VERTICAL IMPACT FORCES DURING BENCH-STEP AEROBICS - EXERCISE RATE ANDEXPERIENCE

The purpose of this study was to determine the effects of two benchste p exercise speeds on vertical impact forces and to explore this variab le between novices and instructors. 12 women (mean age 24 yr.) randoml y 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 h igher vertical impact forces on a reference (B-8) step height (20.3 cm ). At 33 cycles min(-1), the instructors' and novices' responses mere both higher than those at 30 cycles min(-1). The mean peak vertical im pact force ranged from 1.54 times the body weight for the novice group al 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 non uniform increases in the production of vertical impact force across ot her step heights at the faster (13 cycles min(-1)) speed. Thus, experi ence with bench-step exercise may afford an ability to make uni form a nd force-absorbing adjustments in the resultant vertical impact forces al increased speeds.