Is indoor cycling as good as riding outside?

Yes, indoor cycling is as good as riding outside for building fitness, and in some ways better. Indoors you pedal the whole time. There are no red lights, no descents and no coasting, so a 45 minute indoor session often has more real work in it than a 45 minute ride outside.

Outside has its own advantages, though, so most cyclists end up doing both.

What indoor does better

• Time efficiency. Every minute is pedaling. A 40 minute interval session can be hard and complete.
• Control. You can hold an exact power or heart rate, which makes intervals easy to repeat.
• Weather and safety. No traffic, no ice, no dark evenings.
• Schedule. You can ride at 6am or 10pm.

What outdoors does better

• Bike handling. Cornering, braking, riding in a group and holding a line only come from riding outside.
• Variety. A changing route keeps long rides interesting.
• Cooling. Indoors there's no airflow, so you'll sweat a lot more and feel hotter at the same effort. A strong fan helps and so does drinking more.
• Mental break. Plenty of people like being outside more than staring at a wall, and that matters for consistency.

Little differences you'll notice

Heart rate usually runs a bit higher indoors at the same effort because of the heat. Your numbers on a smart trainer also won't match your outdoor numbers exactly. Treat them as separate scales and compare indoor to indoor.

Indoor sessions can also be hard on your sit bones because you never shift position on the road. Move around on the saddle now and then, and it's worth getting your fit checked if something hurts.

How I'd split it

If you ride 3 times a week, I'd do the hard interval session indoors, where it's easy to control, and the long easy ride outside. In winter or bad weather, indoors can carry the whole week without losing much.

Both kinds of ride can count toward a League of Fitness match. Rides sync from Apple Health and are scored by heart rate zones, so a hard indoor interval session and a long easy ride outside each register for the effort you put in.

Stop and see a doctor if you feel chest pain or dizziness during a hard session, especially in the heat.