The invention relates to a device to assist in the practice of a physical activity session by an person. The device has an electronic means for determining the real-time physical effort to be provided by said person during said session, implementing a control law having, as an output, a parameter that corresponds to the physical effort to be provided (EPF) and, as an input, data collected while the force is being applied, essentially comprising: the measurement of the heart rate (FC) of said person the measurement of the respiratory rate (FR) of said person and one or more indices (EVA) of strenuousness of the effort as perceived by said person, to be specified by said person during the effort, and in which said control law depends essentially on respective programmed thresholds which should not be exceeded, essentially comprising: the maximum heart rate (FCM), the maximum respiratory rate (FRM), and the maximum value or values associated with said index or indices of strenuousness.
