The effect of total work on cardiorespiratory function

The purpose of this study was to determine the effects of training at three levels of caloric expenditure on selected cardiovascular fitness variables. In order to observe the isolated effects of total work (kilocalorie expenditure during exercise), intensity and frequency of training were held constant at specified levels that exceeded proposed training thresholds for these factors.

For this 16 week investigation, 34 sedentary male volunteers (ages 18-24) were randomly assigned to one of three groups involved in expending a prescribed number of kilocalories each exercise session. The three groups were: a 150 kcal/session group, a 300 kcal/session group, and a 450 kcal/session group. Jogging was the mode of training. A control group was drawn from the same population. Each experimental group trained three times per week at 80% of maximum heart rate for 16 weeks. Testing was done after 8 weeks and after 16 weeks of training. The subjects were evaluated by resting measures (resting heart rate, weight, and a sum of six skinfold sites) and exercise measures derived from a treadmill test (heart rate response to a fixed submaximal task, maximum heart rate, and VO2 max). At eight weeks, only the 450 kcal/session group was superior to the control group in V02 max. At 16 weeks, only the 450 kcal/session group showed significant improvements compared with the control group in resting heart rate, weight reduction, and VO2 max. No other significant differences were found between groups. It was concluded that total work per session was the important training factor when intensity and frequency were above threshold levels. It was further concluded that, for young men, it may be necessary to expend more than 300 kcal/session in order to make cardiovascular fitness changes.