Method of determining the training intensity of a person (2), whereby time intervals RRi (13) between consecutive heartbeats are recorded whereupon from sequences of these time intervals RRi (13) a sequence of standardised intervals rri (14) is generated through mathematical modelling. From two consecutive standardised intervals rri (14) and rri+1 points in a Poincaré plot are generated and with regard to the principal horizontal axis X0 (16) of a confidence ellipse of these points a standard deviation SOL is calculated. From pairs of values formed of a mean value RRMV of the sequence of intervals RRi (13) and the standard deviation SOL for further sequences of standardised intervals rri (14) a training intensity curve (20) is then produced for the person (2) whereby the training intensity curve (20) is produced from pairs of values of the heart frequencies HF (HF=1/RRMV) corresponding to the mean values RRMV and the standard deviations SOL.