1 week down, 2 to go

Started the 2nd week of the SMSP interavals today



2 sets of 6reps of 2min on 2min off today. Again, I tried 310W. First set went pretty well. But the 2nd set I bogged down the last 3. I tried dropping power to 300 and still couldn't really finish the rep.



Had some Soy milk right afterwards, then a small bottle of Endurox after a shower. Couldn't stomach any food.



Tomorrow it's some more 1min intervals, then off Sat, then I'll try and get outside for and hour easy. Weather is supposed to be pretty nice, into the 50s.



Doing the intervals on the Tacx Flow has been really good.



I like the ergo mode of set and forget. However, I've been contemplating looking into a used Computrainer because those are supposed to be the standard. The Tacx is a great value but some stuff I read made me question it's accuracy in ergo mode at higher MPH.



Found some cool stuff on the net that some guys did in comparing a Tacx to an SRM. In Slope mode it looked like the Tacx tracked the SRM very closely:





But in ergo mode there was an error associated with higher speeds. This chart :







The guy that wrote this stuff explains the above graph with this:

The chart may be a bit hard to interpret so I should probably explain. The idea of an ergo is that you set the wattage you want (say, 250W) and off you go (Ron Popeil would say, "set it and forget it"); the ergo will match the load so that whatever speed you ride, you'll be generating 250 watts. So in an ideal world you'd want the percent error to be independent of your speed. The chart plots the error against kph (or, in this case, the ratio of the wattage setting to the speed), and if the ergo worked well

the pattern would have zero slope.



The observed pattern doesn't have zero slope.

Instead, it says that in ergo mode the Flow's electronic braking system fails to increase the load by the appropriate amount to keep power constant as wheel speed increases. If you look only at the black dots (where the scale factor is set at 100), it says that if you set the ergo for a constant 250W, the Flow will only have zero error if you're riding at 23kph. At 28kph, the Flow is only able to produce enough braking force to generate an actual load of about 200W (about a 20% error). At 36kph, the Flow was actually producing about 40% less load than it should have. The scaling factor moves the curve up and down, but doesn't fix the basic underlying problem.



The good news is that the error is stable and predictable. The bad news is that the slope of the error is huge, which sort of defeats the entire intent of the ergo feature.

But hell, what really matters is that I'm pushing myself outside the comfort zone and if I am unable to complete the set, than that is a pretty good indicator that I'm not lolly-gagging around. I could start doing the intervals in slope mode where it just tells you what the power output is rather than holding at a set power level, but that requires constant monitoring and modifying pedaling rather than just put your head down and go.



I actually bought a Computrainer resistance unit on ebay last year, and have been waiting to put together a jury rigged system, but a computrainer stand alone costs $200. That was less than I got the Tacx for. An older computrainer with the old load generator will go for $400 or less on ebay, but it has no cadence function, and to upgrade to use the new load gen. that I have would cost a lot for a whole new handlebar controller.



The thing is that I only use the damn thing for intervals. Set a wattage and do the interval. I wouldn't use it for the graphics, or pedal scan, etc. So the computrainer is really overkill for what I'd want it for, but it's accuracy is what I'm looking at.



I know for many cyclists all this focus on intervals and training is over the top. But let's face my reality. Little time, no daylight, lots of other things/projects/hobbies, etc. W/o the races to focus on and these prescribed workouts I don't think I would do anything on the bike during winter except on the weekends provided I could get out. I want to race. I want to race well. I want to rage out there. In order to do that I have to train. For me, having a set plan helps me motivate and focus to train. Just riding along doesn't work for me. Just riding along fast, now that makes me happy. Of course know that the term fast is only relative .