A method of assessing the performances of an athlete that performs a gymnastic exercise, comprising the steps of: - providing a measuring device and removably associating said measuring device to the body of the athlete or to equipment for performing said gymnastic exercise, said measuring device comprising a transducer having at least one accelerometer; and, using processing means: a) determining, during the gymnastic exercise, a first sequence of values, identifying the acceleration of said body of the athlete or said equipment for performing said gymnastic exercise, along a preset axis (x,y,z); b) processing said first sequence of values by integral calculation to obtain a second sequence of values identifying speed; c) processing said second sequence of values by calculating the least squares regression coefficients to generate a third sequence of values; d) subtracting said third sequence of values from said second sequence of values to obtain a fourth sequence of values identifying the speed at which said body of the athlete or said equipment for performing said gymnastic exercise moves; e) informing said athlete, during said gymnastic exercise, about at least one value representative of said performance of said athlete, said at least one value being determined as a function of said fourth sequence of values f) processing said fourth sequence of values by integral calculation to obtain a repetition value identifying the number of repetitions performed during said gymnastic exercise; characterized in that said step f) comprises the steps of: f1) providing a threshold value (Th); f2) processing said fourth sequence of values by integral calculation to obtain a sixth sequence of values; f3) selecting a portion of values (S6') belonging to said sixth sequence of values; f4) processing said portion of the sequence of values (S6') by standard deviation calculation to obtain a sequence of processed values (S6"); f5) comparing said threshold value (Th) with each value of said sequence of processed values (S6") and, if said processed value is higher than said threshold value (Th), generating said repetition value; f6) informing said athlete, during said gymnastic exercise, about said repetition value representative of the number of repetitions performed by said athlete during said gymnastic exercise. - providing a measuring device and removably associating said measuring device to the body of the athlete or to equipment for performing said gymnastic exercise, said measuring device comprising a transducer having at least one accelerometer; and, using processing means: a) determining, during the gymnastic exercise, a first sequence of values, identifying the acceleration of said body of the athlete or said equipment for performing said gymnastic exercise, along a preset axis (x,y,z); b) processing said first sequence of values by integral calculation to obtain a second sequence of values identifying speed; c) processing said second sequence of values by calculating the least squares regression coefficients to generate a third sequence of values; d) subtracting said third sequence of values from said second sequence of values to obtain a fourth sequence of values identifying the speed at which said body of the athlete or said equipment for performing said gymnastic exercise moves; e) informing said athlete, during said gymnastic exercise, about at least one value representative of said performance of said athlete, said at least one value being determined as a function of said fourth sequence of values f) processing said fourth sequence of values by integral calculation to obtain a repetition value identifying the number of repetitions performed during said gymnastic exercise; a) determining, during the gymnastic exercise, a first sequence of values, identifying the acceleration of said body of the athlete or said equipment for performing said gymnastic exercise, along a preset axis (x,y,z); b) processing said first sequence of values by integral calculation to obtain a second sequence of values identifying speed; c) processing said second sequence of values by calculating the least squares regression coefficients to generate a third sequence of values; d) subtracting said third sequence of values from said second sequence of values to obtain a fourth sequence of values identifying the speed at which said body of the athlete or said equipment for performing said gymnastic exercise moves; e) informing said athlete, during said gymnastic exercise, about at least one value representative of said performance of said athlete, said at least one value being determined as a function of said fourth sequence of values f) processing said fourth sequence of values by integral calculation to obtain a repetition value identifying the number of repetitions performed during said gymnastic exercise; f1) providing a threshold value (Th); f2) processing said fourth sequence of values by integral calculation to obtain a sixth sequence of values; f3) selecting a portion of values (S6') belonging to said sixth sequence of values; f4) processing said portion of the sequence of values (S6') by standard deviation calculation to obtain a sequence of processed values (S6"); f5) comparing said threshold value (Th) with each value of said sequence of processed values (S6") and, if said processed value is higher than said threshold value (Th), generating said repetition value; f6) informing said athlete, during said gymnastic exercise, about said repetition value representative of the number of repetitions performed by said athlete during said gymnastic exercise.