Abstract
PURPOSE:: We have previously demonstrated differences in high-resolution accelerometry (HRA) between trained and untrained runners. The purpose of this study was to determine if differences in HRA parameters or oxygen cost of running could be detected in collegiate distance runners before and after a competitive season. METHODS: Procedures were approved by the Eastern Michigan Human Subjects Review Committee. Seven intercollegiate distance runners (21.7 ±1.4 yr, 68.1±6.7 kg, 69.3±4.2 ml/kg/min) performed two discontinuous incremental treadmill trials (T1 and T2), separated by 12 weeks. Trials consisted of 3 min stages starting at a speed equivalent to 20km pace minus 50m/min and increasing speed 15 m/min until exhaustion. 20 km paces were established using a 3 km and 10 km standard field test and extrapolation using the Mercier nomogram. Expired gasses were collected with an Oxycon Mobile (Viasys, CA). HRA was collected in g's from portable wireless nodes (Microstrain, VT) streaming at 617 Hz, which were affixed to the lower back superficial to the L3 vertebrae. Root mean square (RMS) of accelerations in the vertical (VT), medial/lateral (M/L) and anterior/posterior (A/P) axes, and resultant scalars (RES) were determined using Signal Express 3.0 (Labview, TX). The ratio of axial RMS/RES (RA) and axial RMS relative to speed (EC) were examined for all axes. From VO2 and RER, O2 cost (O2C; ml/kg/km) and energy expenditure (EE; kcal/kg/min) were also determined. Variables were compared using MANOVA (SPSS, IL), a = 0.05. RESULTS: Significant trial effects were observed where VT-RMS, VT-RA, VT-Ec and ML-Ec were reduced at T2 vs. T1, while AP-RA and AP-Ec increased (P <.01). Differences in metabolism indicated a shift toward reduced fat utilization with an increased RER (P<.05) and a trend for increased O2C (P=.09) at T2 vs. T1. No effect was observed for EE (P=.55) CONCLUSIONS: Differences in running dynamics among intercollegiate distance runners before and after a competitive season can be identified with the use of HRA. These differences are in contrast to those reported elsewhere between trained and untrained runners. Additionally they are not reflective of changes in EE or trends in O2C. Therefore more work is necessary to determine the effects, if any, that these changes may have on performance.
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