Lifting Won't Hurt Your Watts-per-Kilo. Thirty Years of Cyclist Studies Settle It.

A climber I ride with in early summer last year — the kind who weighs himself in the morning and again before dinner and treats the second number as data — told me he'd be skipping the gym again that winter. He'd just come off a season where he held a new personal best up the local twelve-minute climb, and he was convinced the reason was that he'd finally gotten his weight down to where he wanted it. "If I start squatting I'll just put it back on," he said. "I've seen guys do leg day and turn into rugby players. I can't afford the legs." He genuinely believed this. He had spent two seasons reading climber forums and looking at thin pros, and he had concluded, like most cyclists do at some point, that the gym was for people who weren't serious about W/kg.

The thing is, his fear has been studied for thirty years. Repeatedly. In well-trained cyclists, in elite cyclists, in women, in men, in Masters athletes. The result keeps coming back the same way and almost nobody who actually rides bikes for a living believes the bulking myth anymore. But the climber on the local Strava segment, the one debating whether to spend a winter under a barbell, still does. So it's worth walking through what the data actually says and, more importantly, why the biology won't let you bulk in the way you're afraid of even if you tried.

The Fear, Stated Plainly

The W/kg-anxiety story that lives in most climbers' heads goes like this. Muscles get stimulated. Stimulated muscles grow. Growing muscles weigh more. More weight means more grams to drag up the hill. Therefore squat equals slower climb. The logic looks airtight on a napkin.

It falls apart the moment you check what actually happens when cyclists train. Hypertrophy in skeletal muscle is a dose-dependent response. It requires a lot of mechanical tension over a lot of weeks, with a recovery and nutrition environment that lets the build-back-better signal complete. A cyclist riding fifteen hours a week in zone two and a couple of VO2 sessions and the occasional race is not running that environment. They're running a different environment — one that's about as hostile to bulking as you can engineer without trying.

Which means the relevant question isn't "will lifting make me bigger." It's "how much bigger does the body actually let a high-volume cyclist get from a normal strength block." The cycling literature has answered this question many times. The answer keeps coming back as: a small, focal increase in the muscles you trained, almost no change on the scale.

What the Studies Actually Found

Rønnestad, Hansen, and Raastad's 2010 paper in European Journal of Applied Physiology is the cleanest male-cyclist version. Twelve weeks of heavy strength training added to normal cycling in well-trained athletes — half-squats, single-leg leg press, single-leg hip flexion, calf raises, twice a week, in the four-to-ten rep range at progressively higher intensities. The strength group's thigh muscle cross-sectional area went up. Their 40-minute time trial power went up. Their maximum aerobic power went up. Their bodyweight did not. In some subjects it dropped slightly because the strength block came with normal training-season fat loss that washed out the small lean mass addition. The control group, doing pure cycling, made no progress on Wmax or 40-minute power and saw no change in thigh CSA either.

Vikmoen and colleagues' 2016 study in Scandinavian Journal of Medicine & Science in Sports did the same thing in female cyclists, which matters because the bulking fear in cycling is most acute among women and the bulking risk in women is, biologically, the lowest. Eleven weeks. Quadriceps CSA went up 7.4 percent — a real, measurable hypertrophy response in the trained muscle. Bodyweight didn't move. Forty-minute time trial power improved 6.4 percent. Cycling economy improved. Fractional utilization of VO2max climbed from about 79 percent to about 82 percent. The Wingate peak — the test of raw anaerobic power — went up almost thirteen percent. The control group, doing only their normal cycling, made none of these gains.

Vikmoen and Rønnestad's 2021 comparison paper in Journal of Functional Morphology and Kinesiology sat the male and female datasets side by side and asked whether women responded differently. They didn't, except that cycling economy improvement was actually more pronounced in women than men. Quad CSA growth was, if anything, slightly larger on the female side (7.4 percent versus 4.6 percent), and bodyweight was unchanged in both groups. The Wingate peak improvements were 12.7 percent for women, 9.4 percent for men. Whatever the bulking fear is responding to, it is not responding to the data.

The 2025 Llanos-Lagos meta-analysis in European Journal of Applied Physiology pooled seventeen of these studies, 262 cyclists, and reached the same conclusion at scale. Heavy strength training reliably improves cycling efficiency, anaerobic power, and time-trial performance in trained cyclists. The pooled bodyweight comparison between strength and control groups: no difference.

The cyclists we see in Dorsi who lift two days a week through the off-season are the same ones whose bodyweight reads flat year over year on the morning scale. The gym work is doing exactly what the literature says it does. The muscles being trained are getting denser and stronger. The number on the scale isn't moving because the number on the scale is being held by something else entirely.

Why the Body Won't Let You Bulk

This is the part most cyclists never get explained to them, and it's the part that closes the question. You can't easily bulk as a high-volume cyclist because your endurance training is, at the molecular level, actively suppressing the hypertrophy pathway.

Skeletal muscle growth runs primarily through mTOR signaling — a cascade that turns on after heavy resistance work and orchestrates the protein-synthesis program that builds new contractile machinery. Endurance training runs primarily through AMPK signaling — a different cascade that responds to sustained energy depletion and orchestrates the mitochondrial-biogenesis and oxidative-capacity program that makes a cyclist a cyclist. The two pathways are partly antagonistic. AMPK activation suppresses mTOR. This is the same molecular biology underneath the interference-effect literature in concurrent training (Coffey and Hawley described the canonical version of it in 2007), and it cuts both directions: hard endurance work blunts the hypertrophy signal, and chronic endurance volume keeps AMPK chronically active enough to keep that blunting going.

Translated: a cyclist doing more than four hard endurance sessions a week is running an internal environment where the hypertrophy signal, even after a hard lift, doesn't quite complete the way it would in a sedentary lifter eating in surplus. The body isn't getting the "build big muscles" instruction loudly or consistently enough to actually do so. You can stimulate the muscle, you can get stronger, you can densify the fibers — but to actually pack on the kilos of mass that the bulking fear imagines, you would need to drop most of the cycling volume that defines you as a cyclist. People who lift seriously and don't ride seriously can hypertrophy. People who ride seriously and lift seriously cannot, much.

This is also why the typical female-cyclist result — bigger relative CSA change than men, same absolute bodyweight — makes biological sense. Women run lower baseline anabolic hormone levels, so the absolute mass increase from strength work is smaller for the same relative change in the trained muscle. The cycling volume is still suppressing systemic hypertrophy. The local muscle responds. The total mass doesn't shift.

The frustration this should produce, if you're actually trying to gain muscle, is that you can't. The relief it should produce, if you're trying to climb fast, is that the protective mechanism is automatic. You don't need willpower. You need to ride your normal volume and lift, and the molecular biology will handle the bulking risk on your behalf.

The Female Data Deserves Its Own Section

I want to spend a beat here because the female cyclist data is the strongest answer to the strongest version of the fear, and it gets less airtime than it should.

The bulking myth is loudest among female cyclists. The fitness internet is full of women saying they avoid squats because they "got too bulky" the one time they tried. The cycling internet inherits some of that and adds its own — many female amateurs hold a baseline conviction that their bodies will respond to a barbell the way a hormonally male bodybuilder's would. The Vikmoen 2016 cohort was twenty trained female cyclists, randomized, eleven weeks, the same protocol used in the male studies. Heavy weights, four-to-ten reps, multiple sets, twice a week. At eleven weeks the strength group had measurably bigger quadriceps and identical bodyweight. They also had a measurably better 40-minute time trial — 6.4 percent better, the kind of improvement most riders chase for a season. The control group had none of these things.

The follow-up comparison work (Vikmoen and Rønnestad, 2021) is even more direct about the asymmetry: female cyclists got slightly better relative outcomes than male cyclists across cycling economy and Wingate peak. The fear and the data are pointing in opposite directions and have been for a decade. The right reading of the data, if you're a female cyclist, is that strength training is probably more valuable to you than to your male training partner, not less.

The aesthetic concern underneath this often isn't really about W/kg at all — it's about a body image worry transplanted into cycling discourse. That's a different conversation, and worth having honestly. But it should be had as the conversation it actually is, not as a pseudo-physiological argument about climbing performance that the cycling research already settled.

What This Means for the Climber on the Segment

Strip the science down and the practical picture for a W/kg-anxious climber is straightforward.

A normal strength block — twice a week through the off-season, heavy compound work in the four-to-six rep range, somewhere between eighty and ninety percent of 1RM — will add a few hundred grams of lean mass to your legs over a couple of months. It will not add it to your stomach. It will not add it to your arms (you're not training your arms). The scale, if you also eat normally and keep your cycling volume up, will read what it usually reads, plus or minus the half-kilo of daily variation that's about hydration.

The watt side of the W/kg equation, meanwhile, is what's actually moving. Your 40-minute time trial power is going up because cycling economy is improving — your quads, with bigger and more force-capable fibers, are using a smaller fraction of their maximum to push the same pedal stroke. The slow fibers that carry your tempo and threshold work get "strength-ified" — they spend more of their time in the cycling pace below their force ceiling, which delays type II recruitment, which spares glycogen, which extends durability. Your sprint, which you might think you don't care about, is up nine to thirteen percent — meaningful when you have to close a gap on a climb or attack on a steep ramp. None of this comes at a kilogram cost.

The climber on the segment who skipped lifting last winter to "protect" his W/kg gave up the watts side of the ratio to defend the kilogram side, and the kilogram side wasn't actually under threat. He was paying real performance for an imaginary protection.

W/kg Is the Reward, Not the Cost

The cleanest way to think about this is to stop framing strength training as something a climber tolerates in spite of W/kg and start framing it as one of the few things in a training year that directly grows W/kg from the watts side without doing anything to the kilos. Cycling volume can grow watts, but slowly, and with diminishing returns once you're already trained. VO2 work can grow watts, but at high recovery cost. Strength work grows watts via cycling economy improvements and neuromuscular adaptations that you can't easily get any other way, at a cost in mass that the literature has been failing to measure for thirty years.

The cyclists who treat the gym as a winter project, two sessions a week, simple compound lifts done heavy, generally come into spring with the same scale weight, slightly more dense legs, slightly better climbing economy, and a sprint that didn't used to exist. They are the version of themselves that they wanted to be without giving anything up. The climber who skipped the gym to protect his weight is the version who came back to the same hill at the same kilograms and the same watts as last year, and who will probably read this article in May and start a block in October if he's honest with himself.

The bulking fear is the most expensive small belief a cyclist can hold. It survives because nobody bothers to look up the studies and because the gym still feels, to a lot of climbers, like enemy territory. But the territory is friendly. The data has been clear for three decades. The mechanism is in the very training you're already doing. Watts go up, kilos stay flat, the ratio improves, the climb gets faster. That's not the cost of lifting. That's the entire point of it.