Vertical Impact Forces during Bench-Step Aerobics: Exercise Rate and Experience

The purpose of this study was to determine the effects of two bench-step exercise speeds on vertical impact forces and to explore this variable between novices and instructors. 12 women (mean age 24 yr.) randomly performed 8-min. protocols of the “basic” bench-stepping technique and a more advanced “travel” technique at 30 and 33 cycles · min.⁻¹. Analysis showed that the faster exercise rate yielded significantly higher vertical impact forces on a reference (B-8) step height (20.3 cm). At 33 cycles · min.⁻¹, the instructors' and novices' responses were both higher than those at 30 cycles · min.⁻¹. The mean peak vertical impact force ranged from 1.54 times the body weight for the novice group at 30 cycles · min.⁻¹ to 1.87 times the body weight for instructors at 33 cycles · min.⁻¹. A comparison of the groups' force curves showed a distinctive pattern in the loading of the impact forces. Specifically, the instructors consistently produced a transitory decrement in force prior to attaining peak force. In addition, the novices exhibited nonuniform increases in the production of vertical impact force across other step heights at the faster (33 cycles · min.⁻¹) speed. Thus, experience with bench-step exercise may afford an ability to make uniform and force-absorbing adjustments in the resultant vertical impact forces at increased speeds.