The present study aimed to provide further evidence on the usefulness of non-linear cardiac measures when examining the output of the cardiac system. Scale-invariant self-similarity and entropy, in addition to heart rate variability (HRV) given by time- and frequency-domain measures were calculated in a sample of N = 55 healthy adolescents (M_age = 14.122, SD_age = 0.698) during 10-min positive (non-stressful) and negative (stressful) interactions with their mothers. We also explored sex influence in adolescents’ cardiac output using both HRV measures and non-linear cardiac measures. Repeated measures MANOVA revealed a marginal within-group effect for HRV measures, F(3,51) = 2.438, p = 0.075, η²_p = 0.125), and a significant within-group effect for non-linear cardiac measures, F(6, 48) = 3.296, p = 0.009, η²_p = 0.292, showing a significant decrement in adolescents’ cardiac complexity during the negative interaction. No significant effect for sex was found in either non-linear cardiac measures or HRV measures, but results suggest lower cardiac scaling in females than in males. These findings suggest a real-time scale predominance in heart rate output when adolescents face an aversive situation and support the importance of non-linear cardiac measures to gain insight into the cardiac system and its regulatory mechanisms. Further research is needed to examine sex-differences in cardiac complexity during aversive situations.

本研究旨在为检查心脏系统输出时非线性心脏测量的有用性提供进一步的证据。在N  = 55 名健康青少年（M_年龄 = 14.122，SD_年龄 = 0.698）的样本中计算了尺度不变的自相似性和熵，以及由时域和频域测量给出的心率变异性 (HRV )。与母亲进行 10 分钟的正面（无压力）和负面（压力）互动。我们还使用 HRV 测量和非线性心脏测量探讨了性别对青少年心输出量的影响。重复测量 MANOVA 揭示了 HRV 测量的边际组内效应，F (3,51) = 2.438, p = 0.075, η ² _p  = 0.125)，以及非线性心脏测量的显着组内效应，F (6, 48) = 3.296, p  = 0.009, η ² _p = 0.292，表明在负相互作用期间青少年心脏复杂性显着下降。在非线性心脏测量或 HRV 测量中都没有发现对性别的显着影响，但结果表明女性的心脏比例低于男性。这些发现表明，当青少年面临厌恶的情况时，心率输出的实时量表占优势，并支持非线性心脏测量对于深入了解心脏系统及其调节机制的重要性。需要进一步的研究来检查在厌恶情况下心脏复杂性的性别差异。