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 09-03-06, 05:03 AM   #1
kuan
Twincities MN
Thread Starter
 
kuan's Avatar
 
Join Date: May 2005
Location: Salsa, Cannondale, Surly.
Bikes:
Posts: 2,527
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Rainy Day Thoughts on Fat Burning and HR

Compare two individuals. Both have a MHR of 190. #1 is an athlete and has a RHR of 40, the #2 has a RHR of 60. OK. They both want to lose a few pounds.

Example 1: Using Karvonen, 50% for #1 is 115. For #2 50% is 125.

Does #1 burn a higher percentage of fat because he's at a lower HR?

Example 2: If both workout at the same HR of 125, that's 57% for #1 vs. 50% for #2.

Does #2 burn a higher percentage of fat because he's at a lower HR percentage?

I've read in a lot of places that fitter people burn a higher percentage of fat at a higher HR percentage but never figured out why. Is it then just a matter of looking at the numbers, the only adaptation responsible being a more efficient cardiovascular system?

My suspicion is #1 is correct and #2 is wrong. Thoughts anyone?
__________________
www.marrow.org
kuan is offline   Reply With Quote
Old 09-03-06, 06:56 AM   #2
NoRacer
Isaias
 
NoRacer's Avatar
 
Join Date: Sep 2005
Location: Essex, MD
Bikes: Ridley X-Fire (carbon, white)
Posts: 5,178
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
What is not disclosed in either example is the lactate threshold of each individual. Since carbohydrate usage increases to around 85-90% once one goes anaerobic, if person #1's threshold is near 50% of MHR (geez, this guy's out of shape for an endurance athlete! Maybe, he's a sprinter.) then he'll be burning less fat and more carbs even though his heart rate is lower.

Low Resting Heart Rate (RHR) is only an indication of fitness, if over time the stroke volume of the heart increased as an adaptation to exercise, otherwise, it may be simply influenced by drugs (i.e., blood pressure medicine) or just be low sans exercise adaptation naturally.
NoRacer is offline   Reply With Quote
Old 09-03-06, 10:56 AM   #3
sfrider
Oil it!
 
sfrider's Avatar
 
Join Date: May 2006
Location: San Francisco, CA
Bikes:
Posts: 1,201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by kuan
I've read in a lot of places that fitter people burn a higher percentage of fat at a higher HR percentage but never figured out why.
The more fit you are, the greater the stores of intramuscular fat. The problem with analyzing VCO2/VO2 ratios is it doesn't tell whether it's intramuscular or subcutaneous fat that's being burned.
sfrider is offline   Reply With Quote
Old 09-03-06, 12:18 PM   #4
kuan
Twincities MN
Thread Starter
 
kuan's Avatar
 
Join Date: May 2005
Location: Salsa, Cannondale, Surly.
Bikes:
Posts: 2,527
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by NoRacer
What is not disclosed in either example is the lactate threshold of each individual. Since carbohydrate usage increases to around 85-90% once one goes anaerobic, if person #1's threshold is near 50% of MHR (geez, this guy's out of shape for an endurance athlete! Maybe, he's a sprinter.) then he'll be burning less fat and more carbs even though his heart rate is lower.

Low Resting Heart Rate (RHR) is only an indication of fitness, if over time the stroke volume of the heart increased as an adaptation to exercise, otherwise, it may be simply influenced by drugs (i.e., blood pressure medicine) or just be low sans exercise adaptation naturally.
That kinda falls in place too. Can we assume that a person with a RHR of 40 should have a higher LT than a person with a RHR of 60? At least in most cases?

Intramuscular fat? Does the body discriminate about what type of fat to burn?
__________________
www.marrow.org
kuan is offline   Reply With Quote
Old 09-03-06, 01:14 PM   #5
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
yeah, I think it's more related to LT than HR. It's the muscular-force that determines fat vs. carb. utilization and once you're exerting so much force that you're over LT, very little fat is burned. So it would appear that using lower-gears and spinning would utilize more fat because it requires less muscle-force for the same speed. Which raises HR too.

As for LT vs. RHR.... I'm not sure if there's a correlation since LT can occur over a variable range depending upon gearing. Pushing bigger gears would have LT occur at say... 150bpm while spinning smaller gears would have LT be around 170bpm. As you get more fit, RHR drops while LT increases..

"I've read in a lot of places that fitter people burn a higher percentage of fat at a higher HR percentage but never figured out why. Is it then just a matter of looking at the numbers, the only adaptation responsible being a more efficient cardiovascular system?"

It's partly muscle-efficiency, that is, aerobic-power generated for any given amount of oxygen consumed. With training, LT and VO2-max does increase, but not as much as muscle-efficiency. You may see a 10-20% increase in LT & VO2-max, but power-generated at LT can increase by 100-200%. Let's take some examples, if subject #1 & #2 start out with the same fitness, same MHR and LT levels. They can both generate about 200watts @ LT around 170bpm. But #2 does more training and increases his muscle-efficiency more to 400watts @ LT and same 170bpm. These two guys go for a ride later at the same 200watts output. Subject #1 is riding at 90% of his LT at that output, while #2 is riding at only 50%. Subject #2 will be burning more fat because his muscles are operating at a much lower percentage of their max and will be utilitizing a higher percentage of low-twitch aerobic muscles.

One of the most efficient athletes I ever saw at the OTC the summer I was there was a football player. He generated the most power per oxygen consumed they've ever tested... unfortunately his mass and bulk would limit his potential as a cyclist.

"Intramuscular fat? Does the body discriminate about what type of fat to burn?"

I haven't found anything on discriminating between intramuscular fat vs. adipose tissue. I would suspect that your body redistributes this anyway. What I read is that higher triglyceride-levels in the blood does increase fat-burning. This can be triggered by various glycogen-sparing techniques like coffee that stimulates glucagon production and triggers the fat-cells to dump their supply into the bloodstream to be used for fuel helping stretch out the glycogen supply and fending off the bonk for longer.

Last edited by DannoXYZ; 09-03-06 at 01:21 PM.
DannoXYZ 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 10:19 PM.