body fat and performance

["Beth Glace" <lb@nismat.org>]

Hi all,
I will probably straddle the 2 opposing opinions listed below.  

<<<scores of 4-6 did better was that they had the fat stores to burn! 
 The really thin horses with no fat stores pooped out, and they may 
 have benefitted from Tom carbo feeding at 1 1/2 hour intervals to > 
keep them going because they had no gas in the fuel tank! >>>>

*** Body
fat is not gas in the fuel tank--it's extra baggage. What > you're
talking > about here in better body condition is stored muscle
glycogen, not > stored fat. Do you really believe that the difference
in body weight > between properly fed and poorly fed equine athletes
in hard training > is body fat? A > delusion.****


We just completed 2 studies of ultramarthoners at the Vermont 100.  
One of the few predictors of performance found to be significatnt was 
low body weight.  These are humans running for 24 -30 hours, with 
essentially no stopping.  While their body fat is likely higher than 
athletes running shorter events, they also tend to be an older group 
[mean age 49 yrs], and as we all know, we get fatter as we get older. 
 Nontheless,  body fat was directly correlated with finish time:  
higher body fats, higher [slower] times.  Furthermore, for both men 
and women, non finishers weighed significantly more than finishers.  
the race this year was extremely hot, around 100 F, so the extra 
weight probably impaired thermoregulation.  However, we found similar 
results last year when conditions were far more moderate.  

The observation that thin horses do not do as well as fatter horses 
is interesting, but I wonder if the thinner horses had not been fed 
as well coming into the event, or were just not good eaters in 
general, and thus entered the event in a more depleted state. Is it 
possible that some of these horses were just overtrained or 
overraced?   In most human and animal studies 
[rodents] of substrate use, a majority of fat used during exercise 
comes from lipid stores in the muscle, rather than adipose stores.  
We all know that training increases the amount of carb stored in the 
muscle, but not all of us realize that training also increases the 
amount of fat stored in the muscle.  At exhaustion, both 
intramuscular fat and glycogen stores will be depleted, underscoring 
the importance of both energy sources in exercise.  If the horse has 
been training hard, and intake has not kept up with expenditure, 
both of those stores might be less than optimal on race day.

 In terms of the horses, you can't argue with the observation that 
well fed [cared for?] horses will do better in long duration events 
than thinner [overtrained? poor eaters?] horses.  Obviously "fat" 
animals will not do well:  too much weight [baggage] and probably 
less training.  I do think that there is a little bit more leeway in 
very long duration exercise for body weight, as compared to the 
"racing lean" weights seen for shorter events.  

Compromise?
Regards,
Beth
Klass Act 


Beth Glace, MS, CDN
Nicholas Institute of Sports Medicine and Athletic Trauma
Lenox Hill Hospital
New York, NY


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