Differences in static and dynamic bike fit with 3d motion capture
Journal Title: Journal of Science and Cycling - Year 2014, Vol 3, Issue 2
Abstract
Background: Bicycle fitting is the adjustment of bicycle configuration to suit rider requirements through appropriate placement of contact points; pedals, saddle and handlebars (Burke 1994: Clin Sports Med, 13(1), 1-14). Traditional fitting uses static assessment of parameters such as knee angle through the bottom of the pedal stroke and saddle setback measured by knee over pedal horizontal separation (KOPS) (Holmes et al., 1994: Clinics in Sports Medicine 13(1), 187). Dynamic fitting is now increasingly popular through video analysis or 3d motion capture. However no comparison has been made of differences between static and dynamic measurement or assessment reported of the reliability of motion capture for bicycle fitting. Purpose: To investigate the repeatability of key bike fitting kinematic parameters and differences between static and dynamic conditions. Methods: 15 subjects performed repeated motion capture trials over three sessions in both static and dynamic conditions. Markers were applied to anatomical landmarks and kinematics collected using a Vicon 3d motion capture system. Results: Typical intra-session errors for angular parameters ranged from 1.7° (4.2°) for dynamic (static) knee flexion to 4.2° (4.9°) for ankle plantarflexion. Typical error for KOPS was 6.6 mm (12 mm). Significant (p<0.001) differences between static and dynamic conditions were observed for all parameters. Knee flexion was 5.4° greater in dynamic conditions (95% CI 3.5°, 7.4°). Corresponding dynamic ankle plantarflexion was 7.8° greater (5.9°, 9.6°) and hip flexion 5.1° greater (3.8°, 6.5°). KOPS was 7.7 mm further forward in dynamic conditions (3.3, 12.1) and dynamic ankle plantarflexion at KOPS was 3.6° greater (1.8°, 5.4°). Discussion: Typical errors showed moderate repeatability indicating the system was fit for purpose but these errors require consideration in the fitting process. Differences between static and dynamic parameters appear to originate at the ankle, with a tendency for riders to drop their heels when stationary. Conclusion: Common guidance to fit to a knee angle between 25-35° should be adjusted to 30-40° for dynamic measurement.
Authors and Affiliations
M Corbett| Institute of Sport and Exercise Science, University of Worcester, United Kingdom, J Bevins| Institute of Sport and Exercise Science, University of Worcester, United Kingdom
Potentiation of sprint cycling performance: the effects of a high-inertia ergometer warm-up
Background: Individual response to acute post-activation potentiation (PAP) stimulation is affected by factors such as the conditioning protocol design, training status, and biomechanical similarity of the conditioning a...
Differences in visual information-seeking behavior between expert and novice time-trial cyclists
Introduction: Pacing can be defined as an ability to distribute available energy resources during the race (Hettinga et al., 2006). It’s a determinant of athletic performance, affected by an interaction between previous...
An updated approach to incremental cycling tests: Accounting for internal mechanical power
Incremental cycling tests are typically used to determine blood lactate thresholds to monitor training and to form the basis for prescribing training zones. With minimal additional post-processing of the data normally co...
A contiguous ramp and all-out exercise test to determine critical power in competitive cyclists
Background: Critical power (CP) represents the highest metabolic rate at which oxygen uptake and blood lactate stabilizes during exercise and is strongly associated with endurance exercise performance. Determination of C...
Low dose fish oil increases the omega-3 index improving cycling efficiency and heart rate recovery
Background: Dietary fish oil provides long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The heart (Charnock et al., 1986: Annals of Nutrition and Met...