**3. Heart rate in people with ID**

Heart rate (HR), expressed by a number of cardiac cycles per minute, is a commonly used indicator of intensity, cardiorespiratory fitness, and sympathetic activation in sports and exercise. The long-term endurance training should lead to a reduced resting HR [20]. Furthermore, individuals with Down syndrome exhibit reduced peak HR, and in severe and profound ID, HR can be used to assess the information about emotions as a lower HR in the first 6 seconds of stimulus presentation was observed when presenting a negative stimulus [21, 22].
