PURPOSE: To evaluate the metabolic and cardiovascular response during four different high intensity aerobic interval training (HIT) protocols with similar total work output.
METHODS: Eight young physically active subjects participated in five different bouts of exercise over a 3-wk period, where VO2 and HR were continuously monitored. Protocol one consisted of 20 min continuous exercise at ∼70% of VO2max. Protocols 2, 3, 4, and 5 were interval based with a work:active rest period (in seconds) of 30:30, 60:30, 90:30, and 60:60 respectively. Each interval protocol was at a workload corresponding to 90% VO2max as determined by a maximal graded exercise test, and each resulted in ∼10 minutes of work but differed in the rest duration. Active rest was carried out at a workload corresponding to ∼35-40% VO2max.
RESULTS: The 90:30 HIT protocol resulted in the highest VO2, HR, RPE, and blood lactate whereas the 30:30 protocol resulted in the lowest of these parameters (P < 0.05). The total caloric energy expenditure was lowest in the 90:30 and 60:30 protocol (∼150kcal) (P < 0.05), whereas the other 3 protocols averaged ∼200 kcal. The immediate post-exercise blood pressure was similar across all protocols.
CONCLUSIONS: These finding indicate that varying the work-to-rest ratio affects the metabolic response to HIT, and that HIT performed at 90% of VO2max is physiologically feasible and may be used as an alternative approach to training middle-aged subjects, but with less time commitment.