You know the ride. A gran fondo or a long summer sportive that you'd have eaten alive in your thirties, and somewhere around the third hour the wheels come off — not your legs, exactly, but your whole system. Heart rate drifting up for no extra power, head going fuzzy, the strange feeling of being cooked from the inside. You finish it, but you survive it rather than ride it.
And the honest question afterwards is: why did that hurt so much more than it used to?
The easy answer is "I'm older and less fit." But that's not really it. A well-trained masters rider can be every bit as fit as their younger self and still cook on a hot day, because the thing that's changed isn't the engine — it's the cooling system. Your body's ability to shed heat blunts with age in three specific ways, and most riders have never had it explained to them. When I dug into the thermoregulation research and the work of people like Professor Stephen Cheung, who's spent a career studying how cyclists handle heat, the picture got a lot clearer — and a lot more fixable.
The cooling system has three parts, and all three fade
Your body has a few tools for getting rid of the heat you generate when you ride. The two big ones are sweating — evaporating fluid off your skin pulls heat away — and skin blood flow, where your body sends warm blood out to the surface to dump heat into the air. Behind both sits thirst, the signal that tells you to put the fluid back. After 40, all three of these quietly degrade.
Sweat response drops and starts later. Your sweat glands produce less sweat per gland with age, and crucially, sweating kicks in at a higher core temperature than it used to. So you've already heated up more before your main cooling system even switches on, and when it does, it's working with reduced output. The same effort in the same conditions leaves a 55-year-old running a higher core temperature than the 35-year-old next to them.
Skin blood flow declines. Getting heat from your core to your skin depends on the blood vessels near the surface opening up to carry warm blood out. That dilation response weakens with age — less blood reaches the skin, so less heat gets dumped, so more of it stays trapped in the core. It's like trying to cool a hot engine with a radiator that's slowly silting up.
Thirst becomes a weaker, later signal. This is the dangerous one. Older adults reliably under-drink in the heat, not through carelessness but because the thirst mechanism itself blunts with age. By the time a masters rider actually feels thirsty, they can already be significantly dehydrated — and dehydration makes everything worse, because there's less blood volume to send to the skin and less fluid available to sweat. The cooling system needs water to work, and the signal telling you to supply it has gone quiet.
Put those three together and the gran fondo that cooked you isn't a mystery. You ran hotter for the same effort, you cooled less efficiently, and you were half a litre down before your body bothered to mention it. None of that is a fitness problem. It's a thermoregulation problem, and it responds to a different set of fixes.
The good news: heat training still works — adjusted
Here's where it turns, because the picture isn't fatalistic. Heat acclimation — deliberately exposing yourself to heat to force the adaptations — still works after 50. The body still responds. It just needs the dose and the timeline adjusted for a masters physiology.
When I had the heat-training conversation on the podcast around Remco's heat work, the mechanism that makes acclimation so valuable came through clearly: repeated heat exposure expands your plasma volume — the watery part of your blood — which gives you more fluid to both sweat with and circulate. You start sweating earlier and more, your heart rate and core temperature drop at a given effort, and the whole system gets more efficient. For a masters rider whose baseline cooling has blunted, that's not a marginal gain. It's clawing back some of exactly what age took away.
The catch is the protocol. The classic heat-acclimation block — daily heat sessions over one to two weeks — is built around younger physiology. For masters riders, the smarter approach is:
Start with a lower dose. Shorter, gentler heat exposures to begin with — think 20–30 minutes of easy riding in the warmth, or a controlled post-ride sauna, not an all-out hour in a hot room on day one.
Ramp over a longer window. Stretch the adaptation across three or four weeks instead of compressing it into one or two. The adaptations still come; they just arrive a little more slowly, and rushing them only adds heat strain on top of training load you have to recover from.
Watch your recovery like a hawk. Heat sessions are real physiological stress. Layered on top of hard training and the slower masters recovery window, they can quietly dig a hole. Treat a heat block as load that has to be accounted for, not a free add-on.
If you want the full structure, the complete heat-training guide lays out the standard protocols — just read them through the masters lens above: lower starting dose, longer ramp, more recovery. And if your acclimation is happening on the turbo over winter or in a cool climate, the indoor heat-management approach covers how to manage the trainer-room temperature so you're adapting on purpose rather than just suffering — it sits inside the wider indoor training system we've built around exactly this kind of controlled, deliberate work.
Hydration: drink to a plan, not to thirst
Because thirst has gone unreliable, the single most important change a masters rider can make is to stop trusting it as the primary signal. In the heat, you drink proactively — to a plan — and use thirst only as a backstop.
The plan starts with knowing your own numbers, because sweat rate varies enormously between riders. The simplest way to find it: weigh yourself naked before a hard hour in the heat and again straight after, accounting for anything you drank during. Every kilo lost is roughly a litre of fluid you didn't replace. Do that a couple of times in different conditions and you'll have a sweat rate you can actually plan around instead of guessing.
From there:
Set an hourly drinking target and hit it on a schedule. Sip regularly rather than waiting for the gulp of thirst that arrives too late. On a genuinely hot, hard ride that might be 750ml to a litre an hour or more for a heavy sweater — but use your own number, not a generic one.
Match your sodium to your sweat, not to a label. Dr Allen Lim — the physiologist behind Skratch Labs, who built his early hydration work fixing exactly this problem for pro teams — has made the point for years that hydration is about replacing what you actually lose, and that the heavy, salty sweaters need far more sodium than the marketing default. If you finish rides with salt crusted on your kit and your bottles taste weak, you're probably a salty sweater who needs a stronger mix. The electrolytes and sweat-rate guide walks through how to dial this in for your own physiology.
Pre-hydrate, and don't over-correct. Start hot rides topped up rather than trying to claw back a deficit mid-ride. But the goal is replacing losses, not drowning yourself — over-drinking plain water on a long, hot day dilutes your sodium and brings its own problems, which is exactly why the sodium side matters as much as the volume.
The medication blind spot
There's one more age-related factor that almost never gets mentioned in cycling heat advice, and masters riders need to know about it: medications. By 50 and beyond, a meaningful share of otherwise fit riders are on something for blood pressure, and some of the most common drugs interfere directly with how you handle heat. Diuretics — water tablets — deliberately reduce your fluid volume, which is exactly the wrong direction in the heat. Beta-blockers blunt the heart-rate and blood-flow response your body uses to shed heat and can leave you more prone to overheating. Some other antihypertensives affect skin blood flow too.
None of this means you stop taking prescribed medication or stop riding — it means you ride aware. If you're on something for blood pressure or your heart, the sensible move is a quick conversation with your doctor about exercising in heat, an extra margin of caution on the hottest days, and even more diligence about proactive hydration, because the drug may be quietly working against your cooling system on top of everything age has already done. It's not a reason to be afraid of the heat. It's a reason to plan for it with eyes open rather than wondering why you cooked on a day that didn't seem that bad.
Ride the conditions, not your memory
The last piece is tactical, and it's about respecting the body you have now rather than the one you remember. On a big effort in real heat, the smart masters move is to take the hottest part of the day out of the equation where you can — start earlier, finish before midday on the worst days, use the shade and the descents to cool. Pour water over your head and neck; evaporative cooling on the skin helps when your own sweat system is doing less of the work. And learn the early warning signs of heat strain — dizziness, chills, goosebumps, or the alarming one, suddenly stopping sweating — and treat them as a hard stop, not something to push through. At any age those are warnings; with a blunted cooling system, the margin between warning and trouble is smaller than it used to be.
This connects to everything we cover about training and recovering as a masters rider. When I had Dr Andy Galpin on the podcast talking about getting faster after 40, the through-line was that the masters athlete doesn't necessarily need less — they need their physiology accounted for rather than ignored. Heat is one of the clearest examples. The fitness is there. The cooling system just needs managing, and it absolutely can be.
You're not soft — your radiator just needs help
The story you've probably been telling yourself is that the heat used to be fine and now it isn't, and that's just what getting older feels like. Half right. The heat genuinely is harder, but not because you've gone soft — because three specific cooling mechanisms have blunted, and every one of them responds to a deliberate plan.
Acclimate with a lower dose and a longer ramp. Drink to a schedule built on your real sweat rate, not to a thirst signal you can no longer trust. Match your sodium to your losses. Take the worst of the day out of your biggest efforts. Do that and the same gran fondo that cooked you becomes one you ride rather than survive — at any age.
If you're not sure whether your bad days in the heat are a thermoregulation problem, an under-fuelling problem or a deeper recovery one, that's what the Plateau Diagnostic is for. It looks at the whole system — training, fuelling and recovery together — and shows you where the real limiter is. Three minutes, free. Because the work was never your problem. Making sure your body can do it on a hot day is the bit worth getting right.