Diablo TT

By the numbers… Analyzing the Diablo Time Trial
Rider: ck

Anyone who spends half as much time as I do reviewing and analyzing performance numbers will appreciate this blog entry. Let me start by saying that I think this is the best threshold performance event in the bay area. The distance and slope are perfect for 30 minutes of pure pain and suffering. At the end of the ride, you get benchmark data to gauge your fitness and mental sanity level. I’m not saying this event is fun… it’s not, but that shouldn’t stop you from coming out. Knowing your body, and the event day conditions to put out your absolute best time is a tall order to fill. I’ve never pushed and maintained such a sustained level of discomfort as I do in this event. For better or worse, it a nice snapshot in time... let's take a look -

First let's look at the weather, it’s important!
2007 – Winds calm, partly cloudy, temps in the low 70’s, air clear
2008 – Winds 3-8 mph, sunny, temps in the low 80’s, air poor

Last year we totally lucked out with the weather. Other than “ideal” temps, the race day was almost perfect. This year a light headwind, high temps and really poor air quality all worked against us. As a general rule of thumb, every 10 degrees temperature difference will vary your heart rate 5 beats per minute (+10 degrees = +5 beats/min). Depending on your max hr, you might be looking at a 3-5% increase in hr, which surely has an affect on your performance.

Observations: This year I have to say the burn in my lungs after the race was painful. Given the fact that my "vital" stats where all down from last year, I have to think that the air quality played a large part in this. I will say that driving over the Bay Bridge today, the East Bay was almost obscured by a blanket of dark brown smog. Local fires also added to the air quality problems. The valley floor from up on Diablo was obscured by the smog/smoke as well. I think the record heat of the previous two days and a lack of fog and wind brought us right up there with LA air quality...

Ok, let’s look at the raw data…

Average Speed: 2007 - 12.97 2008 - 13.10
Max Speed: 2007 - 30.23 2008 - 27.47
Average Cad: 2007 - 88 2008 - 86
% Of Time in Zone 4: 2007 - 8% 2008 - 23%
% Of Time in Zone 5: 2007 - 92% 2008 - 77%
Average HR: 2007 - 183 2008 - 181
Average Watts: 2007 - 303 2008 - 325

My stats (for reference only): HR Info (I use 92-100% for Zone 5 simply because I consider anything in Zone 5 to be unsustainable for any reasonable length of time… ie, my cracking point. 92-93% is where it's at for me) Max HR 196 Zone 4 166-180 (85-91%) Zone 5 181-196 (92-100%)

Observations: I clearly danced the line here between Zone 4 and Zone 5. Rule of thumb, your Max HR drops 1 beat/min per year, so these stats seem about right to me. I'm also certain my fitness level this year is better than last, so it's no surprise my HR was down slightly.

Splits (click them):
Observations: For the first 4.5 miles of the race I consistently lost time against my effort from last year (13 seconds). In the last 1.75 miles, I took off 34 seconds beating my time from last year by 21 seconds. Again, I think the wind and air quality had a lot to do with this with the beginning portion of the ride. In the first mile, which tends flat, I lost 6 seconds from 2007. My max speed for this section shows why, the difference between years was 2.76 mph slower this year. I think the headwind was the main factor, but air quality and heat continued to play a role as I made my way up the mountain. As my speeds slowed when I started to climb, the wind became less of a factor. In fact, the higher I got today, the calmer the winds got.

The last mile this year is where I really felt a difference. The splits show this is where I had started to fall apart the year before, while this year I maintained a consistent pace.

2007 (click graph to enlarge)

Note my HR disappear in to the red around mile 0.5... Green line is average speed -

2008 (click graph to enlarge)

















This year I had set the goal for myself at 27:45. Given last years conditions, I estimated my power output would have had to be around 317 watts, a little less than a 5% increase. Even though my time was significantly slower than my goal, the actual effort was about 7% more. So for kicks, 325 watts with 2007 conditions would be a +/- 27:15 time... ok, maybe next year! Regardless, I think this exercise shows the usefulness of looking at all forms of data, because HR alone doesn't necessarily show actual effort.