ANALYSIS | Why is Jonas Vingegaard focussed on heat training to beat Tadej Pogacar?

As the Tour de France approaches, every detail in a contender’s preparation is scrutinised. So when a fan, Josep Termens, spotted Jonas Vingegaard training in 30-degree heat, fully kitted out in long sleeves and tights, it sparked curiosity. “It was 30 degrees, and he was wearing long sleeves and tights,” Termens noted.

To the casual observer, it might have seemed odd, even uncomfortable. But for those following the evolving science of endurance training, Vingegaard’s choice fits a growing trend among elite cyclists: heat adaptation training.

The idea is simple but the physiology is very complex. Training in hot conditions, especially while deliberately over dressed, forces the body to respond to thermal stress. This leads to a cascade of adaptations that are highly valuable not just for racing in heat, but also for enhancing overall endurance performance, even in cooler weather.

So, let’s find out why Vingegaard is dressed for winter in June!

When an athlete trains in heat, their core body temperature rises more quickly and remains elevated for longer. To cope, the body initiates several changes:

Plasma volume expansion: One of the first and most important responses is an increase in plasma volume, the liquid part of blood. More plasma means more blood volume, which improves cardiovascular stability, enhances oxygen delivery, and aids thermoregulation. This is particularly useful during long climbs or sustained efforts. E.g. Col de la Loze!

Improved sweat response: Training in heat also increases the sweat rate and improves the body’s ability to begin sweating earlier. This helps regulate core temperature more efficiently during competition.

Reduced HR: As the body adapts, athletes often see a reduction in heart rate at a given power output or pace, due to more efficient cooling and improved cardiac function. It’s the same reason altitude training is valued too.

Increased Mitochondrial Efficiency: Some studies suggest that heat stress may enhance mitochondrial function, increasing the muscles’ ability to produce energy aerobically. In a Grand Tour, that can translate into better sustained efforts deep into stages or over consecutive days.

It would be easy to assume that Vingegaard is simply preparing for hot conditions in France. After all, recent editions of the Tour have included searing stages in southern France, the Pyrenees, and the Alps, often surpassing 35 degrees Celsius. But what makes heat training particularly attractive is that the benefits extend well beyond acclimatisation.

Even if race day temperatures are moderate, the circulatory and muscular improvements from heat stress persist. Unlike altitude training, which requires long adaptation blocks and can negatively impact high intensity power in the short term, heat training delivers measurable gains in aerobic efficiency without major trade-offs.

And who, in previous edition has (allegedly) struggled in the heat?

Tadej Pogacar.

Yes, last year he won at a canter, but that wasn’t the case in 2023. In particular on the Col de la Loze, a mix of altitude, heat, and fatigue saw Vingegaard spectacularly crack Tadej Pogacar.

Moreover, heat adaptation can be achieved relatively quickly, some athletes notice changes within five to ten sessions of training in heat or using over dressing strategies. For someone like Vingegaard, who is still building form, the technique offers a low risk way to maximise physiological return in a compressed timeline, with now just two weeks until the Tour begins.

Of course, this isn’t without drawbacks. Training in high temperatures or while over dressed places a significant strain on the body, increasing the risk of dehydration, electrolyte imbalance, and even heat illness if not carefully monitored. It also reduces the absolute intensity an athlete can sustain during the session, meaning heat blocks are often used for endurance rides rather than intervals.

All in all, it is incredibly uncomfortable.

But Vingegaard, riding with the support of Team Visma | Lease a Bike’s performance staff, is unlikely to be mismanaging the process. If anything, the choice to wear tights and long sleeves in the midday sun is a clear signal that his preparation is back on track and focused on physiological efficiency rather than optics.