Exploring the effects of trunk acceleration on saddle position and the drag coefficient
Keywords:
Accelerometer, Trunk, Drag, Regression, CyclingAbstract
Triathletes often use a time trial bicycle with an increased seat tube angle combined with aerodynamic handlebars that allow for a decreased upper body and trunk to improve aerodynamics. In this respect, the adjustment of the seat tube and saddle is an important feature of fitting bicycle to triathlete to positively impact performance. Limited published evidence concerning trunk acceleration, saddle position and aerodynamics by way of the drag coefficient (Cd) in triathlon cycling makes comparisons difficult. Therefore, an overground varied cycle cadence in a previously validated saddle position was conducted to detect differences in trunk acceleration magnitude whilst a multivariable linear regression was used to estimate Cd based on saddle position, trunk acceleration and cadence. Data was collected by a trunk-mounted triaxial accelerometer to estimate kinematic determinants of triathlete cycling performance in conjunction with trunk acceleration magnitude and cadence that contribute to Cd. Seven participants completed a 1 x 5 km overground cycling trial at varied cadence on a characteristic triathlon circuit. Multiple linear regression was used to estimate that cycling at higher cadences increased trunk acceleration magnitude with a projected Cd of 0.277. Longitudinal trunk acceleration represented 39% of the outcome variable explained by the model. To illustrate the practical relevance of the statistical models, mean total trunk acceleration and cadence were applied to predict Cd. Higher magnitudes of total trunk acceleration combined with cycling at a cadence of 95-100 rev/min¹ resulted in greater Cd (0.283).
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