If you’ve ever gone for a run and a bike ride, you probably felt like you worked a lot harder on the run — especially if you’re new to cycling. It’s a common issue for athletes, and it’s not just in your head.
It’s been repeatedly shown that athletes’ heart rates are generally higher on the treadmill than on a stationary bike, says Hirofumi Tanaka, a professor of kinesiology at the University of Texas at Austin. This is true even at the same perceived rate of exertion. Cycling heart rates are usually about 8–12 beats per minute lower, though it depends on individual characteristics — and the difference can be as little as six beats per minute or as much as 15 beats per minute.
Why that happens is a bit complicated. “It’s actually a tough question to answer,” says Tanaka.
WHY CAN’T I BIKE AS HARD AS I RUN?
One of the main explanations is that running involves more muscle mass than cycling. You only really use your legs in cycling — unless you’re standing and rocking on the bike. In running, the pumping motion of your arms means you use those muscles more. Running also increases oxygen delivery in your blood and creates a larger cardiac output.
Running involves eccentric muscle contractions, while cycling is only concentric contractions, says coach Joe Friel, author of “The Triathlete’s Training Bible.” Eccentric means the muscle is contracting while also lengthening. “It’s much harder on the body,” says Friel.
The other factor is that “running is a weight-bearing activity,” says Fabien Basset, an associate professor in human kinetics at Memorial University in Newfoundland, whereas the bike supports your weight while you ride.
On the bike, you aren’t fighting momentum, but in running you essentially put the brakes on with each step. When your foot hits the ground it stops your forward motion. You can’t coast in running, but you can in cycling.
All of this doesn’t mean that running is necessarily “harder,” but it does mean it can seem harder. Your heart may be working more for the same effort, and your muscles and joints may be getting more impact. All kinds of different physiological effects and stresses between the two sports have been studied extensively.
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WHEN IS CYCLING ACTUALLY HARDER?
For experienced cyclists, the gap between cycling and running drops. (Conversely, it’s biggest for experienced runners who have never ridden before.) The more athletes bike, the more efficient they become at cycling. They are able to push themselves harder, recruit cycling-specific muscles and “optimize their energy production,” says Basset. Tanaka adds that “if you’re going to be good at cycling, you have to do bike training.”
You can narrow the heart-rate gap between the two sports by biking more, doing standing sprints or riding uphill. Uphill cycling actually mimics running most closely, in terms of how your body reacts.
“Climbing a hill on a bike makes the two more similar,” says Friel, partially because you have to fight gravity, partially because different muscles are recruited and more of the body is engaged, and partially because (at least for most people) you can’t coast and you have to work harder.
WHAT DOES THAT MEAN FOR YOUR TRAINING?
If you’re just trying to get in a good workout, coach Mike Ricci says a good rule of thumb is about a 2:1 ratio — a 30-minute easy run is about the same amount of total work as an hour-long easy ride.
It’s also common for him to have his athletes adjust their heart-rate training zones so that they’re slightly lower for the same efforts on the bike.
In an old research paper, Bassett says he showed if you express output as a percentage of VO2 max, there isn’t a difference between running and cycling. You can use his approximate calculation to make sure your work effort is on target: (VO2 max heart rate – your resting heart rate) x the targeted percentage of VO2 max + your resting heart rate — assuming you know your VO2 max heart rates for cycling and for running.
For example, if your VO2 max heart rate on the bike is 200 and your resting heart rate is 60 and you want to do efforts at 80% of max, then use (200 – 60) x 80% + 60 = 172 as your target heart rate.
The other possibility is you just need to ride harder, says Ricci. Because so many of us come to cycling after having ridden as kids or coasting on beach cruisers, we have a tendency to go easier. You also can keep moving forward without pedaling, which many of us do.
To teach athletes to go harder, Ricci will have them do sprints or hill repeats. “If they feel like they can’t hurt on the bike, I’ll have them stand up,” says Ricci.
It may seem like it’s not the worth the effort to bike, but in the long run cycling actually has more potential to be a harder workout, because running is generally limited by impact and stress. “There is none of that in cycling,” says Friel.