Proponents of variable resistance machines claim that greater strength gains can be achieved with these devices than with more conventional training equipment. Two experiments are described that compare variable resistance exercises with traditional free-weight exercises. In the first experiment, static strength and vertical jump gains resulting from training three times a week for 13 weeks with the recommended programs of two different variable resistance leg machines are compared to gains made from a program of box squats (dorsal thigh parallel to floor) using olympic barbells.
In the second experiment, gains in static strength achieved from training on a variable resistance biceps brachii machine, three times a week for eight weeks, are compared to gains obtained from curls performed with free-weights. Analysis of variance on the gain scores with the pretest as a covariate was used to compare the effects of the various programs. The findings indicated that exercises performed with variable resistance machines and free-weights were equally effective at developing strength. A finding, which varies from accepted belief, was that one set to failure was as effective as three sets of six repetitions with 80% of one repetition maximum (1 RM); this may warrant future study.
© 1981 National Strength and Conditioning Association