Computrainer Session - weight not input correctly
 

I got on a computrainer and did a 41k with 2 big hills and some small rollers, I finished in 1 hour 10 mins, and averaged 244 watts.

But when I looked into the profile I was running on, it was setup for a rider weight of 133kg. My time was up so I could only coax a short 3 mile run with the weight set to the proper 77kg (or should I be adding in the bike/clothes etc?)... when I did this it felt as if the wattage was much higher for the same effort - I averaged 290 watts for the 3 miles on spent legs (and I wasn't burnt out at the end) and when it was set to 133kg I could barely get it up to 290 watts with totally fresh legs, let alone sustain it for any period of time.

I've tried to find how the computrainer uses weight... what I see is that it uses it to calculate the resistance - which sounds like to me if I put out 250 watts I would just go slower set to 133kg vs 77kg (especially on the hills), but I'm not sure if the wattage reading would be different - I know it absolutely matters on my trainer at home and a weight change very much alters the power readings relative to my effort, but thats not a computrainer.

Anyone know how this works? I may go back and compare the readings/feeling to two extremes, like 20kg and 150kg.. but maybe someone has already done this/knows what would happen? Maybe there would be a way to calculate what the difference would be if the weight was set correctly?

It would take longer to do the simulated climbs

Power is just braking torque * flywheel angular velocity. If the virtual course is steeper or your virtual self is heavier, the software simply figures a slower virtual road speed for you. The power reading is more or less what you do and isn't influenced by your virtual mass. In other words, virtual speed, distance, etc., are the dependent variables.

On the computrainer the weight does virtually nothing. Because you were riding courses it simply affected your speed/time.

FWIW - most "real" TT'rs here in the Chicago area don't do Indoor TT's on the computrainer because they are constantly pissed seeing guys they normally stomp outside be close or even beat them on computrainers.

What are you hoping to learn or find out from the session? The power you put out over the time you put it out is accurate as long as it was correctly calibrated before starting (coast down test). the weight put into the system is meaning less for that.

If you're wanting to know if you could beat others at the indoor TT well....it's kind of meaningless. If you want to know if you can beat them in the real world...only real world racing will tell you. If you want to know something about your power output then you have it.

This is what I wanted to know. I wanted a flat course so I could more freely do intervals (20 min power test, max power, etc)... but the guy didn't set it up for that. It wasn't calibrated in any way, so I suppose the number itself isn't a good reference at all.

Clearly alot more goes into an actual race, I just wanted to have an idea of the power I was putting out and I have a general reference now - although the downhills skew the average as I ran out of gear/got out of my optimal cadence range for extended periods of time and generally put out less power on them.

My goal is to do a 40k in less than an hour - so this is working toward that goal. I have a 3.6 mile loop I love to ride out in Matteson that I will attempt a real hour test next week. Overall all I care about is what the stopwatch says and what the race results are (this is my first year)

I hope you're not too disappointed.

Not at all :). Great learning experience - going to go back and might pick the "ironman florida" course, I hear its very flat. Though I might take some time to setup a totally flat 40k ride so I can measure a reference 20 minute FTP and come back to measure progress over time. The hills throw off the readings... not so much the climbs but the decents. For true "course training" I'd rather be out on the road - I know balance and position are so extremely important I don't want to overlook them in any way.

For 20 minutes I'm certain I can get into the high 200's... if not 300. Note also that I have to ride 15 miles to get to this shop, no complaints IMO it makes the readings a bit more realistic.

The 32 miles from the shop to my friends house in the burbs after the above 41k was murderous though - particularly the last 6 miles since it was not only getting colder I was really feeling the pain.