I can’t get my heart rate up on the bike, even when I feel I’m pushing hard. I grind up hills, spin through flats, and yet it’s hard to get above 120–130 bpm. I run at 160 bpm and race at 170-180.
Cycling is a very muscle‑specific sport. Unlike running, where your whole body (and the impact forces) drive your cardiovascular response, cycling isolates the work to your legs. If your leg muscles—particularly your quads, glutes, and hamstrings—aren’t strong enough to generate high power, you’ll fatigue locally before your heart and lungs get taxed. In other words, your legs give out before your cardiovascular system even gets a chance to climb to higher zones.
The chart shows my average HR on bikes (blue) and runs (red). It’s not completely dominant, but the trend is clear. When I run, my heart rate easily climbs into the 170s, but when I’m biking—even pushing hard—I struggle to get above 110 bpm. I looked into this a bit and it’s a well-documented physiological difference between running and cycling, rooted in both biomechanics and cardiovascular dynamics.
Running is a full-body, weight-bearing activity that recruits a large number of muscle groups: not just the legs, but also the core and upper body for stabilization. That broad muscle recruitment demands more oxygen, more energy, and therefore a higher cardiac output. My heart needs to pump faster and harder to meet that demand, especially when I’m running uphill or accelerating. In contrast, cycling primarily engages the lower body—quads, glutes, hamstrings—and even though those muscles are working, the overall systemic demand is lower.
Then there’s body position. On a bike, I’m seated, often with my torso leaning forward. This posture actually helps venous return—the process of blood returning to the heart—by reducing gravitational resistance. With improved preload, the heart can eject more blood per beat (higher stroke volume), so it doesn’t need to beat as frequently to achieve the same cardiac output. The net result: lower heart rate for the same level of oxygen delivery.
Cycling is also non-weight-bearing. There’s no impact, no ground reaction force, and no constant stabilization with every stride. That reduces overall neuromuscular and cardiovascular load. The metabolic cost of supporting body weight is significantly lower on the bike, which means less activation of the sympathetic nervous system, less catecholamine release (like epinephrine and norepinephrine), and therefore a lower heart rate response.
There’s also something to be said for specificity and conditioning. I’ve trained myself to run hard. My body is used to ramping up HR and oxygen delivery for running efforts. But biking is a different motor pattern, and if I haven’t trained those muscles or systems to handle high-load aerobic work on the bike, the heart rate won’t respond the same way. Even if it feels hard—because my legs are burning from lactate buildup or local muscular fatigue—that doesn’t mean the cardiovascular system is stressed enough to elevate heart rate.
Finally, effort on the bike can be deceptive. I have a power meter and I can keep that up around 200W, but I really want to get to 250 on average. But unlike running, where ground contact and muscle engagement are rhythmic and consistent, cycling effort can be variable and harder to quantify.
So when I’m on the bike and can’t get my heart rate up, it’s not that I’m not working. It’s that the cardiovascular, positional, and neuromuscular dynamics of cycling fundamentally produce a lower heart rate for a given perceived effort. Understanding that helps me train smarter—and recognize that heart rate alone isn’t the full story.
How do I fix this?
I have to boost leg power.
Here’s how I’m thinking about tackling this problem. The issue isn’t just cardiovascular—it’s neuromuscular. My body simply isn’t trained to fire the right motor units efficiently on the bike. Running is second nature by now, but biking demands different recruitment patterns and muscle coordination, especially from muscles like the glutes and vastus lateralis. If the neuromuscular system isn’t trained, I won’t be able to sustain the output needed to drive my heart rate up, regardless of how hard I feel like I’m working.
The second factor is muscular endurance. If my legs tire early, they become the limiter before the heart even gets close to max output. That’s a clear sign I need both more time in the saddle and targeted strength work. The science here is pretty strong: exercises like leg press, lunges, and single-leg squats directly build the muscle groups responsible for power on the bike. They also improve neuromuscular coordination, increase muscle fiber recruitment, and raise fatigue resistance.
From a ride programming perspective, I need to develop the ability to push higher cadences under moderate resistance—specifically 1–2 minute spin-ups at 100–110 RPM. This builds speed and muscle efficiency at higher outputs without requiring massive torque. Over time, it can help train the neuromuscular connection to sustain higher intensities at lower perceived effort.
I’ll also lean hard into hill repeats—4 to 6 sets of 3-minute climbs with full recovery. This kind of session pushes VO2 max systems and helps develop lactate tolerance. It’s the cycling equivalent of running strides uphill. Those 3-minute intervals are long enough to tax both aerobic and anaerobic systems and short enough to allow full engagement without form breakdown. And it’s repeatable, so I can track progress.
But the foundation is really about hitting all energy systems: tempo, threshold, and VO2. I’m planning to ride three times a week: one session focused on tempo or threshold with 8–20 minute intervals; one session focused on VO2 with 2–4 minute intervals; and one longer aerobic ride to build endurance and efficiency. That progression covers the full spectrum of adaptation—from mitochondrial density to lactate clearance to neuromuscular economy.
As for gear, I love my setup right now. My bike felt great today, and honestly, a $30 computer is giving me everything I need at this stage. I’m not yet fit enough to fully benefit from better equipment. The marginal gains would be there, sure—but the main limiter is still my body, not the bike. Fitness comes first.
And on tools—Apple Watch does estimate VO2 max, though it’s more accurate for running than cycling unless paired with a power meter and heart rate strap which are on ant+. But ultimately, the real measure will be how I feel on the bike and whether I can start getting that heart rate up into higher zones consistently. That’s the goal—and this plan gives me a roadmap to get there.