Traditionally movie film has been the major medium by which investigators have analyzed, described and quantified the temporal and spatial characteristics of human motion. In addition, movie film has been used to estimate the forces resulting from the acceleration of the human body and its parts. Predictions of muscle force and reactive forces at the joints have also been made based upon film analysis. Although high speed filming was described as early as 1910, its use in the study of human motion was primarily from the 1960's onward. Filming at rates greater than 24 frames per second (fps) technically can be considered high speed. Most of the early human motion analysis was conducted using cameras operating at not greater than 128 fps, usually at 64 fps. These were relatively inexpensive cameras. The ultra-high speed cameras, however, were used to some extent during the early 1960's and became standard equipment in the well equipped University Biomechanics Laboratories for human motion analysis in the 1970's. As early as 1970 there were no fewer than four cameras capable of operating at speeds greater than 1000 fps. Cost, lack of comparable sophistication in analysis techniques, and operating complexities were primary factors in these ultra high speed cameras not being used to study human motion prior to the late 1970's. Human motion, even now, is usually recorded with cameras operating between 60 and 250 frames per second.