90, 120 and 150 g/h of glucose + fructose over 3 h of cycling in trained men: exogenous oxidation rose with the dose (1.23 → 1.48 → 1.62 g/min), whole-body carbohydrate oxidation did not rise from 120 to 150 g/h (2.6 g/min both), exercise capacity afterwards did not differ between 90, 120 and 150 g/h, and the modelled best dose was 107 g/h (95% CI 92-122) with wide individual variation
Eight trained males cycled for 3 hours and then did an exercise capacity test at 150% of lactate threshold. A first familiarisation trial used 10 g/h maltodextrin; the following trials were randomised to 90, 120 or 150 g/h of a 1:0.8 maltodextrin-to-fructose drink enriched with [U-13C] glucose-fructose.
Participants
n=8 trained males.
Protocol
3 h of cycling, then a capacity test at 150% of lactate threshold.
Familiarisation at 10 g/h maltodextrin (first, not randomised); randomised trials at 90, 120 and 150 g/h, maltodextrin:fructose 1:0.8, 13C-enriched.
Key Results
Exogenous carbohydrate oxidation rose with dose: 1.23 ± 0.35, 1.48 ± 0.44 and 1.62 ± 0.45 g/min at 90, 120 and 150 g/h (all P < 0.05), with within-trial ranges of 0.3, 0.6 and 0.9 g/min.
Whole-body carbohydrate oxidation was the same at 150 and 120 g/h (2.6 ± 0.3 g/min both, P = 0.97), higher than at 90 (2.3 ± 0.5) and 10 g/h (1.7 ± 0.7).
Blood glucose was lower at 10 g/h (3.8 mmol/L) than at 90, 120 and 150 g/h (4.6, 4.6, 4.8; no difference among the higher doses).
Total exercise duration was shorter at 10 g/h (2:41:28 ± 0:24:47) than at 90 (3:04:59) and 120 g/h (3:05:24) (both P < 0.05) and than at 150 g/h (3:00:39 ± 0:07:00, P = 0.06, not significant); no differences between 90, 120 and 150 g/h.
Modelled optimal dose for exercise capacity: 107 g/h (95% CI 92-122).
Authors' conclusion: 150 g/h does not increase whole-body carbohydrate oxidation versus 120 g/h; variation in the ergogenic dose and in exogenous oxidation supports personalising intake.
Practical Application
For a trained rider on a ~3-h effort, going from 120 to 150 g/h burned more of the drink but not more carbohydrate overall and did not extend the capacity test; 90, 120 and 150 g/h did not differ significantly (n=8), and the modelled sweet spot was ~107 g/h (92-122). This study found no gain above 120 g/h.
Individual exogenous oxidation varied by up to 0.9 g/min at the same intake: find the athlete's own rate in training rather than copying a number. Not from this paper; the base's own practice: the gut ladder in SYNTH-02.
Inference: the 150 g/h mean total time (3:00:39) is below the 3-h ride plus test of the 90 and 120 g/h trials; the abstract does not say why.
Limitations
n=8 trained males; no women, no untrained riders; competitive level not given in the abstract.
The 10 g/h trial was the familiarisation, done first and not randomised — its shorter duration is confounded by order and learning.
One 3-h protocol and a capacity test, not a race or time trial; nothing beyond 3 h.
Gastrointestinal symptoms are not reported in the abstract.
How this entry was checked and changed
Why this level
randomised crossover with isotope tracers, but n=8 and the 10 g/h comparison is confounded by order