Flight time is the period during which the body is fully airborne. In running it is the interval between toe-off of one foot and initial contact of the other. In jumping it is the time from takeoff to landing.
Flight Time in Running
Walking has no flight phase, because one foot is always on the ground. Running alternates between ground contact and flight. As speed increases, flight time typically lengthens relative to ground contact time. The ratio between flight and contact can help describe running style and how a runner changes with speed or fatigue.
Flight Time in Jumping
Jump height can be estimated from flight time with a standard projectile equation: height equals gravitational acceleration multiplied by flight time squared, divided by eight. The formula assumes the body leaves and returns to the ground in the same position. This makes flight time a practical, low-cost method for tracking jump performance.
Measuring It on Video
- Use a side view, with the feet and ground clearly visible
- Mark the last frame of contact at takeoff and the first frame of contact at landing
- Count the frames between them and divide by the original capture frame rate
- Higher frame rates, such as 120 or 240 fps, reduce timing error
- A fast shutter speed and good lighting make the moment of contact easier to identify
Common Pitfalls
- Tucking the legs or landing with bent knees and hips lengthens flight time and inflates estimated jump height
- Landing on the toes versus flat-footed changes the landing frame
- An error of one frame at low frame rates can noticeably change the result
- Slow-motion clips must be timed using capture frame rate, not playback speed
- Flight-time jump height is an estimate and may differ from force-plate or other measurement methods
For consistent results, use the same jump technique, landing instructions, camera position, and frame rate across sessions.