Full length articleA kinematic method for footstrike pattern detection in barefoot and shod runners
Introduction
There has been a growing interest in the mechanics associated with different footstrike patterns (FSP) during running, especially in light of the suggested relationship between FSP and injury [1], [2], [3]. FSPs can be classified into three groups. A rearfoot strike (RFS) is one where the heel hits the ground first, a midfoot strike (MFS) is one where the foot lands flat on the ground and forefoot strike (FFS) is where the ball of the foot first strikes the ground. It has been reported that about 75% of all shod runners are RFS, 24% are MFS, and the remaining 1% are FFS [4], [5]. However, barefoot running is almost always associated with a FFS or MFS pattern [6], [7].
While FSP can be visually classified into one of the three types, it is quantified by the strike index (SI), using a force plate [8]. This is a measure of the location, at initial contact, of the center of pressure (COP) along the long axis of the foot as a percentage of the total foot length. The calculation is detailed in Fig. 1. A SI of 0–33% indicates a RFS, 34–67% a MFS, and 68–100% a FFS. Unfortunately, force data are not always available, as in the natural running environment, or when running on a conventional treadmill. The advent of instrumented treadmills does allow the calculation of SI during continuous running. However, these force treadmills inherently introduce more noise to the force data than those force plates that are floor-embedded. This noise adds significant error to the COP calculation, and is especially troublesome when forces are low at initial contact. However, the location of the COP should be related to the orientation of the foot at contact, with a more dorsiflexed position associated with a lower SI. As a result, the angle of the foot segment in the sagittal plane at footstrike may be provide a surrogate measure of SI.
Therefore, the purpose of this study was to determine whether SI can be estimated in the absence of force data, using the kinematic measure of the footstrike angle (FSA) of the foot. It was hypothesized that as FSA increased (towards more of a rearfoot strike) SI would decrease in both barefoot and shod runners across a range of FSP.
Section snippets
Methods
Twenty healthy runners (10 female, 10 male, aged 27.8 ± 8.9 yr, running 20.7 ± 13.0 min/week) with various natural FSPs were recruited from the University of Delaware and surrounding community. Each subject had markers placed on their right foot (Fig. 2). After subject calibration, anatomical markers were removed. Subjects ran across a force plate (Bertec, Columbus, OH) until five trials were collected at 1000 Hz for each condition. Each subject ran utilizing RFS, MFS, FFS and barefoot (BFS)
Results
In the shod condition, FSA was strongly correlated with SI, R = 0.92 (p < 0.01). The linear regression model with FSA is shown in Eq. (1) and Fig. 3.
FSA was again strongly correlated with SI in the barefoot condition (R = 0.86, p < 0.01). The linear regression model is shown in Eq. (2) and Fig. 3.
Six shod and three barefoot footstrikes were classified as MFS by the SI. These trials were used to determine criteria for FSP classification. The mean FSA
Discussion
The purpose of this study was to determine whether FSA could serve as a surrogate for the SI, an established measure of FSP. FSA was found to be a strong predictor of SI for both the shod and barefoot conditions. The FSA data appear to be appropriately partitioned into the correct ranges of SI, as the MFS are centered about 0°, corresponding to foot-flat, and RFS and FFS are in good agreement with the SI and visual determination. This is especially true for the shod running. The explained
Conclusion
FSA was significantly correlated with SI in both barefoot and shod conditions. These data suggest that FSA is an acceptable measure of FSP when force data are not available for both barefoot and shod runners.
Conflict of interest
Study sponsors were not involved in the study design, collection, analysis and interpretation of data, writing of the manuscripts or the decision to submit the manuscript for publication.
Acknowledgements
Funding: Drayer Physical Therapy Institute, DOD W911NF-05-1-0097, and NIH 1 S10 RR022396.
References (8)
- et al.
Ground reaction forces in distance running
J Biomech
(1980) - et al.
Lower extremity mechanics in runners with a converted forefoot strike pattern
J App Biomech
(2000) - et al.
Biomechanical factors associated with tibial stress fracture in female runners
MSSE
(2006) - et al.
Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners
Clin J Sport Med
(2009)
Cited by (219)
Effect of midsole hardness and surface type cushioning on landing impact in heel-strike runners
2024, Journal of BiomechanicsInfluence of foot strike patterns and cadences on patellofemoral joint stress in male runners with patellofemoral pain
2024, Physical Therapy in SportLower extremity joint stiffness of autistic adolescents during running at dual speeds
2023, Journal of Biomechanics
- 1
Tel.: +1 302 831 4263.