The longitudinal variability of ground reaction forces in experienced and inexperienced runners

The hypothesis of a 'movement pattern fixation' or 'movement stereotype' for running was tested by measuring four ground reaction force variables on three separate test sessions in a longitudinal study. Of the four variables chosen to investigate this hypothesis, two reflected the shock absorption characteristics of a runner plus footwear and two reflected characteristics of running style. The former two were the magnitude of the vertical force impact peak, and the force load rate leading to this peak, while the latter two were the impulses of the breaking and propulsion phases of foot contact obtained from the anterior-posterior component of the ground reaction force. Two groups of subjects were used, seven experienced runners and seven inexperienced runners. The results showed evidence of a 'movement pattern fixation' in seven of the fourteen subjects. Thirteen subjects showed substantial differences (p < 0.001) in one or more variable, while only one subject did not show any difference in any variable across all test sessions. Differences between experienced and inexperienced runners were small for the shock absorption variables, but marked for the running style variables. Generally inexperienced runners demonstrated greater braking and propulsion impulses, and greater variability in these two variables, indicating that they were using a less economical action. It is concluded that a movement pattern fixation was shown to exist, and has implications for the testing of sports equipment. These implications are to do with the conditions required to establish the efficacy of sports equipment through athlete response testing.