HIGH-INTENSITY INTERVAL EXERCISE IN CHRONIC HEART FAILURE: COMPARISON OF CARBOHYDRATE AND LIPID OXIDATION

Abstract

high-intensity interval exercise has been extensively used with athletes and healthy subjects. There are a few evidences that it could improves physiology and functional capacity in heart failure patients, but still some answers about muscle metabolism need to be addressed. substrate oxidation was compared during 4 different high intensity intermittent exercise (HIIE) protocols in patients with heart failure and reduced ejection fraction (HFREF). Eighteen males (56±17 years, LVEF: 28±7%) randomly performed 4 HIIE with measurement of gas exchange. Exercise intensity protocols were set at 100% of peak power output (PPO). Interval duration was 30 seconds (A and B) or 90 seconds (C and D), and recovery was passive (A and C) or active (50% of PPO in B and D). Energy expenditure was calculated using Weir equation and substrate oxidation (glucose: CHO, and lipid) was calculated by the Frayn equation (for quantitative measure) and from a table of non-protein respiratory quotient (qualitative measure) using gas exchange analysis. mean O2peak was 17.8 ± 4.6 ml/min/kg (or 1.54 ± 4.6 L/min) and peak power output was 109 ± 31 Watts. At rest, fat oxidation averaged 0.13 ± 0.04 g/min, representing 68 ± 22 % of total substrate utilisation. CHO oxidation averaged 0.16 ± 0.1 g/min representing 31 ± 22% of total. During exercise, absolute CHO oxidation significantly decreased and absolute lipid oxidation significantly increased in each HIIE protocol (P<0.0001). Protocol B induced higher energy expenditure after 8-10 minutes of exercise compare to passive recovery modes (A and C) (P<0.0001). Short duration intervals with passive recovery (mode A) resulted in significantly lower CHO oxidation in absolute terms compare to modes with active recovery (B and D) (P<0.0001). In relative terms (%), CHO oxidation in mode A was significantly lower than mode C only, after 8-10 minutes of exercise. Lipid oxidation in absolute terms was significantly lower in mode C compare to the other 3 modes of HIIE at time 8-10 min whereas in relative terms it was significantly lower than mode A only (P<0.0001). All together, these 4 HIIE protocols showed increased lipid oxidation over time, and short interval duration with passive recovery showed higher lipid oxidation compared to the others. the choice of an active mode during HIIE may favors glucose oxidation during exercise in patients with HFREF, if the improvement of glucose metabolism is targeted.