Following the public rollout of watchOS 27, athletes and everyday fitness enthusiasts across Reddit and community forums report severe discrepancies in workout tracking. Users operating Apple Watch Series and Ultra models note that previously rock-solid indoor workouts—specifically treadmill sessions and under-desk walking pads—now suffer from severe undercounting of steps, distance, and pacing.
The root of the issue stems from Apple's revised motion processing architecture in watchOS 27. Engineered to filter out incidental wrist movements and prevent false-positive stride counting, the new algorithm appears to treat low-impact or steady-arm indoor walks as background noise rather than active exercise.
Intriguingly, runners observe that the Apple Watch continues tracking overall background steps relatively accurately when no workout session is active. However, launching an official "Indoor Walk" or "Indoor Run" session engages a stricter heuristic gatekeeper that aggressively discards cadence oscillations. Even after resetting fitness calibration data in the iPhone Watch app and completing standard 20-minute outdoor GPS calibration walks, indoor treadmill runs consistently report distances 20% to 40% below treadmill machine consoles.
Preserved Benefit: The tightened motion filtering architecture effectively eliminates false-positive step accumulation during desk work, keyboard typing, and transit commuting.
Explicit Trade-Off: The aggressive noise-filtering heuristic misclassifies steady-state treadmill walks and stationary running as incidental drift, degrading workout fidelity for indoor gym athletes.
While athletes await a software patch in upcoming point releases, fitness analysts recommend temporary adaptations. Enabling outdoor GPS runs whenever possible forces the core pedometer model to retrain stride length across varying cadence levels. Additionally, ensuring a natural, fluid arm swing during indoor treadmill sets prevents the watch from misinterpreting steady grip on treadmill handrails as complete stationarity.
To examine how customized pacing intervals and stride adjustments affect your target race splits, test your numbers on our Running Pace Calculator, or explore high-contrast telemetry dials in our watch face gallery.