RESUMO
PURPOSE: The purpose of this study was to develop and test a simplified deceleration technique for measurement of aerodynamic and rolling resistances in cycling. METHODS: Coast-down tests were performed in level hallways with an experienced cyclist as the rider. Average initial velocities were 2.5-12.8 m x s(-1)) The deceleration technique was simplified by the use on only three switches and a derivation that did not require an assumption that deceleration is constant. The effective frontal area (AC(D)) and coefficient of rolling resistance (CR) were then calculated through a derivation from the equation for resistive forces opposing motion. Method reproducibility was tested by comparison of results for four tests of 30 trials under identical conditions. Method sensitivity was tested by performing 30 trials with three different rider head positions and four different transported mass conditions. RESULTS: Analysis of variance revealed that there were no differences among the results in the reproducibility study for either AC(D) or C(R). Furthermore, the reproducibility tests revealed mean errors of only 0.66% and 0.70% for AC(D) and CR, respectively. ANOVA identified a significant increase (P < 0.001) in rolling resistance with external loading and a significant effect (P < 0.001) of head position on AC(D). Mean (+/-SD) values for AC(D) and C(R) from tests in a racing aeroposture with the head up, the head in line with the trunk, and the head in an intermediate position were 0.304 +/- 0.011, 0.268 +/- 0.010, and 0.262 +/- 0.013 m2, respectively. C(R) averaged 0.00368 in the three head positions. CONCLUSIONS: The findings indicate that this simplified deceleration technique is satisfactorily reproducible and sensitive for measurement of aerodynamic and rolling resistances in cycling.
