The science of cadence: find your optimal RPM indoors
Cadence is more than a personal quirk. Indoors, your chosen RPM changes how you produce watts, how fast you fatigue, and how efficiently you ride. Because a smart trainer’s inertia, ERG mode, and cooling environment differ from outside, the cadence that works on the road may not be your best choice on the trainer.
How cadence changes power, fatigue, and efficiency
Power is torque times cadence. For the same power, you can push harder on the pedals at a lower RPM or spin faster with less force per stroke. Each strategy stresses your body differently.
- Higher cadence (e.g., 90–105 rpm): Lower muscular force per stroke, higher cardiovascular and breathing demand. Good for reducing local leg fatigue and for efforts near threshold and above.
- Lower cadence (e.g., 55–75 rpm): Higher torque per stroke, lower heart rate for a given power at first, but more local muscular fatigue. Useful for strength-endurance and torque development.
- Energy cost is U-shaped: At easy powers, a lower cadence can be more oxygen-efficient, but as power rises toward FTP and VO2max, an optimal cadence shifts upward to protect the muscles and sustain force production.
- Neuromuscular fatigue: Very high cadences challenge coordination. If you bounce at the hips or lose a smooth pedal stroke, you’re above your controllable range for that day.
Indoors, flywheel inertia and trainer control matter. Low inertia (small flywheel, low gear) feels like pedaling up a steady climb and nudges you toward slightly higher torque at a given cadence. In ERG mode, if cadence drops, the trainer increases resistance to hold the target watts. That raises torque and can start the “spiral of death.” Managing cadence is your best control dial.
Recommended cadence by training zone
Use these as starting points, then fine-tune with testing.
| Zone | Typical power | Cadence target | Why it works |
|---|---|---|---|
| Endurance (Z2) | 55–75% FTP | 80–95 rpm | Comfortable, aerobic efficiency, low joint stress |
| Tempo/Sweet spot | 76–90% FTP | 85–95 rpm | Balances cardio load and muscular fatigue |
| Threshold | 91–105% FTP | 90–100 rpm | Protects muscles at high force, improves sustainability |
| VO2max | 106–120% FTP | 95–110 rpm | Shifts stress to cardiovascular system to hit target watts |
| Neuromuscular/sprints | Maximal | 100–120+ rpm | Leverages speed of contraction for peak power |
| Torque/strength-endurance | Z2–Z3 | 55–70 rpm | Builds force production and pedal stability |
Rule of thumb: as power rises, preferred cadence rises. Your “all-day” RPM is often 80–95; your threshold RPM is usually ~5–10 higher.
A simple test to find your indoor sweet spot
Repeat this for each zone that matters to your plan (Z2, sweet spot, threshold):
- Warm up 10–15 minutes, including a few 1-minute spin-ups to 110 rpm.
- Choose a fixed target power in the zone (e.g., 90% FTP for sweet spot).
- Do 3 x 5 minutes at that power with different cadences: 80 rpm, 90 rpm, 100 rpm. Recover 3 minutes easy between.
- Record heart rate, RPE, and how your legs vs breathing feel. Note smoothness and any bouncing.
- Pick the cadence that gives the lowest RPE and heart rate drift with steady form. That’s your current optimal RPM for that zone.
Retest every 4–6 weeks or after an FTP change. As fitness improves, your comfortable high-end cadence often creeps upward.
Cadence workouts for the trainer
- High-cadence spin-ups: 6–10 x 30 seconds at 110–120 rpm in Z1–Z2, 60–90 seconds easy. Focus on quiet hips and a light grip.
- Torque builders: 4–6 x 6 minutes at 60–70 rpm in Z2–Z3, seated, steady core. Recover 3 minutes easy. Do these with ERG off to control gearing.
- Cadence pyramids: 3 x 8 minutes in upper Z2. Change RPM every 2 minutes: 80 → 90 → 100 → 90. Learn how each cadence feels at constant watts.
- Threshold cadence alternations: 3–4 x 8 minutes at 95–100% FTP. Alternate 2 minutes at 90 rpm, 2 minutes at 100 rpm. Teaches control under stress.
- VO2 max cadence focus: 5–6 x 2–3 minutes at 110–120% FTP at 100–110 rpm. Aim for smoothness first, then speed.
Example 60-minute session (ERG off recommended) - 10 min Z2, include 3 x 20 s spin-ups to 115 rpm - 4 x 6 min @ 88–92% FTP: #1 at 85 rpm, #2 at 90 rpm, #3 at 95 rpm, #4 choose best 3 min easy between - 10 min Z2 @ chosen cadence - 5 min easy warm-down
Common indoor cadence pitfalls (and fixes)
- ERG spiral of death: If cadence starts dropping, hit pause or shift to resistance mode, spin up to target RPM, then resume. Use a slightly higher gear to increase flywheel inertia.
- Bouncing at high RPM: Lower cadence by 5–10, focus on a quiet core, and check saddle height. Add short high-cadence drills to expand your controllable range.
- One-cadence-fits-all: Match cadence to the goal of the interval. Strength-endurance needs 55–70 rpm; VO2 work often needs 95–110 rpm.
- Heat and dehydration: Poor cooling elevates heart rate and makes high cadence feel harder. Use two strong fans and drink 500–750 ml per hour for Z2, more for hard work.
- Chasing a number: Smooth power beats exact RPM. Stay within a 3–5 rpm window that keeps form and target watts.
Set up, monitor, and progress
- Pick the right mode: Use ERG for steady aerobic or threshold work when cadence is stable. Use resistance/level mode for torque drills and sprints.
- Gearing for feel: A mid-to-high gear increases flywheel inertia and smooths the pedal stroke. A low gear reduces inertia and feels like climbing.
- Track trends: Review cadence distribution in your training log by zone. Aim for range, not perfection.
- Integrate with zones: Note your preferred RPM at Z2, sweet spot, threshold, and VO2. Revisit after FTP changes.
- Recover well: If legs feel heavy at your usual RPM, drop cadence 5–10 and keep watts on target. Use recovery days to practice relaxed, smooth pedaling.
The right cadence indoors is the one that lets you hit your target watts with the least wasted energy and the best form for the session’s goal. Build a broad cadence toolbox, then select the tool that matches the interval.
