On Saturday, May 5, 2012, Trismarter triathlete, Danielle Kehoe toed the line at Ironman St. George. Much has been written about the 2012 edition of Ironman St. George, including the wild winds of biblical proportions that appeared seemingly out of nowhere during the swim portion of the race, forcing literally hundreds of athletes to drop out less than an hour after starting the race. Those who made it through the swim had 45 mile per hour gusts to contend with on the bike, making this Ironman one of the toughest on record. Ten hours, 45 minutes, and 33 seconds after starting this race, Danielle found herself crossing the finish line, not only as the fastest female amateur, but also the third fastest overall female athlete of the day.
While the bike splits were not amazing simply based on duration, every athlete in this race will tell you that finishing the bike in this race in six hours was nothing short of stellar! With the usage of power meters in training and racing, it becomes much more clear when race conditions play such a huge role in the outcome, showing just how much work the athletes are actually doing. The following is an analysis of Danielle’s bike split, which shows the high effort she was producing to be able to finish with the third fastest time on the bike.
General analysis shows that Danielle averaged 171 watts, a little more than 78% of her functional threshold power (FTP), and 3.14 w/kg, for 6 hours. She had an average speed of 18.46 mph. Because the bike portion of an Ironman is essentially an individual time trial (non-drafting) event, it’s not unusual to see normalized power (NP) fairly close to average power. In the case of Danielle during IMStG, this holds true, as her NP is 180 watts. Her total Training Stress Score (TSS) was 405.7 – a measurement of total fatigue and effort during the race. To put this figure in perspective, a TSS score of 100 means the rider spent 1 hour of riding at his or her functional threshold.
One general statistic that some may find interesting is her average cadence: 78 rpm. In triathlon, we generally practice a higher cadence of 85+ rpm. The reason for this is that a lower cadence has a larger impact on the muscles in our legs, and because triathlon is swim-bike-run, keeping a higher cadence during the bike portion of the event helps to save our legs for executing a fast run off of the bike. In Danielle’s case, a lower cadence seems to have had only a minor impact on her leg muscles, if at all. She ran the fourth fastest marathon on the day for all female athletes. As Danielle’s coach, I can tell you that her natural tendency is to “grind big gears” for long periods of time. While she and I are working to improve her efficiency on the bike in order to save strength for the run, in the case of this race specifically (and maybe in general as well), an argument can certainly be made that when an athlete is conditioned properly, there is no reason to obsess over molding that athlete into what is considered current standard practices, such as keeping a high cadence. The proof is in pudding!
Further analysis shows that Danielle’s power in the first loop of the course was at 180 watts (NP of 186 watts), while her power in the second loop was 160 watts (NP of 168 watts). Note again that average power and normalized power are not very different. A drop in average power of slightly more 11% in the second loop was not ideal, however, in an ironman bike split, it’s quite common to see, especially when weather plays a factor, as it did on this day. Based on the split times of the female athletes ahead of Danielle, it’s very likely that nearly everyone was performing in a similar manner. Additionally, the extreme windy conditions during the first half of the bike died down substantially, which likely altered the athletes’ perception of pacing. Proof of this is shown by the fact that Danielle’s speed was only slightly slower (.14 mph) in the second loop.
Bike Split Summary By The Numbers:
5’2”, 120 pounds (54.43 kg)
Threshold power: 218 W, 4.0 w/kg
Training Stress Score: 405.7 TSS
Energy: 3660 kj
Average Cadence: 78 rpm
Max Cadence: 170 rpm
Average Watts: 171 W
Normalized Power: 180 W
Max Watts: 617 W
Peak 20 min: 193 W
Peak 60 min: 188 W
Peak 3 hrs: 185 W