The effect of different surfaces on ground reaction forces during running : a single-individual design approach

Knowledge of the forces acting on a performer when running on different surfaces is important for injury prevention and treatment. The aim of this study was to determine the effect of three different surfaces upon selected ground reaction force parameters linked to injury in running for three individual participants. Three healthy male participants completed 25 trials in 3 surface conditions (running track, carpet and no-covering), running at 3.8m.sec-1 over a Kistler 9281CA force platform (1200Hz). For each individual, five one-way analyses of variance were performed for each dependent variable (peak: vertical impact force, propulsive force, vertical loading rate, medial and lateral forces). The single-individual design allowed individual-specific recommendations to be made based upon, for example, a non-significant difference in peak vertical loading rate for participant 3 (104±14kN.sec-1 on carpet; 97±12kN.sec-1 on track: p>0.01) compared to a significant difference observed for participant 1 (165±15kN.sec-1 on carpet; 233±41kN.sec-1 on track: p<0.01). The design used also revealed significant differences in medio-lateral forces (e.g. participant 2 peak medial force: 117±34N on no-covering; 83±18N on track: p<0.01), since the differences were not masked by high inter-individual variability, as may occur in group designs.