Relationship Between Streaming Triaxial Accelerometry And VO2 During Treadmill Locomotion On An Uphill Grade

Abstract

INTRODUCTION: High resolution accelerometry (HRA) has been used increasingly for gait analysis, while lower resolution "activity monitors“ have been used to estimate energy expenditure. The purpose of this study was to test the reliability of HRA in repeated trials and determine if HRA could be used as a valid proxy for VO2 during uphill locomotion on a treadmill. METHODS: Procedures were approved by the EMU-HSRC. Ten recreationally active students (27.7±7.4 yr, 62.7 ±12.7 kg, 43.9±6.4 ml/kg/min) performed two incremental treadmill trials at 10% grade, starting at 2 kph and increasing 2 kph every two minutes until volitional exhaustion. Metabolic gasses were collected using an Oxycon Mobile (Viasys, CA) and averaged over 15 sec intervals. Data was streamed at 625 Hz from wireless, triaxial accelerometers (Microstrain, VT) affixed to the lower back of subjects corresponding to the L4-L5 segment. Raw signal from three axes, vertical (V), medial/lateral (M/P) and anterior/posterior (A/P) was integrated to obtain resultant (RES) acceleration vectors (Matlab; Mathworks, MA). Axial root mean square (RMS) calculations using the last minute of acceleration data, per stage, were also computed (LabView, v 8.6, National Instruments, Austin, TX) and compared to relative VO2 using pearson‘s correlation (SPSS, IL; a=.05). RESULTS: Axial RMS test-retest correlations were 0.93, 0.96, 0.73 and 0.96 for V, M/L, A/P and RES, respectively (p<.001), and Chronbach‘s Alpha was 0.96 (p<.001). Highly significant, strong correlations of individual axes and VO2 were 0.80, 0.76, 0.60, 0.90 and.97 for V, M/L, A/P, RES and speed, respectively (p<.001). Curve fit regressions showed a linear fit was best for RMS of RES vs VO2, but a quadratic fit of RES vs speed exhibited an r = 0.94 (p<.001). CONCLUSIONS: These data indicate HRA is a reliable tool for the determination of RES, VO2 and speed, in addition to the typical biomechanical analyses during uphill locomotion. Further study is warranted to compare these relationships in subjects of varied training status, as well as other locomotive conditions.