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A closer look at "The hour"
Coaches deliver the inside scoop on Bridie O’Donnell’s record-setting track performance
Consistent pacing is the key to tackling "the Hour," which Dr. Lane describes as "one of the purest time-trial events." "It's all about establishing the highest sustainable work rate," he explains. "To achieve this, the athlete has to stick to a narrow power output band and subsequently a narrow cadence band." Physiological testing on the track, combined with data from previous time-trial and road-racing performances, established the output Bridie could sustain for a full 60 minutes. "On the track everything comes back to lap time," Lane says. "Knowing the power output Bridie could sustain, and knowing the conditions of the day - temperature, barometric pressure and humidity - her lap 'schedule' was set at 19.26 seconds."
Bridie rode a 55 x 14 gear combination (that's 102.9 gear inches). Again, this was determined by extensive data collection. "During early testing sessions we trialed a bigger gear than the one that was used during the attempt," Lane recalls. "While this bigger gear better replicated some previous performances on the road, we saw less consistency through a much wider range of cadence and power output values. The bigger gear appeared a good option for the shorter duration efforts, but proved hard to control for the full duration the Hour Record attempt required."
During the first 6 minutes, Bridie's 19.15-second lap average was considerably faster than her schedule required. But Lane wasn't concerned. "The next 18 minutes were all about control and ensuring the effort was sustainable. This saw average lap times sitting right on schedule, with 19.23, 19.19 and 19.23 seconds for consecutive 6-minute blocks, taking us up to the 24-minute mark." From the halfway point onwards, average lap times came back down to 19.10-19.15 seconds. Indeed, between the 42nd and 48th minute, the team saw the fastest laps of the attempt, with an average of 19.10 seconds. Overall, Bridie's average lap time was 19.16 seconds.
POWER OUTPUT AND CADENCE
Bridie’s peak power output at the start was 530 Watts and her average power during the first lap was 387 Watts. By the end of the first lap, Bridie’s cadence was up to 99 rpm and her speed approached the range she sustained for the remainder of the attempt (as you can see in the chart below).
By the 2:30 mark Bridie had established her “steady state effort,” Lane says, adding that “the consistency of the effort was remarkable (as shown in the 3D analysis of power and cadence below).”
Figure 2: 3D power / time plot courtesy of Today's Plan. From front to back, the z-axis displays 6-minute windows. Power range is displayed along the x-axis and percentage of time displayed on the y-axis.
The wider distribution of power output in the opening 6 minutes was due to acceleration from the standing start and the typical adrenaline-fuelled overshoot of the pacing schedule, Lane explains. Power output distribution also increased as the hour progressed due to the onset of fatigue and a subtle rise in average work rate toward the end of the effort.
Bridie's target cadence for the Hour Record attempt was 96 rpm, which again was right on target: Most of her ride was spent in the 95-97 rpm range. "This highlights her consistency and the validity of our gearing choices and pacing strategy," Lane adds.