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aim of this case study was to examine energy expenditure (EE) in one
cyclist during an extreme endurance cycling race - the "XXAlps
2004" (2,272 km distance and 55,455 m altitude) which was completed
in 5 days and 7 hours - and whether the energy deficit derives primarily
from the degradation of subcutaneous adipose tissue or loss of muscle
mass. Energy intake (EI) was continuously recorded. EE was estimated
using two different methods: 1) Continuous heart rate recording using
a portable heart rate monitor (POLAR® S710) and 2) using
the individual relationship between heart rate and oxygen uptake (VO2)
determined under laboratory conditions. Body composition was assessed
by measuring body mass, skinfold thickness and extremity circumferences.
The cyclist lost 2.0 kg body mass, corresponding to 11,950 kcal (50
MJ). Fat mass was reduced by 790 g (7,110 kcal; 30 MJ) and fat free
mass by 1.21 kg (4,840 kcal; 20 MJ). Circumferences of the lower extremities
were reduced, in contrast skinfold thickness at the lower limbs increased.
Energy deficit (ED) was calculated as the difference between EI and
EE. Energy deficit using continuous heart rate monitoring was 29,554
kcal (124 MJ), and using the individual relationship between heart
rate and VO2 was 7,111 kcal (30 MJ). The results show that
the difference between ED due to decreased body mass and ED estimated
from continuous heart rate monitoring was 74 MJ (124 MJ - 50 MJ).
In contrast the difference between ED due to decreased body mass and
ED estimated from laboratory data was 20 MJ (30 - 50 MJ). This difference
between methodologies cannot properly be explained. Body mass and
skinfold thickness may be overestimated due to hypoproteinemic oedemas
during endurance exercise. Data from the present study suggests the
individual relationship between heart rate and VO2 may
provide a closer estimation of EE during extreme endurance exercise
compared with corresponding data derived from continuous heart rate
monitoring using the POLAR® S710.
KEY
WORDS: Extreme endurance, cycling, heart rate monitoring, energy
expenditure.
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