Anatomical and biomechanical correlates of performance in cycling

McLean, Brian D. (1991). Anatomical and biomechanical correlates of performance in cycling PhD Thesis, School of Biomedical Sciences, The University of Queensland.

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Author McLean, Brian D.
Thesis Title Anatomical and biomechanical correlates of performance in cycling
School, Centre or Institute School of Biomedical Sciences
Institution The University of Queensland
Publication date 1991
Thesis type PhD Thesis
Supervisor Professor A.W. Parker
Dr. Mario Lafortione
Total pages 377
Language eng
Formatted abstract
Performance in cycling is a direct result of the provision of angular impulse to the bicycle cranks. However the efficiency with which this impulse is applied and the resistance to these motive forces will also influence cycling performance. The pedalling technique which underlies the production of angular impulse to the crank has been described biomechanically, but factors which influence pedalling technique, and hence cycling performance, have not been well documented. Furthermore, the influence of pedalling technique on the physiological efficiency of cycling has received little attention. The aim of this thesis was to investigate the influence of anatomical and biomechanical parameters on cycling performance. Specifically, emphasis was placed on factors that affect pedalling and thus cycling performance, and on the relationship between pedalling technique and the physiological economy of cycling.

Cycling is one of the few sports where performance is determined by physical output in direct interaction with a mechanical device. Consequently, the relationship between the anthropometry of the performer and the dimensions of the bicycle may have some significance in terms of cycling performance. To investigate this relationship the anthropometric profiles of 35 competitors in the 1987 Australian Track Cycling Championships were measured and found to be similar to that shown by the general athletic population. No proportions, although differences were apparent between cyclists competing in short duration high power events and those in the endurance events.

In general, absolute size with respect to segment girths, and absolute strength were greater for the short duration athletes. No relationship was found between the absolute or relative proportions of the lower limb segments and cycling performance. However, the mean percentage of saddle height to lower limb length was 99%, a value very close to those previously determined to produce optimum performance.

Muscle length is the common variable that is influenced by the interaction of seat height, lower limb segment length and joint kinematics during pedalling. The seat height subjectively set by competitive cyclists in conjunction with their individual segment lengths may place the lower limb muscles in an advantageous position with respect to their length - tension characteristics. Accordingly, length changes in eight muscles of the lower limb were investigated during pedalling in competitive cyclists to describe the nature of muscle length characteristics determined by their chosen seat height of 99.4% of lower limb length. In comparison with the range of total active muscle length available in these muscles, the ranges utilized during bicycle pedalling were small. Further, in most of the lower limb muscles this seat height caused the contraction lengthening cycle to be in a region close to the muscles maximum active length. With respect to the muscle length - tension curve, the muscle length characteristics found during pedalling at the chosen seat height are advantageous for producing muscle tension.

The influence of the pedalling technique on the physiological economy of cycling performance was investigated using concurrent augmented feedback of the torque characteristics from the bicycle crank. Cyclists attempted to improve their pedalling technique using this biomechanical feedback and the relationship between pedalling technique and the metabolic cost of pedalling was studied. Immediately it was introduced, cyclists exposed to feedback produced less negative torque in the pedal upstroke than a similiarly trained group not exposed to feedback. Following four weeks of feedback training the differences in pedalling technique had increased, and although reduced, the difference remained one week post training. Oxygen consumption was greater in those cyclists exposed to feedback only when it was initially introduced. Following four weeks of training and at one week post training there was no difference in oxygen consumption between the groups. Thus during the period of the study, improving pedalling technique did not improve the physiological economy of cycling.

To examine the relationship between the physiological economy of cycling and long term adaptation to an effective pedalling technique elite cyclists were compared to recreational cyclists. Analysis of detailed differences in pedalling technique was undertaken in conjunction with oxygen uptake measurements to determine if a relationship existed between differences in pedalling technique and the metabolic cost of pedalling. The elite cyclists showed a different pattern of force application on the pedals than the recreational cyclists. However the biomechanical effectiveness of this force application considered around the complete pedal stroke was not different between the groups. The metabolic cost of pedalling was also not different between the groups.

To further examine any relationship between the physiological economy of cycling and pedalling technique, as well as more fundamental biomechanical parameters reflected by joint torque, a study of the optimization of physiological and mechanical variables over a range of cadences was conducted. Increases in cadence over a range from 60 to 120 RPM caused changes in the kinematic patterns of the foot during cycling as well as changes in the components of force applied to the pedal. The effectiveness of pedal force application during the pedal stroke decreased with increasing cadence, and showed no relationship with the gross mechanical efficiency of pedalling. Five cost functions based on joint torque respectively at the hip, knee, ankle, hip and knee combined and the hip, knee and ankle combined were also assessed. The optimum cadence predicted from each cost function was compared with a criterion value of optimum cadence predicted from gross mechanical efficiency. Only that cost function based on knee joint torque predicted an, optimum cadence which was not different from that predicted by gross mechanical efficiency. This finding suggests that the activity of the knee musculature underlies the phenomenon of optimum cadence.

These studies indicate that mechanical aspects such as lower limb segment length and the effectiveness of force application during pedalling have little influence on cycling performance and suggest that parameters related to muscle mechanics are determinants of performance in cycling.

Keyword Cycling -- Physiological aspects.
Human mechanics.

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
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