Biomedical subjects

S A Kavouras

Publications and source records attributed to S A Kavouras.

10 recordsLinked to original sources

PubMed2006

Effect of hydration state on testosterone and cortisol responses to training-intensity exercise in collegiate runners.

Exercise intensity powerfully influences testosterone, cortisol, and testosterone : cortisol ratio (T:C) responses to endurance exercise. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to endurance exercise and training. This study examined the effect of running intensity on testosterone, cortisol, and T : C when exercise was initiated in a hypohydrated state. Nine male collegiate runners (age = 20 +/- 0 y, height = 178 +/- 2 cm, mass = 67.0 +/- 1.8 kg, body fat % = 9.8 +/- 0.7 %, V.O2max = 65.7 +/- 1.1 ml.kg (-1).min (-1)) completed four 10-min treadmill runs differing in pre-exercise hydration status (euhydrated, or hypohydrated by 5 % of body mass) and exercise intensity (70 % or 85 % V.O2max). Body mass, urine osmolality, and urine-specific gravity documented fluid balance; blood samples drawn pre-, immediately post-, and 20 min post-exercise were analyzed for testosterone, cortisol, and T : C. Except for heart rate measured during the 70 % V.O2max trials, heart rate, V.O2, and plasma lactate were similar between euhydrated and hypohydrated conditions for a given intensity, suggesting hypohydration did not measurably increase the physiological stress of the exercise bouts. Furthermore, hydration state had no measurable effect on testosterone concentrations before, during, or after exercise at either intensity. Regardless of exercise intensity, cortisol concentrations were greater during hypohydration than euhydration pre-exercise and 20 min post-exercise. Additionally, T : C was significantly lower 20 min post-exercise at 70 % V.O2max when subjects were initially hypohydrated (T : C = 0.055) versus euhydrated (T : C = 0.072). These findings suggest that depending on exercise intensity, T : C may be altered by hydration state, therefore influencing the balance between anabolism and catabolism in response to running exercise performed at typical training intensities.

Adult↗

PubMed2004

Dietary intake and nutritional practices of elite Greek aquatic athletes.

To investigate whether aquatic athletes follow optimal dietary intake, 58 athletes, all members of the Greek national swimming and water polo teams, were tested. Dietary intake was assessed at the nutrient, food, and food group level using the 24-h recall method and a food frequency questionnaire. Mean energy intake for males and females was 14.3 and 8.5 MJ, respectively. Mean carbohydrate consumption for male and female athletes was 4.5 g/kg and 3.8 g/kg of body weight, respectively. Fat intake was 153 g for males and 79 g for females. A significant number of the athletes (71% of the males, 93% of the females) did not meet the Dietary Reference Intakes for at least one of the antioxidant vitamins. The data suggest that athletes of both genders consumed too much fat and too little carbohydrate. Insufficient fruit and vegetable intake was related to low intake of antioxidants.

Adolescent↗

PubMed2001

Perceptual responses in the heat after brief intravenous versus oral rehydration.

PURPOSE: The purpose of the study was to compare the effects of a brief period (20 min) of intravenous (IV) fluid rehydration and oral (ORAL) rehydration on ratings of perceived exertion (RPE), thirst, and thermal sensation (TS) during exercise in the heat. METHODS: After dehydration (-4% of body weight), eight nonacclimated highly trained cyclists (age = 24 +/- 1 yr; VO2 = 61.4 +/- 0.8 mL.kg.min-1) performed three experimental trials. Rehydration (randomized, cross-over design) included: 1) ORAL (0.45% NaCl) equal to 50% of prior dehydration; 2) IV (0.45% NaCl) equal to 50% of prior dehydration; and 3) a control (CON), no fluid trial. Subjects then cycled at 74% VO2peak until volitional exhaustion in a hot environment (37 degrees C). RESULTS: Central (C-), local (L-), and overall-RPE (O-RPE) were significantly higher in CON compared to ORAL and IV at minutes 5 and 15 of exercise. C-RPE responses at minute 5 of exercise were lower (P < 0.05) during ORAL compared with IV, and C-RPE and O-RPE responses at minute 15 were lower (P < 0.05) during ORAL compared with IV. TS responses during CON were higher (P < 0.05) than ORAL and IV at minute 5, and TS was higher (P < 0.05) during IV versus ORAL at minute 15. TS were significantly correlated with all RPE responses at minute 15 in all trials. Thirst ratings were lower (P < 0.05) during ORAL compared with CON and IV at minutes 0, 5, and 15. CONCLUSION: It was concluded that ORAL resulted in lower RPE, thirst, and TS compared with CON and IV during exercise in the heat.

Administration, Oral↗

PubMed2001

Increased renal tubular sodium reabsorption during exercise-induced hypervolemia in humans.

We tested the hypothesis that renal tubular Na(+) reabsorption increased during the first 24 h of exercise-induced plasma volume expansion. Renal function was assessed 1 day after no-exercise control (C) or intermittent cycle ergometer exercise (Ex, 85% of peak O(2) uptake) for 2 h before and 3 h after saline loading (12.5 ml/kg over 30 min) in seven subjects. Ex reduced renal blood flow (p-aminohippurate clearance) compared with C (0.83 +/- 0.12 vs. 1.49 +/- 0.24 l/min, P < 0.05) but did not influence glomerular filtration rates (97 +/- 10 ml/min, inulin clearance). Fractional tubular reabsorption of Na(+) in the proximal tubules was higher in Ex than in C (P < 0.05). Saline loading decreased fractional tubular reabsorption of Na(+) from 99.1 +/- 0.1 to 98.7 +/- 0.1% (P < 0.05) in C but not in Ex (99.3 +/- 0.1 to 99.4 +/- 0.1%). Saline loading reduced plasma renin activity and plasma arginine vasopressin levels in C and Ex, although the magnitude of decrease was greater in C (P < 0.05). These results indicate that, during the acute phase of exercise-induced plasma volume expansion, increased tubular Na(+) reabsorption is directed primarily to the proximal tubules and is associated with a decrease in renal blood flow. In addition, saline infusion caused a smaller reduction in fluid-regulating hormones in Ex. The attenuated volume-regulatory response acts to preserve distal tubular Na(+) reabsorption during saline infusion 24 h after exercise.

Adult↗

PubMed2000

Intravenous versus oral rehydration during a brief period: responses to subsequent exercise in the heat.

PURPOSE: The purpose of this study was to assess whether a brief period (20 min) of intravenous (i.v.) fluid rehydration versus oral rehydration differentially affects cardiovascular, thermoregulatory, and performance factors during exhaustive exercise in the heat. METHODS: Following dehydration (-4% of body weight), eight nonacclimated highly trained cyclists (age = 23.5 +/- 1.2 yr; VO2peak = 61.4 +/- 0.8 mL x kg x min(-1); body fat = 13.5 +/- 0.6%) rehydrated and then cycled at 70% VO2peak to exhaustion in 37 degrees C. Rehydration (randomized, cross-over design) included: 1) CONTROL (no fluid), 2) DRINK (oral rehydration, 0.45% NaCl) equal to 50% of prior dehydration, and 3) IV (intravenous rehydration, 0.45% NaCl), equal to 50% of prior dehydration. Thus, in the DRINK and IV treatments subjects began exercise (EX) at -2% of body weight. RESULTS: Exercise time to exhaustion was not different (P = 0.07) between DRINK (34.9 +/- 4 min) and IV (29.5 +/- 3.5 min), but both were significantly (P < 0.05) longer than CONTROL (18.9 +/- 2.7 min). Plasma volume was better (P < 0.05) restored during IV than CONTROL and DRINK at pre-exercise and 5 min EX, but different (P < 0.05) from only CONTROL at 15 min EX. Plasma lactate during DRINK was lower (P < 0.05) than IV at 15 min EX and postexercise. Heart rate during CONTROL was greater (P < 0.05) than DRINK and IV from 0-8 min EX, and greater (P < 0.05) than DRINK from 10-14 min EX. Rectal temperature during DRINK was less (P < 0.05) than IV from 0-24 min EX. Mean weighted skin temperature during DRINK was less (P < 0.05) than IV from 4-12 min EX. CONCLUSIONS: Thus, despite no statistically significant performance differences between DRINK and IV, it appears that certain physiological parameters were better maintained in the DRINK trial, and the trend toward performance differences may be important to elite athletes.

Administration, Oral↗

PubMed2000

Intravenous versus oral rehydration during a brief period: stress hormone responses to subsequent exhaustive exercise in the heat.

The purpose of this study was to determine if intravenous fluid rehydration, versus oral rehydration, during a brief period (20 min) differentially affects plasma ACTH, cortisol, and norepinephrine concentrations during subsequent exhaustive exercise in the heat. Following dehydration (DHY) to Eth 4% of body weight, 8 nonacclimated highly trained males (age = 23.5 +/- 1.2 years, VáO2peak = 61.4 +/- 0.8 ml á kg á min-1, % body fat = 13.5 +/- 0. 6%) cycled to exhaustion at 74% VáO2peak in 36.8 C on three different occasions. These included: (a) no fluid (NF), where no fluid was provided during the rehydration period; (b) DRINK, where oral rehydration (0.45% NaCl) was provided equal to 50% of the prior DHY; and (c) IV, where intravenous infusion (0.45% NaCl) was provided equal to 50% of the prior DHY. Exercise time to exhaustion was not different (p =.07) between the DRINK (34.86 +/- 4.01) and IV (29.48 +/- 3.50) trials, but both were significantly (p <.05) longer than the NF (18.95 +/- 2.73) trial. No differences (p >.05) were found for any of the hormone measures among trials. The endocrine responses at exhaustion were similar regardless of hydration state and mode of rehydration, but rehydration prolonged the exercise time to exhaustion.

Administration, Oral↗

PubMed1998

Urinary indices during dehydration, exercise, and rehydration.

This investigation evaluated the validity and sensitivity of urine color (Ucol), specific gravity (Usg), and osmolality (Uosm) as indices of hydration status, by comparing them to changes in body water. Nine highly trained males underwent a 42-hr protocol involving dehydration to 3.7% of body mass (Day 1, -2.64 kg), cycling to exhaustion (Day 2, -5.2% of body mass, -3.68 kg), and oral rehydration for 21 hr. The ranges of mean (across time) blood and urine values were Ucol, 1-7; Usg, 1.004-1.029; Uosm, 117-1,081 mOsm x kg-1; and plasma osmolality (Posm), 280-298 mOsm x kg-1. Urine color tracked changes in body water as effectively as (or better than) Uosm, Usg, urine volume, Posm, plasma sodium, and plasma total protein. We concluded that (a) Ucol, Uosm, and Usg are valid indices of hydration status, and (b) marked dehydration, exercise, and rehydration had little effect on the validity and sensitivity of these indices.

Adult↗

PubMed1997

Bioimpedance spectroscopy technique: intra-, extracellular, and total body water.

The purpose of this study was to test the validity of a multiple frequency bioimpedance spectroscopy (BIS) technique that estimates extracellular fluid volume (ECV), intracellular fluid volume (ICV), and total body water (TBW). Thirteen healthy males (mean +/- SD: age, 23 +/- 3 yr; body mass, 80.6 +/- 14.7 kg) had their TBW and ECV measured by ingesting dilution tracers (7.27 g deuterium oxide, 1.70 g sodium bromide; blood samples at 0 and 4 h). ICV was calculated as TBW minus ECV. Impedance was measured (50-500 kHz) at rest, on a nonconducting surface, with a BIS analyzer. Electrode placement, posture, exercise, food/fluid intake, and ambient temperature were controlled. Dilution measures (TBW, 51.00 +/- 9.30; ECV, 19.88 +/- 3.14; ICV, 31.12 +/- 6.80 L) and BIS volumes (TBW, 50.03 +/- 7.67; ECV, 20.95 +/- 3.33; ICV, 29.04 +/- 4.51 L) were significantly different for ECV (P < 0.01) and ICV (P < 0.05); some individual differences were large. The correlation coefficients of dilution versus BIS volumes (r = 0.93 to 0.96) were significant at P < 0.0001; SEEs were: TBW, 2.23 L; ECV, 1.26 L; and ICV, 1.71 L. We concluded that BIS is valid for between-subject comparisons of body fluid compartments, is appropriate in clinical settings where change in ECV/ICV ratio is important, and should be used by comparing the required level of accuracy to the inherent technique error/variance.

Adult↗

PubMed1997

Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake.

This investigation examined the distinct and interactive effects of initial hydration state, exercise-induced dehydration, and water rehydration in a hot environment. On four occasions, 10 men performed a 90-min heat stress test (treadmill walking at 5.6 km/h, 5% grade, 33 degrees C, 56% relative humidity). These heat stress tests differed in pretest hydration [2 euhydrated (EU) and 2 hypohydrated (HY) trials] and water intake during exercise [2 water ad libitum (W) and 2 no water (NW) trials]. HY+NW indicated greater physiological strain than all other trials (P < 0.05-0.001) in heart rate, plasma osmolality (Posm), sweat sensitivity (g/degrees C.min), and rectal temperature. Unexpectedly, final HY+W and EU+W responses for rectal temperature, heart rate, and Posm were similar, despite the initial 3.9 +/- 0.2% hypohydration in HY+W. We concluded that differences in pretest Posm (295 +/- 7 and 287 +/- 5 mosmol/kg for HY+W and EU+W, respectively) resulted in greater water consumption (1.65 and 0.31 liter for HY+W and EU+W, respectively), no voluntary dehydration (0.9% body mass increase), and attenuated thermal and circulatory strain during HY+W.

Adult↗

PubMed1997

Physiological and psychological effects associated with high carbon dioxide levels in healthy men.

BACKGROUND: Perception of CO2 in ambient air may be of fundamental importance to the health, safety, and job performance of persons occupationally exposed to increased levels of CO2. Few studies have examined the perceptual responses to inhaled CO2 at levels between 6-10%. HYPOTHESIS: We hypothesized that healthy, highly-active men would be able to determine the difference between 6% and 8% CO2 concentrations. METHODS: Thirty-two male students (21 +/- 1 yr) served as subjects. Experimental trials (counterbalanced design) included breathing air (control, 21% O2, 79% N2), 6% CO2 (21% O2, 73% N2), and 8% CO2 (21% O2, 71% N2) conditions. The Body Sensations Questionnaire (BSQ) was completed twice during each trial. RESULTS: End tidal CO2 (FETCO2) and BSQ values increased (p < 0.05) as a function of the percentage of inhaled CO2. Respiratory rates during the 8% trial were greater (p < 0.05) than control and 6% CO2 trial measures. BSQ scores were significantly correlated with FETCO2 and respiratory rate measures during the 6% and 8% CO2 conditions. CONCLUSIONS: We conclude that these subjects recognized their exposure to both the 6% and 8% CO2 concentrations, and their responses were more profound during the 8% CO2 condition.

Adult↗