Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Training & Nutrition Learn how to develop a training schedule that's good for you. What should you eat and drink on your ride? Learn everything you need to know about training and nutrition here.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 02-04-12, 09:28 PM   #1
billydonn
Council of the Elders
Thread Starter
 
billydonn's Avatar
 
Join Date: Jul 2008
Location: Omaha, NE
Bikes: 1990 Schwinn Crosscut, 5 Lemonds
Posts: 3,761
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Power Meter Puzzler

How can you have two rides of equal duration (50 minutes), both indoors on a trainer using the exact same equipment, where you go farther (i.e. faster) on one, yet produce fewer Kilojoules (i.e. less work)? Here are the particulars:

Jan 24- 12.8 miles, Avg power 127, Normalized power 165.... 413 Kj
Feb 2- 13.3 miles, Avg power 136, Normalized power 149.... 408 Kj

Jan 24 ride was a series of 1-minute intervals
Feb 2 ride was a set of 5 minute intervals.


Perhaps I do not understand Kilojoules... can someone please clarify?
Attached Images
File Type: jpg PA file.jpg (95.6 KB, 8 views)
billydonn is offline   Reply With Quote
Old 02-05-12, 07:01 AM   #2
Nikephoros
Stratiotika ktemata
 
Join Date: Aug 2006
Location: Vero Beach, FL
Bikes:
Posts: 284
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Possible explanation #1: power and effort do not increase in a linear fashion, so doing those 1 minute power intervals averages out a little higher.

Possible explanation #2: those numbers are well within the margin of error.
Nikephoros is offline   Reply With Quote
Old 02-05-12, 09:59 AM   #3
gregf83 
Senior Member
 
Join Date: Jun 2008
Location: Vancouver, BC
Bikes:
Posts: 7,338
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Quote:
Originally Posted by Nikephoros View Post
Possible explanation #1: power and effort do not increase in a linear fashion, so doing those 1 minute power intervals averages out a little higher.
This. Most trainers are designed to simulate outdoor riding so resistance increases with the square of speed. Putting out 30% extra power will only give you a 10% increase in speed.
gregf83 is offline   Reply With Quote
Old 02-05-12, 10:43 AM   #4
bored117 
Senior Member
 
Join Date: Jun 2010
Location: Riverside, CA
Bikes: Helium SL DA DI2, Defy Advanced 0 Di2, 6KU Fixie
Posts: 1,041
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Or in another way of saying... your burnt energy vs. work performed is not linear depending on level of effort. (Guess that's why you train for efficiency on certain discipline).
bored117 is offline   Reply With Quote
Old 02-05-12, 01:54 PM   #5
asgelle
Senior Member
 
Join Date: Apr 2006
Location: Albuquerque, NM
Bikes:
Posts: 3,213
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Quote:
Originally Posted by billydonn View Post
How can you have two rides of equal duration (50 minutes), both indoors on a trainer using the exact same equipment, where you go farther (i.e. faster) on one, yet produce fewer Kilojoules (i.e. less work)? Here are the particulars:

Jan 24- 12.8 miles, Avg power 127, Normalized power 165.... 413 Kj
Feb 2- 13.3 miles, Avg power 136, Normalized power 149.... 408 Kj
Work (J) equals power (W) times time (s). It doesn't matter how the power was applied; total work is the integral of instantaneous power over the duration of exercise (i.e., linear). For the two cases, 127 W over 49:56 (2996 seconds) is 380.5 kJ. 136 W gives 408 kJ.

So the question is where did your 413 kJ number come from?
asgelle is offline   Reply With Quote
Old 02-05-12, 04:25 PM   #6
billydonn
Council of the Elders
Thread Starter
 
billydonn's Avatar
 
Join Date: Jul 2008
Location: Omaha, NE
Bikes: 1990 Schwinn Crosscut, 5 Lemonds
Posts: 3,761
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by asgelle View Post
Work (J) equals power (W) times time (s). It doesn't matter how the power was applied; total work is the integral of instantaneous power over the duration of exercise (i.e., linear). For the two cases, 127 W over 49:56 (2996 seconds) is 380.5 kJ. 136 W gives 408 kJ.

So the question is where did your 413 kJ number come from?
It comes from here... it is from Cycleops Power Agent software. it was attached to my post but here it is again:
Attached Images
File Type: jpg PA file.jpg (95.6 KB, 8 views)

Last edited by billydonn; 02-05-12 at 04:30 PM.
billydonn is offline   Reply With Quote
Old 02-05-12, 05:12 PM   #7
asgelle
Senior Member
 
Join Date: Apr 2006
Location: Albuquerque, NM
Bikes:
Posts: 3,213
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Quote:
Originally Posted by billydonn View Post
It comes from here... it is from Cycleops Power Agent software. it was attached to my post but here it is again:
You can write or publish it as many ways as you want; it doesn't add any more value. What I was asking was how was the data measured, recorded, stored, and manipulated. Errors in any of those could cause errors in the displayed average power and work. In your case, it's clear there's an error in the calculated work. Without examining the data train, there's no way of knowing for sure where that's coming from. You might want to start by checking total work against the product of average power and time to see how many are off.
asgelle is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 09:39 PM.