Author(s): JONES, R., ARETA, JL. ATKIN, V. PUGH, JN. & LOUIS, JB., Institution: LIVERPOOL JOHN MOORES UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1728

INTRODUCTION:
A high dietary carbohydrate (CHO) intake 36-48h pre-competition to enhance muscle glycogen stores is considered a prerequisite for optimal endurance exercise performance [1]. However, the only two double blinded CHO loading studies both reported no difference in cycling performance between high and moderate CHO intakes [2,3]. Further, seminal studies within the area have implemented nutritional interventions with limited ecological validity considering current recommendations (overnight fast/no CHO during exercise [4]). As such, this study investigated the effect of CHO loading on endurance cycling performance under real world nutritional conditions whilst controlling placebo effects.
METHODS:
In a double-blind repeated measures design, 9 endurance trained males (31 ± 10 yrs; 78.3 ± 6.7 kg; VO2max, 63.4± 5.2 mL/kg/min; PPO, 367 ± 37W; LT 188 ± 24W) completed 3x4 days of dietary control and prescribed exercise designed to mimic pre-competition practices of endurance cyclists. Day 1 standardised nutritional status with a moderate CHO intake and high intensity cycling session. Day 2 and 3 participants consumed 6, 8 or 10 g/kg/d CHO and completed light cycling exercise (taper), with blinding achieved by providing 6 g/kg/d CHO as food, and the remaining CHO as taste and colour matched drinks. Day 4, participants completed a 2.5 h performance test (2 h at 95%LTDmax and ~30 min work done time trial [TT]), with 60 g/h of CHO provided throughout. TT performance and power over time was analysed using one- and two-way repeated measures ANOVA. Effect sizes (ES) are provided as partial eta squared.
RESULTS:
TT completion time (36 min 46s ± 4 min 18s, 34 min 55s ± 5 min 12s and 35 min 46s ± 5 min 56s; P= 0.16, ES= 0.21), mean power output (226 ± 22, 239 ± 29 and 234 ± 29W; P = 0.10, ES= 0.26) and power output over time (P = 0.09, ES= 0.26) was not significantly different between 6, 8 or 10 g/kg/d, respectively. There was no trial order effect (P = 0.30), however 4 participants identified the 6 g/kg/d condition.
CONCLUSION:
In conclusion, the ergogenic effects of CHO loading with a high vs moderate CHO intake for endurance cycling performance, under real world nutritional conditions (high CHO availability during exercise), remains unclear.

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