# Human Psychophysiological Activity Estimation Based on Smartphone Camera and Wearable Electronics
## 2 Related Work
### Relationships between Heart Rate, Breath and Psychophysiological Activity  
Human pulse and breath are the main measurements that characterize calm. The authors of the paper [4] identified them as the main psychophysiological activity factors related to the psychophysiological activity process (see Table 1). An example of pulse changes has been presented in an experiment about the differences between Chi and Kundalini types of meditation [7]. Figure 1 shows the pulse changing after the meditation practice starting. The heart rate varied in a range of over 30-35 beats/min within 5 s in some of the subjects. It correlates with breath rate, but the most significant fact is pulse decreasing after the meditation starting. Another experiment shows the increasing of the parasympathetic and reducing sympathetic nerve activity as well as increasing overall heart rate while practicing the Acem technique [8]. The presented heart rate is less than the average human heart rate. Two presented experiments show that pulse decreasing does not depend on the meditation technique. Moreover, this decreasing is also presented in general meditation exploring [9; 10], but the decreasing tendency cannot be easily unified. One more experiment has been studied in [11]. The authors say that different meditative/breathing protocols may evoke common heart rate effects, as well as specific responses. The results support the concept of a meditation paradox, since a variety of relaxation and meditative techniques may produce active rather than quiescent cardiac dynamics, which are associated with prominent low-frequency heart rate oscillations or increases in the mean resting heart rate. A similarity in heart rate variability during the relaxation response and segmented breathing can be noted. Both interventions induced prominent, relatively low-frequency oscillations in heart rate, which were associated with slow breathing at the same slow frequency. Compared to baseline, for both the relaxation response and segmented breathing, there is an increase in dynamic range, with an up to 20 beats/min change in heart rate occurring over 10 s. The respiration spectrum during segmented breathing shows a dominant peak at the mean breathing rate, as well as higher harmonics due to the nonlinearity of the signal. In contrast, during the breath of fire, the respiratory rate is markedly increased (up to 132 breaths/min). Compare this response with the atypical pattern noted in one of the subjects, where breath of fire was associated with low-frequency heart rate oscillations. Another considered body measurement is breathing. Visual analyses of the data showed a decrease in respiration rate during the meditation from a mean of 11 breaths/min for the pre- and 13 breaths/min \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **Rest** & **Meditation** & **Difference** & **\(p\)-Value** \\ \hline Respiration rate/min & \(16.9\pm 1.9\) & \(16.3\pm 1.8\) & 0.52 (\(-\)0.05 to 1.9) & 0.072 \\ Heart rate/min & \(72.6\pm 10.9\) & \(71.6\pm 10.6\) & 0.92 (\(-\)0.15 to 1.98) & 0.088 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Heart rate measures during the Acem meditation technique [4]. Figure 1: Heart rate changes during Chi and Kundalini meditation techniques [4]. for the post-baseline to a mean of 5 breaths/min during the meditation, with a predominance of abdominal/diaphragmatic breathing. There was a noticeable decrease in respiration rate during the meditation (5 breaths/min) when compared to the pre- (11 breaths/min) and post-baseline periods (13 breaths/min). The decreases in respiration from 11 (pre-baseline) and 13 (post-baseline) to 5 breaths/min, with continued slow breathing at 5 breaths/min during the meditation period, demonstrate significant meditative control (see Figure 2). It suggests a decrease in arousal that appears consistent with other findings on the physiological correlates of meditation that show a decrease in respiration.