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 11-16-05, 02:06 AM #1 adxm Senior Member Thread Starter     Join Date: Aug 2005 Bikes: Posts: 289 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Is wattage output directly linked to calories burned? I've upped my riding amount significantly in the past year or so and as a result am in much better shape. I use a Polar HRM that estimates calories burned from heart rate, and it has been giving lower and lower readings for the same ride and same pace, because my heart rate is lower. I also use a program that estimates calories burned based on speed, drag, climbing, etc, which I believe to be just calculating wattage output and deriving calories from that. Now it makes sense that wattage would be a much better indicator of calories burned (energy burned -> power out), but how much does your body's efficiency play a role in this? It seems plausible that if I rode with someone untrained for biking at 100W for an hour, I would burn less calories because I'm better tuned to the activity. Basically: am I necessarily burning the same calories by doing a given route at the same speed, even as this becomes less of a perceived effort for me to do so?
 11-16-05, 09:51 AM #2 plin Senior Member     Join Date: Jun 2005 Location: Grenoble, France Bikes: Decathlon 9.2, Peugeot Posts: 245 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Good question. Power calculations are a better indicator of energy expenditure than HR monitor because energy output and HR are not linearly correlated. Here is how to calculate energy expenditure using power : Energy = power output x time. Power is measured in watts (W) and time in seconds, which gives an answer in joules (j). 1cal = 4.19 j, Example : 500 kj would be 119 kcal. however, the body is about 20 - 25% efficient, which means that you expend 4 - 5 times the energy, i.e., ~ 500 kcal. So basically in the end to get the number of calories spent in one hour, just take your average wattage for an hour and multiply by 3600(seconds in one hour) then divide by 1000 (to get the number in kilo calories). By the way, the best way to measure power output is with a power meter like PowerTap. I use a spreadsheet but it only gives an average for a climb and not instantaneous values. I envy people who can dish out over 1k for a PowerTap hub.
11-16-05, 05:22 PM   #3
cyclezen
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Quote:
 Originally Posted by plin Example : 500 kj would be 119 kcal. however, the body is about 20 - 25% efficient, which means that you expend 4 - 5 times the energy, i.e., ~ 500 kcal. So basically in the end to get the number of calories spent in one hour, just take your average wattage for an hour and multiply by 3600(seconds in one hour) then divide by 1000 (to get the number in kilo calories).
An interesting sidebar...
Read, just a few days ago that Eddy Merckx, back in his prime underwent a test for 'power'. Turns out he was able to maintain over 450 watts for an entire hour (455 was his average) without reaching 'failure' (not sure that is the right term). Not done up to that point.
Using your formula that's a prodigious 1638 calories for the hour...
one would asume that subsequent hour record holders would be up around there as well.
Anyone have similar comparo numbers for riders from later eras (Hinault, LEmond, Indurain, Armstrong, Ullrich, etc...)?

 11-16-05, 09:14 PM #4 tekhna Senior Member   Join Date: Jul 2005 Bikes: Posts: 2,407 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 1 Post(s) 455 watts. Wow. I can do 225 or so. Maybe.
 11-16-05, 11:12 PM #5 adxm Senior Member Thread Starter     Join Date: Aug 2005 Bikes: Posts: 289 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) That's a handy formula. Basically I was primarily interested in that efficiency component, and how much that actually changes with conditioning. From more detailed searching I see it's almost always in 21-23% range among trained cyclists. On a side note, I just got a V02 max test today as part of a medical study and reached exhaustion at 450 watts, after about 15 minutes of ramping up. I couldn't imagine holding that for an hour! I was in a world of hurt! For me, 'failure' at that point would definitely be the right term!
11-17-05, 12:02 AM   #6
cyclezen
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Quote:
 Originally Posted by adxm That's a handy formula. Basically I was primarily interested in that efficiency component, and how much that actually changes with conditioning. From more detailed searching I see it's almost always in 21-23% range among trained cyclists. On a side note, I just got a V02 max test today as part of a medical study and reached exhaustion at 450 watts, after about 15 minutes of ramping up. I couldn't imagine holding that for an hour! I was in a world of hurt! For me, 'failure' at that point would definitely be the right term!
Ive never had the opportunity to do a real test for 'power'. Would be fun to try, even well past 'prime', at 56, it would be fun to know... I have those silly Kcalorie numbers off the crap exercycles at the gym and could extropolate via that formula, but how close are those things anyway? Plus they are **** for 'position'. After 30 minutes I just can't wait to get off it...

Back to 'Watts of the Titans' of the hour record...
found this WAY COOL page , has great tech numbers for all the hour record holders
the numbers just blow me away! and then I scroll down to Eddy's Numbers - gawd...
I remember reading about all of them, since Ole Ritter's record in 68, its been great to follow these when they were announced. Shame they regressed the record back, tech innovation is part of the sport. it certainly doesn't negate Ole or Eddy's efforts. Cycling is about man and machine and as each improves, so should the distances...
Anyway, my next fun project is to accummulate a full series of pics with each of the Hour Holders on the equipment they used - would be a fun comparo...

 11-17-05, 04:27 PM #7 fuzzthebee bzzzz     Join Date: Feb 2005 Bikes: Posts: 360 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Indurain averaged 510 watts for his 1 hr record, and he weighed 81 kilos.
 11-17-05, 04:47 PM #8 jscott Member   Join Date: Nov 2005 Bikes: Posts: 34 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Interesting formula: From Engineering Handbook Strong healthy young man HP=0.5-0.13log(t) t in minutes World Class Athelete HP=0.65-0.13log(t) t in minutes This is from 1996 1 HP= 745 Watts For 1 hour SHYM= 201 Watts For 1 hour WCA= 312 Watts Yes calories burned are proportional to work. Remeber technique can massively improve efficiency I bet Indurain has great technique
11-17-05, 10:02 PM   #9
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 Originally Posted by fuzzthebee Indurain averaged 510 watts for his 1 hr record, and he weighed 81 kilos.
This would be HUGE numbers ...

Last edited by cyclezen; 11-17-05 at 10:23 PM.

 11-17-05, 11:01 PM #10 erhan Newbie     Join Date: Apr 2005 Bikes: Posts: 708 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Very interesting subject. I've been keeping a database of my rides, and after applying the formula, I found out that my average power is usually between 210 and 245 watts. That's better than I thought . I have a quick question. I also found that when I went riding with my girl friend my power output was about 70 watts. She was trying hard and I was just matching her pace. Does that mean that her hourly power average is also 70 watts?
 11-17-05, 11:29 PM #11 DannoXYZ  Senior Member     Join Date: Jul 2005 Location: Saratoga, CA Bikes: Posts: 11,621 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 15 Post(s) At that pace, yes... You can crank it up to 250 watts and see if she can keep up...
 11-22-05, 11:08 AM #12 sch Senior Member   Join Date: May 2003 Location: Mountain Brook. AL Bikes: Posts: 3,190 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 79 Post(s) Makes you wonder what the wattage output was in the TT winners in last years TdeF where LA and 1-2 others were averaging 33.5mph over 50km or so courses. Steve