Journal of Applied Physiology, Vol 56, Issue 1 18-23, Copyright © 1984 by American Physiological Society
Determinants of increased energy cost of submaximal exercise in obese subjects
B. Anton-Kuchly, P. Roger and P. Varene
The energy cost of submaximal cycling exercises is studied in 23 obese (OS)
and 13 lean control (LS) subjects at 1) a constant pedaling frequency (60
rpm) and at various work loads [external work loads (Wmec) up to 100 W] for
one group of OS and LS, and at 2) constant Wmec (brake free and 60 or 70 W)
and various frequencies (38-70 rpm) for a second group of OS and LS. The
total energy expenditure (WO2) is calculated from O2 consumption (VO2)
measured in both conditions and is compared with anthropometric data. The
results show that at rest or at the same Wmec, WO2 is always greater in OS
than in LS. At rest the quotients of WO2 over body surface area are not
significantly different. At work the difference in WO2 cannot be explained
by the muscular mechanical efficiency, which is not statistically different
in OS (26 +/- 7.8%) and LS (25 +/- 4.6%). The calculated increase in the
work of breathing of OS can account only for 5-15% of the energy
overexpenditure. The energy cost of leg movement is estimated in brake-free
cycling trials; it is significantly greater in OS than in LS (118 J
compared with 68 J/pedal stroke), but when divided by leg volume the
figures are not different (9.2 compared with 8.5 J X dm-3 X pedal
stroke-1). Leg moving may account for approximately 60-70% of the energy
cost of moderate exercise in cycling OS. The remaining difference in WO2
between OS and LS (20-30%) may be explained by an increase in muscular
postural activity related to the lack of physical training of OS.
