I Reverse-Engineered My Apple Watch to See If My Rehab VO2 Max Was Real

After a severe ankle injury, I investigated whether the Apple Watch's VO2 Max estimates are reliable enough to track my recovery. The device uses sophisticated neural networks and "prediction deltas" to extrapolate elite fitness levels from simple brisk walks. Recent 2025 and 2026 studies confirm that while slight offsets exist, the watch is a highly accurate tool for tracking physiological trends.