Time to take-off (TTO) is defined as the time taken from the beginning of the jump movement to the instant of toe-off.
The time to take-off is a variable of interest in determining contributors to jump technique, strategy and timing efficiency with counter-movement depth often having the biggest influence on time to take-off. Eg: A deep countermovement depth where the athlete squats down to the floor will often have a longer time to take-off, where as a small countermovement depth with minimal hip and knee bend will have a short time to take-off
Practically it can be used to look at jump technique changes with ideal results being whatever strategy produces the highest jump height with the shortest time to take-off as typically athletic individuals have minimal time to execute the most effective strategy.
Research by Viera and Tufano in combat fighters and physically active males found similar time to take-off results of approx 0.7 seconds whilst jump height results were higher in the fighter group showing that while the strategy may be the same (TTO) the output can be different (jump height).
References:
Vieira A, Tufano JJ. Reactive strength index-modified: reliability, between group comparison, and relationship between its associated variables. Biol Sport. 2021 Sep;38(3):451-457. doi: 10.5114/biolsport.2021.100363. Epub 2020 Nov 4. PMID: 34475626; PMCID: PMC8329976.