The purpose of this investigation was to determine the level of cardiovascular stress elicited by continuous and prolonged circuit resistance training (CRT). Each of the 11 men who volunteered as a subject were tested to determine oxygen consumption and heart rate responses to a submaximal and maximal treadmill protocol and a CRT session consisting of 10 exercises and 10 repetitions at 40% of 1 repetition maximum (1RM) for each station with 4.6 circuits performed. The physiological stress of the CRT in this study was evident by the sustained heart rate of more than 70% of maximum for 16.6 minutes, with the last 12 minutes at more than 80%. Despite the large anaerobic component in CRT, VO2 was sustained at 50% or more of maximum for the final 12 minutes. Treadmill running, involving large muscle groups, increased VO2 more rapidly than CRT, where alternating larger and smaller muscle groups were used. In addition, at the same VO2 heart rate differed significantly between the 2 modes of activity. Heart rate in CRT was higher (at 165) than the heart rate of 150 found during treadmill running at the same 50% VO2. Such workouts may be used in a training cycle in classical linear periodization or in a nonlinear program day targeting local muscular endurance under intense cardiorespiratory conditions, which may help individuals develop enhanced toleration of physiological environments where high cardiovascular demands and higher lactate concentrations are present.
(C) 2004 National Strength and Conditioning Association