Foot strike patterns after obstacle clearance during running.
OBJECTIVE
Running over obstacles of sufficient height requires heel strike (HS) runners to make a transition in landing strategy to a forefoot (FF) strike, resulting in similar ground reaction force patterns to those observed while landing from a jump. Identification of the biomechanical variables that distinguish between the landing strategies may offer some insight into the reasons that the transition occurs. The purpose of this study was to investigate the difference in foot strike patterns and kinetic parameters of heel strike runners between level running and running over obstacles of various heights.


METHODS
Ten heel strike subjects ran at their self-selected pace under seven different conditions: unperturbed running (no obstacle) and over obstacles of six different heights (10%, 12.5%, 15%, 17.5%, 20%, and 22.5% of their standing height). The obstacle was placed directly before a Kistler force platform. Repeated measures ANOVAs were performed on the subject means of selected kinetic parameters.


RESULTS
The statistical analysis revealed significant differences (P < 0.004) for all of the parameters analyzed. The evaluation of the center of pressure and the ground reaction forces indicated that the foot strike patterns were affected by the increased obstacle height. Between the 12.5% and 15% obstacle conditions, the group response changed from a heel strike to a forefoot strike pattern.


CONCLUSIONS
At height > 15%, the pattern was more closely related to the foot strike patterns found in jumping activities. This strategy change may represent a gait transition effected as a mechanism to protect against increased impact forces. Greater involvement of the ankle and the calf muscles could have assisted in attenuating the increased impact forces while maintaining speed after clearing the obstacle.
Scholten
Shane D
SD
HPER Biomechanics Laboratory, University of Nebraska at Omaha, Omaha, NE 68182, USA.
Stergiou
Nicholas
N
Hreljac
Alan
A
Houser
Jeremy
J
Blanke
Daniel
D
Alberts
L Russell
LR
D000328:Adult; D005260:Female; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006365:Heel / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011312:Pressure; D012420:Running / Q000502:physiology*; D013314:Stress, Mechanical