Reply to 'Comment on Photoplethysmography sampling frequency: pilot assessment of how low can we go to analyze pulse rate variability with reliability?'.

In his Comment, Hejjel argued that some contents previously published by us were inappropriate for the statistical analysis of pulse rate variability due to high inter-individual dispersion. He also claimed that data collection over 5 min for short-term HRV analysis and data collection for an abnormal range of people were required. In order to give our perspective on these issues, we will discuss and clarify some of the existing literature and our own work on this subject, underlining the difference between electrocardiogram and photoplethysmogram.