What is it about weight loss that improves performance?

Memeologist wrote:

wellnow wrote:

Laws of physics. Although there is no formula for predicting improvement from weight loss, because you have to learn a longer stride to get the benefits.

So a 3% loss of fat should give you a 3% improvement in pace in a long run (where wind resistance is negligable)but that improvement will only happen if your stride length/rate improves 3% with the same endurance ability.

So a 100% loss of fat should give you a 100% improvement in pace in a long run (where wind resistance is negligable)but that improvement will only happen if your stride length/rate improves 100% with the same endurance ability.

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Give it a try and get back to us.

An Engineer wrote:

I'd LOVE to see your mathematical justification for why this is the case.

wellnow wrote:

Laws of physics. Although there is no formula for predicting improvement from weight loss, because you have to learn a longer stride to get the benefits.

So a 3% loss of fat should give you a 3% improvement in pace in a long run (where wind resistance is negligable)but that improvement will only happen if your stride length/rate improves 3% with the same endurance ability.

No, and neither can anyone give a mathematical justification for any predictive formula.

Just sayin that you DON'T improve pro rata with % fat loss, because initially, economy/efficiency worsens as you lose fat. I think this happens because we become familiar with certai stride lengths for a given effort, and in order to get the full mechanical efficiency benefit of fat loss, you have to work over a long period of time to gain that longer stride.

Yes, there SHOULD be a small improvement in stride length from fat loss, but it isn't guaranteed. There are so many variables in training that it may actually help to focus on training improvements with only very slightly reduced calorie intakes.

No, and neither can anyone give a mathematical justification for any predictive formula.

Just sayin that you DON'T improve pro rata with % fat loss, because initially, economy/efficiency worsens as you lose fat. I think this happens because we become familiar with certai stride lengths for a given effort, and in order to get the full mechanical efficiency benefit of fat loss, you have to work over a long period of time to gain that longer stride.[/quote]

Where do you get this "longer stride in order to be more efficient" stuff and what does that have to do with weight loss? Increasing stride length will cause ground contact in front of the hips instead of underneath (see earlier post). This "longer stride" business contradicts the FACT that ground contact and driving forces down increase speed. Increased stride length turns that into a pulling force.

http://www.youtube.com/watch?v=5D56ZAvcxN0

Notice ground contact underneath not in front of the hips and they aren't reaching for a greater stride length

And what does this have to do with weight loss?

WHAT? are you crazy? What has that got to do with my point?

Your brain in not functioning properly.

pose chi wrote:

I did mean 90 steps on each side (L/R) per minute. You smartass.

So do you "run" with one side at once, or both sides at once, which means you would be hopping along for 90 "steps" with both feet.

Your post is way off topic but I don't think you understand what it means to increase stride length. You can increase stride length without over-striding. Look at that video again. Do you think Haile is faster then you just because he has a high turnover or does he have a greater stride length?

chikin wrote:

No, and neither can anyone give a mathematical justification for any predictive formula.

Just sayin that you DON'T improve pro rata with % fat loss, because initially, economy/efficiency worsens as you lose fat. I think this happens because we become familiar with certai stride lengths for a given effort, and in order to get the full mechanical efficiency benefit of fat loss, you have to work over a long period of time to gain that longer stride.

Where do you get this "longer stride in order to be more efficient" stuff and what does that have to do with weight loss? Increasing stride length will cause ground contact in front of the hips instead of underneath (see earlier post). This "longer stride" business contradicts the FACT that ground contact and driving forces down increase speed. Increased stride length turns that into a pulling force.

Notice ground contact underneath not in front of the hips and they aren't reaching for a greater stride length

And what does this have to do with weight loss?[/quote]

chikin wrote:

Where do you get this "longer stride in order to be more efficient" stuff and what does that have to do with weight loss? Increasing stride length will cause ground contact in front of the hips instead of underneath (see earlier post). This "longer stride" business contradicts the FACT that ground contact and driving forces down increase speed. Increased stride length turns that into a pulling force.

I should also point out that, as well as misinterpreting what I am saying, this paragraph doesn't even make sense.

I did a stride length analysis of Gebreselassie and Bekele in the World Championship 10000m in Paris 2003, the one where they started slow and got faster and faster.

Their stride lengths went from around 2.06 meters at 66.5 seconds/lap pace with 175 strides/minute, to 1.94 meters at 61.7 seconds/lap pace with 200 strides/minute

Then when Bekele kicked he went up to 240 strides/minute at 2.0 meters, 12.5 seconds/100m pace.

He did similar things in the World XC Champs in March 04.

So the conclusion I draw is that as they get tired in the race, they can still increase the pace with a slightly shorter stride but higher stride rate. In the final sprint, more power is available initially as the most powerful fast twitch fibers are recruited, enabling a long very fast stride at the end of the race.

If you run faster, with the same stride rate, you will have a longer stride, without necessarily causing the foot to land in front of the hips.If you lose weight (excess fat), you will get faster, and have a longer stride.

chikin wrote:

Where do you get this "longer stride in order to be more efficient" stuff and what does that have to do with weight loss? Increasing stride length will cause ground contact in front of the hips instead of underneath (see earlier post).

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And what does this have to do with weight loss?

I don't see it quite like that.First, if you have lighter legs, you gain in efficiency, because it's easier to lift and move lighter legs, and maintaining the same stride rate costs less energy.Second, we don't become familiar with a stride length, but an overall running pattern, for a corresponding effort. The stride length is just the end result of how we learned to run. If we reduce the mass gradually over time, by losing weight, there is no loss of economy/efficiency, and the stride length will increase immediately and proportionally, with the same running style, and effort.I also think there is a problem with the original question, in that there are too many scenarios. I think of weight loss considering too much my own weight gain history. I learned to run, and competed, as a teenager at 130-140 pounds. Then I stopped for a long while, and ballooned up to 180 pounds. After resuming running, to control my weight, I dropped down to between 150-160 pounds. Now given this history, I think I should be more mechanically efficient at 150 pounds, than 180, given my formative years and experience at 140 pounds.

wellnow wrote:

...

Just sayin that you DON'T improve pro rata with % fat loss, because initially, economy/efficiency worsens as you lose fat. I think this happens because we become familiar with certai stride lengths for a given effort, and in order to get the full mechanical efficiency benefit of fat loss, you have to work over a long period of time to gain that longer stride.

rekrunner wrote:

I don't see it quite like that.

First, if you have lighter legs, you gain in efficiency, because it's easier to lift and move lighter legs, and maintaining the same stride rate costs less energy.

Second, we don't become familiar with a stride length, but an overall running pattern, for a corresponding effort. The stride length is just the end result of how we learned to run. If we reduce the mass gradually over time, by losing weight, there is no loss of economy/efficiency, and the stride length will increase immediately and proportionally, with the same running style, and effort.

Yes, it's easier to lift and move lighter legs, but that doesn't necessarily make you more efficient. If you ran 17 minutes for 5k weighing 170 pounds, could you run 14 minutes weighing 140 pounds? That would be a good indicator of effective weight loss and training, but the reality for most runners is that they don't get anywhere near those gains, because they don't learn to hold the required stride length.

Well your example is probably a bit extreme. I wonder if it's possible to be 30 pounds overweight, and run a 17 minute 5K. At some point, you start losing muscle, and then get slower. (Otherwise, I would be elite at 125 pounds.)I see your point, and I don't disagree with the your claim about maintaining efficient stride lengths, but just don't agree with your implied magnitude of the losses or gains.My point (gut feeling) is that weight loss (excess fat) will lead to some significant and immediate improvements, without having to wait to learn a new stride, for simple mechanical physics reasons, like F=m*a, or KE=(1/2)*m*v^2, or W=m*d, not to mention other contributing factors like improved heat dissipation, or less impact on joints.We don't learn a simple stride length (say 1.96 meters) so much as more complicated sequence of muscle activation patterns, timings, forces, etc. While I agree we may lose some initial efficiency if the loss of weight creates temporary imbalances, which requires some retraining, I simply doubt it's of the magnitude of Tom Osler's 2 seconds per pound per mile estimate.But that's just my gut feeling. I'm not aware of anyone who has looked at the question. Are you? Unfortunately, weight loss due to training changes a few other factors (stronger muscles, and better efficiency/economy), so it's hard to attribute improvements to any single cause.

wellnow wrote:

Yes, it's easier to lift and move lighter legs, but that doesn't necessarily make you more efficient. If you ran 17 minutes for 5k weighing 170 pounds, could you run 14 minutes weighing 140 pounds? That would be a good indicator of effective weight loss and training, but the reality for most runners is that they don't get anywhere near those gains, because they don't learn to hold the required stride length.

I lost 2 lbs last week and improved my 5k time 14 seconds!!! (cut 1200 calories a day)

I really don't care why!!

I think that to really take advantage of the weight loss, you have to have a very strong conviction and self belief. How many runners really want to be elite? Very few. I know because I ask runners this question regularly.

If you want to be elite, and have a very strong conviction and self belief, you don't need weight loss.

wellnow wrote:

I think that to really take advantage of the weight loss, you have to have a very strong conviction and self belief. How many runners really want to be elite? Very few. I know because I ask runners this question regularly.

Um, if you are 10lbs overweight it is not usually cause you have fat hands.