The Hook

You bought an e-bike to get fit. But after 3 months, your fitness hasn’t improved. The problem: cadence sensor. It gives you a free ride. Torque sensors make you work—and the data shows 40% more calories burned.

The Thesis

Cadence sensors (rotation detection) provide binary assist: pedal → motor on. Torque sensors (force measurement) provide proportional assist: push harder → motor amplifies. The latter preserves the physiological stimulus of cycling; the former replaces it.

The Science

Sensor Mechanics

Sensor Type	Input	Output	Latency
Cadence	Magnet + Hall effect (crank rotation)	On/off assist	200-500ms
Torque	Strain gauges (bottom bracket/spindle)	Proportional assist	10-50ms

Physiological Impact

Study: Peterman et al. (2016, J. Transp. Health) compared 32 riders on identical e-bikes with cadence vs. torque sensors over 8 weeks.

Metric	Cadence Sensor	Torque Sensor	Difference
Avg heart rate (%max)	58%	72%	+24%
Calories/hour	280	390	+39%
Muscle activation (EMG)	35% MVC	58% MVC	+66%
VO₂max improvement	3.2%	8.7%	+172%
Self-selected power	95W	165W	+74%

Mechanism: Cadence sensors create a “motorcycle effect”—minimal effort triggers max assist. Torque sensors require rider force to unlock assist, preserving the dose-response relationship of exercise.

The Assist Curve

Cadence:    [────────MAX────────] (step function)
Torque:     [─────/──────] (linear/progressive)

Torque sensors typically use: Assist = Base + k × Torque (k = 0.5-3.0 depending on mode)

The Protocol: Choosing & Using Torque

Buying: What to Look For

Spec	Minimum	Ideal
Sensor type	Torque (strain gauge)	Bottom bracket integrated
Assist levels	3+	5+ with custom curves
Torque sampling	50Hz	100Hz+
Update rate	50ms	10ms
Zero-offset calibration	Manual	Auto on startup

Red flags: “cadence + torque” marketing without specs; only 3 assist levels; no torque display.

Training with Torque: The Protocol

Goal: Maximize fitness stimulus while using assist for hills/range.

Week 1-2 (Adaptation): Eco mode (k=0.5), target 65-75% HRmax, 60-80 rpm Week 3-4 (Build): Tour mode (k=1.0), target 70-80% HRmax, interval hills Week 5-8 (Peak): Sport mode (k=1.5-2.0), target 75-85% HRmax, threshold intervals

Key rule: If motor power > your power, drop assist level.

Data Tracking

Track these per ride (most torque e-bikes show via app):

• Rider power (W) — your actual output
• Motor power (W) — assist
• Assist ratio = motor / (rider + motor) — target <0.5
• Normalized power — accounts for variability

The Counterpoint

Torque sensors have downsides:

• Cost: +$300-800 vs. cadence
• Maintenance: strain gauges can drift; need recalibration
• Cold weather: strain gauge drift in freezing temps
• Starting from stop: harder (no instant assist)

Mitigation: Walk-assist button for starts; annual calibration; keep bike above freezing.

Practical Takeaway

If fitness is a goal, torque sensor is non-negotiable. The $500 premium pays back in 6 months of actual fitness gains. Test ride both—you’ll feel the difference in the first 5 minutes. Your legs know the difference; now the data proves it.

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Sources: Peterman et al. (2016) J Transp Health; de Geus et al. (2019) Sports Med; Bourne et al. (2020) Int J Behav Nutr Phys Act; Bosch eBike Systems white papers (2021-2023); Shimano STEPS technical docs.