Carbohydrate loading in human muscle: an improved 1 day protocol
Trained athletes are generally held to reach maximal muscle glycogen after about 3 days of a carbohydrate-rich diet, without a depletion phase. Eight endurance-trained men ate 10 g of high-glycaemic-index carbohydrate per kg body mass per day for 3 days while physically inactive, with biopsies before and after 1 and 3 days.
Glycogen rose from 95 to 180 mmol/kg wet mass after only 1 day and stayed there; fibre-type staining showed type I, IIa and IIb fibres were also maximal after 1 day. The authors conclude that inactivity plus a high carbohydrate intake lets trained athletes reach maximal glycogen within 24 h.
Participants
n=8 endurance-trained male athletes ("eight endurance-trained male athletes").
Protocol
Diet: 10 g·day⁻¹·kg⁻¹ body mass of high-carbohydrate, high-glycaemic-index foods for 3 days.
Activity: physically inactive throughout.
Muscle biopsies: before loading, and after 1 and 3 days.
Periodic acid-Schiff staining with densitometry for glycogen in type I, IIa and IIb fibres.
Key Results
Muscle glycogen: 95 (5) → 180 (15) mmol·kg⁻¹ wet mass after 1 day [mean (SE)], P < 0.05.
No further rise over the next 2 days of the carbohydrate-rich diet.
Fibre-type densitometry: only 1 day of high carbohydrate intake was needed for glycogen to reach maximal levels in type I, IIa and IIb fibres.
Practical Application
In eight endurance-trained men resting and eating 10 g of high-glycaemic-index carbohydrate per kg body mass per day, muscle glycogen rose from 95 to 180 mmol/kg wet mass after one day and did not rise further over two more days. To "how many days do I need to carb-load?": in this study one day was enough, when that day combined rest with a very high carbohydrate intake.
Rest was part of the protocol. The abstract does not test loading while training.
Inference, not tested here: 10 g/kg is 700 g of carbohydrate for a 70-kg athlete (arithmetic, not from the abstract), which is hard to eat without low-fibre, high-glycaemic-index foods; rehearse the menu before a race week.
Limitations
n=8 men; no control group and no women.
No performance outcome; glycogen only.
Athletes were inactive; the result may not hold if training continues on the loading day.
Sampling at 1 and 3 days only, so whether less than 24 h would suffice is not known.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level
uncontrolled pre–post, n=8