Description:
Despite the rapid growth of mass-participation road cycling, little is known about the dietary, metabolic and behavioral responses of ultra-endurance cyclists. This investigation describes physiological responses, perceptual ratings, energy balance,
and macronutrient intake of 42 men (mean ± SD; age, 38±6 y; height, 179.7±7.1 cm;
body mass, 85.85±14.79 kg) and 6 women (age, 41±4 y; height, 168.0±2.9 cm; body
mass, 67.32±7.21 kg) during a summer 164-km road cycling event. Measurements
were recorded one day before, and on Event Day (10.5 h) at the start (0 km), at two aid
stations (52 km and 97 km), and at the finish line (164 km). Ambient temperature was
>39.0°C during the final 2 h of exercise. Mean finish times for men (9.1±1.2 h) and
women (9.0±0.2 h) were similar, as were mean gastrointestinal temperature [TGI], four
hydration biomarkers, and five perceptual (e.g., thermal, thirst, pain) ratings. Male
cyclists consumed enough fluids on Event Day (5.91±2.38 L; 49% water) to maintain
body mass within 0.76 kg, start to finish, despite a sweat loss of 1.13±0.54 L·h-1 and
calculated energy expenditure of 3,115 Kcal·10.5h-1
. However, men voluntarily underconsumed
food energy (deficit of 2,594 Kcal, 10.9 MJ), and specific macronutrients
(carbohydrates, 106±48 g; protein, 8 ± 7 g; and sodium, 852 ± 531 mg) between 0530
and 1400 h. Also, a few men exhibited extreme final values (i.e., urine specific gravity of
1.035 to 1.038, n=5; body mass loss >4 kg, n=2; TGI, 39.4 and 40.2). We concluded that
these findings provide information regarding energy consumption, macronutrient intake,
hydration status and the physiological stresses that are unique to ultra-endurance
exercise in a hot environment.