Allen C Lim

University of Colorado at Boulder, Boulder, Colorado, United States

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Publications (10)37.96 Total impact

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    ABSTRACT: Drag area (Ad ) is a primary factor determining aerodynamic resistance during level cycling and is therefore a key determinant of level time trial performance. However, Ad has traditionally been difficult to measure. Our purpose was to determine the value of adding field-measured Ad as a correlate of level cycling time trial performance. In the field, 19 male cyclists performed a level (22.1 km) time trial. Separately, field-determined Ad and rolling resistance were calculated for subjects along with projected frontal area assessed directly (AP ) and indirectly (Est AP ). Also, a graded exercise test was performed to determine [Formula: see text] peak, lactate threshold (LT), and economy. [Formula: see text] peak ([Formula: see text]) and power at LT were significantly correlated to power measured during the time trial (r = 0.83 and 0.69, respectively) but were not significantly correlated to performance time (r = - 0.42 and -0.45). The correlation with performance time improved significantly (p < 0.05) when these variables were normalized to Ad . Of note, Ad alone was better correlated to performance time (r = 0.85, p < 0.001) than any combination of non-normalized physiological measure. The best correlate with performance time was field-measured power output during the time trial normalized to Ad (r = - 0.92). AP only accounted for 54% of the variability in Ad . Accordingly, the correlation to performance time was significantly lower using power normalized to AP (r = - 0.75) or Est AP (r = - 0.71). In conclusion, unless normalized to Ad , level time trial performance in the field was not highly correlated to common laboratory measures. Furthermore, our field-measured Ad is easy to determine and was the single best predictor of level time trial performance.
    Full-text · Article · Aug 2015 · PeerJ
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    ABSTRACT: To compare the demands of a 6-d stage race using field measures of power output and HR in male (n=8) and female (n=10) competitive cyclists. HR and power output were monitored in males and females competing in separate races on identical courses including a prolog (4 km), four circuit/road races (mean ± SD: 118 ± 23 km), and a criterium (47 km). All subjects participated in laboratory-based exercise testing within 2 wk of the race. Compared with females, males took 10%, 22%, and 10% less time to complete the prolog, circuit/road races, and criterium, respectively. For males, power output in the prolog, circuit/road races, and criterium averaged 405, 247, and 278 W, respectively. For females, power output averaged 295, 160, and 205 W, respectively. During the prolog, the percent time spent below, at, and above the lactate threshold was 29%, 9%, and 62%, respectively, for males and 24%, 7%, and 69%, respectively, for females. For the circuit/road races, these values were 57%, 10%, and 33%, respectively, for males and 62%, 10%, and 28%, respectively, for females. During the criterium, these values were 51%, 6%, and 43%, respectively, for males, and 50%, 8%, and 42%, respectively, for females. Although men had faster finishing times and higher absolute power outputs, no significant difference was found between men and women in their relative power response. These findings suggest that pacing strategy is based on relative exercise responses and not on absolute exercise responses.
    Full-text · Article · May 2011 · Medicine and science in sports and exercise
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    ABSTRACT: To develop a protocol for isolating changes in aerodynamic and rolling resistances from field-based measures of power and velocity during level bicycling. 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. 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). 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.
    Full-text · Article · Sep 2010 · Medicine and science in sports and exercise
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    ABSTRACT: PURPOSE:: To compare the demands of a six-day stage race using field measures of power output and heart rate in male (n=8) and female (n=10) competitive cyclists. METHODS:: Heart rate and power output were monitored in males and females competing in separate races on identical courses including a prologue (4 km), 4 circuit/road races (mean ± SD: 118 ± 23 km), and a criterium (47 km). All subjects participated in laboratory based exercise testing within two weeks of the race. RESULTS:: Compared to females, males took 10%, 22%, and 10% less time to complete the prologue, circuit/road races, and criterium respectively. For males, power output in the prologue, circuit/road races, and criterium averaged 405, 247, and 278 watts respectively. For females, power output averaged 295, 160, and 205 watts respectively. During the prologue, the percent time spent below, at, and above the lactate threshold was 29%, 9%, and 62% respectively for males and 24%, 7%, and 69% respectively for females. For the circuit/road races, these values were 57%, 10%, and 33% respectively for males and 62%, 10%, and 28% respectively for females. During the criterium, these values were 51%, 6%, and 43% respectively for males, and 50%, 8%, and 42% respectively for females. CONCLUSIONS:: Though men had faster finishing times and higher absolute power outputs, no significant difference was found between men and women in their relative power response. These findings suggest that pacing strategy is based on relative exercise responses and not on absolute exercise responses.
    Full-text · Article · Sep 2010 · Medicine and science in sports and exercise

  • No preview · Article · May 2005 · Medicine & Science in Sports & Exercise

  • No preview · Article · May 2005 · Medicine & Science in Sports & Exercise
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    Full-text · Article · May 2003 · Medicine & Science in Sports & Exercise

  • No preview · Article · May 2003 · Medicine & Science in Sports & Exercise
  • A C. Lim · B M. Turner · L R. Sweeney · W C. Bymes

    No preview · Article · May 2002 · Medicine & Science in Sports & Exercise

  • No preview · Article · May 2002 · Medicine & Science in Sports & Exercise