S. Brundle et al., Comparison of fructose and glucose ingestion before and during endurance cycling to exhaustion, J SPORT MED, 40(4), 2000, pp. 343-349
Background. Pre-exercise and exercise ingestion of fructose and glucose dur
ing cycling exercise were compared.
Methods. Experimental design: Seventeen trained subjects ingested a placebo
prior to and during a cycling test to exhaustion at 75% VO2max (control gr
oup = CG). One week later, subjects were matched on exercise time to exhaus
tion (ETE) and assigned to a fructose group (FG) or a glucose group (GG). S
ubjects then performed a second cycling test to exhaustion, ingesting fruct
ose or glucose doses. For all groups (CG, FG and GG), blood was drawn befor
e and at timed intervals during exercise to determine glucose, lactate and
free fatty acid (FFA) levels.
Results. The ETE for CG was less than either FG (p<0.02) or GG (p<0.001) bu
t FG and GG were similar, FG and GG did not show any differences in blood l
actate or blood FFA during the ETE. However, CG FFA levels were higher than
those of FG (p<0.02) prior to exercise.
Conclusions. This study demonstrated that fructose and glucose are of equal
value in prolonging ETE in endurance cycling. Ingesting fructose before an
d during exercise apparently provided a more constant supply of glucose to
be available to the working muscles. The more stable blood glucose levels w
ith fructose ingestion may be beneficial in reducing perceived exhaustion,
and thereby allowing for an enhancement in exercise performance.