Role of the work-to-rest ratio in high-intensity interval exercise on heart rate variability and blood pressure in sedentary obese men

Objective: The effect of different durations of high-intensity interval exercise (HIIE) on heart rate (HR) variability (HRV) and blood pressure (BP) in obese men. Materials and Methods: The study was a repeated measure and conducted in a counterbalanced order. Fifteen young obese men participated in five exercise tests on a cycle ergometer as follows: (a) graded exercise test to determine exercise intensity, (b) constant-load exercise test at 40% of HR reserve (HRR) for 20 min, (c) the 30:30 HIIE protocol at 80% of HRR (30 s of exercise followed by 30-s recovery intervals for 20 min), (d) the 60:60 HIIE protocol at 80% of HRR for 20 min, and (e) the 60:30 HIIE protocol at 80% of HRR for 15 min. HRV and BP were recorded before exercise, at the end of exercise, and at 30 min after exercise. Participants also provided feedback regarding the pleasure and excitement to exercise. Results: HRV recovery was greater in the 30:30 HIIE protocol and lesser in the 60:30 HIIE protocol. The mean arterial BP exhibited postexercise hypotension. Peak rate pressure product during exercise was highest in the 60:30 protocol and lowest in the 30:30 protocol. The participants preferred the 60:60 HIIE protocol in terms of pleasure and excitement. Conclusions: Interval exercise of 1:1 ratio model is recommended over the 2:1 ratio for obese men, with better physiological responses to the 30:30 HIIE protocol and better psychological responses to the 60:60 HIIE protocol.