The new science of climbing: Studying Sepp Kuss’ physiology at the University of Colorado

In a detailed study, we compare Sepp Kuss to two trained amateur riders, and offer tips and tricks on how you can climb better.

Photo: Casey B. Gibson

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Editor’s note: This article ran in the January/February 2018 issue of VeloNews, before Sepp Kuss went on to win the Larry H. Miller Tour of Utah, win a stage of the Vuelta a España, and serve as a super domestique to Primož Roglič at the 2020 Tour de France.

FOR MANY CYCLISTS, climbing offers the ultimate riding experience. So, while we’ve all heard of power-to-weight, why is there so little else known about what it takes to be an angel of the mountains?

VeloNews managing editor Chris Case and coach Trevor Connor set out to correct that. With the help of the University of Colorado Sports Medicine and Performance Center and first-year LottoNL-Jumbo pro Sepp Kuss, they delve into the science of climbing.

There’s a throbbing inside my skull. My arteries frenetically pound, presumably delivering oxygen to my violently contracting muscles. I’m pretty sure those muscles aren’t receiving all they really need, as they quiver and quake. I tell myself this is meant to be fun, that I’m doing this in pursuit of science. As I ride through many cyclists’ dream landscape — picturesque mountain scenery, seductive switchbacks snaking out of sight — all I actually see are the drips of sweat hitting my top tube and a patch of pavement 10 feet in front of me.

I’m not dying — not yet. I’m merely climbing as hard as I can.

I’m familiar with this feeling of torment since it’s the calling card of maximum effort. I’ve felt this anguish before on every hard uphill, fighting against gravity, when everything is spent and nothing is left behind — only the methodical, perceptible decline into agony. This day, however, there is a greater purpose than some Strava PR.

I keep repeating to my addled self that my time is going to be published for all the world to see. Must. Go. Faster. But it hurts. Oh god, does it hurt. I break the climb into smaller, more digestible chunks, attempting to trick myself into going faster, hurting less, drifting away to a more pleasant place.

Nothing works. Climbing is bloody hard.

TO MANY RIDERS, THERE’S no better character-shaping component to cycling than riding uphill. No matter if you’re heavy or light, predisposed to floating or destined to sink, you can learn more about what you’re made of — how deep you can suffer and what joy can be wrung from that suffering — from a leg-cracking climb. Maybe that’s because the rise over run of a climb is really about mind over matter — you versus physics. It can be as much about power-to-weight as it is about the power of the brain.

Yet, there are significant gaps in our understanding of the biomechanics and science that govern this important component of cycling. The physiological rules that govern climbing remain somewhat of a mystery, in part because it’s very hard to study the activity in a laboratory — stationary trainers cannot measure gravitational pull.

“It’s very hard to replicate the physiological and metabolic demands of climbing in the lab,” says Iñigo San Millán, director of the University of Colorado Sports Medicine and Performance Center.

For this story, I set out to examine the science around climbing, alongside Trevor Connor, VeloNews’s training expert. Over the course of weeks, we subjected ourselves to several scientific tests that could measure this mysterious activity. We worked with San Millán, physiologist Jared Berg, and Ryan Kohler, the performance manager at the Center. We also enlisted the help of pro rider Sepp Kuss (LottoNL-Jumbo), to help us understand how a WorldTour-level rider’s physiology compares to that of amateurs.

Trevor and I looked to answer a few key questions: Is, as conventional wisdom holds, climbing simply a matter of power-to-weight ratio? In other words, is power-to-weight a perfect predictor of your time up a climb? How much do terrain and technique come into play? And finally, do different rider types have an advantage on different types of climbs?

Some of what we found won’t surprise you — people who consider themselves climbers excel on steep, technical climbs. Those who like to time trial at a steady pace aren’t so fond of that variable terrain. What will surprise you are the ways in which different rider types go about reaching their limits.

While our experiments may not appear in The Proceedings of the National Academy of Sciences anytime soon, the concepts we applied are based firmly within the scientific method. We had three riders — two pure climbers and a time trialist — complete individual time trials on three different climbs around Boulder, Colorado. Each rider’s lactate levels were taken at the conclusion of each climb. We also captured live biomechanical information for each rider with a Leomo device, which quantifies and tracks a cyclist’s movements in real-time, including everything from pelvic angles to dead spots in their pedal stroke.

We chose climbs that offered varying levels of steepness and consistency of grade. The famous Flagstaff Mountain Road climb was chosen for its varying steepness, while the ascent of Lefthand Canyon offered a consistent and shallow grade. Finally, the super-steep first pitch of Magnolia Road had us gasping.

Sepp and I played the role of the pure climber, while Trevor was the time trialist, given his physiology and strengths. Ultimately, we all suffered in the name of science.
So, what did we find?

Power? CHECK! Weight? LOOOOW. Anything else?

We’ve all heard of power-to-weight ratios. There are even calculations that claim to predict whether you can win a climbing stage given just this one number. Pros talk about the infamous 6 watts/kg threshold needed to be a contender at a grand tour.

In many ways, this was the simplest discovery of our experiment. Basically, yes, it all comes down to power-to-weight. (See “Power-to-weight is king.”) Since power-to-weight determines performance, it appears the only way to improve performance is to improve power or lose weight.

Fine. But does your physiological threshold (think FTP) determine your power-to-weight on a climb? Based on what we found, we need to revise our answer to “not exactly.”

(For the sake of this discussion, we aren’t discussing gear or aerodynamics. We’re science geeks, but if we delved into rolling resistance, position, or standing vs. seated muscle-firing patterns, it would take a book to fully discuss.)

I’M CASUALLY CHATTING away with the physiologist, the guy who will soon prick my ear to measure my lactate levels. I know once the test really begins the pain will become relentless. I stare at the wall in front of me, covered in the jerseys of former Tour stage winners, world champions, dignitaries, and celebrities of the cycling world that have previously walked through the doors of this Performance Center. A physiological lactate threshold test is a special treat: Breathe hot, dry air as you wrestle upon your bike, wrenching every last bit of power out of yourself while a scientist pokes your ear and methodically clicks away at his computer nearby. The test begins, and I stare at the researcher in front of me. “Can’t you see that I’m dying?” I think. No response. The power output I must sustain clicks up a notch. I know where I’m headed, in watts, and I keep pedaling right for it, though I’m actually going nowhere fast.

Time machines vs. mountain goats

When it comes to improving our time up a climb, we seem to be slaves to the power we put out and how religious we are about skipping dessert. Physics appears to give us little wiggle room.

But, there is still another factor. Does the number you produce in the lab — the one you paid for with an hour of effort and a swollen ear — determine what you can average up a climb? This is where the answer seems to be a little less pre-destined. It all comes down to what type of rider you are.

In 1999, Sabino Padilla led research that helped define four distinct rider “types”: time trialist, climber, flat-lander, and all-rounder. This research was expanded by Alejandro Lucia a year later. The result is the appearance of distinct “morphotype-specialists.” Each type has a clearly defined role during the different phases of a race.

Padilla was actually attempting to answer the question of which type of rider has the advantage in a grand tour. Was winning as simple as who was lightest? The study looked at 24 of the top cyclists in the world. Complex formulas were used, but once they were added up, the outcome was heavily influenced by something called allometric scaling. This concept helps explain the differences between climbers and time trialists since it explains the scaling of things as they grow. As our bodies change in size, not everything about them scales equally. For example, if a 200- pound person was suddenly twice as tall, their weight wouldn’t just double to 400 pounds; they’d be a whopping 1,600 pounds. This is because while height only has one dimension, mass has three dimensions. So, when height doubles, mass increases by a factor of three.

So, what does allometric scaling have to do with cycling? In allometry, every one of our physiological attributes — height, surface area, VO2max, and so on — has a scaling factor relative to mass. Some scale more, some less, and some equally.

In cycling, where weight is paramount, that’s important. When you drop even five pounds, you’re scaling a whole slew of variables — not all of them for the better.

Dr. David Swain developed some of the original allometric scales for cyclists and found there were a few key components, including aerodynamics, the energy cost of climbing, and VO2max. Here’s how they approximately scale relative to mass:

– Power: scales evenly with mass* (*functional mass such as muscle, and not your spare tire — there’s no cost to losing that weight)
– Aerodynamics: scales by 0.33 with mass
– Energy cost: scales by about 0.79 with mass
– VO2max: scales by 0.75 with mass

What do those numbers mean? Power-to-weight is critical to climbing, but as long as we’re only talking muscle mass, power scales evenly with mass, giving lighter riders no real advantage. Climbers are also significantly less aerodynamic since frontal area — the key factor in aerodynamics — is two-dimensional and doesn’t scale equally. This is why climbers struggle on the flat stages of the Tour. Smaller riders also incur a greater energy cost going uphill — while power scales with body weight, bikes don’t get proportionally lighter and air resistance still affects them as they would a larger rider’s bike.

Where small climbers have an allometric advantage is in their VO2max. Much of that advantage is offset by the greater energy cost of climbing, but not all of it. The greater energy costs mean their threshold power-to-weight isn’t going to let them beat a time trialist to the top by going steady. That’s why they have to use their better VO2max to attack.

Author Chris Case suffers through a lactate threshold test at the University of Colorado Sports Medicine and Performance Center while physiologist Jared Berg takes a blood sample. Photo: Brad Kaminski |

Now, back to the research of Dr. Padilla and the distinct morphotypes of riders.

Flat-landers had the best outright power, making them a danger on the flats and in a sprint finish where absolute power is more important than power-to-weight. Relative to their weight, the light climbers had the best top-end power and VO2max. They also had a better ability to tolerate high lactate levels and generate more power anaerobically. However, they were less aerodynamic and, surprisingly, had a slightly lower power-to-weight than the time trialists at threshold. Put into race terms, the climbers had a ferocious ability to attack on a hill, but ultimately the time trialists had the capacity to ride steady and match or beat them to the top. To add to the time trialists’ advantage, they had the best absolute power and power-to-weight at threshold of all four types.

The researchers were surprised to find that the mid-weight time trialist, and not the skinny climber, had the advantage in a grand tour. San Millán, who has worked with many Tour contenders, wasn’t surprised.

“You need a balance,” he points out, noting that the winners of the Tour de France tend to be around 68 to 70 kilograms.

What does this have to do with our subjects and, more importantly, you? For our test, Trevor was the time trialist, due to his physiology and riding style. Sepp and I were the climbers since our physiology is suited more to steep, long climbs. How did it play out?

On both long climbs, Trevor was limited by his measured physiological threshold, averaging only 106 percent of that mark. With a time trialists’ consistency, he averaged exactly 319 watts on both climbs, despite the dramatic difference in terrain.

While Trevor struggled on the most variable terrain of Flagstaff, Sepp and I took advantage of our natural ability to employ big bursts of power well above threshold. Our ability to tolerate above-threshold anaerobic power allowed us to average around 120 percent of our physiological threshold — well above what most physiologists would predict.

It’s no surprise that Sepp and I performed very consistently relative to each other on all the climbs, while Trevor performed relatively better on the steadier climb of Lefthand Canyon.

Below, we take a closer look, utilizing heat maps of our efforts to help explain the trends we saw. (Click to enlarge.)

(click to enlarge)

WHAT WE’RE SAYING may not be surprising: Relatively speaking, climbers perform better on steeper and more variable terrain while time trialists prefer flatter and steadier climbs.

What’s fascinating is to go deeper into why that is. Our experiment exposed a hypothesis: Climbers may be better able to maintain homeostasis when they can vary their pace. In other words, to climb at their best, they actually need to attack.

Lucia’s study found that climbers have a better tolerance for momentary lactate accumulation. This seemed to be the case with Sepp and me. We didn’t pay a price for big turns of speed. For example, my biggest surges of power had minimal impact on my heart rate. Climbers may need a variable pace to take advantage of their lactate tolerance, but still need moments when they back o to clear the lactate.

During times of steady pacing, climbers can struggle. While Trevor had the exact same wattage for Lefthand and Flagstaff and his lactates were similar (6.1 vs 4.6), both Sepp and I averaged lower power but had significantly higher lactates on the steady Lefthand climb (9.4 vs 6.4 for Chris; 9.8 vs 5.6 for Sepp.) Basically, we performed relatively worse, but our bodies struggled more. Physiologically, it would seem, we couldn’t manage lactate as well as a time trialist when we didn’t have opportunities to vary our pace.

Pedal envy

As we’ve already seen, Sepp was the best at holding a steady cadence and not bogging down on steep stretches. Did that consistency provide a biomechanical advantage that allowed him to make the most of his physiological limits? By using Leomo’s Type-R motion sensors, we were able to collect real-time biomechanical data from Sepp and Trevor on the steepest and most technical of the climbs, Magnolia Road.

Each rider experienced more of a dead spot in his pedal stroke when standing. Trevor was in and out of the saddle far more than Sepp. Sepp had a more fluid pedal stroke and better foot angles. In essence, Sepp glided over the terrain while Trevor fought it.

An analysis of their left and right pedal strokes (below) clearly shows that Sepp was smoother and more economical. Dots indicate where dead spots occurred in the pedal stroke and at what wattage, while the colors indicate at what cadence. The better the pedal stroke, the fewer the dots.

The biomechanical data show that Sepp’s greater capacity to ride above his physiological threshold was at least partially due to a more economical pedaling technique. This allowed him to make the most of his physiological aerobic limits.

To develop biomechanics like Sepp and be as economical with your aerobic engine as possible, focus on a steady, high cadence, and don’t bog down. Try to stay seated as much as possible, even on steep gradients. Also, spend dedicated time tuning your pedal stroke with both neuromuscular and cadence work while climbing. (See “Sepp’s Favorite Workout” below.)

Finally, notice the big difference between Trevor’s left and right pedal strokes. His left leg was clearly struggling; this was due to a nagging back issue. As we’ll see on the next page, such problems can often be easily identified and corrected by the right strength and conditioning therapist.

Climbing is about maximizing every ounce of energy to cheat gravity. Better technique, smarter tactics, better climbing. Long live long climbs.

Sepp Kuss launches into his effort up Flagstaff Mountain. Photo: Brad Kaminski |

Soar like a condor

Different types of riders can take advantage of various physiological strengths. Here are our tips for becoming a better climber.

Time trialists

Ride very steady and close to thresholdYou tend to have the highest physiological threshold and steadiest power-to-weight of all rider types. Yet, you pay a price if you go too far over that threshold. Ignore the attacks and go your own pace.

Stay seated
Standing is less efficient at lower intensities because of the extra energy required by the arms and core. As a general rule, climb seated. In fact, all riders tend to have better biomechanics when seated.

Ride to your strengths
If it’s a long and steady climb, you may be able to hurt the climbers who prefer variable gradients. Drive a hard tempo. On steep, variable climbs, responding to attacks will take a heavy toll. Ride your own race.


Vary your pace
Physiologically, climbers seems to struggle with steady power output. Look for opportunities to surge and recover.

Don’t stare at your power
While time trialists are limited by their threshold, climbers are less so. Vary your pacing and don’t worry too much if your average power seems high compared to your last FTP test.

Stand for hard efforts
Everyone can produce more power when standing, but smaller riders pay less of an energy cost. Look for opportunities to stand more, especially on steep grades or when attacking.

Ride to your strengths
Take advantage of steep pitches and variable grades to hurt time trialists. On steady climbs, don’t let them dictate the pace. Instead, attack and break their spirit.


Have a pacing strategy
Don’t go out too hard, and find an overall pace that’s at your limit but not over it. How do you find that pace? Practice.

Keep a steady cadence and learn to spin
Climbing at lower cadences may feel natural but our biomechanics suffer and our muscles fatigue faster. Improve your fatiguability by working on climbing cadence.

Learn how to grind
Sometimes a climb is just too steep to spin up. Prepare for these pitches. Do torque work riding at a sustained 45 to 50 RPM. Kuss, for example, will do a 20-minute block consisting of two minutes at 40 RPM, then two minutes at 110 RPM, all while climbing and sustaining a solid power output.

Attack over the tops of climbs
We naturally tend to hold a steady velocity on steep pitches and then accelerate as the grade decreases. So, if you want to put out a big burst of power, use it where you get the biggest advantage — over the top of steep stretches and not on the steep pitch itself.

Core power
A strong core is essential for staying stable while climbing, especially when out of the saddle. Without a strong core, your form and economy will break down.

Pass on the cake
If you want to climb with the best, dropping some of that non-functional mass (i.e., your “spare tire”) is the simplest way to boost your power-to-weight. Just do it in a healthy manner, and target nine percent body fat for men and 11 percent for women.

Sustained but not steady training
Even time trialists can benefit from training their ability to respond and recover. Try doing “over-unders,” alternating between efforts just above and below threshold.

Sepp’s favorite over-under workout

Two 20-minute blocks: Each block consists of five segments, with each segment comprising a three-minute sub-threshold effort, followed by a one-minute VO2max burst; promptly return to sub-threshold. Repeat.

This special episode of Fast Talk takes a deeper dive into our in-house experiment. Joining us for the podcast is Ryan Kohler of the University of Colorado Sports Medicine and Performance Center, who helped with the experiments on the road.

The VeloNews Fast Talk podcast is your source for the best advice and most interesting insight on what it takes to become a better cyclist. Listen in as VeloNews managing editor Chris Case and columnist Trevor Connor discuss a range of topics, including training, physiology, technology, and more.

Fast Talk is available on all your favorite podcast services, including iTunes, Stitcher, Google Play, and Soundcloud. If you enjoy the podcast, please consider taking a moment to rate and comment on iTunes after listening.

VeloNews thanks the University of Colorado Sports Medicine and Performance Center for their assistance with this article. Learn more at

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