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The 40km Project Part XV – Power Analysis

In Part XIV, I promised a more detailed power analysis of the Heckston TT. Here it is!

As I’m still getting used to all these numbers, and since the Heckston TT was only my second ride ever with the PowerTap, I’ve obviously got a lot to learn still. However, here’s what I have found interesting so far.

First, the basics:

  • Distance: 40km
  • Time: 59:06
  • Average Speed: 40.61km/hr
  • Max Speed: 52.56km/hr
  • Average Cadence: 96
  • Max Cadence: 121
  • Elevation: mostly flat (only 113m of climbing)
  • Average Heart Rate: 180
  • Max Heart Rate: 196
  • Weight: 65kg
  • Average Power: 293W
  • Max Power: 735W


The course for the TT was the OBC Heckston TT course, which is near Kemptville, ON.


My overall average speed was 40.61km/hr. Yes, this is technically the first time I’ve cracked the hour in a 40km TT. Of course, it doesn’t really count, as the goal of the 40km Project was to do so on the Calabogie Course. That will have to come next year ;) The first half of the TT was into the wind, and my average was 37.8km/hr. After the turn, the tailwind pushed me to a 44.7km/hr average.


My average cadence was 96, and max was 121. This is only sightly lower than other TTs, where I have averaged a bit closer to 100 (the last few Calabogie’s have seen averages of 98, 102, 99, 102 and 96.)

Heart Rate

Interestingly, my average heart rate was 180, which is higher than I’ve ever done in a TT (or any other time ever.) This comes after my earlier conclusion that I am unable to maintain a high heart rate as well as I could last year.  Apparently this is not the case, and I attribute this to my better warmup. That, and the PowerTap telling me when I was slacking off!


OK, so here’s where things get interesting and new to me! My average power over the full 40km was 293 watts. This works out to 4.5 watts/kg. The first half of the TT saw me average 299 (4.6W/kg), while the second half I averaged 286 (4.4W/kg). My max wattage came in at 735, which occurred right off the start line as I got up to speed. My second highest peaked at 601W after the turnaround point. Aside from those two peaks, I was able to keep the power fairly constant (good!) in the 280-320W range.

My peak intervals break down like so:

  • Peak 5s: 693W
  • Peak 10s: 679W
  • Peak 20s: 557W
  • Peak 30s: 481W
  • Peak 1m: 415W
  • Peak 2m: 379W
  • Peak 5m: 335W
  • Peak 10m: 319W
  • Peak 20m: 307W
  • Peak 30m: 301W

Interstingly, these all took place at the start of the TT. This makes sense for the short bursts, as that accounts for my push to get up to speed from a dead stop. However, I was surprised to see that my peak 20 and 30 minute intervals were the first 20 and 30.  I guess that means I didn’t do as well as I thought at pacing myself – I was hoping to see a negative split here. However, I can only imagine what the numbers would have looked like if I hadn’t tried to rein myself in at the start. Thing would likely have been much more lopsided!

Now, looking at these numbers, I’m not super impressed with my power output. However, considering this is a TT, and it’s all about consistency, things don’t look so bad. For example, our lazy Wednesday night right last night saw a peak 5s of 958W, and a peak 2m of 401W, which are both quite a bit higher than I turned in during my TT. However, my peak 5m last night was a mere 247W, whereas in the TT it was 335W.  A big difference over longer time periods! I’d go so far as to say that (especially on a flat TT course) you are doing it wrong if you see 2/5/10/20 minute intervals that are way different than each other. Consistency is key!

One of the cool features of Golden Cheetah is the Critical Power graph. It will use your collection of data to estimate your power output over any given length of time. I don’t have a lot of data in Golden Cheetah yet, so this is based on few data points and thus will likely change a lot. However, it still gives a neat idea of how I can perform. Here’s an example:

Critical Power

Critical Power

Note that the current ride selected in the “Activity History” list is shown as the black line (in this case, I have the TT selected.) The red line is your ‘best ever’ effort over that time period, and mousing over the line will show the power value and the date you achieved that high. The red dashed line is the ‘best fit’ curve, which shows the predicted best effort based on all of the data currently being analyzed by GC. You’ll see that in my example, it’s predicting my Critical Power at 1 minute would be 560W. The vertical bands correspond to your “Power Zones.”  Notice that if you follow the black line (TT values), I spent virtually no time in zones one through five, which makes sense.

GC gives the option to graph all sorts of fun things. Here are some examples:

TT Power Distribution

TT Power Distribution

This graph shows my my time spent at various power output levels. As expected, it forms a nice ‘bell curve’ and shows that I stuck between 200 and 400W almost exclusively. Compare this to a group road ride, where speed/work is not nearly as consistent (again, from last night’s Wed Perth group ride):

Road Ride Power Distribution

Road Ride Power Distribution

Golden Cheetah also gives an option to create 3D graphs. Here’s one for “Natural Cadence Selection” which is pretty neat. It shows your power vs. cadence vs. % of time, and is colour coded by Power Zones.  It’s a lot of data to interpret, but clearly shows that my ‘sweet spot’ is in that 80-108 range of cadence, where I spend most of my time, and put out 200-400W. The high Wattage ‘spikes’ (red on the right side) are all very short time periods (no surprise) and all occur at lower cadences (below 80). Again, this makes sense given they occur either at the start, turn around point, or possibly on a hill.

Natural Cadence Selection

Natural Cadence Selection

Phew! I think that’s enough numbers for now. I’m going to give my eyes a rest! Thanks for reading (if you made it this far!) and feel free to download Golden Cheetah and give it a shot! I’d be interested in hearing your thoughts!

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