REF-144 · Ørtenblad et al., 2024 · European Journal of Applied Physiology · Paper

Four hours of race-like intermittent riding at 100 g CHO/h cut 6-min time-trial power by ~10% and peak power by ~6% in twelve elite cyclists

And none of the fresh lab measures (LT1, efficiency, fat oxidation, VO₂peak) predicted who faded most

Blimited evidenceMeasured on elite to world-class athletesWritten before October 2026, being re-checked

Participants

Twelve elite and professional road cyclists (median age 23 y, body mass 71.5 kg, VO₂peak 73.6 [71.2; 76.0] mL·kg⁻¹·min⁻¹).

Protocol

Fresh: a graded submaximal test for the first lactate threshold (LT1), gross efficiency (GE) and maximal fat oxidation (MFO), and a maximal 6-min time trial. On a separate day: a 4-h intermittent cycling protocol with 100 g/h of carbohydrate, with substrate use and peak power output (PPO) measured every hour, followed by another 6-min time trial.

Key Findings

6-min time-trial power fell by 10% [4; 15] and peak power by 6% [0; 6] after the 4-h protocol.
The losses came with a lower anaerobic energy contribution and a lower VO₂peak in the final test; average VO₂ during the 6-min effort was unchanged.
No strong association between the fall in 6-min power or PPO and any fresh laboratory measure — LT1, gross efficiency, maximal fat oxidation or VO₂peak.

Practical Application

Fuelling at 100 g/h does not make a rider durable. Even elite riders lost about a tenth of their 6-min power after four hours of race-like work; durability has to be trained and planned for (SYNTH-32).
Test durability directly, not by proxy. Fresh LT1, efficiency and fat-oxidation numbers did not predict who faded — a hard effort after a long ride tells you; the fresh profile does not.
The loss is at the top end — anaerobic contribution and VO₂peak in the final effort — so a late attack or the last climb is where it shows, not the steady pace.

Limitations

n = 12 elite men, one laboratory protocol and one intake (100 g/h) with no comparison intake.
An ergometer simulation of a stage, not a race.
Re-entered from the abstract after the earlier figures were found not to match it; the full text has not been re-read.
How this entry was checked and changed
Why this level

regraded 2026-09-26 from A: within-subject observational, n=12 elite

Content correction 2026-09-26

Until today this entry reported muscle-biopsy glycogen by fibre type (~550 → ~350 mmol/kg, Type I first), a doubling of fat oxidation, and a 6-min time trial PRESERVED at ~440 W after the protocol. The published abstract reports the opposite on the headline outcome — 6-min TT power FELL by ~10% — and mentions no biopsies.

The glycogen and fat-oxidation figures could not be traced to the paper and were removed. The separate note of 2026-07-06, that REF-426 is a different study, still stands.

Content correction 2026-09-27
Cross-reference blurbs carried figures and claims not checked against the cited entries ("100g/h even better", "344-519g", "+21% fat oxidation", "conserves glycogen"); reduced to neutral topic labels.