Nicolas Arciniegas, Jeff T. Wight, Will M. White, David R. Hooper, George G.A. Pujalte, FACSM. Jacksonville University, Jacksonville, FL.

BACKGROUND: In distance running, pelvis kinematics have received little attention compared to the ankle, knee, and hip. Also, few studies have reported pelvis data for the swing phase. Pelvis kinematics are important to study since they are likely to impact overall running biomechanics. In this study, we analyze pelvis motion and stride-to-stride variability (SSV) in college runners to better understand the overall pelvis motion used by competitive runners. PURPOSE: Analyze swing phase pelvis motion and SSV for all three planes (sagittal, frontal, transverse) and determine if there are significant differences (among the planes). METHODS: The participants were 8 Division I cross-country runners (19.5±1.2 years; 50+ miles per week). For the data collection, participants ran 3 minutes on the laboratory treadmill at an 8-minute/mile pace (data collected at 3-minutes). The motion-capture data was collected at 200Hz using 6 Vicon Bonita motion-capture cameras and 3DGAIT software. Ten strides were used to generate average plots (normalized to 101 data points) for the pelvis motion in all three planes. The 10 plots were averaged to generate an overall waveform for the pelvis in each plane. The pelvis motion, in each plane, was determined by calculating the range of each waveform. SSV was determined, in each plane, by calculating the standard deviation across the 10 strides. One-way ANOVAS were used to test for significant differences among the three planes (p=0.05). Bonferroni post-hoc analysis was used for follow-up testing. RESULTS: For the swing phase, the pelvis had significantly more total motion (p<0.01) in the frontal plane (16.0°±5.6°) compared to both the sagittal plane (6.2°±2.0°) and transverse plane (5.6°±1.8°). There was no significant difference between the sagittal and transverse plane. For the swing phase SSV, the frontal plane (0.99°±0.31°) was significantly greater (p<0.01) than the transverse plane (0.55°±0.20°) and significance was approached (p=0.04) when compared to the sagittal plane (0.69°±0.18°). There was no significant difference between the sagittal and transverse plane SSV (p=0.15). CONCLUSION: During swing, pelvis motion was by far the greatest in the frontal plane; the frontal plane motion was more than double that of the other two planes. The frontal plane also had the greatest SSV.

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