Effects of hydraulic circuit training on cardiovascular function

The effect of hydraulic circuit training (HCT) on cardiovascular (CV) function was assessed in 32 healthy middle-aged males (X age = 42.2 +/- 2.1 yr). Maximal aerobic power (VO2max), with simultaneous measurement of stroke volume (SV) and cardiac output (CO), by impedance cardiography, was assessed pre- and post-training. Subjects were randomly assigned to a nonexercising control group, a cycle training group (cycle), or one of the two HCT groups. Training groups participated in a 9 wk program, 3 d.wk-1. Subjects assigned to HCT exercised on a 9 station circuit, completing 3 circuits.d-1. Each circuit consisted of three 20 s work intervals at each station with a 1:1 work:rest ratio. One HCT group (HCTmax) completed the maximal repetitions possible (RM) during each work interval. The other HCT group (HCTsub) exercised at 70-85% of RM. Following training VO2max (ml.kg-1 min-1) was significantly increased in all training groups (18.0, 12.5, and 11.3% for cycle, HCTsub, and HCTmax groups, respectively; P less than 0.05). The increase in VO2max observed in the cycle group was significantly greater than that recorded by the two HCT groups (P less than 0.05). For all three training groups, the increase in VO2max was associated with increases in SVmax and COmax (P less than 0.05 for both). These findings suggest that both maximal and submaximal HCT programs can elicit improvements in cardiovascular fitness.