Individual Performance Optimization of Elite Cyclists

Luca Oggiano, Lars Sætran and Lars Morten Bardal

Norwegian University of Science and Technology, Department of Energy and Process Engineering

K. Hejes vei 2b 7042, Trondheim, Norway

Keywords: Aerodynamics, Biomechanics, Wind Tunnel Testing.

Abstract: The present work focuses on individual posture optimization with the aim to individually reduce the drag

and increase the power output on six elite cylists. In order to be able to quantify the changes in drag, power

output and VO2max, wind tunnel tests combined with power output and oxygen intake measurements were

carried out on each of the athletes tested. Drag measurements were performed in the large scale wind tunnel

at NTNU at a constant wind speed of 14.2m/s using a AMTI high frequency force plate. Simultaneously

with the drag measurements, the volume of oxygen intake and the power output generated by the athletes

during the test in different positions were acquired respectively with a Metamax II portable analyzer from

Cortex Biophysic and a Tacx Bushido cycling rig. The main results show that lowering the handlebar while

raising the seat in order to obtain a smaller frontal area and a straighter back, lowers the aerodynamic drag

but will possibly affect the volume of oxygen intake. The handlebar repositioning leaded to similar results

and it might then be questionable whether it is worth reducing the air resistance if the athlete does not sit as

comfortably. In most cases a lower handlebar positioning and a narrower set up of the handlebar resulted in

a considerable drag reduction without compromising the volume of oxygen intake. Being the present work a

preliminary test, no statistical results are presented but as an overall conclusion, it can be pointed out the

need to couple drag force measurements with oxygen intake and power production measurements in order to

have a clearer picture of the effectiveness of the wind tunnel testing.

1 INTRODUCTION

The aerodynamic drag is the main opposing force

that cyclists need to overcome with their generated

power and it counts as 90% ((De Groot et al., 1995,

Di Prampero, 2000, Oggiano et al., 2008)) of the

total forces acting against the athletes motion,

leading to the fact that even small reductions could

then lead to a large improvement in terms of

performances.

(Debraux et al., 2012) gives a clear overview of

the parameters that affect the drag on cyclists and on

the existing methods and theories used to measure it,

minimize it and reduce it, with particular focus on

frontal area direct and indirect measurements and on

frontal area reduction. In his review Debraux also

lists the different methods of assessment of

aerodynamic drag used by different authors dividing

them in wind tunnel tests, linear regression analysis

models, traction resistance measurement methods

and deceleration methods. The author also points at

pros and cons of each measuring method. However,

most methods and tests often focus only on drag (or

frontal area) reduction by modifying and adjusting

the athletes position on the bike, often discarding or

neglecting the side effects that a postural change

might induce in terms of biomechanical and

physiological effectiveness.

A number of authors (Atkinson et al., 2007,

Broker et al., 1999, Di Prampero, 2000, Heil et al.,

2001, Olds, 1998, Olds, 2001, Olds et al., 1995,

Padilla et al., 2000) on the other hand tried to create

mathematical models in order to be able to estimate

the power output generated by the athlete depending

on its posture and on the power required to

overcome the drag and the other resistive forces.

These models often use the posture as input,

modeling the frontal area and the drag and

successively assuming the needed power output.

The present study aims to individually optimize

cyclists performances by simultaneously measuring

oxygen intake, aerodynamic drag and power output

generated in a wind tunnel test. All the adjustments

on the cyclists posture were done keeping the

athletes posture within the parameters stated in the

UCI regulations (UCI, 2012).

Oggiano L., Sætran L. and Morten Bardal L..

Individual Performance Optimization of Elite Cyclists.

DOI: 10.5220/0004988700790083

In Proceedings of the 2nd International Congress on Sports Sciences Research and Technology Support (icSPORTS-2014), pages 79-83

ISBN: 978-989-758-057-4

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

Figure 1: Bike measurements by UCI regulations (UCI,

2012).

The test was conducted in the large industrial

wind tunnel at NTNU in Trondheim. During the test,

six athletes from the Norwegian Cycling Federation

(NCF) were tested, of which five were from the

Under-23s and one from the Paralympics team.

Physiological data about the athletes were

previously collected.

Figure 2: Possible modifications to the handlebar by UCI

regulations (UCI, 2012).

2 EXPERIMENTAL SETUP

The large industrial wind tunnel at NTNU in

Trondheim was used for the test. The tunnel has a

test section which is 12.5 m long, 2.7 m wide and

1.8 m high, and it is able to reach a maximum wind

speed up to 30 m/s. During the test, the speed was

set at a constant value 14.2m/s. The test section is

equipped with an AMTI BM600400HF force plate

which is able to measure forces in 6 directions (3

forces and 3 moments on the 3 axes). The forces

were acquired using an in-house made Labview

program.

The power output generated by the cyclists

during the test was acquired with a fully wireless

Tacx Bushido trainer (REF). The Bushido trainer

was modified and welded to a steel plate and bolted

to the force balance. The front wheel was equipped

with an electric motor to add rotation at the correct

speed. The whole unit was under the wind tunnel

floor to avoid disturbances on the flow field.

The Volume of Oxygen intake (VO2max) was

measured using a Metamax II portable metabolic

analyzer 3.9 ( Cortex biophysics GmbH,Leipzig,

Germany ), previously evaluated by (Medbø et al.,

2008) The analyzer has built-in sensors to measure

O2 and CO2 , barometer and thermometer, and it

measures the flow of exhaled air using a turbine

flow meter placed in the breathing mask. The

instrument was calibrated against ambient air and

gas of known concentration of O2 (16%) and CO2

(4%) the morning before testing. The concentration

of O2 and CO2 in the room were measured before

each athlete started its respective session. The

analyzer was mounted under the wind tunnel floor to

avoid flow disturbances.

3 METHODS

Six athletes with different ages and body

characteristics were chosen for the test (table 1). The

test was carried out on the NTNU wind tunnel with a

constant wind speed of 14.2m/s. During the test,

5minutes samples at 1000Hz were acquired and the

mean values for V02max, Power Output generated

and drag force were acquired.

Being this test an individual test focused on

improving the posture of each of the athlete more

than in finding general conclusions, each athlete was

asked to assume their regular time trial posture and

their natural posture was successively modified

within the UCI rules trying to reduce the frontal area

and straighten their back without compromising the

comfort. Small adjustments were then individually

suggested for each athlete in order to be able to

reduce the drag and possibly increase the power

output and the VO2 intake. Only a limited number

of adjustments were tried for each athlete and they

were obtained adjusting the width and height of the

handlebar and the height of the seat.

The adjustments used were chosen for each

athlete basing the choice on a qualitative analysis of

the reference posture:

a) Vertical adjustment of the handlebar: lowering

the handlebar leads to a frontal area reduction

but it also leads to a lower efficiency due to a

more compressed posture. Raising the

handlebar has the opposite effect.

b) Horizontal adjustment of the seat: directly

influences the "seat tube angle" (STA). Larger

icSPORTS2014-InternationalCongressonSportSciencesResearchandTechnologySupport

Table 1: Participants and adjustments.

Subject 1 Subject 2 Subject 3 Subject 4 Subject 5 Subject 6

Age 213823 21 2018

Weight [kg] 71 71 69 78 79 76

Height [cm] 185 179 185 183 194 193,5

Resting heart rate [bpm] 42 41-46 39 – 45 45

Maximum heart rate [bpm] 204 189 202 196 190 203

Adjustments

high a high a high a lower a low a high

forward b forward c high c low + a high e tight c high

high +

tight e tight e tight c low + b forward e wide

STAs have been proven to give an increase in

power outputs and a reduction in drag

(Ettema and Lorås, 2009).

c) Vertical adjustment of the seat: it directly

influences the back of the athletes. It is know

that a flatter back can help lower the drag, but

can provide lower efficiency.

d) Horizontal adjustment of the handlebar in the

longitudinal direction. It directly affects the

back posture of the cyclist. If the handlebar is

pushed forward, the shoulders are lower and

thus the frontal area can be reduced. Opposite

effects can be found when the handlebar is

adjusted in the opposite direction.

e) Horizontal adjustment of the handlebar in the

cross-flow direction (adjusting distance

between the brackets): increasing the distance

between the arms leads to lower drag.

Figure 3: Type of adjustments made to handlebar and

seat.

Not all the adjustments were used for the six

athletes but only individual adjustments based on

comfort response and qualitative analysis of the

reference posture were made (Table 1).

4 RESULTS

The adjustments are summarized in figure 4 where

the increase or decrease of drag, VO2max and

power generated are presented in percentage in a

columns plot.

Adjustment a - The vertical handlebar

adjustment was tested on all athletes, lowering or

raising it depending on the reference posture of the

participant. The results relative to this adjustment

seem to consistently prove that lowering the

handlebar results in lower drag while raising it

produces an increase in drag. At the same time,

lowering the handlebar increases the VO2

consumption while raising it leads to a lower VO2

consumption. The link between power output

generation and handlebar adjustment does not

show consistent results but it seems the adjustment

seems to differently affect each participant.

Adjustment b - Moving the seat forward

(adjustment b) did not affect the athletes drag but it

created a noticeable fall in VO2 consumption. A

large increase on power output was also noticed

for participant 1 while this didn’t happen for

participant 2. During the test it was however

noticed that participant 1 was more comfortable

and stable in holding this position than participant

2 and this might explain the difference.

Adjustment c - Raising the seat showed in

general induce a flatter back on the athletes,

making this change beneficial both in terms of

drag reduction but also in term of power

production. However, there is a maximum limit for

the seat high and some athletes already had their

seats set to the maximum. Raising the seat over

this limit leads to lower efficiency and lower

power production.

Adjustment d – Moving the handlebar forward

proved to have an effect on drag reduction and

power production. However, this adjustment was

performed only for participant 1 in combination

with the seat raising.

Adjustment e - Narrowing the handlebar leads

to narrower arms and generate a smaller frontal

area but this adjustment resulted to be somehow

less comfortable for the riders. No increase in

power production was noticed.

Some combinations of adjustments were also

performed following the athletes inputs and

resulted in large increases in power production and

IndividualPerformanceOptimizationofEliteCyclists

Figure 4: Individual results for the 6 participants. The first column ( solid blue filling) represents the drag change in

percentage with respect to the reference posture, the second column ( solid white filling) represents the change in

percentage of VO2 consumption with respect to the reference posture and the third column ( blue oblique lines filling)

represents the power output change in percentage with respect to the reference posture.

reductions in drag. The combination c_high+d_

forward for participant 1and the combination

c_low+a_high for participant 4 proved that in some

cases small individual adjustments are able to

dramatically improve the performances.

As an overall comment, all the athletes except

for participant 6 were able to reduce their VO2

consumption, increase their power output and

reduce their drag with small adjustments to their

reference position. If the drag reduction plays a

large role at higher speeds, the VO2 reduction has

a great impact on the riders performances at lower

speeds where the aerodynamic drag is negligible

and the riders can use less oxygen .

5 CONCLUSIONS

Six athletes were tested in the NTNU wind tunnel

laboratory and their performances were analyzed

measuring simultaneously the drag, the VO2

consumption and the power output generated.

It was impossible to complete a full matrix of

adjustments to the athletes’ positions but, even

with small adjustments, simultaneous gains in

terms of VO2 reduction, drag reduction and power

output increase were noticed.

The results show that individual adjustments

can lead to large improvements in terms of

performances and but they are too variable and too

individual to be able to draw general conclusions

thus a deeper analysis with a larger number of

participants should be carried out in order to be

able to generalize the results.

REFERENCES

Atkinson, G., Peacock, O. and Passfield, L. 2007.

Variable versus constant power strategies during

cycling time-trials: Prediction of time-savings using

an up-to-date mathematical model. Journal of Sports

Science, 25, 1001–1009.

Broker, J. P., Kyle, C. R. and Burke, E. R. 1999. Racing

cyclist power requirements in the 4000-m individual

and team pursuits. Medicine and Science in Sports

and Exercise, 31, 1677–1685.

icSPORTS2014-InternationalCongressonSportSciencesResearchandTechnologySupport

De Groot, G., Sargeant, A. and Geysel, J. 1995. Air

friction and rolling resistance during cycling.

Medicine and Science in Sports and Exercise, 27,

1090–1095.

Debraux, P., Grappe, F., Manolova, A. V. and Bertucci,

W. 2012. Aerodynamic drag in cycling: methods of

assessment. Sports Biomechanics, 10, 197–218.

Di Prampero, P. E. 2000. Cycling on earth, in space and

on the moon. European Journal Applied of

Physiology, 82, 345–360.

Ettema, G. and Lorås, H. W. 2009. Efficiency in cycling:

a review. European Journal Applied of Physiology,

106, 1–14.

Heil, D. P., Murphy, O. F., Mattingly, A. R. and

Higginson, B. K. 2001. Prediction of uphill time-trial

bicycling performance in humans with a scaling-

derived protocol. European Journal of Applied

Physiology, 85, 374–382.

Medbø, J. I., Mamen, A., Welde, B., Von Heimburg, E.

and Stokke, R. 2008. Examination of the metamax i

and ii oxygen analysers during exercise studies in

the laboratory. Scand J Clin Lab Invest, 597–604.

Oggiano, L., Sætran, L., Leirdal, S. and Ettema, G.

2008. Aerodynamic optimization and energy saving

of cycling postures for international elite level

cyclists. The Engineeeing of Sport 7., 597-604.

Olds, T. 1998. The mathematics of breaking away and

chasing in cycling. . European Journal of Applied

Physiology, 77, 492-497.

Olds, T. 2001. Modelling human locomotion. Sports

Medicine, 31, 497–509.

Olds, T. S., Norton, K. I., Lowe, E. L. A., Olive, S.,

Reay, F. and Ly, S. 1995. Modeling road-cycling

performance. Journal of Applied Physiology, 78,

1596-1611.

Padilla, S., Mujika, L., Angulo, F. and Goiriena, J. J.

2000. Scientific approach to the 1-h cycling world

record: A case study. Journal of Applied Physiology,

89, 1522–1527.

UCI 2012. UCI regulations.

IndividualPerformanceOptimizationofEliteCyclists