Is gross efficiency lower at acute simulated altitude than at sea level?
OBJECTIVE
The purpose of this study was to test the assumption that gross efficiency (GE) at sea level (SL) is representative of GE at altitude (AL). It was hypothesized that an increased cost of ventilation and heart rate, combined with a higher respiratory-exchange ratio, at AL might result in a decrease in GE.


METHODS
Trained men (N = 16) completed 2 maximal incremental tests and 2 GE tests, 1 at SL and 1 at an acute simulated AL of 1500 m (hypobaric chamber). GE was determined during submaximal exercise at 45%, 55%, and 65% of the altitude-specific power output attained at VO2max.


RESULTS
GE determined at the highest submaximal exercise intensity with a mean RER ≤1.0, matched for both conditions, was significantly lower at AL (AL 20.7% ± 1.1% and SL 21.4% ± 0.8%, t15 = 2.9, P < .05).


CONCLUSIONS
These results demonstrate that moderate AL resulted in a significantly lower GE during cycling exercise than SL. However, it might be that the lower GE at AL is caused by the lower absolute exercise intensity.
MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, The Netherlands.
Dionne A
DA
Noordhof
Thijs
T
Schoots
Derk H
DH
Hoekert
Jos J
JJ
de Koning
D000208:Acute Disease; D000328:Adult; D000531:Altitude; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D055815:Young Adult