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General Category => The Science of Running => Topic started by: Lybi on March 21, 2012, 12:54:52 am

Title: Optimal Weight and Running Speed
Post by: Lybi on March 21, 2012, 12:54:52 am
Hey guys!  I recently started running again after a long break in which I gained weight.  :-[ As I am getting used to running again, I am surprised at how my pace is gravitating toward a much slower "easy pace" than before.  So I was wondering, has anyone ever explained the relationship between weight and speed, like 5 extra pounds will slow you down about 5% or something like that?  Obviously weight slows you down, but how much?  I thought maybe we could get some really experienced, consistent runners to make an experiment of running the same course on different days with the same effort, and taking a backpack or something with weights in the pockets to see about how much 5, 10, 15, 20 lbs. affects pace. 3 miles should be enough to get some data. Ideally, heart rate would be about the same each time, so heart rate monitors would be awesome.  What do you think? Anyone want to furthur the science of running? This could be an important tool for motivation for runners who have some pounds to drop (which probably excludes YOU, dear reader, but still.)  Thoughts welcome!


Title: Re: Optimal Weight and Running Speed
Post by: allie on March 21, 2012, 08:02:44 am
very interesting. i have a weighted vest with removable weights -- i'm going to try this...

Title: Re: Optimal Weight and Running Speed
Post by: Jake Krong on March 21, 2012, 11:04:12 am
I think there are actually a handful of scientific studies that have been published on this topic. I know I've read something along the lines of a 1% decrease in body mass (esp if its mostly excess body fat) will result in a 1% increase in running speed. Less mass = less oxygen needed = improved efficiency. I've also heard the old rule of thumb that every excess pound adds ~1 second/mile. Of course there is a point of diminishing returns and when you cross that point even by a tiny amount, the results can be disastrous.

This would be a cool study for a ex-phys student to take on!

Title: Re: Optimal Weight and Running Speed
Post by: dave rockness on March 21, 2012, 04:19:04 pm
I've read up to 2-3 seconds per/mile per/pound.  Wish I can remember where.  Certainly it depends upon optimal weight- some can't afford to lose more and improve.  I'd also be interested in feedback from others. 

Title: Re: Optimal Weight and Running Speed
Post by: Lybi on March 21, 2012, 05:38:08 pm
Thanks, Allie!  A weighted vest is a great idea!  I can't wait to see your results. 

Title: Re: Optimal Weight and Running Speed
Post by: Nate Page on March 22, 2012, 08:02:49 am
I like the idea of a weighted vest to get a general idea of the effects of weight.  Something I think might play a large roll in weight and running is the metabolic requirements of the extra tissue you are carrying around.  Any extraneous fat and muscle is going to require a portion of your cardiac output. You increase your cardiac output to some physiological maximum during exercise and there is a shunting of blood to skeletal muscle (via vasodilation of arterioles in skeletal muscle and constriction in other tissues) but fat, skin, and other "non-running" tissues are still going to be getting at least a little blood flow.  So I think that the extra mass is the most important consideration when thinking about weight and running, these little physiological things may add up

Title: Re: Optimal Weight and Running Speed
Post by: Lybi on March 23, 2012, 03:48:38 pm
Wow, Nate, nice vocab. So you are saying that not only is extra energy required to move the extra poundage, but also, the extra tissue is a bit of a drain on the blood and oxygen needed for the running muscles, right?  Which do you think is the more important influence

Title: Re: Optimal Weight and Running Speed
Post by: Kam on March 24, 2012, 01:45:31 pm
From an 8th grade physics standpoint, Work = Mass x distance.  The more mass you are carrying around, the more work it is going to take to cover the distance.  If you are running heavier, you are doing more work, i.e. using more calories, generating more heat, not to mention increasing the force on your feet, legs and joints.  In longer runs, a calorie deficit and overheating can be disastrous...
Along with you, I can't wait for allie to publish her results.

Title: Re: Optimal Weight and Running Speed
Post by: Nate Page on March 26, 2012, 09:19:01 am
Lybi:  Yes, That's the jist of what I wrote but in the end I think that just lugging around the extra weight itself is the biggest issue.  I'll be excited to see what allie comes up with

Title: Re: Optimal Weight and Running Speed
Post by: Andrea North on April 05, 2012, 10:43:33 am
Here's a very recent article on this topic -

Title: Re: Optimal Weight and Running Speed
Post by: allie on April 05, 2012, 11:06:08 am
this is exactly what i was thinking about when i was running with the 5 extra pounds on monday. while doing an experiment such as this can provide some interesting data on how your HR and pace are affected by adding extra weight, it is not equivalent to carrying extra weight that you can't simply "unstrap" when you are done running. one is an instant change to your body, while another is put on gradually over time.
if i strap on an extra 25 lbs. and take off on a run, i think it's safe to assume that it would be much harder on my body than if i slowly gained 25 pounds over the course of a year or two but continued to run every day (at least in terms of HR and pace -- my garmin doesn't measure the energy cost of running or mechanical work output). the other issue is the unnatural weight distribution when you are wearing a backpack.

Title: Re: Optimal Weight and Running Speed
Post by: Michelle Lowry on April 26, 2012, 04:14:48 am
I am wearing a weighted vest but I can't take it off! 
What is interesting is that I have not been at my lowest running weight (which is about 123 and I am 5'6", theoretically it should be even lower but I haven't been able to go lower for a sustained period).  At about 5-7 lb heavier, I just ran a PR type race (it was an odd distance).  I do believe that I am carrying around more and could race better with less, but at the same time, this last training cycle I did not focus on eating like a champion and I think the removal of that psychological stress helped me in other ways.  I would like to get back to 123, but not if it means medium-grade psychosis.

Title: Re: Optimal Weight and Running Speed
Post by: Adele Kimbrough on April 26, 2012, 10:47:02 am
Michelle, congratulations on the recent pr; you're an awesome runner! (And I think your "substantial" breakfast on race day helped provide some good fuel for your race.) 

Runner's World magazine had a recent article on "disordered eating", and the effect anorexia can have on running.,7120,s6-241-285--14203-F,00.html is a rather long article, but it chronicles a runner who went from 158 lbs down to about 130 lbs in an effort to get faster, then decided he was being neurotic about his diet and went back up to around 150 lbs.  It's important to realize that everyone has a different body type, and that some body types don't respond well to overly restrictive diets.  The article also implies some runners might be more at risk of stress fractures if they don't consume enough nutrients. 

BTW, I'm not an elite runner (more like an old slow lady) and have found that if I'm trying to lose weight and don't take in enough calories I have zip zero energy (I can still run, but I'm not motivated and am really slow with no real improvement). But if I focus on eating lots and lots of healthy fruits, veggies, lean protein & dairy, and show moderation in eating treats (ie, 1 or 2 brownies instead of 1/2 the pan of brownies), I feel great, enjoy my runs, and still usually lose about a pound a month!

Title: Re: Optimal Weight and Running Speed
Post by: Bonnie on May 15, 2012, 07:19:23 pm
I think that there is some sort of "cut-off" in terms of normal for runners that are running at their optimal weight and when they are carrying too many pounds ... but what is "optimal" for some might not be optimal for others; even those that are in their best shape.  I personally don't think this has anything to do with bone mass either. 

Even though compared to most elite runners I would be considered heavy when I have been running at my optimal weight, now that I am down 11 pounds (and counting), I have to say I don't feel any faster.  I think I have an ideal weight that is on the "heavier-than-some" range (like Nick Symmonds and Chris Solensky).  It just so happens that my "I feel healthy" weight is smack dab in the middle of the ideal range for my height ... now that I am on the lower end (which is healthy for some of you), I don't feel as good.

Title: Re: Optimal Weight and Running Speed
Post by: Michelle Lowry on May 24, 2012, 08:52:46 pm
Great article Adele.  I definitely see some of the disordered eating in me, and it's a good reminder to be balanced and mindful.  A good rule of thumb is that if you are thinking about food all the time (whether fantasizing, planning how to restrict, or elsewise) then you're a bit off kilter.  That's me  :-\

Title: Re: Optimal Weight and Running Speed
Post by: Sasha Pachev on June 07, 2012, 01:27:20 pm
Hobie Call ran a low 17 5 K with 30 lb vest. His weight is 142lb, I believe. He would have run a low 15 or maybe a little under without it. Rough approximation from that experiment could be t_orig * ((weight + extra_weight)/weight)^0.95, so 8:00 mile = 480 seconds for a 150 lb runner who picks up extra 25 lb becomes 480*((150+25)^0.95)=555 seconds or 9:15 per mile. If you want to do the computations, just substitute the parameter names (like t_orig or weight) with numbers and paste it into Google search box.

However in practice it all depends on the nature of the excessive weight. How is it distributed and how does it affect your biomechanics? Does its presence create a metabolic/blood flow/heart power/etc inefficiency of some kind?

I think it is a mistake to focus on weight alone. Excessive weight is only one of the many symptoms of the lack of fitness, and in some cases it may not be present. Sometimes increases in fitness can be accompanied by a weight gain, or a weight loss can happen along with the loss of fitness. One of my training partners dropped from 135 lb to 125 lb at first when he stopped training, then got back up to 145 lb, for example. Apparently, the body responded first by losing the muscle mass, and only then began to accumulate fat at a fast rate.

So short answer - if you lack the fitness and feel heavy, the fix is a good balance of training, eating, and sleeping. The fitness will improve, and the weight will arrive at its optimal point.

Title: Re: Optimal Weight and Running Speed
Post by: Jeff Linger on June 28, 2013, 12:27:51 am
I think that one thing that hasn't been addressed in this conversation yet is the distribution of weight in terms of 'simply weight (adding vests)' and 'how weight is distributed in terms of fat'. Men who gain weight tend to gain it viscerally (it accumulates around the organs, compressing in on them). Women gain it it below the skin, but not so much around the organs (forgot the word for it, subcutaneously I think). My guess is that in terms of performance, men's performance would actually decrease more with excess weight versus women (speaking relatively here) in terms of strict weight gain. Visceral fat is burned easier than subcutaneous fat I believe. When the effect of weight gain is considered and its impact on the various running systems, I don't think one can simply strap on weight and equate it to weight gain in terms of performance. The runner with a vest is still a more fit runner than the runner who has gained weight. In other words, it is not just the weight that's a factor. For various reasons I've struggled over the last few years to 'get back to where I was'. The end result is has been about 10-20 pounds weight gain (I'm down to about 10 now). I used to run home from work with my work stuff on my back (about the same 10 pounds I have now). I can say that running with the backpack, despite the sloppy weight swing that effected my cadence, was much easier and faster. The fat weight gain impacts so many other systems that are not impacted when simply running with added weight that doesn't belong to you, so to speak.