QTc interval prolongation during recovery from brief high-intensity intermittent exercise in obese adults

The risk of malignant arrhythmias is higher during extremely intense exercise and after its cessation. It is still unclear whether high-intensity interval exercise (HIE), an increasingly popular option in preventive and rehabilitative medicine, can lead to an impaired electrophysiological milieu, as revealed by QT interval prolongation on an electrocardiogram. This study investigated heart rate-corrected QT interval (QTc) dynamics during recovery from HIE in obese adults. In total, 13 obese males (age: 24.3 ± 4.6 years old; body mass index: 31.6 ± 4.1 kg/m²) underwent: (1) HIE: an HIE session of four 30-s all-out cycling efforts interspersed with 4‑min recovery periods; (2) REC: a recovery session 24 h after HIE; and (3) CON: a control session of no treatment. The QT interval was measured before HIE, REC, and CON, and then at 30-min intervals thereafter, for up to 3 h. QTc values were obtained using Bazett, Fridericia, Framingham, Hodges, and Rautaharju correction formulas. Acute HIE led to a significant increase in QTc for each correction (by 5–47 ms, all p < 0.05), and QTc was significantly longer during early recovery from acute exercise (HIE) compared with CON corrected with the Bazett (by 49 ms), Fridericia (by 11 ms), Hodges (by 27 ms), and Rautaharju (by 15 ms) formulas (all p < 0.05). Further, the QTc for each correction at most of the observation points in the REC trial was significantly longer (by 5–10 ms, all p < 0.05) than the corresponding value of the CON. In conclusion, in obese adults, the risk of QTc prolongation increased after brief HIE, and the risk may be sustained for more than 24 h.