Refining the deceleration capacity index in phase-rectified signal averaging to assess physical conditioning level

BackgroundDeceleration capacity (DC) of heart rate is a measure of cardiac vagal modulation. This study introduced a DC adaptation (Modified Index) that measured the velocity of change in the phase-rectified signal averaging curve, and assessed its ability to discriminate athletes from controls.Materials and methodsThe Modified Index was compared to Standard DC approach in a prospective case–control study. Subjects were classified according to maximal metabolic equivalents as the control group (CG) and athlete group (AG). The Modified Index was compared to Standard DC and classical approaches (RMSSD and HF) by the area under receiver operating characteristic curve (AUC) using 10,000 bootstraps.ResultsIn Standard DC and Modified Index bootstrap median values were (ms), respectively, 11.80 and 17.94 (p < 0.01) in CG, and 25.98 and 45.62 in AG (p < 0.01). AUC (mean ± SD) was 0.70 ± 0.12 for Standard DC and 0.96 ± 0.04 for Modified Index (p < 0.01).ConclusionsModified Index appropriately discriminates athletes from healthy sedentary subjects.