Abstract
The study aim was to examine the effects of mild hypertonic
and isotonic hypohydration on endurance performance. Fifteen
males completed three randomized 48-hr trials, where energy
intake was standardized throughout. On day 1 participants
completed a time to exhaustion (TTE1) after which they began
one of three trials. On the control trial (CON) participants consumed
adequate fluid to maintain euhydration. On the isotonic
hypohydration trial (IH), participants consumed the same fluid
as on CON, but at 0800 hr on day 3 they consumed 0.65 mg/kgof the diuretic furosemide. On the hypertonic hypohydration
trial (HH), drinking fluids were restricted to 2 ml/kg/day for
48 hr. After 48 hr, the participants completed a second time to
exhaustion (TTE2). Hydration and perceptual measures were
assessed before each TTE, and thermoregulatory, cardiovascular,
and perceptual measures were obtained during exercise.
Before TTE2, dehydration on HH and IH was 1.9% and 2.0%
of body mass, respectively. Plasma osmolality was higher on
HD compared with CON and IH (286 ± 4, 296 ± 6, 286 ± 4;
CON, HH, and IH, respectively; p < .01 vs. CON and IH) and
plasma volume loss was only observed on IH (1.7 ± 6, –0.3 ± 6,
–6.6 ± 4; CON, HH, and IH, respectively; p < .01 vs. CON and
HH). Compared with CON endurance performance in TTE2 was
reduced by 30% after HH (p < .05, d = 1.3) and 39% after IH
(p < .01, d = 1.9). During TTE2, mean perceived exertion was
greater in both HH and IH (p < .01 vs. CON). The reduction in
endurance performance after HH was probably caused by differences
in mood (vigor decreased 32% and fatigue increased 85%)
and perceptual comfort (thirst increased 100%). The addition
of cardiovascular strain is tentatively suggested as the cause
for the greater reduction in endurance performance after IH
(stroke volume decreased 7%). Isotonic hypohydration causes
a greater reduction in endurance performance than hypertonic
hypohydration evoked by prolonged fluid restriction.
| Original language | English |
|---|---|
| Pages | S7 |
| Publication status | Published - 1 Feb 2013 |
| Event | International Sport and Exercise Nutrition Conference - Northumbria University, Newcastle upon Tyne, United Kingdom Duration: 13 Dec 2012 → 15 Dec 2012 |
Conference
| Conference | International Sport and Exercise Nutrition Conference |
|---|---|
| Abbreviated title | ISENC 2012 |
| Country/Territory | United Kingdom |
| City | Newcastle upon Tyne |
| Period | 13/12/12 → 15/12/12 |