Following a brain injury (BI) in addition to all other systems, there can be a failure in the
control of the autonomic system activity. Heart rate (HR) has its own normal variability.
Heart rate is controlled by the Sympathetic and Parasympathetic systems. Therefore,
monitoring HR variability (HRV) can help us evaluate the balance of the two systems and their
efficiency.Decrease in HRV was found to be in correlation with death among patients in the
acute stage following ABI. Decrease in HRV is a pre-stage of HR irregularity and ventricular
fibrillation.This disturbance can have a great impact on the patients health condition. In
addition there was found an inverse correlation between this situation and the rehabilitation
outcomes. Based on this data there is a great importance in monitoring HRV during
rehabilitation among patients following BI while the patients are required to perform
physical activity.The aim of this work is to check whether we can replace the traditional way
of measuring HR by EKG Holter (gold standard) with a more simple,accessible tool-the POLAR
The aim of this work is to check if the data collected from a POLAR watch is reliable
compared to the data collected from an EKG holter.