(51) Cycling time trial performance with varied crank arm lengths utilizing a smart bike and augmented reality software in active young adults.

BACKGROUND: The selection of crank arm length (CAL) is a crucial factor influencing various cycling metrics such as cadence, cycling power, muscle activations, and ultimately cycling performance. Despite abundant previous research demonstrating changes in cycling economy and biomechanical factors across a wide range of CALs and relatively short duration (e.g., 30 sec), there still exists a gap in understanding the specific effect of CAL on cycling time trial performance from a practical standpoint.

Purpose: To identify whether cycling metrics and cycling time trial performance are affected by different CALs.

Methods: Fourteen subjects (8 male; 6 female) voluntarily participated in the study (age: 21.4 ± 1.5 yrs., height: 1.73 ± 0.11 m, body mass: 77.8 ± 17.3 kg, BMI: 25.8 ± 2.5 kg/m²). In a balanced crossover design, each subject completed three cycling time trials with different CALs (165 mm, 170 mm, 175 mm) on three separate occasions along a designated virtual course (distance: 11.65 km, elevation: 34.1 m). The experimental sessions were conducted using a smart bike (KICKR BIKE, Wahoo, Atlanta, GA) and augmented reality software (Rouvy, Vimperk, CZ). Prior to the first session, the bike fit was assessed and adjusted for comfort, and it remained constant across three trials except for the CALs. Repeated measures ANOVA was conducted to analyze the effect of CAL on various cycling metrics: cadence (rpm), pace (m/sec), power (W), time trial performance (min), energy expenditure (kJ), average heart rate (bpm), and rate of perceived exertion (RPE), with appropriate post hoc tests as needed. The significance level was set at p < 0.05.

Results: Cadence (p < 0.01), pace (p < 0.001), and time trial performance (p < 0.001) showed significant differences across CALs. Specifically, 175 mm showed a lower cadence (96 +7 rpm), slower pace (6.7 ± 0.7 m/sec), and longer time to completion (28.6 ± 2.7 min) than both 165 mm (100 ± 9 rpm, 7.2 ± 0.9 m/sec, 26.7 ± 2.4 min) and 170 mm (100 ± 7 rpm, 7.0 ± 0.6 m/sec, 27.6 ± 2.5 min). However, no statistical differences were shown across CALs in cycling power (p = 0.54), energy expenditure (p = 0.44), average heart rate (p = 0.59), and RPE (p = 0.29).

Conclusions: CALs significantly influenced cycling time trial performance by affecting cadence and pace without impacting overall cycling power, energy expenditure, heart rate, and RPE. PRACTICAL APPLICATIONS: Based on the results of this current study, cyclists aiming for faster completion time at a given distance may benefit from selecting a shorter CAL (i.e., 165mm), as opposed to the longer CAL.

Acknowledgements: None