Material and methods Subjects Seven skilled soccer players served as subjects in the
present study. The age (range) of the subjects was 26.4 (21-30) years, their weight (66-96) 74.4 kg and their height (1.71-1.88) 1.81 m. In a pre-study test the subjects
kicked a ball 8 times and the ball velocity was measured using a Doppler radar. Of 30 players tested,the 7 with the most constant ball velocity were chosen to participate in the study. In this way it was ensured that the subjects would kick with a relatively constant ball velocity in the laboratory where only 3 trials were
recorded. All subjects gave their informed consent to partici-