Ground Contact Time vs Flight Time: What Do They Actually Tell Us?
Summary
Ground contact time and flight time are among the most commonly measured sprint variables—and the most commonly misinterpreted. Here's what each metric actually means and when to use them.
Timing systems that measure individual ground contact and flight phases have become increasingly accessible, and with them has come a rush to interpret every millisecond of contact time as meaningful. Contact time is important — but understanding what it actually reflects, and what it doesn't, prevents a lot of poor training decisions.
Ground Contact Time: What It Reflects
During sprinting, ground contact time (Tc) is the duration from initial foot contact to toe-off. It is a function of two things: how quickly the athlete can apply force, and how much force they need to apply to complete the stride.
In acceleration, contact times are long — 150–200 ms is typical at the first stride — because the athlete is applying large horizontal forces and the ground phase serves as the propulsive event. As the athlete approaches maximum velocity, contact time decreases toward 80–110 ms in elite sprinters, because the role of the contact phase shifts from propulsion to maintaining stiffness.
A short contact time is generally desirable at maximum velocity — it reflects high leg stiffness and efficient elastic energy return. But a short contact time during acceleration is not always beneficial. If the athlete is cutting contact time short during early acceleration, they may be sacrificing propulsive force for the *appearance* of reactiveness. This is a technical error, not a strength.
Morin et al. (2007) showed that ground contact time accounted for significant variance in 100 m performance across a cohort of trained sprinters. But the direction of causality matters: elite sprinters have short contact times because they produce force quickly, not the other way around. Training that artificially shortens contact time without addressing force application rate will not produce the same outcome.
Flight Time: What It Reflects
Flight time (Tf) is the duration from toe-off to the next ground contact. At sub-maximal and maximum velocities, flight time is primarily a function of jump height — specifically, the vertical velocity at toe-off. Longer flight times generally indicate greater vertical impulse during the preceding contact phase.
At maximum velocity, the relationship between flight time and performance is more complex. An athlete spending an excessive amount of time in the air is not applying force and may be losing the benefit of stiffness-driven elastic return. Elite sprinters show relatively constrained flight times at maximum velocity — not because they are trying to minimise flight, but because their stiffness and contact dynamics naturally produce this pattern.
Hunter et al. (2004) noted that step rate at maximum velocity is partially constrained by the flight time the athlete generates — and that elite sprinters are able to achieve high step rates partly because their flight times are not excessive.
What to Do With These Numbers
Use contact time and flight time as diagnostic indicators, not targets. An athlete with consistently long contact times who is performing poorly in acceleration likely has a force application problem — address it with strength and sled work. An athlete with short contact times but poor acceleration has a technical problem — they are not using the contact phase effectively.
At maximum velocity, monitor trends in contact time over a training cycle. A progressive reduction in contact time alongside stable or improving sprint times suggests positive adaptation. An increase in contact time is often an early indicator of fatigue or injury — the nervous system is protecting the athlete by reducing loading rate.
The numbers on the screen mean nothing without the context of what you are trying to achieve and where in the sprint they are measured.
References
Mark Fisher
Founder, Swift Performance
Mark Fisher is the founder of Swift Performance and has spent 30 years designing and building athlete testing equipment used by elite sport programmes and universities worldwide. He has worked alongside researchers and PhD candidates across biomechanics, sprint mechanics, and strength science — developing the hardware and software they use to collect and analyse performance data. His writing comes from three decades at the intersection of applied sport science and precision measurement technology.
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