The Effects of Single versus Multiple Sets of Leg Presses on Myocardial Energy Expenditure

Abstract

A popular trend in exercise regimes is to maximize the amount of work done in a minimum amount of time or maximize work by minimizing rest intervals. It is hoped that reduced rest time will result in dramatic fitness gains. To date, however, no differences in total energy expenditures have been found between high and low rest interval protocols. Unfortunately, total energy expenditures do reflect the metabolic strain experienced by the cardiac tissue. Rather, the rate pressure product [RPP = Systolic blood pressure × heart rate/1,000] has been recommended as a good index to assess cardiovascular metabolic stress, and to help determine the intensity and duration of exercise in developing fitness. PURPOSE: To determine if cardiac energy expenditure (i.e. RPP) differs between high rest (multiple sets) and low rest (single set) exercise protocols. METHODS: 14 untrained college students (5 male, 9 female; Age: 21.1 ± 0.2 years) participated in the study. Exercise intervention consisted of 2 days of multiple sets (4 sets,10 reps @ 150% body weight, 3 min interset rest) and 2 days of single set (40 reps @ 150% body weight) leg presses, randomly assigned in a balanced crossover order. At least 2 days separated each session and all sets were completed as fast as possible. HR and SBP were obtained on the right arm with an automated blood pressure machine at both pre-exercise and immediate post set completion. A paired T-test was used to compare the difference between the average final post set RPP of two trials of each exercise type. RESULTS: Multiple sets RPP (13.7± 0.8) was significantly less (t=6.5×10-5, p<0.05) than the single set RPP (17.5 ± 0.8). CONCLUSION: Contrary to total body energy expenditure research, a single set of exercise exerts more metabolic stress on the cardiovascular system than doing the same work with several rest intervals. Thus, single set of exercise could be used to train when attempting to train cardiac tissue, but multiple sets of exercise is recommended for people with compromised cardiovascular systems.