INVESTIGATION OF MARKER PLACEMENT SCHEMES FOR DETERMINING REARFOOT MOTION"

Abstract

Pxelve female recreational runners (mean age: 24.5 yrs) served as subjects (Ss) to determine whether marker placement affects the measurement of rearfoot motion during conditions of slow and fast running. Measurement of rearfoot motion consisted of touchdown angle (TA) and maximum pronation angle (MPA). METHODS Subjects were filmed at 100 fps while running on a treadmill operating at speeds of 3.58 and 2.44 m/s at a 0% grade. The film was transferred to videotape and digitized on the Ariel Performance Analysis System (APAS). The same three gait cycles were digitized using each of the three marker placement schemes; Scheme 1 (Clarke et al., 1983), Scheme 2 (Nigg, 1986) and Scheme 3 (Novick & Kelly, 1990). A two way ANOVA with repeated , measures (p <. 05) was used to test the hypotheses. RESULTS AND CONCLUSIONS Significant differences were found in TA between schemes 1 and 2 and between schemes 2 and 3 for fast and slow conditions. MPA was also significantly different between schemes 1 and 2 and between schemes 2 and 3 for the slow running condition, however, for the fast running condition, only schemes 2 and 3 were significantly different. TA and MPA were not significantly different from one another when markers were placed on soft tissue of the calf (scheme 1) or on bony tissue of the lower leg (scheme 3). When one marker was placed on soft tissue and the other over the firmer achilles tendon (Scheme 2), TA and MPA were significantly different, most often due to the lateral movement of the soft tissue marker. Marker placement does affect the measurement of rearfoot motion and should receive special attention prior to data collection.