Long-term high-intensity interval training associated with lifestyle modifications improves QT dispersion parameters in metabolic syndrome patients

BackgroundQT dispersion (QTd) is a marker of myocardial electrical instability, and is increased in metabolic syndrome (MetS). Moderate intensity continuous exercise (MICE) training was shown to improve QTd in MetS patients.ObjectivesTo describe long-term effects of MICE and high-intensity interval exercise training (HIIT) on QTd parameters in MetS.MethodsSixty-five MetS patients (53 ± 9 years) were assigned to either a MICE (60% of peak power output PPO]), or a HIIT program (alternating phases of 15–30 s at 80% of PPO interspersed by passive recovery phases of equal duration), twice weekly during 9 months. Ventricular repolarization indices (QT dispersion = QTd, standard deviation of QT = sdQT, relative dispersion of QT = rdQT, QT corrected dispersion = QTcd), metabolic, anthropometric and exercise parameters were measured before and after the intervention.ResultsNo adverse events were noted during exercise. QTd decreased significantly in both groups (51 vs 56 ms in MICE, P < 0.05; 34 vs 38 ms in HIIT, P < 0.05). Changes in QTd were correlated with changes in maximal heart rate (r = ?0.69, P < 0.0001) and in heart rate recovery (r = ?0.49, P < 0.01) in the HIIT group only. When compared to MICE, HIIT training induced a greater decrease in weight, BMI and waist circumference. Exercise capacity significantly improved by 0.82 and 1.25 METs in MICE and HIIT groups respectively (P < 0.0001). Lipid parameters also improved to the same degree in both groups.ConclusionIn MetS, long-term HIIT and MICE training led to comparable effects on ventricular repolarization indices, and HIIT might be associated with greater improvements in certain cardiometabolic risk factors.