Effects of interval and continuous exercise training on autonomic cardiac function in COPD patients

Background and Aim Both interval (IT) and continuous (CT) exercise training results in an improvement of aerobic capacity in patients with chronic obstructive pulmonary disease (COPD); however, their effects on cardiac autonomic function remains unclear. The aim of our study was to evaluate the effect of a supervised CT vs IT on autonomic cardiac function in COPD patients. Methods COPD patients were divided into two different groups according to training modality (IT or CT). Autonomic cardiac dysfunction (ACD) was defined as a heart rate recovery lower than 12 bpm heart rate after the first minute of maximal exercise (HRR1) and an abnormal chronotropic response (CR) to exercise (<80%). Results A total of 29 patients {mean [standard deviation (SD)] age: 68 (8) years, %FEV1: 42 (13) predicted} were trained (15 subjects in the CT group, 14 subjects in the IT group). After training, both groups increased peak oxygen consumption [mean difference ΔVO2 peak: 156 mL/min (P = 0.04) on IT; and 210 mL/min (P = 0.01) on CT], HRR1 [IT, from 10.4 (5) to 13.8 (5) bpm (P = 0.04); and CT, from 14.3 (5) to 17.7 (5) bpm (P = 0.04)] and CR [IT, from 57% (22) to 81% (9) (P = 0.001); and CT, from 48% (28) to 73% (17) (P = 0.001)]. Sixteen patients showed ACD. Among these patients, HRR1 (P = 0.01 for IT and P = 0.04 for CT) and CR (P = 0.001 for IT and P = 0.002 for CT) were enhanced after training. Conclusions Both IT and CT exercise training improve heart rate recovery and CR in COPD patients. These benefits could help to individualize exercise training.