I've been reading and seeing a lot about the new thing in indoor trainers these days, the computer controlled ones that you can pop a DVD in and have it control the tension on the trainer and allow you to watch the images moving as if you were on the course moving at whatever speed you are going on the trainer. It is something I think would be neat to have for the winter time as it would definitely make things a lot more interesting.
I realized yesterday that since I have a PowerTap, I can sort of do the same thing, albeit without the images. I can simply go back ot my recorded power data and work up a workout routine based on any of those rides. So that is what I did for today. A simple 1 hour ride that outdoors covers just over 16 miles and has about 1600' of climbing. I went through the power file and took 5 minute intervals and noted the average power for each one. I then used those values as my target for the efforts on the trainer. Because I was taking an average over a fairly long period of time, I figured the NP value for the ride would be lower, but the overall average should be close.
In fact, what I found in regards to power, was just that. In the outdoor ride on 9/10, my average power was 240W with an NP of 281W. Today's ride on the trainer yielded 236W average power and an NP of 246W. So average power was pretty close and N
P was pretty far apart, reflecting the lack of short really hard efforts I think. This becomes more apparent when you look at a comparison graph of power distribution for the two rides. The blue line is for the outdoor ride while the pink is for today's indoor ride. Note that the indoor ride basically has no "shoulders" but rather rises pretty sharply in the center part of the graph. In contrast, the outdoor ride has less time spent in the center portion, but more in the "shoulders", areas corresponding to active recovery and super-threshold efforts. Oddly enough, in the area of 180W-200W and from 300W -320W, the time spent was pretty close in both rides (5 min and 2 minutes respectively). This seems to indicate that it is those super hard efforts that really drive a high NP value, even when there is significanlty more time spent at lower power levels (12 minutes in Active recovery outdoors compared to only 6 minutes indoors).
So, as can be seen in this next graph, which is power distribution by zones rather than values, it is pretty easy to see that when compared to the outdoor ride, the indoor one had power values forced more towards the center, as would be expected since there is no coasting and no going (inadvertantly most times) well above FT power on climbs.The real suprise (well, sort of) came when I compared graphes of HR distribution by zones. As you can, in the case of HR, everything is shifted to the right, or to higher zones. In the outdoor ride, ~45 minutes (79%) was spent in zones 1-3, 60.8% being in zones 1-2. Today's indoor ride was pretty different, showing only ~32 minutes (51.4%) in zones 1-3 (27.7% in zones 1-2). This is pretty significant, and is even more so when you look at time sp
ent above Tempo levels (zone 3). Outdoors only ~12 minutes was spent in those zones as compared to ~28 today, 233% more time spent at threshold or above.When you compare HR with Power it is easy to see that something is going on that seems to make, at least today, training indoors more taxing on the body than outdoors when average power is kept nearly the same (only 4W difference or 1.7%). I pondered this for a bit and then remembered something I read fairly recently in regards to Floyd Landis and his stage 17 victory at the Tour de France. The relevent quote is:
The fact of the matter is for these athletes, heat dissipation is one of the most important factors determining performance. Either blood is used to cool them or used to deliver oxygen. The cooler the body, the more blood is available for producing power.
This seems to indicate that when training indoors, where ventillation is almost certainly going to be less than you find outdoors, thus making it harder for the body to keep cool from by sweating (or pouring water on yourself), you will have less blood available to deliver oxygen to your working muscles due to the extra needed to keep the body cool. This would naturally result in a higher HR for the same amount of power (in this case avg. HR was 11bpm higher (145 vs 134)), and would like increase the PE of the ride as well.
It will be interesting to see over the course of the winter if this relationship stays relatively constant, and if so, what effect going by the power meter instead of HR monitor will have on my performance next year once I'm back on the road with the PowerTap.
