Research on effort and motivation commonly assesses how the sympathetic branch of the autonomic nervous system affects the cardiovascular system. The cardiac pre-ejection period (PEP), assessed via impedance cardiography, is a common outcome, but assessing PEP requires identifying subtle points on cardiac waveforms. The present research examined the psychometric value of the RZ interval (RZ), which has recently been proposed as an indicator of sympathetic activity, for effort research. Also known as the initial systolic time interval (ISTI), RZ is the time (in ms) between the ECG R peak and the dZ/dt Z peak. Unlike PEP, RZ involves salient waveform points that are easily and reliably identified. Data from two experiments evaluated the suitability of RZ for effort paradigms and compared it to a popular automated PEP method. In Studies 1 (n = 89) and 2 (n = 71), participants completed a standard appetitive task in which each correct response earned a small amount of cash. As expected, incentives significantly affected PEP and RZ in both experiments. PEP and RZ were highly correlated (all rs ≥ 0.89), and RZ consistently yielded a larger effect size than PEP. In Study 3, a quantitative synthesis of the experiments indicated that the effect size of RZ’s response to incentives (Hedges’s g = 0.432 [0.310, 0.554]) was roughly 15% larger than PEP’s effect size (g = 0.376 [0.256, 0.496]). RZ thus appears promising for future research on sympathetic aspects of effort-related cardiac activity.

关于努力和动机的研究通常评估自主神经系统的交感分支如何影响心血管系统。通过阻抗心动图评估的心脏射血前期 (PEP) 是一种常见结果，但评估 PEP 需要识别心脏波形上的细微点。目前的研究检验了 RZ 间隔 (RZ) 的心理测量值，该值最近被提议作为交感神经活动的指标，用于努力研究。RZ 也称为初始收缩时间间隔 (ISTI)，是 ECG R 峰值和 dZ/dt Z 峰值之间的时间（以毫秒为单位）。与 PEP 不同，RZ 涉及易于可靠识别的显着波形点。两项实验的数据评估了 RZ 对于努力范式的适用性，并将其与流行的自动化 PEP 方法进行了比较。在研究 1 ( n  = 89) 和 2 ( n  = 71) 中，参与者完成了一项标准的食欲任务，其中每个正确的反应都会赚取少量现金。正如预期的那样，激励措施在两个实验中都显着影响了 PEP 和 RZ。PEP 和 RZ 高度相关（所有r s ≥ 0.89），并且 RZ 始终比 PEP 产生更大的效应量。在研究 3 中，实验的定量综合表明，RZ 对激励的响应的效应大小（Hedges 的g  = 0.432 [0.310, 0.554]）比 PEP 的效应大小（g  = 0.376 [0.256, 0.496]）大约大 15% 。因此，RZ 对于未来与努力相关的心脏活动的交感神经方面的研究似乎很有希望。