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[RC] CHO/altitude - Ridecamp Guest

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Authors CS Fulco, KW Kambis, AL Friedlander, PB Rock, SR Muza, A Cymerman
Title   Carbohydrate supplementation improves time-trial cycle performance 
during energy deficit at 4,300-m altitude
Full source     Journal of Applied Physiology, 2005, Vol 99, Iss 3, pp 867-876

Carbohydrate supplementation (CHOS) typically improves prolonged time-trial 
(TT) performance at sea level (SL). This study determined whether CHOS also 
improves TT performance at high altitude (ALT; 4,300 M) despite increased 
hypoxemia and while in negative energy balance (similar to 1,250 kcal/day). Two 
groups of fasting, fitness-matched men performed a 720-kJ cycle TT at SL and 
while living at ALT on days 3 (ALT3) and 10 (ALT10). Eight men drank a 10% 
carbohydrate solution (0.175 g/kg body wt) and eight drank a placebo (PLA; 
double blind) at the start of and every 15 min of the TT. Blood glucose during 
each TT was higher (P < 0.05) for CHOS than for PLA. At SL, TT duration 
(similar to 59 min) and watts (similar to 218 or similar to 61% of peak watts; 
%SL Wpeak) were similar for both groups. At ALT, the TT was longer for both 
groups (P < 0.01) but was shorter for CHOS than for PLA on ALT3 (means  SE: 80  
7 vs. 105  9 min; P < 0.01) and ALT10 (77  7 vs. 90 5 min; P < 0.01). At ALT, 
%SL Wpeak was reduced (P < 0.01) with the reduction on ALT3 being larger for 
PLA (to 33  3%) than for CHOS (to 43  2%; P < 0.05). On ALT3, 02 saturation 
fell similarly from 84  2% at rest to 73  1% during the TT for both groups (P < 
0.05), and on ALT10 O-2 saturation fell more (P < 0.02) for CHOS (91  1 to 76  
2%) than for PLA (90  1 to 81  1%). %SL Wpeak and 02 saturation were inversely 
related during the TT for both groups at ALT (r >= -0.76; P <= 0.03). It was 
concluded that, despite hypoxemia exacerbated by exercise, CHOS greatly 
improved TT performance at ALT in which there was a negative energy balance.


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