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

Allen C. Lim, Eric P. Homestead, Andrew G. Edwards, Todd C. Carver, Rodger Kram, William C. Byrnes

Research output: Contribution to journalArticle

22 Scopus citations


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 κPa) 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-1) conditions at constant velocities (acceleration <0.5 m•s-2) 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.

Original languageEnglish (US)
Pages (from-to)853-860
Number of pages8
JournalMedicine and Science in Sports and Exercise
Issue number5
StatePublished - May 1 2011
Externally publishedYes



  • Drag coefficient
  • power tap
  • srm
  • testing

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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