Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise-Induced Muscle Damage in Elite Runners
Participants
n=20 male elite mountain runners who had previously undertaken nutritional and gut training.
Protocol
Single mountain marathon with ~4000 m cumulative slope (distance not stated in the abstract)
Three intake groups during the race:
EXP: 120 g CHO/h
CON: 90 g CHO/h (the CHO intake recommendation)
LOW: 60 g CHO/h (regular intake of ultra-endurance athletes)
Muscle-damage markers (CK, LDH, GOT, urea, creatinine) measured before the race and 24 h afterwards
Internal exercise load calculated from RPE during and after the race
Key Results
Internal exercise load during the race was significantly lower in EXP (3805 ± 281 AU) than in LOW (4688 ± 705 AU) and CON (4692 ± 716 AU); p = 0.019
CK, LDH and GOT at 24 h: significantly lower in EXP (120 g/h) than in LOW and CON (CK p = 0.019; LDH p < 0.001; GOT p = 0.003)
Muscle damage and exercise load were closely correlated (R = 0.742; p < 0.001)
The abstract reports no result for urea, creatinine, GI symptoms or race time
Mechanism
Inference, not tested: higher exogenous CHO → less reliance on endogenous glycogen → lower internal load → attenuated membrane disruption (CK leak). The study measured markers and RPE-based load, not glycogen use.
Practical Application
In 20 gut-trained elite male mountain runners, 120 g CHO/h during a ~4000 m D+ mountain marathon gave lower muscle-damage markers (CK, LDH, GOT) at 24 h and lower RPE-based internal load than 90 or 60 g/h — for long, hard mountain races the higher rate protected recovery better than the standard 90 g/h recommendation.
Not from this paper: the CHO ratio rule (1:0.8 maltodextrin or glucose : fructose for intakes ≥90 g/h) is carried by SYNTH-02; this abstract does not state the CHO composition used.
Limitations
Single race only — multi-day stages not tested
Elite males — females and masters athletes not studied
Three arms from n=20 gives roughly 7 per group
Markers taken at 24 h only; performance (race time) not reported in the abstract
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A: parallel randomized trial, n=20 in three arms
Content correction 2026-09-27
"35 km, ~2500 m D+" -> abstract gives ~4000 m cumulative slope and no distance.
"0.8:1 fructose:maltodextrin" -> not in the abstract; moved to a "Not from this paper" line pointing to SYNTH-02.
"Urea, creatinine trend better", "GI distress no difference", "trend toward faster performance" -> none reported in the abstract; removed. Added the internal-load (RPE) result the abstract does report.
Level A -> B+ (parallel randomized trial, n=20 in three arms).
Descriptions of REF-144 repeated its pre-2026-09-26 version (muscle biopsies, glycogen/fibre-type depletion, fat oxidation doubling, power "preserved/maintained" at 100 g/h). The corrected entry took no biopsies and reports 6-min power FALLING ~10% after 4 h at 100 g/h; descriptions updated.
Full text (checked 2026-10-12)
The race was an official 42.195 km mountain marathon in Oiartzun at 10 °C with total cumulative slope of 3980.80 m (1990.40 m positive and 1990.40 m negative) (full text).
All groups took the same 30 g maltodextrin (glucose) and fructose gels (ratio 2: 1), every 15, 20 and 30 min for EXP, CON and LOW respectively, with no other food and water ad libitum (full text).
Gut training was personalised by each athlete's nutritionist and required CHO intakes of up to 90 g/h at least 2 days/week in the 4 weeks before the race (full text).
Of 26 randomized runners, 6 withdrew during the race (3 with injury and 3 with gastrointestinal problems—reflux and/or flatulence), leaving 6 in LOW, 7 in CON and 7 in EXP (full text).
Race time did not differ between groups (LOW 4:38:33, CON 4:44:27, EXP 4:31:36; p = 0.871), nor did RPE (p = 0.409) or race intensity (p = 0.290) (full text, Table 2).
From pre to 24 h, CK rose 155.9 ± 39.5% in EXP vs 976.2 ± 631.3% in LOW and 963.4 ± 713.3% in CON; LDH rose 8.5 ± 8.5% vs 46.7 ± 15.5% and 36.7 ± 16.6%; GOT rose 27.2 ± 23.5% vs 161.6 ± 98.2% and 152.1 ± 64.6% (full text).
Urea rose significantly in all three groups, with no group-by-time differences for glucose, urea or creatinine (full text, Table 1).
Diet was controlled: 9 g CHO/kg/day for 48 h before the race, a breakfast of 2 g CHO/kg 3 h before, a recovery shake of 1.2 g CHO/kg with 0.3 g/kg whey, then 9 g CHO/kg over the next 24 h (full text).