Heart rate
RS 800CX
HEART
Heart rate (HR) was used as an objective biomarker of meditation ability to indirectly assess how well the participants followed the meditation exercise. The time (in seconds) between two heart beats (NN interval) was recorded at rest at the beginning of the experimental session and during both interventions using the heart rate monitor POLAR RS 800CX RUN (Polar Electro Öy, Kempele, Finland). During the resting state, participants were asked to close their eyes, remain still, and let their mind wander without falling asleep or meditating.The mean heart rate (HR) in beats per minute (bpm) was computed as in Before computing HR, raw NN data were preprocessed by excluding: i) NN values that were higher than 1.5 seconds or lower than 0.4 seconds (considered as artefacts), ii) NN values that were below or above 3×SD of the participant’s mean (considered as outliers), and iii) equal adjacent NN values associated to the non-detection of the cardiac activity by the device. Time-series that lost more than third of their data points after preprocessing were excluded. Overall, this led to the loss of eight observations (amongst 129 observations in total) in four meditators: three at resting-state, three during AL and two during MM. Those four participants were thus not included in data analysis.