Endurance running performance after 48 h of restricted fluid and/or energy intake.
OBJECTIVE
To determine the effect of a 48-h period of either fluid restriction (FR), energy restriction (ER), or fluid and energy restriction (F + ER) on 30-min treadmill time trial (TT) performance in temperate conditions.


METHODS
Thirteen males participated in four randomized 48-h trials (mean +/- SD: age, 21 +/- 3 yr; VO2max 50.9 +/- 4.3 mL x kg(-1) x min(-1)). Control (CON) participants received their estimated energy (2903 +/- 199 kcal x d(-1)) and water (3912 +/- 500 mL x d(-1)) requirements. For FR, participants received their energy requirements and 193 +/- 50 mL x d(-1) water to drink, and for ER, participants received their water requirements and 290 +/- 20 kcal x d(-1). F + ER was a combination of FR and ER. After 48 h, participants performed a 30-min treadmill TT in temperate conditions (19.7 +/- 0.6 degrees C). A separate investigation (N = 10) showed the TT to be highly reproducible (CV 1.6%).


RESULTS
Body mass loss (BML) was 0.6 +/- 0.4% (CON), 3.2 +/- 0.5% (FR), 3.4 +/- 0.3% (ER), and 3.6 +/- 0.3% (F + ER). Compared with CON (6295 +/- 513 m), less distance was completed on ER (10.3%) and F + ER (15.0%: P < 0.01). Although less distance was completed on FR (2.8%), this was not significantly different from CON.


CONCLUSIONS
These results show a detrimental effect of a 48-h period of ER but no significant effect of FR on 30-min treadmill TT performance in temperate conditions. Therefore, these results do not support the popular contention that modest hypohydration (2-3% BML) significantly impairs endurance performance in temperate conditions.
Oliver
Samuel J
SJ
School of Sport, Health and Exercise Sciences, University of Wales, Bangor, United Kingdom.
Laing
Stewart J
SJ
Wilson
Sally
S
Bilzon
James L J
JL
Walsh
Neil
N
D000328:Adult; D001786:Blood Glucose; D015992:Body Mass Index; D003681:Dehydration; D004032:Diet; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005440:Fluid Therapy; D006801:Humans; D008297:Male; D009752:Nutritional Status; D010807:Physical Endurance / Q000502:physiology*; D015203:Reproducibility of Results; D012420:Running / Q000502:physiology*; D013217:Starvation; D013997:Time Factors
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified