Case Study: Personal Best Climbing Old La Honda
When assessing performance for a personal best, conditions must be the same, or conclusions will be erroneous.
For a hill climb (ascent), a grade of 7% or more lasting at least 15 minutes on a hill protected from wind is a good way to go, such as Old La Honda Road.
Two factors must be considered—
- Total riding weight (TRW): body weight + clothing + bike + water bottle, etc; pick up your bike, step on the scale and get your total riding weight.
- Accurate power (and time): a power meter with consistent results accurate to 2% or better.
- Ideally, the same wheels and bike, but so long as both bikes are similar in efficiency, this should not be a significant factor by more than 1-2%.
When assessing one attempt to another, one must absolutely consider TRW on a climb; carrying 5 or 10 extra pounds has a substantial influence on the time!
Keep reading below for analysis of these graphs.
Click for larger graphs.
Let’s analyze two efforts on Old La Honda Road, my personal-best time trial climb.
The first effort was on my Trek Madone 6.9 SSL with an SRM 7950 power meter. I was in peak fall condition and I pulled off extra weight from the bike (water bottle, saddlebag, etc), and in summer jersey, no tights, etc.
The second effort was on my Look 595 Ultra, also the SRM 7950 power meter. I carried a saddlebag, water, lighting system and tail-light, and wore a double layer on top as well as tights and heavier shoes— winter gear. It was not a totally maximal effort, but very close.
2011-10-30: 18:05 (1085 sec), 387.2 watts @ 163 bpm, TRW = 193.0
2012-02-11: 19:59 (1199 sec), 351.9 watts @ 159 bpm, TRW = 201.5
At first glance, I was really disappointed in the 2012 effort. But analysis shows this to be a misplaced feeling. In fact, it shows huge potential for a new personal best.
What would have happened if my TRW had been 193 pounds on the 2012 effort (instead of 201.5 pounds)? We can predict:
1199 * (193/201.5) = 1148 seconds, or 51 seconds faster due to lower weight.
Now add in the wattage difference (which has a multiplier effect on the time calculated for the lower weight); what if I had gone for a maximal effort and matched wattage? We can predict:
1148 * (351.9/387.2) = 1043 seconds, or 105 seconds faster!
In short, matching weight AND wattage, the predicted time would be 17:23, which would beat my personal best time by a robust 42 seconds!
At these low speeds (~11 mph), I figure that 85% of the weight/watt gain translates into climbing speed (some goes into increased wind resistance). That would still yield a time 36 seconds faster, 17:29.
There are limits to accuracy because the power meter is rated only for 2% accuracy, and the weight has to be estimated unless one drives to the ascent and gets the weight immediately before and after the ascent (for an average weight while climbing).
Translating to a goal
These calculations are reliable for predicting results; based on my careful tracking of hundreds of ascents up Old La Honda that track power and TRW; I know the predictions to work quite accurately by data analysis.
In short, a personal best of 17:29 should be achievable by eliminating the extra body weight and clothing and gear, and matching recent wattage. What a great incentive! A realistic goal, not a fantasy.
There is also a HUGE incentive to work on VO2 Max and lactate threshold, shooting for a goal of 410 watts, which I believe I can achieve based on 2006 power measurements.
1148 * (351.9/410) = 985 seconds = 16:25 less 15% efficiency loss = 16:50
There is stares me in the face: achieving a TRW of 193 pounds and 410 watts, I should be able to do a blisteringly fast 16:50 (which is considered extremely fast on Old La Honda). On the other hand, maybe I’ll never get to 410 watts! But at least it’s not a fantasy goal; it’s about a 5% improvement over last year’s best.
Furthermore, if TRW drops to 185 pounds (lean race weight) and I can maintain the same power output when that lean, in theory that time would drop to about 15:44. Few middle-aged riders manage to pull off that kind of time on OLH.
That’s all speculation until and unless I train up my wattage and drop my body weight. And so two clear goals for 2012 emerge from this analysis.