Imagine standing at your front door with a five-kilometre journey ahead. Without a car or convenient bus route, you face a choice: walk for an hour or cycle and arrive in just fifteen minutes, barely breaking a sweat. For many, the bicycle is the obvious choice, and science explains why this two-wheeled marvel feels so effortless compared to walking.
The Global Appeal of Cycling
With over a billion bicycles estimated worldwide, cycling stands as one of humanity's most ingenious inventions for personal transport. It allows us to travel faster and cover greater distances while expending significantly less energy than walking or running. But what exactly makes pedalling feel so much easier than pounding the pavement? The answer lies in the elegant interplay between human physiology and bicycle engineering.
The Simple Genius of Bicycle Design
At its core, a bicycle is a wonderfully simple machine: two wheels, pedals that transfer power through a chain to the rear wheel, and gears that let us fine-tune our effort. This apparent simplicity masks sophisticated engineering that perfectly complements our biological capabilities.
When we walk or run, we essentially fall forward in a controlled manner, catching ourselves with each step. Our legs must swing through large arcs, lifting heavy limbs against gravity with every stride. This swinging motion alone consumes substantial energy. Consider how tiring it would be to swing your arms continuously for an hour; walking involves similar energetic costs for your legs.
Circular Motion Versus Impact
On a bicycle, your legs move through a much smaller, circular pedalling motion. Instead of swinging your entire leg weight with each step, you're simply rotating your thighs and calves through a compact cycle. The energy savings are immediately noticeable, but the real efficiency gains come from how bicycles transfer human power to forward motion.
When walking or running, each footstep involves a mini-collision with the ground. You can hear it as the slap of your shoe against the road and feel it as vibrations through your body. This represents energy being lost, literally dissipated as sound and heat after being sent through muscles and joints.
Walking and running involve another inefficiency: with each step, you actually brake yourself slightly before propelling forward. As your foot lands ahead of your body, it creates a backwards force that momentarily slows you down. Your muscles then work extra hard to overcome this self-imposed braking and accelerate you forward again.
How Wheels Revolutionise Efficiency
Bicycles solve these problems through one of humanity's great inventions: wheels. Instead of collisions, you get rolling contact where each part of the tyre gently "kisses" the road surface before lifting off. No energy is lost to impact, and because the wheel rotates smoothly with force acting perfectly vertically on the ground, there's no stop-start braking action. The force from your pedalling translates directly into forward motion.
Optimising Muscle Performance
Bicycles also help our muscles work at their optimal capacity. Human muscles have a fundamental limitation known as the force-velocity relationship: the faster they contract, the weaker they become and the more energy they consume. This explains why sprinting feels so much harder than jogging or walking—your muscles work near their speed limit, becoming less efficient with every stride.
Bicycle gears elegantly solve this problem. As you accelerate, you can shift to higher gears so your muscles don't have to work faster while the bike gains speed. Your muscles can remain in their sweet spot for both force production and energy expenditure. It's like having a personal assistant continuously adjusting your workload to keep you in the peak performance zone.
When Walking Still Has Advantages
Despite cycling's clear efficiency advantages, bicycles aren't always superior. On very steep hills exceeding approximately 15 percent gradient (where you rise 1.5 metres every 10 metres of distance), your legs struggle to generate sufficient force through the circular pedalling motion to lift both you and the bike uphill. We can produce more force by pushing our legs straight out, making walking or climbing more effective in such extreme conditions.
This limitation explains why we wouldn't pedal up Mount Everest even if roads were built there. However, the opposite holds true for descents. While cycling downhill becomes progressively easier (eventually requiring no energy at all), walking down steep slopes actually becomes more challenging.
Once gradients exceed about 10 percent (dropping one metre for every ten metres of distance), each downhill step creates jarring impacts that waste energy and stress joints. Walking and running downhill isn't always as effortless as we might expect.
The Numbers Speak for Themselves
The evidence is compelling: cycling can be at least four times more energy-efficient than walking and eight times more efficient than running. This remarkable efficiency stems from minimising three major energy drains: limb movement, ground impact, and muscle speed limitations.
So next time you effortlessly cruise past pedestrians during your morning commute, take a moment to appreciate the biomechanical masterpiece beneath you. Your bicycle isn't merely a transportation device but a perfectly evolved machine that works in partnership with your physiology, transforming raw muscle power into graceful, efficient motion.
About the author: Anthony Blazevich is a Professor of Biomechanics at Edith Cowan University. This article is republished from The Conversation under a Creative Commons licence.
