Differences between ECG and pulse when measuring heart rate and reactivityunder two physical and two psychological stressors

To test the level of agreement of heart rate and reactivity to stressor tas ks as measured via noninvasive ECG and pulse, 38 healthy subjects underwent four stressor tasks: mental arithmetic, reaction time, cold pressor and bi cycling. Data on resting and stressor heart rate were collected via ECG and photoplethysmography, and heart rate reactivity was calculated via five me thods noted in the wider literature. Results indicated that, although resti ng heart rate values did not differ significantly across the two instrument s, there were some significant differences in heart rate during certain per iods of mental and physical stress reactivity. Calculation of heart rate re activity revealed that there were few significant differences between data from the two measures but that the tasks themselves produced markedly diffe rent patterns of reactivity, questionning assumptions underlying comparison of reactivity data under different stress tasks. Implications for the asse ssment of reactivity are discussed.