Page| Circuit Training Brief Overview By Len Kravitz, Ph.D. Circuit training was developed by R.E. Morgan and G.T. Anderson in 1953 at the University of Leeds in England (Sorani, 1966) . The term circuit refers to a number of carefully selected exercises arranged consecutively. In the original format, 9 to 12 stations comprised the circuit. This number may vary according to the design of the program. Each participant moves from one station to the next with little (15 to 30 seconds) or no rest, performing a 15- to 45-second (or more) workbout of 8 to 20 repetitions (or more) at each station (using a resistance of about 40% to 60% of one-repetition maximum). The program may be performed with exercise machines, hand-held weights, elastic resistance, calisthenics or any combination. By adding a 30-second to 3-minute (or longer) aerobics station between each station, referred to as aerobic circuit training, the method attempts to improve cardiorespiratory endurance as well (although this has not been conclusively supported in experimental research). Variations of this aerobic circuit training model include performing 2, 3, 4 or more exercise stations in series, and then performing the aerobics station. Benefits of Circuit Training Numerous investigations have been completed measuring the physiological benefits of circuit weight training. Circuit weight training has been shown to increase muscular strength from 7% to 32% while decreasing the percent of fat from 0.8% to 2.9% (Gettman & Pollock, 1981). Gettman and Pollock's review of the literature also showed an increase of fat-free weight (1 to 3.2 kg) with no subsequent change in body weight. Kilocalorie expenditure has been estimated to be approximately 5 - 6 kcal per minute for women and 8 - 9 kcal per minute for men (Hempel & Wells, 1985; Wilmore, Parr, & Ward, 1978). In terms of cardiovascular function, studies have shown little to mild improvement in aerobic capacity (5% to 9.5%) from participation in circuit weight training as compared to other aerobic modalities (5% to 25%) (Kass & Castriotta, 1994; Peterson, Miller, Quinney, & Wenger, 1988). Kass and Castriotta support the contention that the mild increases in aerobic capacity are due primarily to increases in fat-free mass from the circuit weight training, and not changes from the main factors affecting aerobic capacity: cardiac output (heart rate x stroke volume) or arterial-venous oxygen difference (exchange of oxygen and carbon dioxide at the cellular level). Traditionally, individuals with cardiovascular disease and hypertension have been discouraged from performing any type of resistance exercise. However, circuit training performed at a moderate intensity (40% of repetition maximum) in cardiac patients has demonstrated significant increases in strength (13% to 40%), with no cardiac or orthopedic complications (Kelemen et al., 1986; Stewart, Mason, & Kelemen, 1988). Furthermore, circuit weight training does not appear to elevate resting blood pressure or heart rate, and may beneficially lower resting diastolic blood pressure in borderline hypertensives (Harris & Holly, 1987). Very little information is available on the psychological benefits of participation in circuit weight training. However, with law enforcement officers positive changes in mood, anxiety, depression and hostility have been observed (Norvell & Belles, 1993). |
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