Exercise data apparatus (100) for use in the body of a user during the exercise, comprising: an electrocardiogram detector (140) for detecting the electrocardiogram data of said user during the exercise； fixing means (120) for fixing the electrocardiogram detector in the chest of said user； a motion detector (130) to detect body movement data indicating the steps of said user during the exercise； a processor (194) for calculating the exercise data based on the electrocardiogram data detected by the electrocardiogram detector and the body movement data detected by the motion detector, exercise data comprising a distance from said user； an output device (220) for informing said user of the calculated exercise data； input means (230) for entering the body height and sex of said user； characterized in that the processor is programmed in order to determine a variable stride of said user for the calculation of the distance, distance that is calculated by multiplying the variable stride by the user's steps during the exercise, variable stride that is determined according to sex, body height and the rhythm of said user according to the formula: where: F is the pace in steps per second G is the gender coefficient: 0.7 for women / 0.8 for men H is the body height in meters a, b and c are parameters whose values depend on F as shown below: [a, b, c]>； = [0, 0, 0.5] (F <；1.5 Hz) [a, b, c]>； = [0, 3, 1.5, 0.5] (1.5 Hz <；>； = F <；2.0 Hz) [a, b, c]>； = [0.8, 1.9, 0.55] (2, 0 Hz <；>； = F <；2.5 Hz) [a, b, c]>； = [-0.5, 2.9, 1.15] (2.5 Hz <；>； = F <；3.3 Hz) [a, b, c]>； = [0, 0, 0.97] (F>；>； = 3.3 Hz)Aparato de datos de ejercicio (100) para usarse en el cuerpo de un usuario durante el ejercicio, quecomprende: un detector de electrocardiograma (140) para detectar los datos del electrocardiograma de dicho usuariodurante el ejercicio； medio de fijación (120) para fijar el detector de electrocardiograma en el pecho de dicho usuario； un detector de movimie
