Process for measuring or determining a reaction time of an athlete at the start of a race by means of a personalised transponder module positioned on an upper part of the body of the athlete and a base station of a measurement system, the transponder module comprising at least a signal receiver unit, a processing unit for data, measurements or commands, a transmitter unit for data and/or measurement and/or command signals, and at least one first motion sensor (7, 8) to supply measurement signals to the processing unit, said first motion sensor comprising a gyroscope with one, two or three measurement axes, the process comprising the steps of: - activating the personalised transponder module following the receipt of a wake-up signal in the receiver unit, - measuring the speed of rotation and the angle of rotation of the transponder module on the athlete by the gyroscope following at least the signalling of a starting signal of the race, - determining variations in rotation of the transponder module following the starting signal in the processing unit, - transmitting the measurement signals directly or formatted, as well as data signals on the basis on the variations in rotation of the transponder module by the transmitter unit to the base station, - determining a reaction time of the athlete at the start of the race on the basis of the variations in rotation of the transponder module in the base station or in the processing unit of the transponder module, taking into account the angle of rotation of the transponder module worn on the upper part of the body of an athlete, the angle of rotation must be defined above a defined threshold to confirm a real start of the race of the athlete, and - determining a possible false start, if the defined reaction time is below a time threshold determined following an integration of the speed of rotation of the athlete with the transponder module with the time after the generation of the starting signal. - activating the personalised transponder module following the receipt of a wake-up signal in the receiver unit, - measuring the speed of rotation and the angle of rotation of the transponder module on the athlete by the gyroscope following at least the signalling of a starting signal of the race, - determining variations in rotation of the transponder module following the starting signal in the processing unit, - transmitting the measurement signals directly or formatted, as well as data signals on the basis on the variations in rotation of the transponder module by the transmitter unit to the base station, - determining a reaction time of the athlete at the start of the race on the basis of the variations in rotation of the transponder module in the base station or in the processing unit of the transponder module, taking into account the angle of rotation of the transponder module worn on the upper part of the body of an athlete, the angle of rotation must be defined above a defined threshold to confirm a real start of the race of the athlete, and - determining a possible false start, if the defined reaction time is below a time threshold determined following an integration of the speed of rotation of the athlete with the transponder module with the time after the generation of the starting signal.