This paper is adapted in part from a thesis written for the degree of Master of Arts from New York University, New York, and was supported in part by research grant RT-1 (c6) from the Social and Rehabilitation Services, Department of Health, Education, Welfare, Washington, DC under the designation of New York University as a Rehabilitation and Training Center, and in part from grant FR00291 from the United States Public Health Service. Reprinted from Physical Therapy with the permission of The American Physical Therapy Association: Moffroid and Whipple: Specificity of Speed Exercise. Phys Ther 50:1692-1700, 1970.Resistive exercise is employed to increase functional performance. Weight lifting has been the traditional program of resistive exercise to increase muscular force (strength). Ten years ago Hellebrandt found that the amount of work done is not as important as the rate at which it is done. The purpose of this study was to determine the specific effects on muscular endurance and on muscular force of two different training speeds. The two training programs administered to two different groups were slow maximal exercise (low power) and rapid maximal exercise (high power). Speed of exercise was found to be specific for muscular endurance and for force increases at and below the exercise speed. J Orthop Sports Phys Ther 1990;12(2):72-78.