Measuring changes in aerodynamic/rolling resistances by cycle-mounted power meters.

Abstract:

PURPOSE:To develop a protocol for isolating changes in aerodynamic and rolling resistances from field-based measures of power and velocity during level bicycling. METHODS:We assessed the effect of body position (hands on brake hoods vs drops) and tire pressure changes (414 vs 828 kPa) on aerodynamic and rolling resistances by measuring the power (Pext)-versus-speed (V) relationship using commercially available bicycle-mounted power meters. Measurements were obtained using standard road bicycles in calm wind (<1.0 m·s) conditions at constant velocities (acceleration <0.5 m·s) on a flat 200-m section of a smooth asphalt road. For each experimental condition, experienced road cyclists rode in 50-W increments from 100 to 300 W for women (n=2) or 100 to 400 W for men (n=6). Aerodynamic resistance per velocity squared (k) was calculated as the slope of a linear plot of tractive resistance (RT=power/velocity) versus velocity squared. Rolling resistance (Rr) was calculated as the intercept of this relationship. RESULTS:Aerodynamic resistance per velocity squared (k) was significantly greater (P<0.05) while riding on the brake hoods compared with the drops (mean ± SD: 0.175 ± 0.025 vs 0.155 ± 0.03 N·V). Rolling resistance was significantly greater at 60 psi compared with 120 psi (5.575 ± 0.695 vs 4.215 ± 0.815 N). CONCLUSIONS:These results demonstrate that commercially available power meters are sensitive enough to independently detect the changes in aerodynamic and rolling resistances associated with modest changes in body position and substantial changes in tire pressure.

journal_name

Med Sci Sports Exerc

authors

Lim AC,Homestead EP,Edwards AG,Carver TC,Kram R,Byrnes WC

doi

10.1249/MSS.0b013e3181fcb140

subject

Has Abstract

pub_date

2011-05-01 00:00:00

pages

853-60

issue

5

eissn

0195-9131

issn

1530-0315

journal_volume

43

pub_type

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