Power meter

FTP (Functional Threshold Power) is the maximum power you can sustain for 60 minutes, expressed in watts. It is the central value of all power-based training. Based on your FTP, seven training zones are calculated: from active recovery (zone 1, <55% FTP) to anaerobic capacity (zones 6–7, >120% FTP). The standard test involves a 20-minute maximum effort, from which 95% of the average power is taken. An FTP is generally between 2.0 and 2.5 W/kg for a recreational cyclist, 3.5 to 5.0 W/kg for a competitive amateur, and 6.0 W/kg and above for professionals.

A unilateral sensor measures one leg and doubles the reading; a bilateral sensor measures both legs separately and provides a left/right balance. For most cyclists, the error introduced by unilateral measurement is small if the imbalance is less than 5% (which is usually the case). It can become significant after 3 hours of effort (the stronger leg compensates more) or in cyclists with a significant imbalance. The added value of bilateral measurement is primarily diagnostic: identifying a muscular imbalance to correct it via bike fitting or targeted strengthening. For simple training on a single leg, bilateral measurement is not essential.

Expect to pay €300 to €600 for a functional entry-level model, and €600 to €1,200 for a mid-range bilateral model. Left-crank-only sensors (Stages, 4iiii at €300–500) are the most affordable entry point. The Favero Assioma Duo pedals (dual-sided, ~€700) offer one of the best quality-precision-price ratios on the market. The Shimano FC-R9100-P (€990) and Quarq (~€800–1,000) cranksets offer seamless integration for a unique bike. The top-of-the-range SRM Origin (€1,500–2,000) and Shimano Dura-Ace (€2,000+) are reserved for professional competitors or very demanding amateurs.

Yes, if the aim is to improve in a structured way and avoid overtraining. The sensor allows you to tailor your rides to specific intensities rather than relying on how you feel or your heart rate (which varies more depending on stress, heat and fatigue). For an amateur cyclist riding 3,000 km a year with goals of weight loss, participating in cyclosportives or improving endurance, knowing your target watts for Zone 2 (basic endurance) and Zone 4 (threshold) provides a concrete structure for your training. However, without using an analysis app (TrainingPeaks, Garmin Connect, Strava), the data is of little use.

The two tools complement each other, but the power meter is more objective and responsive. Heart rate is influenced by heat, stress, caffeine, accumulated fatigue and illness: two sessions with the same power output may show very different heart rates. The power meter measures the actual power output in real time, with no delay. It allows you to precisely control intervals, manage your effort on climbs and avoid starting too fast. Heart rate remains useful for monitoring recovery (resting heart rate) and assessing your overall fitness over the long term. Ideally, you should combine the two: a power meter to gauge effort, and heart rate as an indicator of recovery.

A ‘zero offset’ or zero calibration must be performed before every ride, especially after a change in temperature. Zero calibration (called ‘Zero Reset’ on Garmin Rally, ‘Calibrate’ in the Shimano interface) resets the strain gauges to zero in the unloaded position to correct for thermal drift. It takes 10 seconds to perform from the GPS computer, with the sensors connected. Failure to calibrate after a rise in temperature (for example, if the bike was in the boot of a car) can skew the data by 3 to 7%. This procedure is automatic on some recent models (Shimano FC-R9100-P) which calibrate themselves at the start of a ride.

Yes, pedal sensors and removable crank sensors are the most versatile solutions. Favero Assioma or Garmin Rally pedals can be unscrewed from the road bike and fitted to the home trainer in a matter of minutes. Stages or 4iiii crank sensors can also be transferred easily (Allen key, 2 minutes). Sensors integrated into the crankset remain on the bike to which they belong. Riding on Zwift or TrainerRoad using your own road bike power data ensures consistency between indoor and outdoor sessions, which is invaluable for tracking progress.

Differences of 3 to 8% between a bike sensor and a home trainer are normal and due to different mechanical losses. A home trainer measures power at the brake (wheel or crankset depending on the model) after transmission losses (chain, cassette). A sensor in the pedals measures power before these losses. Typical discrepancy: the pedal-mounted sensor shows 5 to 8% more than a wheel-driven home trainer, and 2 to 4% more than a direct-drive home trainer. This is not an anomaly: the important thing is that each device is consistent with itself and allows for reliable long-term tracking.

No, it provides raw data that is only useful if interpreted within the context of a structured training programme.The power meter measures your watts, but it is the analysis of this data (via TrainingPeaks, Garmin Connect, WKO) that allows you to identify areas for improvement, training load, accumulated fatigue and peak fitness. Without a training plan and without knowledge of power zones, the figures remain unusable. For the vast majority of amateur cyclists, a power meter paired with a structured app (Garmin Connect Training Plans, TrainerRoad) is sufficient. A coach remains essential for competitive cyclists seeking to maximise their potential.