First 10 mile ‘time trial’

Yesterday I went out for a quick ride around the local estate, to see if the current position on the bike works on the road.  Since my first abortive attempt a few weeks ago I have moved the saddle back quite a long way, to try to get weight off the elbows.  It seems to have worked, I was reasonably comfortable and the bike felt stable.  I am noticeably lower at the front end, too.  So today I rode gently down to the local course to ride it by myself and see what I’m currently capable of.  The nearest point to my house is the turn (the half way point where you turn round and head back), so I decided to ride the course in reverse – it’s 30 minutes gentle riding from my house to the turn, which serves as a decent warm up.  By riding it in reverse I’d save myself an extra 5 miles to the start, as well as an extra 5 miles on the way home, when I’d be knackered.

I’ve also started using Golden Cheetah, which is a free software package that you can use to track rides and a whole host of other clever stuff (power analysis, aerodynamic tests, etc.)  When I got back I uploaded the ride from my Garmin into Golden Cheetah to have a look at the result.  Here’s a snaphshot image of the 10 mile test run:

Screen shot 2013-03-03 at 12.02.55

I have removed some of the data (altitude and cadence) for clarity, and I don’t have a power meter (yet).  The green line shows speed and the blue line shows my heart rate.  The main thing I have taken from this data is the poor pacing.  It’s not a dead flat course, but it’s only gently undulating, yet the data shows a 10mph difference between the fastest and slowest speed.  Tellingly, the fast speed (29mph) was recorded right at the start, and the lowest (19mph), just before the end.  This was on the same rise (obviously riding downhill at the start and uphill at the end).  This is the classic time trial mistake.  Setting off too quickly and paying for it later.  Drilling down into the data, for the first 5 miles I averaged 24.5mph and for the second 5, 22.7mph.  A slight difference is to be expected, because the course is a little bit downhill on average in the first half, and obviously uphill in the second.  But I did not take this into account in advance, I planned to ride the two halves of the course as if they were flat.

Average heart rate was 148bpm, which is slightly lower than I’d expected.  The heart rate data is quite variable, you can see that the peaks in heart rate generally coincide with the troughs in speed.  This is a good thing.  One key point I’ve read over and over again on time trial pacing is that the key to going fast is in not going slow. On the face of it, this is a tautology.  But it means that you should sacrifice your absolute top speed on downhill sections in order to be able to ride the uphill sections as fast as you can.  I think the variability in speed is caused by my not doing enough of this.  The theory behind it is this: the faster you’re going, the more it costs you to go that extra mph.  Increasing from 28 to 29mph on a downhill section is more expensive than increasing from 19 to 20mph on an uphill, because of increased drag at higher speeds.  So in future I will aim to smooth out the speed line, by making the heart rate line more jagged.

I was secretly hoping to get inside 25 minutes for this ride.  Sadly I missed it by 23 seconds.  I learned quite a bit, so I’m hopeful that given the same conditions, next time I’ll be able to break 25 minutes.  Conditions were very good today (low wind) and I might not get a good opportunity again in the near future, but I plan to try and ride the course once per week, weather permitting.


Posted on March 3, 2013, in Training. Bookmark the permalink. Leave a comment.

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