Zone 2 cycling

I trained for and completed Paris-Brest-Paris — 1,200km — primarily through cycling in Zone 2. Over 18 months, I went from having never cycled two days in a row to completing one of the world's great endurance events. Cycling was the perfect vehicle for Zone 2 training: low joint stress, easy to measure intensity, and endlessly scalable.

Finding your Zone 2 on the bike

On the bike, Zone 2 intensity is best tracked by heart rate. Use a chest strap monitor for accuracy — optical wrist sensors can lag and over-read at lower intensities.

Once you know your Zone 2 heart rate range (use the calculator if you haven't already), the goal is simple: keep your heart rate within that range for the duration of the session. On flat terrain this is straightforward. Hills complicate things.

Zone 2 watts: working with power

If you have a power meter or a smart trainer, you can train by watts rather than heart rate. Heart rate is the more important metric — it reflects what your body is actually doing. Power is useful for tracking progress over time.

Your Zone 2 power output will vary based on fitness, fatigue, temperature, and how well fuelled you are. But over weeks of consistent training, the watts you can sustain at your Zone 2 heart rate will increase — that's the adaptation showing up in the data.

Managing hills in Zone 2

Hills are the biggest challenge for Zone 2 cycling. On any significant climb, heart rate will rise toward — and above — Zone 2 unless you slow down dramatically. The right approach:

• Shift early and often. Drop to a lower gear before the climb gets steep rather than grinding up in a big gear.
• Slow down. Accept a lower speed to maintain heart rate. Your ego is the obstacle here, not your fitness.
• Walk if needed. On steep climbs, walking is sometimes the only way to stay in Zone 2. I walked plenty of hills during training. It still counts.
• Use the descents for recovery. Let your heart rate come back down before the next climb.

Flat routes and indoor trainers are genuinely easier for Zone 2 compliance. If you're training seriously for Zone 2 adaptation, choosing flat routes or using an indoor trainer for most sessions makes staying in zone much simpler.

Indoor vs outdoor Zone 2 cycling

Both have a place. Here's the honest comparison:

I used the indoor trainer for the majority of winter Zone 2 sessions — precise control, no interruptions. Outdoor riding dominated the spring and summer, building the endurance and bike handling needed for Audax events. The combination of both is ideal.

Zone 2 cycling for Audax and endurance events

If you're training for a long-distance cycling event — Audax, sportive, ultra-distance — Zone 2 is the foundation of everything. The ability to sustain effort for many hours depends on aerobic capacity and fat oxidation, both of which Zone 2 training builds directly.

My own progression: 300km Audax, 600km qualifier, then Paris-Brest-Paris at 1,200km. Each event was possible because the aerobic base from Zone 2 training was in place. Without it, a 300km event would have destroyed my legs — I would have been burning glycogen the whole way and bonked long before the finish.

With a well-developed aerobic base, even very long events become primarily a fuelling and pacing challenge rather than a fitness one. Your body has the engine. You just need to feed it and manage your effort.