Heart rate variability in exercise and various physiological conditions

The assessment of heart rate variability (HRV), because of its prognostic capability, has become very popular in the last 20 years. However, despite its popularity the physiological interpretation of HRV is still debated. The present article focussed on the evaluation of HRV in different physiological conditions associated to exercise. The distinct relationshipsbetween HRV, training load, overtraining and fatigue are analysed. Although it is recognised that, during dynamic exercise, the heart rate increase is the result of both a parasympathetic withdrawal and an augmented sympathetic activity, the exact contribution of these two mechanisms is still uncertain. Moreover the assessment of HRV during exercise is additionally complicated by the fact that the recorded signal is non-stationary. In conclusion it can be underlined the need for the standardization of the methods of HRV assessment during exercise. Future studies should be performed ideally on large populations and adopting randomized controlled trials in order to ameliorate the assessment of HRV in exercise, to monitor the training and to augment its capability as a tool for the prevention of the overtraining syndrome and to monitor physical fatigue during periods of intensive training.