Differences in Running Mechanics and Economy between Collegiate Runners and Triathletes Identified Using High-Resolution Accelerometers

Abstract

We have previously reported differences in economy between trained and untrained runners using high-resolution accelerometers (HRA) and indirect calorimetry. In these runners though, differences may have been due to discrepancies in metabolic fitness level. PURPOSE: To determine if HRA could identify differences in economy and mechanics of running between collegiate runners (XC) and triathletes (TRI), of comparable metabolic fitness, during treadmill locomotion. METHODS: Procedures were approved by the Eastern Michigan University CHHS Human Subject Review Committee and subjects gave informed consent. 23 runners, 16 XC (22.1±1.5yr, 66.5±5.7 kg, 71.1±5.2 ml/kg/min) and 8 TRI (25.6±3.8yr, 70.8±3.7 kg, 66.2±4.2 ml/kg/min) performed incremental VO2max trials while wearing HRA (Microstrain, VT; 617 Hz). Aggregate acceleration for vertical (VT), anterior/posterior (AP), medial/lateral (ML), axes were recorded and Euclidian resultants were computed (RES). Trials consisted of 3 min stages starting at 8kph and increasing 2kph until exhaustion. Group comparisons were made from 10-18kph, as all subjects completed these stages. Axial root mean square (RMS), RMS relative to speed (EC), and ratio of RMS/RES (RA) were compared between XC and TRI to identify differences in running mechanics between groups. Expired gases were collected using an Oxycon Mobile (Viasys, CA). VO2 and RER were used to determine O2 cost (O2C) and energy expenditure (EE). MANOVAs were performed using PASW 17.0 (SPSS; IL) α=.05. RESULTS: Total weekly training time (14.8±2.1 hr) was not different between groups but XC ran significantly more than TRI(13.5±1.9 vs. 5.6±1.5 hr). All HRA parameters (RMS, EC, RA) were significantly greater for XC vs. TRI in VT, and lower (p<.05) for XC vs. TRI in ML and AP, except MLRA. Significant speed by group interactions (p<.05) were also present for all HRA parameters except MLEC and MLRA. RER was not different between groups (.91±0)indicating similar fitness for XC and TRI, but VO2 and EE were significantly higher for TRI vs. XC (47.4±.5 vs. 40.8±.3 ml/kg/min and.23±.0 vs.20±.0 kcal/kg/min). CONCLUSION: These data show that XC accelerate more in the VT but less in the AP than TRI. Therefore improved running economy with training may come more from reduced accelerations in AP than VT or ML.