Influence of Interval vs Continuous Exercise on Markers of Metabolic Rate During Exercise and Recovery

Abstract

Studies have shown that improvements in body composition after interval training are equivalent or superior to those resulting from continuous, moderate-intensity exercise training, although time and energy expenditure associated with interval training is lower. PURPOSE: To compare exercise and 3-hour recovery VO2, energy expenditure (EE), core temperature, and heart rate (HR), associated with 40 minutes of continuous, moderate-intensity exercise (50-60% of heart rate reserve [HRR]) (CON) with those associated with three models of interval training: 4 (I-4), 7 (I-7), and 10 (I-10), one-minute bouts of exercise at ~90% of maximal heart rate alternated with 1-minute recovery bouts at ~ 50-60% of HRR. METHODS: Nine healthy adults (5 females, 4 males, 23.8 ± 2.8 years, 75.0 ± 9.9 kg) underwent a submaximal exercise test to determine estimated VO2 max. Exercise sessions were then completed in random sequence at least one week apart. RESULTS: Exercise VO2 was 66.0 ± 12.2 L for CON, 17.0 ± 2.9 L for I-4, 30.4 ± 6.9 L for I-7, and 44.3 ± 10.4 L for I-10. EE for each exercise session was 323.5 ± 60.1 kcal for CON, 84.2 ± 19.5 kcal for I-4, 151.0 ± 33.7 kcal for I-7, and 219.5 ± 51.4 kcal for I-10. Average exercise HR was 133.8 ± 4.1 for CON, 142.2 ± 8.2 for I-4, 152.4 ± 5.8 for I-7, and 152.4 ± 5.7 for I-10. Recovery HR in first hour after exercise was higher after I-10 (82.3 ± 6.4 beats/min) than after CON (75.4 ± 8.4 beats•min-1) and I-4 (76.8 ± 7.3 beats•min-1). Recovery HR in 2nd hour after exercise was higher after I-10 (70.8 ± 8.1 beats•min-1) than after CON (66.7 ± 6.7 beats•min-1) or I-4 (67.7 ± 6.9 beats•min-1). Rate of EE was lower in 2nd hour after exercise for CON (1.04 ± 0.15 kcal•min-1) than after I-10 (1.10 ± 0.15 kcal•min-1) or I-4 (1.11 ± 0.18 kcal•min-1). CONCLUSIONS: Though exercise VO2 and EE associated with CON were significantly higher than those associated with any of the interval training sessions, several markers of metabolic rate (HR, EE) were higher during recovery after I-10 than after CON. Differences in the recovery periods after interval training vs CON may partially explain reports that interval training results in similar or greater improvements in body composition when compared with continuous exercise, even with significantly lower exercise energy expenditure.