glycerol

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

Hi Nikki,
there was a discussion about glycerol in the past and you might want 
to check the ridecamp archives.  Glycerol has been used in attempt to 
super hydrate, in the hopes that having more fluid in the system 
would decrease heat stress by permitting a greater sweat rate.  
Glycerol, a sugar alcohol, appears to expand the amount of fluid 
between cells, and decreases the amount of urine produced compared to 
drinking plain water.   Although all of this sounds promising it has 
not consistently benefitted performance in humans.  A study performed 
in 1991 found that glycerol ingested during exercise in a hot 
environment was associated with more gastrointestinal discomfort 
[diarrhea etc], but did not affect heart rate, body temperature, 
sweat rate, perceived exertion or sodium regulating hormones, 
suggesting that there was no benefit to using glycerol [Murray et 
al].  A more recent study, though, did find that endurance was 
improved when  glycerol was used prior to exercise, compared to 
water [Montner et al].  There is not clear consensus as to whether it 
will be useful as an enhancer of exercise performance.  I'd be 
interested to hear what your experiences are while running. 

 Beth Glace, MS Sports 
Nutritionist