Energy intake deficit and physical performance at altitude.
BACKGROUND
Physical performance of sea-level (SL) residents acutely exposed to altitude (ALT) is diminished and may improve somewhat with ALT acclimatization.


OBJECTIVE
A large reduction in lean body mass (LBM), due to severe energy intake deficit during the first 21 d of ALT (4300 m) acclimatization, will adversely affect performance.


METHODS
At ALT, 10 men received a deficit (DEF) of 1500 kcal x d(-1) below body weight (BW) maintenance requirements and 7 men received adequate (ADQ) kcal x d(-1) to maintain BW. Performance was assessed by: 1) maximal oxygen uptake (VO2max); 2) time to complete 50 cycles of a lift and carry task (L+C); 3) number of one-arm elbow flexions (10% BW at 22 flexions x min(-1); and 4) adductor pollicis (AP) muscle strength and endurance time (repeated 5-s static contractions at 50% of maximal force followed by 5-s rest, to exhaustion). Performance and body composition (using BW and circumference measures) were determined at SL and at ALT on days 2 through 21.


RESULTS
At SL, there were no between-group differences (p > 0.05) for any of the performance measures. From SL to day 21 at ALT, BW and LBM declined by 6.6 +/- 3 kg and 4.6 kg, respectively, for the DEF group (both p < 0.01), but did not change (both p > 0.05) for the ADQ group. Performance changes from day 2 or 3 to day 20 or 21 at ALT were as follows (values are means +/- SD): VO2max (ml x min(-1)): DEF = +97 +/- 237, ADQ = +159 +/- 156; L + C (s): DEF = -62 +/- 35*, ADQ = -35 +/- 20* (*p < 0.05; improved from day 3); arm flex (reps): DEF = -2 +/- 7, ADQ = +2 +/- 8; AP endurance (min): DEF = +1.4 +/- 2, ADQ = + 1.9 +/- 2; AP strength (kg): DEF = -0.7 +/- 4, ADQ = -1.2 +/- 2. There were no differences in performance between groups.


CONCLUSIONS
A significant BW and LBM loss due to underfeeding during the first 21 d of ALT acclimatization does not impair physical performance at ALT.
Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA. charles.fulco@na.amedd.army.mil
C S
CS
Fulco
A L
AL
Friedlander
S R
SR
Muza
P B
PB
Rock
S
S
Robinson
E
E
Lammi
C J
CJ
Baker-Fulco
S F
SF
Lewis
A
A
Cymerman
D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D000855:Anorexia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D004038:Diet, Reducing / Q000009:adverse effects; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D008297:Male; D018908:Muscle Weakness / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D015431:Weight Loss / Q000502:physiology*