Previous Experience Influences Pacing during 20-km Time Trial Cycling Dominic Micklewright1, Eleni Papadopoulou1, Jeroen Swart2 & Timothy Noakes2
1. Centre for Sports and Exercise Science, Department of Biological Sciences, University of Essex, Colchester, United Kingdom. 2. UCT/MRC Research Unit for ESSM, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
Correspondence concerning this article should be addressed to Dr Dominic Micklewright, Centre for Sports and Exercise Science, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex, United Kingdom, CO4 3SQ. E-mail:
[email protected]
The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd and its licencees, to permit this article (if accepted) to be published in BJSM and any other BMJ Group products and to exploit all subsidiary rights, as set out in our licence (http://bjsm.bmjjournals.com//ifora/licence.pdf)
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ABSTRACT Objective: To investigate how experience and feedback influence pacing and performance during time trial cycling. Design: Twenty-nine cyclists performed three 20 km cycling time trials using a Computrainer. The first two time trials (TT1 & TT2) were performed either i) without any performance feedback (n=10), ii) with accurate performance feedback (n=10) or, iii) with false feedback showing speed to be 5% greater than actual speed (n=9). All participants received full feedback during the third time trial (TT3) and their performance and pacing data was compared against TT2. Results: Completion time, average power and average speed did not change among the false feedback group but their pacing strategy did change as indicated by a lower average cadence, 89.2(5.2) vs. 96.4(6.8) rpm, p0.05, height, F(2,26)=1.0, p>0.05 or competitive cycling experience, F(2,26)=0.6, p>0.05. The descriptive characteristics of each group are presented in Table 1. Each subject provided written informed consent to take part in the study. All procedures used were conducted in accordance with the Declaration of Helsinki and were approved by ethics committees at the University of Cape Town and the University of Essex.
Table 1. Group descriptive data for age, body mass, height and competitive cycling experience
Blind Group Mean SD
Accurate Feedback Group Mean SD
False Feedback Group Mean SD
Age (years)
35.2
10.3
33.4
5.9
34.4
6.6
Body mass (kg)
77.2
9.8
79.6
10.5
77.9
5.5
Height (cm)
177.1
5.7
176.0
3.9
179.9
8.6
4.6
3.7
6.4
4.8
7.1
6.7
Competitive cycling experience (years) Design
A 3x3 within- and between-subjects experimental design was used in which subjects performed three 20 km cycling time trials (within-subjects factor) while being provided with three different types of feedback (between-subject factor). Time trials were repeated at the same time of day (± 2 hours) with a recovery interval varying between 3-7 days. Subjects were asked to refrain from training for 24 hours before each test. Cycling Ergometry Subjects completed all cycling procedures using their own bike on a Computrainer ProTM cycle trainer (RacerMate, Seattle) that was calibrated according to the manufacturer’s instructions. Participants performed a 5 min selfpaced warm-up before each 20 km time trial. Power, speed and cadence were continuously recorded during each time trial.
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Subjects were randomly allocated to either a blind feedback condition (n=10), an accurate feedback condition (n=10) or a false feedback condition. Subjects in each condition were given different types of feedback during the first two time trials (TT1 and TT2). Blind Feedback Condition (TT1BLIND and TT2BLIND) Blind feedback subjects received no feedback during TT1 and TT2 about their performance, time elapsed or distance covered as a way of promoting uncertain performance beliefs. Subjects were preventing from seeing the CompuTrainer visual display unit or any other feedback devices such as watches, clocks, heart rate monitors or cycle computers. Accurate Feedback Condition (TT1FEEDBACK and TT2FEEDBACK) Accurate feedback subjects were permitted to view the Computrainer visual display unit during TT1 and TT2. This helped to reinforce realistic performance beliefs among these subjects by provided them with continuous accurate feedback regarding the time elapsed, distance elapsed, power output, average power output, cadence, average cadence, speed and average speed. False Feedback Condition (TT1FALSE and TT2FALSE) False feedback subjects received continuous inaccurate feedback showing their performance to be 5% better than true values. This was achieved by miscalibrating a Sigma BC1606DTS wireless cycle computer (Sigma Sport ®, Germany) so that the circumference of the rear cycle wheel was entered as 5% greater than the actual rear wheel circumference causing speed, average speed and distance covered to be displayed as 5% greater than those recorded by the Computrainer Pro. The Sigma cycle computer was not able to display power output. False feedback subjects were not permitted to see any feedback from the Computrainer Pro or other performance devices such as watches, clocks or heart rate monitors. Thus, through successive exposure to false feedback during TT1 and TT2, a genuinely optimistic performance belief was evoked among subjects that they were capable of performing the 20 km time 5% faster than they actually could. Subjects in the false feedback condition were not aware of the deception and this was confirmed during a debrief interview held at the end of the study. Final Time Trial with Accurate Feedback (TT3) During the third cycling time trial (TT3) all subjects, regardless of condition, were provided with accurate performance feedback via the CompuTrainer visual display about time elapsed, distance elapsed, power output, average power output, cadence, average cadence, speed and average speed. The false feedback group were told that the batteries for the cycle computer had failed and reassured that the Computrainer feedback was exactly the same. Ratings of
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Perceived Exertion (RPE) were taken every 4 km during TT3 using the 6-20 Borg scale.18 RPE was not measured during TT1 and TT2 because it may have interfered with reinforcement of beliefs particularly among the blinded cyclists and false feedback cyclists. Prior to performing TT3, subjects in the false feedback condition were reminded of their best time trial completion time and average speed using the false values (+5%) but at this stage were not informed about the deception. A debrief interview, including an explanation of the deception, was conducted once TT3 had been completed. The experimental design is illustrated in Figure 1. Statistical Analysis A power analysis for a 3x3 ANOVA design was performed for sample size estimation using the SAS macro program FPOWER.SAS. The outcome indicated that 24 subjects (8 subjects per condition) would be needed to achieve statistical power of >0.7 assuming a moderate effect size of 0.5. Average power, speed and cadence outcomes were calculated for each warm up, every 1 km segment of each time trial and for the overall 20 km time trial performance. Two-way ANOVA’s were used to analyse condition-by-trial differences in 20 km time trial completion time, average power, average speed and average cadence. Three-way ANOVA’s were used to compare pacing condition-by-trial pacing profiles for power, speed and cadence. Significant interactions and main effects were followed up with planned post hoc comparisons between TT2 and TT3 using paired samples t-tests for within group comparisons and independent sample t-tests for between group comparisons. Paired samples t-tests were also used to compare TT3 RPE values. All results are expressed as means(SD) and effect sizes as partial eta squared (ηp2) or eta squared (η2). RESULTS Warm Up Outcomes No condition or trial differences were detected during the warm up for average power, F(4,40)=0.7, p>0.05, ηp2=0.06, average speed, F(4,40)=0.5, p>0.05, partial ηp2=0.05 or average cadence, F(4,40)=0.7, p>0.05, partial ηp2=0.06. Warm up outcomes are presented in Table 2.
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Table 2. Condition and trial warm up averages for power, speed and cadence.
Blind Group Mean SD
Accurate Feedback Group Mean SD
False Feedback Group Mean SD
TT1
150.2
45.9
167.2
37.3
142.3
39.9
TT2
135.5
43.2
161.1
37.2
143.4
39.2
TT3
145.4
54.5
185.4
40.8
139.3
46.3
TT1
28.8
3.8
30.4
2.7
27.9
4.5
TT2
27.5
4.0
29.7
3.1
27.8
4.5
TT3
28.3
4.6
31.4
2.9
27.4
4.3
TT1
91.0
8.0
95.0
9.7
90.2
12.3
TT2
90.6
8.7
90.8
8.7
89.9
11.3
TT3
86.7
11.8
88.6
8.0
84.9
9.6
Average Power (W)
Average Speed (km/h)
Average Cadence (rpm)
Time Trial Average Power, Speed and Cadence Two-way within- and between-subjects ANOVA results for 20 km average power, speed and cadence are presented in Table 3. Post hoc comparisons between TT2 and TT3 among the blind feedback group showed increased average power, t(9)=-2.5, p
