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Body size and cycling performance BODY SIZE AND CYCLING PERFORMANCE Scott Olive, BApplSci (Exercise and Sports Science) Thesis submitted for the degree of Master of Sports Science (Hons) The University of New South Wales 1996 Body size and cycling performance ABSTRACT In many sports body size, shape and composition are major factors which determine performance. In cycling body size is a determinant of both energy supply and energy demand. On the demand side the primary retarding force encountered by cyclists is air resistance, which is directly proportional to the projected frontal area of the cyclist (~)- On the supply side the rate of power production is a function of body size. This study has formed part of a much larger study into the improve­ ment of cycling performance through the development of a "first-principles" mathematical model of cycling performance. Some of this work has been pub­ lished recently (Olds, Norton, Lowe, Olive, Reay & Ly, 1995; Olds, Norton, Craig, Olive & Lowe, 1995; Olive, Norton, Olds & Lowe, 1993). In this study extensive laboratory testing was used to measure the power supply and anthropometric variables of 53 cyclists (39 male, 14 female). Relationships were determined between anthropometric characteristics and ~- The rela­ tionships between power supply variables and body size were also established using both empirical and theoretical models. A mathematical model of cycling performance was then used to simulate the effects of varying body size, shape composition and position on cycling performance. The major findings of this study were: • The lack of unanimity in previous estimates of ~ is most likely due to technical factors in the measurement process; • ~ is closely related to height, mass and body surface area (BSA) and particularly to the riding position adopted. Contrary to other investigations, the ratio of ~/BSA was found to be independent of body size. Equations have been developed to predict ~ from anthropometric variables and riding position; • Whilst optimal physique is context dependent, both theoretical and empiri­ cal models predict that larger riders have a performance advantage over their smaller counterparts in most situations. 2 Body size and cycling performance "I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person, nor material which to a substantial extent has been accept­ ed for the award of any other degree or diploma of the uni­ versity or other institute of higher learning, except where due acknowledgement is made in the text." Signed: . ..................................... CERTIFICATE OF ORIGINALITY I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, nor material which to a substantial extent has been ac:c:epted for the award of any other degree or diploma at UNSW or any other educ:alional institution, except where due acknowledgement is made in the thesis. Any contnoution made to the mean:h by others, wilh whom I have worked at UNSW or elsewhere, is explic:idy acknowledged in lhe thesis. I also declare that the intellec:tual content of Ibis thesis is the product of my own work, except to the exlent that assistance from others in lhe project's design and conception or in style, presentation and linguistic expression is acknowledged. (Signed) ··· 3 Body size and cycling performance CONTENTS 1 INTRODUCTION 1.1 The cerodynamics of bicycling 1.2 Anthropometry and bicycling 1.3 Allometric theory and similarity systems 1.4 Modelling the effects of body size on performance 1.5 Statement of the problem 2 METHODS 2.1 Anthropometry 2.2 Measurement of projected frontal area 2.3 Allometric analysis 2.4 Statistical procedures 3 RESULTS 3.1 Anthropometry 3.2 Projected frontal area 3.3 Technical considerations 3.4 Allometric analysis 4 DISCUSSION 4 .1 Anthropometry 4 .2 Projected frontal area 4 .3 Technical considerations 4 .4 Allometric analysis 4.5 Directions for future research 5 APPENDICES 5.1 Documentation 6 REFERENCES 4 Body size and cycling performance 1 INTRODUCTION 1.1 The /Erodynamics of Bicycling 1.1.l Rolling resistance 1.1 .2 Air resistance 1.1 .2. 1 The drag coefficient 1.1 .2.2 The projected frontal area 1.1.3 Maximising cerodynami c efficiency 1. 2 Anthropometry and bicycling 1.2. l The anthropometric profile of racing cyclists 1.2.2 Anthropometry and the projected frontal area 1.2.2.1 Anthropometric prediction of projected frontal area of cyclists 1.3 Allometric theory and similarity systems 1.3. l Geometric similarity 5 Body size and cycling performance 1.3.2 Expressing metabolic data: the problem of scaling I .4 Modelling the effects of body size on performance 1.5 Statement of the problem 6 Body size and cycling performance Much of an athlete's potential is determined by their physiological abilities. A great deal of time is expended in laboratories monitoring the power and capacities of the physiological energy systems. One potentially important factor that has received comparatively little scientific attention in the laboratory is the body size of these athletes. The athlete's anthropometric dimensions reflecting body size, shape and composition are variables which may play an important role in determining the potential for success in a chosen sport. Whilst body composition and shape can to a certain extent be manipulated through training, the body size of an athlete is more or less a fixed quantity. The application of anthropometric analysis to sports performance has demonstrated the tendency for individuals to gravitate towards the event to which they are anthropometrically best suited, highlighting the relationship of body size, shape and composition with performance. The existence of optimal body sizes for various sporting events is well documented and has been discussed previously (Ford, 1984). Since a great many factors conspire with physical abilities to create the elite performer, the search for the most suitable body for a sport should ideally be restricted to world class competitors, in whom every detail will be optimised. If an optimal size does exist for a particular sport, the selection process will have eliminated most individuals who do not have the ideal body dimensions. Optimum body sizes are likely to exist in cycling as in other sports, given the relative anthropometric similarities which exist between riders of the same events (McLean & Parker, 1989; Foley, Bird & White, 1989) The differences in the relative size and shape of competitors between events are obvious, and is supported through the identification of anthropometric profiles of these athletes along with both inter- and intra-sport differences. Often a biomechanical advantage is seen to underlie these differences (McLean & Parker, 1989). Research into the identification of optimal body sizes for bicycling has been based on either biophysical first principles or the measurement of energy expenditures of different sized riders (Swain, Coast, Clifford, Milliken & Stray-Gundersen, 1987). The effect of different body sizes on cycling perfor­ mance is related to the different energy demand and energy supply of the 7 Body size and cycling performance various sized riders. In general as body dimensions increase both the energy demand and the energy supply of cycling increase. The net effect of these changes in supply and demand determines performance time. The associated effects of changes in the slope of the terrain and the race distance will also need to be considered. In order for a cyclist to move forward work must be done to overcome both rolling resistance and air resistance. There is also a small amount of resistance offered by the mechanical components of the bicycle itself (ie the friction of the gears, chain, bearings etc). Air resistance is by far the largest retarding force experienced by the cyclist and is a function of the cyclist1s projected frontal area (~), a dimensionless drag coefficient (Co), air density and the relative air velocity. Estimates of the Co have been reported for a range of bodies and it has been suggested that the value of Co remains relatively constant for standard racing bicycles (Whitt & Wilson, 1982). The ~ of racing cyclists has been calculated previously (Capelli Rosa, Butti, Ferretti, Veicsteinas & di Prampero, 1993; Davies, 1980; McLean, 1994; Pugh, 1974; Swain et al., 1987). The data reported for~ of cyclists in the literature have a large range. This variance in measurements exists because some reports have measured i\>TOTAL (ie rider and bicycle) whilst others have measured ~RIDER only and it is often unclear to determine what they have included in their measurements. Reports that either measure ~TOTAL or ~RIDER have been found to still differ despite the similar physical characteristics, racing positions and bicycle type of the rid­ ers between the studies. There is also a lack of technical detail reported, per­ haps suggesting apparent discrepancies in measurement techniques. Cycling is a sport determined by energy expenditure in direct interaction with a mechanical device. It is also a mass-supported sport where air resistance acts as the principal retarding force. It has been suggested that air resistance (or some more easily measured variable such as~) be used to define the proper size denominator for physiological and cardiovascular energy supply. This has subsequently led to relationships being established between body size, ~ and related energy requirements. 8 Body size and cycling performance 1.1 THE lERODYNAMICS OF BICYCLING The mechanical power output generated by a cyclist is used to overcome the external resistance when riding on the flat. The total external resistance (~0 t) retarding motion is equal to the sum of the rolling resistance (~), air resistance (RJ and frictional resistance, which includes the power transmission losses through mechanical parts such as the chain, gears and bearings.

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