Tough hill ride yesterday; Weighted Average vs Normalized Power.
Yesterday morning I heard the hills calling. I decided to head over to Sugarloaf and do a couple grueling loops using a slightly revised version of a hill training loop that I love to hate.
This revised loop is 20.8 miles (33.47 kilometers) in length, and it contains right at 1,650 feet of elevation. You must admit, for Central Florida that’s a decent amount of vertical packed into a 21 mile loop!
This training loop includes: Hunter’s Trace Hill, Makeout Mountain, Mountain Club, The Wall, Horseshoe Hill, Turnpike Road, Buckhill and, of course, Sugarloaf Mountain. The addition of Hunter’s Trace Hill and Mountain Club were suggested by my friend Tracy, and they are short grunt climbs that add a couple hundred feet to the original loop’s elevation total.
We had a lot of rain over the weekend, and the humidity was off the charts when I rolled out. The high humidity combined with near record high temperatures (my Garmin Edge 810 recorded a high of 88°F) made for a very uncomfortable, summer-like ride. I guess I’ve been spoiled by the cooler weather we’ve enjoyed for the past month or two, because I was hurting (more on that below).
I snapped this picture of my aching, sweaty calf after the first loop…
On the first loop I averaged 220 watts, which put my weighted average power/normalized power somewhere in the middle of Zone 3/Tempo (229-274 watts for me, based on my FTP of 305). This was right on target for my ride goal, but I was really hurting. My legs felt good, but my cardio was way off. Not only was my average heart rate too high for that level of effort (164 BPM), but something in the air was making me cough whenever I’d breathe deeply (which was most of the ride).
Between the cardio issues and the heat, I really did feel like crap! In fact, yesterday was the worst I’ve felt on the bike in months.
I decided to do another loop, but I had to back down the intensity a little bit. My average power on the second loop was 184 watts, but my heart rate was still extremely high at 159 BPM. To give an idea of how off that is for me, 184 watts is lower Z2 (Endurance) for me, and not that far above my Z1 (Recovery). My average heart rate on that second loop should have been in the lower 140s, at most.
I finished the ride with a Weighted Average Power of 229 watts (according to Strava), and a Normalized Power (NP) of 245 watts (according to Garmin).
This brings up an interesting issue. I’m not sure why Strava’s weighted average is so different from Garmin’s NP (they are just different names for what should be the same thing: a power average that compensates for changes in ride conditions for a more accurate depiction of power expenditure). Obviously their algorithms differ. I’m not sure which is most accurate. I believe Training Peaks owns the term “Normalized Power” (and pioneered its algorithm), and if Garmin is using it then I must assume they have licensed Training Peak’s technology as well. Anyone know for sure?
Anyway, until I do more research on the differences between the two algorithms, I would tend to put more stock in Garmin’s estimate of 245 watts because, presumably, they are using Training Peaks’ technology, which I trust.
So a NP of 245 watts for the ride is right on target with my ride goal, but I sure had to fight for it. I managed to set seven new personal records for time, but it was painful getting there. Here’s the entire ride with all data on Strava.
When it’s a little cooler outside I want to go back and do 5 loops: 104 miles, 8,260 feet of vertical. Let me know if you are interested in joining. It will be a very, very tough ride.