Pacing strategies during a cycling time trial with simulated headwinds andtailwinds

The aims of this study were to examine the effects of one self-selected and two enforced pacing strategies (constant and variable power output) on cyc ling performance during a time trial in which variable wind conditions were simulated. Seven male cyclists rode their own bicycles on a Computrainer c ycle ergometer, which was programmed to simulate a 16.1 km time trial on a flat course with a 8.05 km h(-1) headwind in the first half of the race and a 8.05 km h(-1) tailwind in the second half of the race. Subjects rode an initial time trial (ITT) at a self-selected pace to the best of their abili ty. The mean power output from this trial was then used to calculate the pa cing strategies in the subsequent two trials: Constant (C)-riders rode the whole time trial at this mean power output; and Variable (V)-riders rode th e first headwind section at a power output 5% higher than the mean and then reduced the power output in the last 8.05 km so that the mean power output was the same as in the initial time trial and in trial C. Power output, he art rate and ratings of perceived exertion (RPE) were recorded every 1.61 k m. Finish times, 8.05 km split times and blood lactate levels, pre- and pos t-exercise (to calculate Delta lactate), were also recorded in each trial. In the ITT, riders chose a mean+/-SD power output of 267+/-56 W in the firs t 1.61 km which was 14% higher than the overall race mean+/-SD of 235+/-41 W. Power outputs then dropped to below the race mean after the first few ki lometres. Mean+/-SD finish times in the C and V time trials were 1661+/-130 and 1659+/-135 s, respectively. These were significantly faster than the 1 671+/-131 s recorded in the initial time trial (p= 0.009), even though over all mean power outputs were similar (234-235 W) between all trials (p= 0.26 ). Overall mean RPE and Delta lactate were lowest in trial V (p <0.05). Per ceived exertion showed a pacing strategy by race split interaction (p <0.00 01), but it was not increased significantly during the first 8.05 km of the V condition when power outputs were 5% higher than in condition C. Heart r ate showed no main effect of pacing strategy (p= 0.80) and the interaction between strategy and race split did not reach statistical significance (p= 0.07). These results suggest that in a 16.1 km time trial with equal 8.05 k m headwind and tailwind sections, riders habitually set off too fast in the first few kilometres and will benefit (10 s improvement) from a constant p acing strategy and, to a slightly greater degree (12 s improvement), from a variable (5%+/-mean) pacing strategy in line with the variations in wind d irection during the race. Riders should choose a constant power when extern al conditions are constant, but when there are hilly or variable wind secti ons in the race, a variable power strategy should be planned. This strategy would be best monitored with `power-measuring devices' rather than heart r ate or subjective feelings as the sensitivity of these variables to small b ut meaningful changes in power during a race is low.