A retrofittable exercise data collection system and method of collection of data concerning the performance of weightlifters and the like which can be attached to a power rack used by weightlifters and detached after use or alternatively set up in freestanding arrangement in which by emitted electromagnetic radiation coupled detectors the movement of a barbell past such emitters may be detected and the speed of passage calculated by determining the interval between occlusion of the detector beams between adjacent detectors, the height of such occluded detectors being related to the portion of the musculature of the weightlifter that is undergoing extension or retraction during exercise.