The analysis of ground reaction forces (GRFs) helps one understand the magnitude and pattern of loading experienced by the body while in contact with the ground in locomotor actions. The GRFs reflect a general indicator of mechanical loading on the musculoskeletal system, establishing the "whole-body biomechanical intensity" of physical activity and allowing the comparison between different activities. Our purposes were to analyze the GRFs produced by step exercise particularly-the force profile, average GRF, peak GRF, impulse, and loading rate-on the ascending and descending movements in 18 skilled women, investigating the differences that exist between 4 stepping-rate conditions and between 4 step patterns. Two force platforms were used. These differences were studied using analyses of variance with repeated measures. Our results show that experienced subjects were able to deal with the increase of movement cadence in terms of external load, maintaining the GRF values at the same levels as the ones obtained for quick walking and moderate step running, activities that are considered safe. The results indicate that lower-extremity external loading can be effectively controlled by varying the stepping rate during step classes. With the correct use of this mechanical control, this activity could be included in exercise and rehabilitation programs. The knowledge about the magnitude of loading helps in selecting proper stepping rates and proper movements for inclusion in classes.