A method for determining an exertion parameter during physical exercise, user-specific performance monitor implementing the method, and computer software product. The method includes determining a propagation variable characterizing the user's propagation; determining a gravitational motion variable characterizing the user's motion in the direction of the gravitational field; calculating an inclination factor proportional to the inclination of a propagation base in accordance with the propagation variable and the gravitational motion variable; calculating a propagation factor proportional to propagation efficiency characterizing the user's ability to move with respect to the inclination of the propagation base, the propagation factor having a different calculated value based on whether the inclination factor is positive or negative for the same base value of the inclination factor; and calculating an exertion parameter that characterizes the user's energy consumption along the propagation route in accordance with the propagation variable, the gravitational motion variable, and the propagation factor.