| The purpose was to determine the energy expenditure during ultradistance
trail running. A portable metabolic unit was carried by a male subject
for the first 64.5 km portion of the Western States 100 running race.
Calibrations were done with known gases and volumes at ambient temperature,
humidity and pressure (23-40.5 °C and 16-40% respectively). Altitude
averaged 1692.8 ± 210 m during data collection. The male subject (36
yrs, 75 kg, VO2max of 67.0 ml·kg-1·min-1)
had an average (mean ± SD) heart rate of 132 ± 9 bpm, oxygen consumption
of 34.0 ± 6.8 ml·kg-1·min-1, RER of 0.91 ± 0.04,
and VE of 86.0 ± 14.3 L·min-1 during the 21.7
km measuring period. This represented an average of 51% VO2max
and 75% heart rate maximum. Energy expenditure was 12.6 ± 2.5 kcals·min-1,
or 82.7 ± 16.6 kcals·km-1 (134 ± 27 kcals·mile-1)
at 68.3 ± 12.5% carbohydrate. Extrapolation of this data would result
in an energy expenditure of >13,000 kcals for the 160 km race,
and an exogenous carbohydrate requirement of >250 kcal·hr-1.
The energy cost of running for this subject on separate, noncompetitive
occasions ranged from 64.9 ± 8.5 to 74.4 ± 5.5 kcals·km-1
(105 ± 14 to 120 ± 9 kcals·mile-1). Ultradistance trail
running increases energy expenditure above that of running on nonundulating
terrain, which may result in underestimating energy requirements during
these events and subsequent undernourishment and suboptimal performance.
KEY
WORDS: Energy expenditure, caloric expenditure, running economy.
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