Reactive Strength (as measured by Reactive Strength Index) is a measure of an individual's ability to rapidly generate force and absorb force during a movement during a countermovement jump (CMJ). It is calculated using the variables of jump height (H) and contact time (CT), as follows:
RSI = (H / CT)
Where H is the height of the jump and CT is the time the individual spends in contact with the ground, measured in seconds.
The RSI represents the individual's ability to rapidly generate force and absorb force during the CMJ. A higher RSI indicates a greater ability to rapidly generate force and absorb force, while a lower RSI indicates a lesser ability.
The results of the RSI can tell us several things, including:
Power output: A higher RSI indicates that the individual is able to rapidly generate more power during the jump, which is important for explosive movements such as sprinting, jumping, and rapid changes of direction.
Muscle force production: The RSI can indicate the individual's ability to rapidly produce force in their muscles, which is important for high-intensity activities such as sprinting and jumping.
Neuromuscular control: The RSI can also indicate the individual's ability to control their muscles and generate force quickly and precisely, which is important for activities such as throwing and rapid movements.
Overall, the RSI is a useful measure for coaches, trainers, and athletes to assess an individual's reactive strength, which is critical for many athletic movements. It can help identify areas for improvement and provide a target for training programs aimed at improving explosive power and muscle force production.