Answer: INTENSITY
Explanation: FITT formula is used for health-related fitness and was designed by The American College of Sport Medicine (ACSM).
FITT is established to put together an efficient workout plan for aspiring to be healthy and healthy individuals.
I stands for Intensity in the FITT principle. Intensity describes the level of difficulty of an exercise. Low intensity level can be adopted at the early stage of an exercise programme and gradually increased to difficult level, in other to avoid burnout.
It is measured based on numbers. The number of sets completed, amount of weight lifted or number of repetitions accomplished, while finding your target heart rate zone and Max heart rate (MHR).