The WattPlan Podcast · Episode 29 · 9 min
How should you pace a hilly race?
Next episodes: How do you taper without losing fitness? · How to pace a 10 mile time trial · How did the fastest sportive riders pace the Quebrantahuesos?
Read the transcript
James. Welcome to the WattPlan Podcast. I'm James. Family man, nine to fiver, collector of the odd podium, builder of WattPlan, and far too fond of a sports science paper at midnight. This one's about the day itself. Everyone tells you to ride at an even, steady power. But on a hilly course, is that actually the fastest way round? Or should I be going harder on the climbs? Lyra, our AI research voice, has the evidence, and the studies are linked in the show notes.
Lyra. Harder on the climbs, easier on the flat and the descents. Even power is close to ideal on a flat course in still air, but once the road tilts, a watt doesn't buy the same speed everywhere. Uphill it buys a lot. On a fast descent it buys almost nothing. So the quickest way round moves your effort to where it pays.
James. Why does a watt buy more uphill? Watts are watts.
Lyra. Because of what you're fighting. On the flat at a decent speed, most of your power goes into pushing air, and air resistance rises steeply with speed, so each extra watt adds very little. On a climb you're slow, so the air hardly matters and nearly all your power goes into lifting you and the bike. There, speed rises almost in step with power, so ten percent more watts gets you up the hill close to ten percent quicker. On the flat, the same extra effort buys only a few percent.
James. And going downhill?
Lyra. The opposite. You're quick, the air dominates, and twenty extra watts on a descent barely move the needle. That's where you recover. Soft pedal, or on the steep stuff, freewheel.
James. Okay, but I've always been told even pacing is best. Was that just wrong?
Lyra. Not wrong, just about a different situation. There's a 2008 review in Sports Medicine by Abbiss and Laursen, which pulled together what was known about pacing. For very short efforts, thirty seconds or less, going all out from the gun seems best. For anything over about two minutes, spreading the effort more evenly may improve times. [2]
James. So even pacing is right after all.
Lyra. Even effort, yes. Even watts, no. On a hilly course, an even effort means spending the same budget, just more of it where the gradient makes it count. And the review was honest about long events. For anything over about four hours, it said knowledge of the best pacing was lacking, and that well trained riders tend to slow progressively once they've hit their peak speed.
James. Which sounds like every sportive I've ever done.
Lyra. It sounds like most people's. Which is why the budget matters. What you can hold for a ride depends on how long it is. For an hour it's about your FTP. For a nine hour day in the hills, about two thirds of it.
James. Two thirds? Why does it shrink that much? I'll be eating all day.
Lyra. Eating keeps you going, but it doesn't stop the slide. The power you can hold falls the longer you ride, and it falls faster for riders whose long rides fade more. So the sensible plan sets the budget for the whole ride from the start. The common mistake is to ride the first hour at a power you could only hold for an hour, then spend the rest of the day paying for it.
James. Guilty. Every single time there's a fast group in the first hour.
Lyra. You and most of the field. And a fast group on the flat is the dearest place to spend your budget, because that's exactly where each extra watt buys you the least speed. Sitting on the back of it is fine. Taking turns on the front for an hour isn't.
James. Right, so how much harder on the climbs? Give me a number I can actually ride.
Lyra. That's what WattPlan's free pacing calculator works out from a route file. It holds the whole ride to that budget, then rides the climbs harder and the flat easier, up to about 1.3 times the flat power on a steep climb, and never harder on a climb than you could hold for its length. On a long hilly day that puts the climbs at about three quarters of FTP. Not threshold all day.
James. Three quarters? That feels really easy for a climb.
Lyra. At the bottom of the first one, sure. Seven hours later it won't. The flat in that plan is lower still, which is where you're tempted to chase wheels and burn the day.
James. But surely if I push every climb, I'll be cooked by the fourth one?
Lyra. That's the right worry, and it's where W prime comes in, the fixed reserve of work you can do above your critical power. The paper behind it is Skiba and colleagues, 2012, in Medicine and Science in Sports and Exercise. With seven people riding hard intervals to exhaustion, they built a model of that reserve draining above critical power and refilling below it. The refill was quicker the further below critical power riders eased off. [1]
James. So the descents and the easy flat are where I pay the climbs back.
Lyra. Exactly. But the refill is always slower than the spend, so capping each climb isn't enough on its own. The calculator also holds the cost of the whole ride to your budget, so every extra watt on a climb is paid for by easier riding somewhere else.
James. What if you're racing something short? A hilly time trial, or a crit?
Lyra. Then the reserve is the whole game. If you race shorter events, the question is where to spend W prime, and the answer is the same physics. Climbs first, flat second, descents never. In a crit each surge is a dip in the reserve, and the further you sink below critical power between them, the faster it comes back. When it's low, sit in.
James. And for those of us who train with power but mostly ride sportives?
Lyra. Know your two numbers before the day, the climb power and the flat power for your route, and ride the flat as a ceiling, not a target. In the app, Route analysis, which is part of Premium, goes further than the free calculator. It uses your own fade from your long rides, and once it knows your critical power, it flags any stretch where your reserve is modelled to drop below about thirty percent.
James. And if you're new to this, no power meter, no idea what FTP is?
Lyra. Then do it by feel. Climbs a little harder than the flat, still able to manage short sentences. Over the top, ease off and let the descent do the work. On the flat, don't chase. The easy mistake is the opposite, hammering the flat with a group and crawling the climbs.
James. Where does all of this stop being science and start being guesswork?
Lyra. In a few places. That review said plainly that the best pacing for very long events wasn't known. The reserve model was built on seven people, and its refill rate is an average. Real riders differ, and heat, fuelling and fatigue shift it. And off-road, loose surfaces and technical sections break the physics, so treat the power targets as guidelines and keep more in reserve.
James. Okay, what am I doing before my next hilly ride?
Lyra. Take the route file for your next event or big ride and run it through the free pacing calculator on wattplan.cc, with your FTP and weight. Write down the power it gives you for the hardest climb. Then ride a hilly loop this week keeping the flat steady and below that, and letting the climbs take the extra.
James. Ceiling on the flat, a bit more on the climbs, freewheel the steep descents. I can already hear myself breaking that rule at the first café stop.
Lyra. Then remember why it works. Your watts are worth most where you're going slowest, so save them for the hills and let the downhills pay you back.
Lyra. The full article and every study we mentioned are on the WattPlan blog, linked in the show notes. And if you've enjoyed this, follow the WattPlan Podcast wherever you're listening, so you don't miss the next one.
James. And if you want a plan built around the time you've actually got, get WattPlan on the App Store or Google Play. Thanks for listening.
Voices produced with ElevenLabs. James's voice is a clone of his own, Lyra is an AI voice, and James reviews every episode.
The fastest way to ride a hilly course is not to hold steady power. This feels counterintuitive, since even effort seems like it should mean even fatigue. But the physics of cycling says otherwise. Understanding why, and how to pace optimally, can save minutes on a challenging route without any change in fitness.
Why isn't even pacing fastest on hilly courses?
On a flat time trial in still air, even pacing is close to optimal. The relationship between power and speed is roughly cubic, so doubling your speed requires eight times the power. This means any variation in effort produces a net loss, because the time you gain going faster is less than the time you lose going slower.
But add a hill and everything changes. On a climb, gravity dominates. The relationship between power and speed becomes much more linear. An extra 20 watts on a steep climb produces a meaningful speed increase. On a descent, aerodynamics dominate, and those same 20 watts produce almost nothing.
The implication is clear. Push harder on climbs, ease off on descents. The question is how much harder, and that's where the physics model comes in.
The Physics, Power Equals Gravity Plus Aero Plus Rolling
Every second on the bike, your power output is fighting three forces.
Gravitational Resistance
On a gradient, you're lifting your entire system weight against gravity.
Power(gravity) = system weight x gravity x speed x gradient
At 80kg system weight on a 6% gradient, gravity alone demands about 195W just to move at 15km/h. On a 10% gradient, that jumps to about 325W at the same speed.
Aerodynamic Drag
Air resistance increases with the cube of speed.
Power(aero) = 0.5 x air density x CdA x speed cubed
At 20km/h this is negligible. At 45km/h it's the dominant force. This is why extra power on a descent barely changes your speed. You're fighting a cubic relationship.
Rolling Resistance
This is the constant friction between tyres and road.
Power(rolling) = coefficient x system weight x gravity x speed
This is roughly proportional to speed and relatively small compared to gravity and aero. Tyre choice and inflation pressure are the main variables.
The Optimal Pacing Strategy
Given these physics, the optimal pacing strategy for a hilly course follows clear principles.
On climbs. Increase power above your average. Gravity dominates, so extra watts translate efficiently into speed. The steeper the gradient, the more you should push.
On descents. Reduce power significantly. Aerodynamics dominate, and extra watts are largely wasted against the cubic drag relationship. Soft-pedal or coast.
On flats. Hold close to your average target power. Both gravity and aero play moderate roles.
Into headwinds. Treat like a moderate climb. Push slightly harder because aero resistance is higher.
With tailwinds. Treat like a moderate descent. Ease off because you're already moving fast and aero gains diminish.
The magnitude of these variations depends on the course profile, your W' reserves, and your durability over the event duration.
W' Balance and the Skiba Model
Your Functional Threshold Power (FTP) or Critical Power (CP) represents a boundary. Below it, fatigue builds slowly enough to last far longer. Above it, you're burning matches from a finite supply.
W' (W-prime) is that finite supply, your anaerobic work capacity, measured in kilojoules. Every second you spend above CP, you're spending W'. The Skiba model (2012) describes how W' depletes and recovers in real time.
Depletion. When power exceeds CP, W' decreases proportionally to the excess power multiplied by time. Riding at CP+50W for 60 seconds costs 3kJ of W'.
Recovery. When power drops below CP, W' recovers exponentially. The recovery rate depends on how far below CP you are and your individual recovery kinetics. Recovery is fast initially, then slows.
Key insight. W' recovery is never as fast as W' depletion. Every match you burn takes longer to earn back than it took to spend. This means match management is critical on multi-climb courses.
When should you go deep and when should you hold back?
Knowing your W' balance transforms pacing decisions.
Go deeper when
- It's the last major climb. No need to save matches if there's nothing left to spend them on.
- The gradient is steep. Extra power translates efficiently into speed on steep gradients.
- There's a long recovery section after. A 10km flat or descent gives time to replenish W'.
- You're in a group. Staying with a faster group saves more energy through drafting than the W' cost of the surge.
Hold back when
- Another hard section is coming soon. Check the route profile. If there's a second climb within 5km, conserve W'.
- You've already used most of your W'. Below about 30% W' remaining, one more surge can empty it, and it only comes back as fast as you can ride below CP. Dipping further risks a complete blowup.
- The gradient is moderate. On 3-4% grades, the speed gains from going above CP are smaller than on steeper pitches.
- You're alone. Without a group to catch or hold, the optimal strategy is usually more conservative.
Practical Pacing Strategies by Course Type
Flat Time Trial
Strategy. Near-constant power with a slight negative split.
Start slightly under target for the first quarter to avoid the adrenaline trap. Build to target for the middle half. Finish a little above target in the final quarter, when you can afford to drain W'.
Hilly Gran Fondo (3-5 hours)
Strategy. Variable power, conservative W' management.
Set an average power target based on your durability-adjusted sustainable power for the event duration. Push 5-15% above target on climbs. Soft-pedal descents. For what 6,589 sportive finishers actually did, see How to Pace a Sportive. Cap the opening hour at what you can hold for the whole ride, so there is less fade to manage later.
Fuelling is critical. Set eat and drink reminders for every 20-30 minutes during easier sections. See our endurance fuelling guide for detailed strategies.
Mountainous Race (Major Climbs)
Strategy. Conservative early, decisive later.
Long mountain stages are won and lost on the final climb. The optimal strategy is to ride conservatively on early climbs (at or slightly below CP) and commit W' expenditure to the decisive sections later in the race. This requires discipline and faith in the pacing plan.
Short Punchy Course (Crits, Circuit Races)
Strategy. Surge-and-recover with W' monitoring.
Repeated short efforts above CP drain W' quickly. Track your balance mentally or on your head unit. If W' drops below 30%, sit in the group and recover. The key metric is average recovery time between surges.
Off-Road Caveats
Physics-based pacing models assume predictable traction and rolling resistance. Off-road surfaces break this assumption in several ways.
- Variable rolling resistance changes second by second on mixed surfaces
- Technical sections require speed modulation independent of power
- Tyre slip on loose surfaces means not all power reaches the ground
- Bike handling demands attention that disrupts power execution
For off-road events, use physics-based power targets as guidelines. The course structure (where the climbs are, where recovery is possible) remains valuable. But expect more variation in actual power versus target, and build in a larger W' reserve than you would for a road event.
Putting It All Together
The science of pacing comes down to three principles.
- Push where power translates to speed (steep climbs, headwinds) and ease off where it doesn't (descents, tailwinds)
- Manage your W' like a budget, spending it where it matters most and recovering it when you can
- Account for duration, because your sustainable power at hour four is lower than at hour one
WattPlan's Route plan puts the climbing and duration principles to work. Upload a GPX file and it produces a segment-by-segment power plan from the physics of the road, your durability and your W'.
Route plan is part of Premium. Build your fitness profile in WattPlan and get Route plan pacing.
Related Reading
- How Route plan builds your race plan
- How to Read Your Power Curve
- Tapering for Your Goal Event
- How Many Carbs per Hour on a Long Bike Ride
Sources
- Modeling the Expenditure and Reconstitution of Work Capacity above Critical Power, Medicine & Science in Sports & Exercise
- Describing and Understanding Pacing Strategies during Athletic Competition, Sports Medicine