REF-799 · Geesmann et al., 2014 · International Journal of Sport Nutrition and Exercise Metabolism, Vol. · Paper · PubMed

Energy Balance, Macronutrient Intake, and Hydration Status During a 1,230 km Ultra-Endurance Bike Marathon

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

Fourteen well-trained riders completed a 1,230 km bike marathon in 42:47 h, eating and drinking as they chose. Energy intake (19,749 ± 4,502 kcal) fell short of expenditure estimated from power output (25,303 ± 2,436 kcal) in 12 of 14 athletes.

Carbohydrate averaged 57.1 ± 17.7 g/h and fluid 392 ± 85 ml/h, and both carbohydrate and fluid intake dropped significantly after km 618. Hydration looked suboptimal already at the start (urine specific gravity 1.022 ± 0.010 g/ml) and did not change significantly during the event.

The authors conclude that riders failed to stay in energy balance, that carbohydrate and fluid intake fell below recommended values in the second half, and that individual strategies against satiety and fatigue may be needed.

Participants

n=14 well-trained participants (abstract: "A group of 14 well-trained participants"), VO2max 63.2 ± 3.3 ml/kg/min. Sex and age are not given in the abstract.

Protocol

Event: 1,230 km bike marathon, completed in 42:47 h.
Food and fluid intake ad libitum, monitored throughout.
Energy expenditure derived from power output.
Urine and blood markers before the start, after 310, 618 and 921 km, after the finish, and 12 h after the finish.

Key Results

Energy intake 19,749 ± 4,502 kcal vs energy expenditure 25,303 ± 2,436 kcal; intake was lower than expenditure in 12 of 14 athletes.
Carbohydrate intake averaged 57.1 ± 17.7 g/h; energy and carbohydrate intake decreased significantly after km 618 (p < .05).
Fluid intake averaged 392 ± 85 ml/h and also decreased after km 618 (p < .05).
Urine specific gravity before the start: 1.022 ± 0.010 g/ml ("suboptimal"); hydration did not change significantly through the event.

Practical Application

In 14 well-trained riders completing a 1,230 km non-stop bike marathon in 42:47 h on self-chosen food and drink, 12 of 14 ate less than they spent (19,749 vs 25,303 kcal), carbohydrate averaged 57.1 g/h and fluid 392 ml/h, and both fell significantly after km 618, in the second half of the ride. To "can I eat and drink to appetite in a two-day ride?": appetite fell away in the second half, so plan intake by the clock rather than by hunger or thirst, and plan specifically for the back half.
The authors' recommendation is to find individual ways around satiety and fatigue (what food still goes down late, how it is carried or handed up); they did not test any.
Riders already started on the dry side (urine specific gravity 1.022). Inference, not tested here: arriving well hydrated is a cheap fix, since hydration then held steady through the event.
Not from this paper; the base's own practice: the carbohydrate-per-hour target for multi-hour events and the gut training that makes it tolerable are in SYNTH-02 and REF-748; this paper shows how far below such targets self-chosen intake can fall late in an ultra.

Limitations

n=14 in one event; sex and age not in the abstract.
Energy expenditure was estimated from power output, not measured directly.
Observational: intake was self-chosen, and the abstract links it to no performance or health outcome.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

observational, n=14