Resumen de Relationship between Running Speed and Initial Foot Contact Patterns.
Bastiaan Breine, Dirk De Clercq, Philippe Malcolm, Edward C. Frederick
AB Purpose: This study assessed initial foot contact patterns (IFCP) in a large group of distance runners and the effect of speed on the IFCP. Methods: We determined the strike index to classify the runners in IFCP groups, at four speeds (3.2, 4.1, 5.1, and 6.2 m[middle dot]s-1), by measuring center of pressure (COP) with a 2-m plantar pressure plate. Such a system allows a direct localization of the COP on the plantar footprint and has a low threshold value (2.7 N[middle dot]cm-2), resulting in more accurate COP data at low ground reaction forces than when obtained from force plate. Results: The IFCP distribution evolves from mostly initial rearfoot contact (IRFC) (82%) at 3.2 m[middle dot]s-1 to more anterior foot contacts with an approximately equal distribution of IRFC (46%) and initial midfoot or forefoot contact (54%) at 6.2 m[middle dot]s-1. Approximately 44% of the IRFC runners showed atypical COP patterns with a fast anterior displacement of the COP along the lateral shoe margin. Apart from the different COP patterns, these atypical IRFC were also characterized by a significantly higher instantaneous vertical loading rate than the typical IRFC patterns. Conclusions: The IFCP distribution changes were due to intraindividual alterations in IFCP at higher speeds. That is, 45% of the runners made one or even two "transitions" toward a more anterior IFCP (and 3% shows some other type of transition between initial foot contact styles as speed increases). However, 52% of the runners remained with the same IFCP.
