Heat training has moved, in three years, from fringe interest to the dominant non-altitude method of raising hemoglobin mass at the World Tour. The 2025 Tour de France was, by most accounts, the heat-training Tour. Pogacar's coach restructured the spring around it. Vingegaard added it as the deficit-closing intervention. EF Education, as ever, ran the most exhaustive protocol of the lot. The shorthand on social media — Pogacar in full winter kit on a turbo trainer in a heated room — is the most visible artefact of the underlying shift.
The core science is no longer contested. The protocol is converging across teams. The performance effect on trained amateurs sits in the same range. The episode of the Roadman Cycling Podcast that walks through the full picture — the studies, the World Tour use cases, and the at-home version a serious amateur can actually run — is the cleanest single-session education on the topic in the cycling content space.
Listen to the full heat training episode →
This piece walks through what the research shows, what the pros are doing, and the home protocol amateurs can run from a spare room.
Where The Numbers Come From
The headline number — 20 to 30 watts of FTP gain, 3 to 4 per cent hemoglobin mass increase, 6 per cent improvement in VO2 max — comes from the 2024 work by Bent Ronnestad and the broader research stream around Carsten Lundby. Both researchers have spent the last decade quantifying the heat exposure response in trained endurance athletes.
The Ronnestad 2024 paper is the clearest demonstration of the locking-in effect. Eighteen elite cyclists completed a three-week altitude training camp. Half added three 50-minute heat sessions per week in the weeks that followed, with the protocol designed to raise core temperature to 38.5 degrees Celsius. The heat-trained group held their elevated hemoglobin mass for three and a half weeks after the altitude camp. The control group lost roughly 71 per cent of their gains over the same period.
The Santiago Lorenzo work showed a faster front-end response. After ten days of heat acclimation, trained cyclists raised VO2 max by 8 per cent and threshold power by 5 per cent. The Norwegian meta-analysis aggregating multiple heat acclimation studies showed an average 23 per cent improvement in endurance test performance and a 6 per cent lift in VO2 max.
The mechanism is well characterised. Heat exposure triggers an immediate plasma volume expansion within the first three days, which alone improves cardiovascular stability and oxygen delivery. From day four onward, the body initiates new red blood cell production — the same hemoglobin mass response targeted by altitude training and by banned substances like EPO. Across roughly two weeks, the changes stabilise. Mitochondrial efficiency improves. Fat utilisation at submaximal intensities rises, sparing glycogen. The skin blood flow response and sweat response both improve, which together drop heart rate at the same power by five to eight beats per minute.
The framing on the podcast is direct. This is the same physiological adaptation altitude training drives, available without leaving home, with a more universal response profile across riders, and with the front-end gains arriving faster.
What The Pros Are Actually Doing
Pogacar's 2025 spring was the most visible heat training programme in the sport. His new coach, Javier Sola, prioritised heat acclimation across the build phase. The visual evidence — Pogacar overdressed on a turbo in a small heated room, sweating through layers, with a core temperature sensor clipped to his heart rate strap — circulated as social media curiosity. The underlying programming was deliberate.
The UAE Emirates physiology team, led by Joran Swart, has published the closest thing to a public version of the protocol. Three heat sessions per week across six weeks raises hemoglobin mass by approximately 4 per cent, comparable to three weeks at 2,100 metres on Mount Teide. The session structure is simple — indoor trainer, small room, no fan, winter clothing, with the core temperature held at 38.5 degrees for 30 to 40 minutes.
Vingegaard's response was visible at the same time. He was photographed training in 30-degree ambient temperatures with full winter kit — the Visma-Lease A Bike physiology team running the same protocol logic against a slightly different intervention design.
EF Education runs the most expansive version. Dr. John Greenwell described in a pre-Tour interview that the team tests riders in heat chambers to baseline sweat rate, sodium loss, and core temperature. They prescribe two parallel approaches. Active heat training — the indoor turbo session in winter kit with no fan — and passive heat training — 40-degree hot baths after riding, immersed up to the neck for 20 to 45 minutes. Ben Healy's yellow jersey at the 2025 Tour, the first Irish yellow since Stephen Roche in 1987, came from inside that programme.
Below the World Tour, the diffusion is rapid. Bora-Hansgrohe coach Dan Lorang has stated that the core temperature sensor changed how the team designs pre-race warm-ups, fluid intake, and clothing choices in race conditions. Lotto Dstny, Trek-Segafredo, and Visma-Lease A Bike are all running active heat protocols. The Core company that manufactures the most popular core temperature sensor reports that 17 of the 21 stage winners at the 2025 Tour de France were sensor users.
For background on the marginal-gains era that produced this kind of protocol thinking, see the dark truth behind Team Sky's marginal gains coverage.
The Home Protocol
The serious amateur version is structurally the same as the World Tour version, scaled to a turbo trainer, a space heater, and a willingness to feel uncomfortable for two weeks.
Equipment. Indoor trainer or stationary bike, in the smallest room available. Winter kit — long-sleeve top, tights, hat, gloves, scarf if needed. A space heater to lift ambient temperature into the 25 to 30 degree Celsius range if the room does not already sit there. No fan. A core temperature sensor clipped to a heart rate strap is the high-confidence option. An in-ear thermometer used between intervals is the lower-cost alternative. A scale for pre- and post-session weight. Room-temperature water with a sodium-, potassium-, and magnesium-based electrolyte mix. A towel.
Session structure. Five to ten minutes warm-up at zone 1 in the winter kit until you start to feel warm. Twenty minutes heat ramp at zone 3 — the power is the easy bit, the layers are doing the work — until core temperature reaches 38.5 degrees Celsius. Thirty to forty minutes at whatever power holds that temperature — typically top of zone 1 to bottom of zone 2, occasionally lower as adaptation develops. Cool-down with the layers stripped off, the windows open, and cold fluids. Total session time is 60 to 90 minutes.
Frequency. Three sessions per week, with at least one easy day between heat sessions. Two to six weeks of training depending on the goal — two weeks for a focused front-end response, four to six weeks for the full hemoglobin stabilisation.
Hydration. At least one litre of room temperature electrolyte fluid per hour during the session. Cold fluids blunt the adaptive response and should be avoided in-session. Weigh yourself before and after. Replace 150 per cent of body weight lost over the next few hours. Lose more than 2 per cent of body weight in a single session and the protocol is too aggressive — pull back the duration or the intensity.
Hard stop signals. Core temperature above 39 degrees, dizziness, nausea, headache, confusion, or any sudden cessation of sweating. Stop immediately, cool down, rehydrate. Repeated heat distress is not the protocol working — it is the protocol breaking down.
For amateurs adding heat training to a structured plan, the Roadman coaching system integrates the protocol into a periodised build phase rather than as a standalone block. For the underlying intensity distribution that the heat sessions sit inside, the polarised training guide is the foundational read. For a faster answer on a specific implementation question, ask the AI coach.
Where Heat Training Fits In A Build Phase
Heat training is most useful when it has a target. For an amateur with a hot summer event — Marmotte, Etape, the Italian gran fondos, anything in the southern Mediterranean or US Southwest — three to four weeks of heat training in the run-up serves the dual purpose of raising hemoglobin mass and pre-adapting thermoregulation for race day. The combination is significantly more powerful than either intervention alone.
For amateurs without a hot event, heat training still raises hemoglobin mass and FTP, but the cost-benefit shifts. The discomfort is real. The protocol requires consistency across multiple weeks. The same calendar window could plausibly support a high-volume aerobic block, a sweet-spot block, or a polarised threshold block. The decision should sit inside a structured plan rather than as a standalone experiment.
The honest framing is that heat training works best as a layered intervention on top of a strong aerobic base, in a deliberate build phase, with a target event that justifies the discomfort. Used as a stunt — three sessions, see what happens — the gains are smaller than the underlying physiology can support and the risk-adjusted return is poor.
For amateurs running TrainingPeaks, the protocol shows up cleanly on the Performance Manager Chart as a multi-week stress block with elevated TSS during the heat sessions. The chronic training load builds. The acute training load rides above it during the block. The training stress balance signals when the next session is sustainable.
What The Roadman Audience Should Take Away
Three things from the conversation translate directly to the serious amateur.
One. The science is solid and the protocol is converging. Heat training is no longer experimental. The underlying physiology is well-characterised, the World Tour has standardised on a narrow range of protocols, and the performance effect for trained amateurs sits in the same band as the elite version. The gains are real, the methodology is reproducible, and the risk-adjusted case for inclusion in a serious build phase is strong.
Two. The protocol works at home with minimal equipment. A turbo trainer, a space heater, a winter jacket, an electrolyte mix, and either a core temperature sensor or a careful in-ear thermometer protocol is the entire kit list. The cost of entry is low. The cost of the discomfort is the actual barrier — heat training is unpleasant, and the riders who treat that discomfort as the work, rather than as a reason to skip the session, are the ones who get the adaptation.
Three. Hydration and stop signals are not optional. Heat training is the closest thing in legal endurance training to a protocol with a real injury risk. The mitigations — pre- and post-session weight, electrolyte replacement, hard temperature caps, immediate stop on distress — are part of the protocol, not optional precautions. Skipping them is how heat training goes from a powerful tool to an emergency room visit.
Listen To The Full Conversation
The full episode — including the deeper detail on the Ronnestad and Lorenzo studies, the EF passive heat protocol, and the Pogacar 2025 build sequence — is on the Roadman Cycling Podcast.
Three sessions a week. Thirty to forty minutes at 38.5 degrees. Two to six weeks of consistent work. The protocol is simple. The discomfort is real. The numbers, for once, are catching the marketing rather than chasing it.
