Fig. 1. Ground reaction forces (GRF) in the frontal plane of a sprinter along a straight path (A) and on a curved path (B). Along a straight path, lateral forces (F_lateral) are negligible and the peak vertical component of the GRF (F_vertical) equals the peak resultant GRF (F_resultant). When running along a curved path, F_lateral comprises a significant portion of the total resultant force. If the upper limit to F_resultant is achieved on the curve as Greene's theory suggested (Greene, 1985), then for the same F_resultant, F_vertical on the curve must be smaller relative to that generated on a straight path. Note that the axis of the fore–aft component of the GRF is coming out of the page in both cases and the fore–aft component is negligible when F_resultant is at its peak.