REF-1237 · Mazza et al., 2026 · Medicine & Science in Sports & Exercise, ahead of print · Paper · PubMed

Does 100 g/h of carbs beat 60 g/h on a long ride?

For late power, yes in one trial: after 4 h, a 15-min time trial fell 6.4% at 100 g/h vs 9.3% at 60 g/h in 15 trained men. 90 g/h not tested.

B+moderate evidenceMeasured on trained to highly trained athletes

Mazza et al. asked whether 100 g of carbohydrate per hour protects late-ride performance better than 60 g per hour, and whether it does so by sparing muscle glycogen.

Fifteen trained male cyclists and triathletes did a 15-min time trial fresh, and again at the end of two 240-min intermittent rides at 60% of their fresh 15-min power with high-intensity intervals, once at 60 g/h and once at 100 g/h (randomised, double-blind, drinks and gels, glucose:fructose 1:0.8), after 24 h on a carbohydrate-enriched diet.

The time trial fell in both conditions, by 9.3% at 60 g/h and 6.4% at 100 g/h (P = 0.025), so power was 9 W higher at 100 g/h. Muscle glycogen fell substantially in both and ended at similar levels (192 vs 209 mmol/kg dry weight, P = 0.56).

Whole-body carbohydrate oxidation fell from 2.6 to 1.9 g/min at 60 g/h but only to 2.3 g/min at 100 g/h, while blood glucose stayed at 5.6-6.1 mmol/L in both. The authors conclude that 100 g/h improved durability without altering muscle glycogen use.

Our reading: in this base, the first double-blind comparison of 100 with 60 g/h on a performance test after a long ride, and with REF-1122 the second crossover in which an intake of 100 g/h or more beat 60 g/h on a fatigued outcome; it does not test 90 g/h, so it supports intakes well above 60 g/h for a 4-h ride but not 100 over 90.

Protocol

Design (from the abstract): randomised, double-blind crossover of two carbohydrate intakes; n = 15 trained men (cyclists and triathletes).
Before: a carbohydrate-enriched diet for 24 h; the amount is not given in the abstract.
Ride: 240 min of prolonged intermittent cycling at 60% of the fresh 15-min time-trial mean power, interspersed with high-intensity intervals (their number and intensity are not given in the abstract).
Feeding: 60 g/h (CHO60) or 100 g/h (CHO100) through beverages and gels, glucose:fructose 1:0.8.
Outcomes: 15-min time trial fresh and after each ride; muscle glycogen from vastus lateralis biopsies before and after the ride; whole-body carbohydrate oxidation by indirect calorimetry; blood glucose.
Not given in the abstract: VO2max or training status beyond "trained", the fresh 15-min power, the order of the fresh test, washout between trials, dropouts, gut symptoms, exogenous (isotope) oxidation, fluid intake, the sample-size calculation, funding and conflicts.

Key Results

Outcome (from the abstract)60 g/h100 g/hP
15-min time trial after the ride, change from fresh−9.3 ± −2.0% (as printed)−6.4 ± −1.7% (as printed)0.025
15-min mean power after the ridereference9 W higher0.028
Muscle glycogen after the ride (mmol/kg dry weight)192 ± 99209 ± 1110.56
Whole-body carbohydrate oxidation, start to end of the ride (g/min)2.6 ± 0.6 to 1.9 ± 0.42.6 ± 0.4 to 2.3 ± 0.5condition × time 0.047
Blood glucose, start to end (mmol/L)5.6 ± 1.0 to 5.7 ± 0.96.0 ± 0.9 to 6.1 ± 0.9time 0.43
Glycogen: "decreased substantially" during exercise in both conditions; the starting values are not given in the abstract.
A number that cannot be right as printed: the time-trial changes carry negative standard deviations ("−9.3 ± −2.0%", "−6.4 ± −1.7%"); a standard deviation cannot be negative, so these are probably typesetting errors, and whether they are SDs or standard errors cannot be checked from the abstract.
Consistency check (our arithmetic): a 2.9-point difference worth 9 W implies a fresh 15-min power of about 310 W, plausible for trained men; the abstract gives no fresh value.

Mechanisms

Measured: more carbohydrate kept whole-body carbohydrate oxidation higher late in the ride; end-of-ride muscle glycogen did not differ; blood glucose was normal and stable at both intakes.
Authors' interpretation: 100 g/h improved durability without altering muscle glycogen utilisation.
Inference: with glucose normal at both intakes and muscle glycogen alike, the benefit is not explained by preventing hypoglycaemia or by sparing thigh glycogen as measured; liver glycogen, more carbohydrate available to oxidise late in the ride and central effects are candidates, and none was measured.This sits against the argued view that carbohydrate helps by preventing hypoglycaemia and that universally high intakes are open to question (REF-476), and with the pooled finding that ingestion rate did not significantly moderate muscle glycogen sparing, with 100 g/h or more rarely tested (REF-1123).
Inference: the same laboratory group ran REF-144, where elite riders at 100 g/h still lost about 10% of 6-min power over 4 h; this trial now gives that intake a comparator.

Practical Application

Does 100 g/h of carbs beat 60 g/h on a long ride? For late power, yes in one trial: after 4 h, a 15-min time trial fell 6.4% at 100 g/h vs 9.3% at 60 g/h in 15 trained men. 90 g/h not tested.
Where it sits in the fuelling ladder: the UCI statement sets 90 g/h for rides over 2.5 h and leaves 120 g/h and above awaiting validation (REF-748); the base's working target for an amateur's 3-6 h event is 80-100 g/h, house practice (SYNTH-02). This trial supports the top of that cell against 60 g/h in trained men; it does not show that 100 beats 90, and it says nothing for 120.
Fuel raises the floor; it does not remove the fade: even at 100 g/h the time trial fell 6.4% after 4 h, as in REF-144 and REF-1122. Late-ride targets still come down (SYNTH-32).
Do not sell high intakes as glycogen sparing: end-of-ride muscle glycogen did not differ detectably between 60 and 100 g/h (192 vs 209 mmol/kg dry weight, P = 0.56); the case for the higher rate is late-ride performance, not muscle sparing (REF-1123).
Earn the rate first: 100 g/h was given as drinks and gels in a 1:0.8 glucose:fructose blend after a carbohydrate-enriched day; gut tolerance was not reported in the abstract. A rider not trained to that rate climbs the gut ladder before a race (SYNTH-02, REF-008).
Two crossovers now point the same way (inference): 120 > 60 g/h for critical power after 3 h (REF-1122, not blinded) and 100 > 60 g/h for a time trial after 4 h (this trial, double-blind). The base's line that 100-120 g/h is "oxidised more", not "proven faster" (SYNTH-02) still holds against 90 g/h and is now qualified against 60 g/h: two crossovers favour the higher intake on a fatigued laboratory outcome, one known only from its abstract, neither a race time.

Limitations

Abstract only. The full text (Wolters Kluwer) was not open access and OpenAlex lists no repository copy; methods details, dropouts, gut symptoms, the interval structure and the fresh power are not given in the abstract.
Small, one laboratory, men only: 15 trained men; women and runners untested.
Two intakes only: 60 vs 100 g/h, no 80, 90 or 120 g/h arm and no water control, so the dose-response shape above 60 g/h is unknown.
The test is a laboratory time trial after a prescribed ride, not a race; whether a 9-W (2.9-point) difference changes a race result was not measured.
Reporting: the negative standard deviations in the abstract cannot be right as printed; exogenous oxidation was not separated from whole-body oxidation in the abstract.
Funding and conflicts: not given in the abstract.
How this entry was checked and changed
Why this level

from the abstract; randomised double-blind crossover, n = 15 (the rubric's B+ floor for crossovers), one laboratory, men only; dropouts, power calculation, VO2max, gut symptoms, the fresh time-trial power and funding are not given in the abstract