Abstract 10704: Myocardial Mass Increases with both Sprint- and Aerobic-type Interval Exercise but not with a Traditional, Continuous Aerobic Exercise in Sedentary Adults: An 8-week Randomized Intervention Study
Introduction: Modern, time-pressed, sedentary adults require a time-efficient exercise protocol. Previous studies indicate that sprint interval training (SIT) improves maximal oxygen consumption (VO2max) mainly through increased oxidative capacity in peripheral muscles, whereas, high-intensity interval aerobic training (HIAT) improves VO2max mainly through improved cardiac function. We tested the hypotheses that (1) SIT and HIAT had greater effects on VO2max than did traditional continuous aerobic training (CAT), and that (2) left ventricular myocardial mass (LVM) increased only through HIAT.
Methods: Forty-two healthy but sedentary male subjects (age, 26.5 ± 6.2 years; BMI, 21.3 ± 1.9 kg·m-2; VO2max, 42.6 ± 6.3 ml·kg-1·min-1; LVM, 105.0 ± 15.7 g) participated in an 8-week, 5 times/wk, supervised exercise intervention study. They were randomly assigned to each (n = 14) of the 3 exercise protocols: SIT (total 5 min) consisting of 7 sets of 30-s cycling at 110∼120% VO2max with a 15-s rest between sets; HIAT (total 13 min) consisting of 3 sets of 3-min cycling at 80∼90% VO2max with a 2-min active rest at 50% VO2max between sets; and CAT consisting of 40 min of cycling at 60∼65% VO2max. We originally developed both the SIT and HIAT protocols for sedentary individuals in our laboratory. We measured VO2max by indirect calorimeter and LVM by 3T-MRI before and after the intervention.
Results: No differences were observed at baseline across the three groups in any of the measures. All subjects completed the 8-week exercise training. There was a significant (P = 0.01) difference between the groups in increased VO2max (SIT, 16.7 ± 11.6%; HIAT, 22.5 ± 12.2%; CAT, 10.0 ± 8.9%). Whereas, we observed significant changes in LVM and resting heart rate (HR) in both the SIT (LVM, +6.5 ± 8.3%; HR, -7.3 ± 11.1%, both P = 0.02) and HIAT (LVM, +8.0 ± 8.3%; HR, -12.7 ± 12.2%, both P < 0.01) groups, but not in the CAT group (LVM, +2.5 ± 10.1%; HR, -2.2 ± 13.3%).
Conclusions: HIAT had the greatest effect on VO2max of the three protocols, but the LVM increased significantly with both the HIAT and the SIT. Both our SIT and HIAT may be useful, time-efficient exercise protocols to improve cardiac activity for sedentary adults.
- © 2012 by American Heart Association, Inc.