The chart you see here is for one of my senior athletes from his 2009 state time trial championship, which he won. He didn’t do the race in 2010 due to an early season crash. His 2011 state TT is coming up next week and so I put this chart together as a lesson and reminder about race management prior to the race. You can click to enlarge it and then read the comments. I won’t go into them in detail here as they should be understandable.
What you may not understand is the chart layout and terminology based on WKO+ software. First of all let’s look at how the course was managed overall. Notice that the chart is divided into quarters of equal length (3.1 miles). He raced each quadrant with a plan for energy expenditure. Here is a quick explanation of the other chart details:
X axis: Time.
Red line: Heart Rate. Y axis on left side.
Blue Line: Speed in miles per hour. Y axis on right side.
Black Line: Power. Y axis on left side.
Green Line (mostly behind black line): Cadence (RPM). Y axis on right side.
RPM: Revolutions per minute. Pedal velocity.
VI: Variability Index. How steadily he produced power. 1.0 means it was quite steady. Anything in excess of 1.05 is too great for a TT (or non-drafting triathlon).
NP: Normalize Power. WKO+ determines this based on quite a tedious formula. It basically is what the rider “felt” the power was like. Another way of thinking about NP is that it is a proxy for the metabolic cost of the ride. NP is almost always higher than average power.
HR: Heart Rate average.
NP:HR: The ratio of NP to HR which is NP divided by HR. High numbers are good as they indicate high power output for a low effort input. The ratio is meaningful only to the given athlete and can’t be compared with another rider’s ratio.
Decoup: Decoupling. A comparison of the NP:HR ratio for the two halves of each quadrant. A rising number means that HR is rising faster than NP. I like to see this below 5% in an aerobic, steady-state race like a TT (or triathlon). That indicates aerobic fitness is sound. Tends to be high in early stages of the race (or workout) as heart rate is rising with warm-up (see Q1). It also increases as effort increases (see Q3). Negative decoupling (as in Q4) is good as it means HR and power are coming back together again as the segment/workout duration increases. This means the athlete has “settled in.”
Although, it appears from the comments that your goal for this athlete is to attain the highest average power for the duration of the TT (averaging about 245 watts for each section), isn't it possible to save more time on the course by varying power depending on the grade?
I remember reading about Alan Lim last year, when he coached Taylor Phinney at the USA National TT Championship, he told Phinney to go a little harder on the uphills, and let off a little on the downhills. The reasoning being that 1 watt at 20mph is worth more time than the same watt at 30mph because wind resistance is logarithmic.
Just to see how much an effect this strategy might have, using the website http://bikecalculator.com/veloUS.html to estimate times by power, I used rider weight at 160lbs, bike weight 18 lbs, clinchers and aerobar on a 5% grade up and 5% grade down for each half of the course at 6.2 mile distances;
an average of 245 watts for both halves of the course produces a time of 42.43 minutes, but varying effort to 250 watts in the first half and 240 in the second half gives an estimated time of 41.88, a difference of about half a minute. If the difference is increased to 255 watts and 235 watts, the difference is more than a full minute.
I've never used a power meter, but I realize that 5 watts is probably too small to be able to precisely target that difference of power in a TT, and other factors influence this strategy, such as if the grade is less steep the effect is less pronounced, rider weight will alter the effect, turns and other technical bits will alter the times, but what might be the other reasons for not adopting this strategy?
The benefit would be small and I realize that this is a somewhat riskier strategy because it would be easier to overly fatigue yourself in the first half of the course, but I'm curious as to the strategy behind the course.
Posted by: Ryan Rodman | 09/21/2011 at 07:27 PM