plus ahead on overall. In a stage that features more than 5,400m of climbing and finishes with slopes tipping over 20%, just conserve your energy, let Quintana go and enjoy his moment in the clouds…
Of course, that’s not in Pogacar’s DNA. While some riders live to train, Pogacar’s a rider who loves to race. And race he did as he reeled in Quintana in the final 2km to win the stage by 29 seconds and extend his lead over second-placed Geraint Thomas to 6:41mins. It was a masterclass of endurance, power and tactical nous. And after speaking to his former coach Inigo San Millan, who now heads up Athletic Bilbao FC’s performance department, it highlighted the Slovenian’s astonishing ability to utilise a substrate that’s enjoying a PR overhaul…
Lactate, the demon?
No matter your level of fitness, whether you’re a cyclist, triathlete or runner, you have at least thing in common with the phenomenon that is Tadej Pogacar: you produce lactate. “Which is why even Poggy slows down at some point,” you ponder. “Lactate really is the devil’s child.”
Yes, lactate, the cause of the burn, the cause of you racing on a Sunday and walking around like your legs are in splints on Tuesday. Lactate really is the anarchic bad-boy/girl of exercise physiology. Hmmm, maybe not. “Not at all,” says San Millan. “In fact, lactate and how you use it can really benefit your performance.”
San Millan is one of the world’s leading authorities on lactate. Not only did he spend years pricking Pogacar’s earlobes and fingertips, the assistant professor’s also part of a team exploring the link between metabolism and cancer at the University of Colorado. We’ll come back to that later but, for now, let’s focus on lactate and exercise, why it’s been demonised for years and its modern-day makeover…
Alongside English physiologist A.V. Hill German physician Otto Meyerhof won the 1922 Nobel Prize in Physiology for his discovery of the ‘relationship between the consumption of oxygen and the metabolism of lactic acid in the muscle’. During one of Meyerhof’s experiments, he sliced a frog in half and dropped its legs in a jar. A clean slice, ensuring circulation and oxygen supply had been well and truly cut. He then sent shockwaves through the poor frog’s legs to make the muscles and contract, and discovered they were bathed in lactic acid.
It led to the idea that a lack of oxygen reaching working muscles results in the build-up of lactic acid, which results in fatigue and slowing you down. It’s a theory that ultimately proved physiologically right and wrong.
Where lactate comes from
Your two major fuel sources are fat and carbohydrate. As many of you will know, it’s fat that predominantly fuels long, low-intensity efforts, switching to carbohydrates for harder efforts. And it’s these harder efforts where lactate pops its head above the pyruvate parapet. Let San Millan explain…
If you’re attacking a climb, competing in a time trial or simply racing to the next lamppost, you rely heavily on glycolytic metabolism, meaning you burn through a lot of glucose. To do this, it’s first converted into pyruvate.
Pyruvate then follows one of two pathways. If oxygen’s present, it’s converted into energy within your muscles’ powerhouses, the mitochondria; if oxygen’s not present in sufficient quantities, like when you’re working really hard, your body creates energy via glycolysis, which takes place within a liquid in your body’s cells called ‘cytosol’. The by-product is the substrate ‘lactate’.
You’re always generating a certain amount of lactate, levels rising like Pog up an Alpine col when intensity is high and the fast-twitch muscle fibres are working overtime. Oh lactate, you diminisher of power.
Well, no; in fact, a good percentage of ‘exercise-used’ glucose actually stems from lactate recycling in a process that’s the reverse of glycolysis, whereby you turn lactate into glucose, and is called ‘gluconeogenesis’.
“This takes place in the mitochondria of slow-twitch muscle fibres,” says San Millan, “and is why mitochondrial function and efficiency are so important for elite athletes. Well, they are what makes them elite athletes.”
Polarised-training proponent
This clearing out lactate for an energy hit derives from the ‘lactate shuttle’, a term coined by a former work colleague of San Millan’s, Professor George Brooks, who discovered that the fitter you are, the more lactate you can ‘shuttle’ back into the mitochondria to use as fuel. He also showed that the lactate levels rise in the fast-twitch fibres but are repackaged for energy in the slow-twitch muscle fibres.
This shifting from fast to slow-twitch is why San Millan’s a proponent of polarised training, whereby you spend much of your riding, running and swimming time training at a low intensity with harder efforts minimal but very hard.
“Zone two work delivers improvements in fat oxidation, which denotes an improvement in mitochondrial function. Zone two is great for both performance and metabolic health,” he says. “However, a modicum of high-intensity work is also important to improve glycolytic capacity in order to improve metabolic performance.”
A high glycolytic capacity is an important attribute of an endurance athlete as it’s the maximum rate at which cells can burn glucose for fuel, so also includes turning lactate back into glucose for more fuel. It’s this, say San Millan, that makes Pogacar one of the greatest cyclists who’s ever lived.
“We had Pogacar and 20 other riders at UAE Team Emirates undertake a 15-minute warm-up at relatively low intensity of two watts per kilogramme (w/kg) of bodyweight. Intensity cranked up by 0.5w/kg every 10 minutes,” he says. “Power output, heart rate and lactate [via blood extraction] were measured throughout the test, including at the end when the riders were exhausted.
“We discovered that lactate-clearance capacity of the stronger riders was incredible. It’s been shown that world-class athletes produce more lactate because they have a higher glycolytic capacity and can also clear it more proficiently. Well, Tadej has one of the greatest glycolytic capacities I’ve ever seen. His recovery capacity was much higher with his lactate returning to normal after only around two minutes while some might take 20 minutes.”
Mitochondria monster
Critical to Pogacar’s ability to recycle lactate for energy is down to the proficiency of his mitochondria which, say San Millan, is a fat, as well as lactate, incinerator. The Basque physiologist revealed that while some riders might be burning 80% carbohydrates and 20% fat at a given intensity of training, the Slovenian’s the opposite. That’s crucial in endurance sport because it means sparing precious glycogen stores for harder parts of the race like a mountain-top finish.
San Millan’s lactate work is a part of a ‘metabolomic’ platform he’s developed where with just a few drops of blood he can analyse between 1,000 and 2,000 parameters of the body. “We can understand how the body functions at a level that we’ve never seen before. Mitochondrial function, cell oxidation, glycolysis, anaerobic capacity, catabolic capacity… We can identify differences between cyclists and see what makes a truly elite athlete.” With this information, San Millan’s created metabolic maps for riders where you can be extremely precise with training by zones.
It's fascinating stuff. But lifesaving? Possibly as his broader clinical and research work in cellular metabolism is attracting widespread interest. While Pogacar and his team possess peloton-leading mitochondria, at least 50% of the United States don’t. And that’s something San-Millan’s looking to rectify.
“It’s a fact that cardiometabolic disease doesn’t exist in the elite-endurance population. That’s despite the weight-loss industry claiming it’s all down to too much sugar. Well, professional riders consume tons of the stuff through energy gels and drinks and they’re fine.
“Cardiometabolic diseases, like cardiovascular diseases, type-2 diabetes and even Alzheimer’s, which will soon be called type-3 diabetes, shows one thing in common: mitochondria dysfunction. They can’t burn glucose efficiently, meaning glucose builds up, giving rise to insulin resistance and eventually type-2 diabetes. The same things happen with fat. You can’t burn it properly, it builds up, leads to inflammatory responses and ultimately cardiovascular disease, weight gain… Mitochondria dysfunction is a big problem.”
Why elites have such impressive mitochondria is down to 30,000km of cycling each year, as cycling not only leads to huge wattages, lean muscle mass and an impressive vascular network, but it also provides the stimulus mitochondria needs to grow and function properly. Without exercise, mitochondria atrophy.
“We know from research that if well-trained athletes stop and become sedentary for two months, their mitochondria drops by 40%. Imagine if you haven’t exercised for 20 years? Throw in over-feeding and your mitochondria is overloaded.”
Exercise and beating cancer
San Millan’s not prescribing a professional cycling career for all; instead, he’s espousing exercise – even if just walking – for a healthier life and not just listening to those who bang the drum for cutting carbohydrates. A happy mitochondria is a happy you.
He’s also continuing his research into cancer and lactate, which stems from his work with athletes. “We can see with riders like Tadej how efficiently they clear out lactate,” he says. “We know that cancer burns through glucose, creating huge amounts of lactate. But unlike when exercising, that lactate isn’t cleared. This is deleterious for the cell and it’s a key player in the cancer process in what’s called ‘carcinogenesis’.”
San Millan and colleagues are looking to reprogramme a cancer victim’s metabolism by, among many options, blocking the enzyme that produces lactate. With his team, San Millán has also developed a first prototype of a nano-particle that can detect cancer. It’s about a thousand times smaller than the diameter of a hair and, in theory, once that nano-particle detects a cancer cell, it can be loaded with medication to kill it. Avoiding killing healthy cells is a challenge, but the research continues.
San Millan’s a fascinating man and it’ll be interesting to see where metabolomics and its impact on cancer research heads. The Basque feels there’s greater opportunities here than genetics. “Which is potentially wonderful and life-extending news,” you ponder once more, “but let’s return to lactate and exercise. Even Poggy’s riding sees the physiological brakes applied at times. Surely lactate is the demon then?”
Well, yes and no. You see, power drops and pain strikes when lactate levels rise, it’s true, but it’s not actually the lactate that’s causing the problem but the hydrogen ions that are produced alongside lactate. Vis-à-vis, hydrogen ions raise muscle and blood acidity that impair performance, which might be down to blocking nerve signals from the brain to the muscle fibres or a psychological element or a combination of the two. Either way, write down ‘lactate is the nectar of life 1,000 times’.
Allez, allez (via pain-free pedalling).
