Plank Timer: Core & Form Check

Turn boring plank holds into a "keep your form" game. Place your phone on your lower back (or in your pocket) and the accelerometer detects posture breaks instantly. ◆ Real-Time Sag Detection ・Calibrate once in proper plank position before starting ・Monitors tilt; instant beep, vibration, and red flash when hips drop or butt rises ・Counts only "perfect form" seconds as valid time. Cheating seconds are excluded ◆ Form Quality Summary ・Shows best time plus break count and hold rate (%) ・Review break moments via waveform to see where form failed ◆ Records, Bests & Streaks ・Update personal bests with net hold time; track daily streaks ・Screen stays on during training; zero fullscreen ads ・Adjust sensitivity from lenient to strict Honest note: This is a placement-dependent basic check, not medical-grade. Auto-switches to stopwatch if phone can't be placed on lower back. Fully offline, on-device processing, no data sent externally (privacy-safe).