Human Performance Technology
When looking at Bridie O’Donnell’s Hour Record performance there are a number of key components that deserve mention. Firstly, we will explain at the role that the pacing strategy played and the subsequent impact that this had on gear choice. Secondly, we overview the event performance as a whole, as viewed through lap splits, power output and cadence.
No discussion of time trial performance would be complete without a look at the pacing strategy that was adopted. The Hour Record is one of the most pure time trial events, where an athlete has no chance of easing off the pedals, no recovery, and no respite. Where in other time trials there is margin for manipulating the dosing of effort according to course profile and conditions, an even pacing strategy is an integral component to a successful Hour Record attempt.
The pacing strategy is about establishing the highest sustainable work rate, allow for clearance of metabolic by-products and to avoid a catastrophic rise in core body temperature. In order to achieve this, the athlete has to stick to a narrow power output band and subsequently a narrow cadence band as well. It all starts with understanding the power output that can be sustained.
Bridie’s pacing strategy was based on the power output that we were confident she could sustain for the 60 minute duration. Physiological testing, through an abundance of data from previous performances and data for every track session performed, allowed us this insight.
On the track everything comes back to lap time. The feedback provided to an athlete during an Hour Record attempt is referenced to lap time. Knowing the power output Bridie could sustain and knowing the conditions (temperature, barometric pressure and humidity) on the day, the pacing strategy was set. Her goal lap time was 19.26 seconds per lap.
The decision of what gear to ride was simply to ensure Bridie was working at the desired cadence and power output to achieve physiological steady state. Gear choice was always confirmed through the power output data that we were collecting.
During early testing sessions we trialed a bigger gear than what was used during the attempt. While this bigger gear better replicated some previous performances on the road, we were seeing 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 that the Hour Record attempt required.
For the Hour Record attempt Bridie rode a 55 x 14 gear combination. In gear inches this is a 102.9 gear.
During the first 6 minutes, on average, Bridie produced considerably faster lap times than the pacing schedule. She was lapping 0.1 second faster than schedule, with a 19.15 second average. This was in part due to the fast opening laps and by no means a concern.
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.
At the 30 minute mark, and through until the finish, average lap times were back down to the 19.10 – 19.15 seconds per lap. Indeed, between the 42nd and 48th minute we saw the fastest lap times of her attempt, with an average of 19.10 seconds per lap.
Overall, the average lap time achieved during this Hour Record attempt was 19.16 seconds per lap. The consistency of lap time data was mirrored by consistency in both power output and cadence. Collectively this demonstrated a perfectly paced effort.
Hour Record Data
During the opening laps Bridie exercised control. The peak power output during the start was 530 Watts and the 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 approaching the pace that she sat on for the remainder of the attempt.
Figure 1: The opening 2 min 30 seconds of Bridie’s Hour Record attempt. Ride graph courtesy of Today’s Plan. Power, cadence, heart rate and speed displayed on the y-axis.
While lap times in the opening 2:30 were faster than schedule (103.5%), Bridie soon settled into a rhythm that she then carried through the rest of the hour.
The Steady State Component:
By the 2:30 mark Bridie had established her steady state effort. The consistency of the effort was remarkable, and can be seen in the 3D analysis of both power and cadence.
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 consistency of her effort is visible in the uniform distribution of the power output in a narrow range around her goal power. In the opening 6 minutes a greater distribution of power output can be seen due to getting up to speed, the initial overshoot and then settling into her pacing schedule. The distribution of her power output increased as the hour progressed, due to the onset of fatigue as well as a subtle lift in average work rate toward the end of the effort.
Figure 3: 3D cadence / time plot courtesy of Today’s Plan. From front to back, the z-axis displays 6 minute windows. Cadence range is displayed along the x-axis and percentage of time displayed on the y-axis.
Bridie’s target cadence for the Hour Record attempt was 96 rpm. This graph displays that the majority of the Hour was spent in the range of 95-97 rpm. Again, this highlights the consistency of the ride, indicating that the correct gear was selected and the correct pacing strategy was implemented.
The Hour Record is undoubtedly one of the greatest physiological and technical challenges in cycling. On the 22/1/2016 Bridie O’Donnell set the new benchmark in the UCI Women’s Hour Record, with a distance of 46.882 km. This was achieved with recognition of both physiological and technical factors, with considerable attention paid to each.
Retrospectively, Bridie executed a perfectly paced attempt. She was able to control her work rate in the early stages and subsequently maintained a consistent lap schedule throughout the entire Hour Record attempt. This was reflected in the remarkable consistency of both power output and cadence.