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Please help me understand my Computrainer results
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I’m fairly new to this forum, but I am impressed by the amount of "science" here. I’ve always just trained by whatever felt right at the time, but it seems several of you use are constantly experimenting on yourselves in your own little human performance laboratories--measuring, recording, evaluating, etc.

Maybe you can help me understand some of the things I’ve always wondered about my Computrainer. I’m pretty anal about recording my workouts in a training log even though I’ve never really done anything with the data other than to compare my progress in one year versus another.

I’ve got the old version Computrainer that uses a Nintendo game and a TV. I almost always ride the same old 13 mile Coors course--sometimes I draft, sometimes I don't. (I’ve noticed that this course is only 12.5 miles on my brother’s newer version of the Computrainer, but the hill profile appears the same. What’s up with that?) Anyway, here are my real questions.

1. I find it much easier to produce power when climbing since I’m at a slower cadence. I can maintain over 400 Watts during a sustained climb but cannot maintain 300 Watts on a descent of say over 3%. When I’m racing a pacer at a fixed power, I always wax him on the climbs then get passed on the descents. Also, my power tends to spike as a downhill transitions into a climb and I try to maintain my momentum. Is this consistent with your experiences?

2. On my best ride, I set the pacer at 380 Watts and beaten him even though I averaged only 365 Watts. I’ve always assumed that this was due to the fact that I try to get up to speed as quickly as possible when I begin to go downhill. (My power is well above my average until I get up to speed.) Then as I continue going downhill my power output is way below average, but it’s enough to allow me to maintain much of the initial speed I gained at the top--so I’m going nearly as fast as the pacer but with much less power. Is this the reason I win with less power?

3. There is a discrepancy between my average power and finishing times. For instance, I’ve been as slow as 34:20 and as fast as 33:07 at an average of 348 Watts. Does this discrepancy occur for the same reason I can beat a pacer with a lower power output? Would my pacing be considered more efficient for my faster effort since I had the same average power but covered the course more quickly? (I don’t really know what those pacing differences were, but I have an idea.)

4. One time after my Nintendo cartridge memory was cleared, I thought I was having the ride of my life because I was going so fast. Then I noticed that my software had reset to the default weight of 140 pounds. I usually keep it at 200 pounds (my estimate of my weight including the bike.) I was surprised by what a huge impact weight had on my speed. I’ve read on this forum that bike weight doesn't matter much unless you’re climbing. If that is true, than body weight shouldn’t matter that much either. I assume the difference I encountered is simply due to Computrainer’s formula for translating power into speed? Do they incorporate an assumption that as the mass increases the frontal area (and drag) does as well?

5. For the first several years that I owned my Computrainer, I hardly ever came out of the saddle. I just sat back and mashed. Recently, I've noticed that I come out the saddle a lot. (Well, not anymore since I got my PCs.) Perhaps I never used to because it "feels" so much different than the road since you're not rocking or anything. But occasionally I'll just do the entire course in 52x12 andstand for the climbs. Do you think this is because I've lost the power I use to be able to generate while in the saddle (I'm 43 now,) or have I just discovered something "new?" Do others ride their trainers out of the saddle much even though the form is so different than the road?

6. Why can’t I coast when going downhill? (Just kidding.)

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Re: Please help me understand my Computrainer results [trifink] [ In reply to ]
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I bought a computrainer June/July last year.
I can't help you explain it - but I can tell you that you are not alone in your first two observations- although my power output is less than yours I have experienced the same results.

Would be interested to learn why - I suspect it is a combination of technique (I am relatively new to cycling)/gearing (on the down hills I just cannot pedal any faster so even though my power output is low my speeed is high) and the mathmatics behind how computrainer calculates watts and average watts.
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Re: Please help me understand my Computrainer results [trifink] [ In reply to ]
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I just thought I'd bump this back to the top of the list since I am still curious about these things. Thanks.
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Re: Please help me understand my Computrainer results [trifink] [ In reply to ]
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Hello,

First off, I don't ahve the Nintendo version, so I can only give you my thoughts on the 3D and PC1 versions. I assume the results are the same.

1. Watts & Hills. When you're going downhill, the resistance is much lower so it's a lot harder to produce more watts. Up hills, the resistance is greatly increased ... especially on that last 6.5% hill on Coors, so it's easier to push more watts. ie: when going downhill, there's less "pushing back" on the pedal so it's almost like it's slipping out from under you when you apply force.

2. Watts & Pacer. The pacer should be kicking your butt in wattage and time. The Pacer rides at 100% efficiency. You do not.

3. Wattage and Time differential. This has everything to do with your efficiency. If you're a masher, you'll pump out tons of watts, but you may not be pedaling as efficiently as other efforts. SpinScan numbers should correlate.

4. I was pretty sure weight mattered whether you're climbing hills or not.

5. 52x12 on Coors? How the hell do you make it up the last hill?

6. Keep dreaming. I'd love this, too!



Hope that helps,

Gill
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Re: Please help me understand my Computrainer results [trifink] [ In reply to ]
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Hello, I have had my computrainer for about 6 years and notice all the things you have noticed in observations 1,2 and 3. I don't know the calculations computrainer uses but my observations are it is relatively easy for me to maintain an average speed of 22 miles per hour on the computrainer for 3 hours but real hard for me to do that on the open road. On the other hand I can do 10-15 minute intervals at 26 miles per hour on the open road and it is quite hard to do on the computrainer for me. (bike +rider =205 pounds).

In regard to #3 on the Coors course going from 300 to 400 watts on a climb provide a several mile per hour speed differential but increasing from 300-400 on the flat does not provide near the same speed differential. I always assumed that was because computrainer was trying to account for the higher wind resistance on the flats and less on the climbs. At higher speed wind resistance accounts for progressively higher resistance. (wind resistance square of speed) So if you did the course 3 ways each averaging 300 watts but #1 350 watts on the climbs and 250 watts on the descents and 300 watts on the flats;#2 300 watts throughout:#3 250 watts on the climbs, 350 on the descents and 300 on the flats, #1 should be the fastest and #3 the slowest. I think this could account for the time variations you are seeing. Same thing should hold true on the road as well

(caveat-actually I realize that climbing 350 watts on a 1 mile hill and descending same 1 mile hill at 250 watts wont equal 300 watts because the time ascending will take longer but the general discussion holds I believe)

No computrainer for me this weekend 65 degrees and first Time trial of season tomorrow.
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Re: Please help me understand my Computrainer results [Gill] [ In reply to ]
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Gill,

Thanks for the response. in Point 2 you said, "The pacer should be kicking your butt in wattage and time. The Pacer rides at 100% efficiency. You do not." This has not been my experience. Like I said, I can beat a pacer set at 380 when I average only 365 (on a hilly course.) So my contention is that the pacer is NOT as efficiently as I.

I think that the lesson from the Computrainer is probably true for the open road. That is, that as you crest to go downhill, you should work hard to get up to speed as quickly as possible then lighten up to recover while maintaining your initial speed. The pacer always takes awhile to get up to speed because he's stuck at 380, but if you bust your hump at 600 or so for just a few seconds you get a huge jump on him. Then you can average less than 300 the rest of the way down the hill and not lose much, then wax him on the next slow rpm climb when it's easier to maintain high power.
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