BALLOR, D. L., M. D. BECQUE, and V. L. KATCH. Metabolic response during hydraulic resistance exercise. Med. Sci. Sports Exerc., Vol. 19, No. 4, pp. 363–367, 1987. Thirteen college-age men underwent a treadmill (TM)-graded V̇O2max exercise test on 1 d and a 24.5-min hydraulic resistive exercise circuit on a following day. Seven exercises were performed in the following order: leg extension, bent-over row, bicep curl, squat, upright row, bench press, and behind-neck press. Each exercise was performed three times with the following work-to-rest timing: 30 s exercise, 30 s rest; 30 s exercise; 30 s rest; and 30 s exercise, 60 s rest (to allow for machine switch-over to the next exercise). Thus, each exercise took a total of 120 s, of which work was for 90 s and rest 120 s. During the circuit, heart rate averaged 153.8 b·min-1 (81.2% of TMmax) and V̇O2 averaged 1.93 1·min-1 (41.4% of TMmax). Oxygen uptake for the individual exercises ranged from 1.52 l·min-1 (32.6% of TMmax) for the behind-neck-press exercise to 2.431·min-1 (52.1 % of TMmax) forthe squat exercise. Heart rate ranged from 135.9 b · min-1 (71.8% of TMmax) for the leg extension exercise to 163.4 b · min-1 (86.3% of TMmax) for the squat exercise. Hydraulic circuit resistance exercise results in an average caloric expenditure of 40.8 kJ · min-1 (9.75 kcal ·min-1).