Giannis Arnaoutis

Educational intervention on water intake improves hydration status and enhances exercise performance in athletic youth

We aimed to evaluate whether an intervention program emphasizing in increased fluid intake can improve exercise performance in children exercising in the heat. Ninety‐two young athletes participated in the study (age: 13.8 ± 0.4 years, weight: 54.9 ± 1.5 kg). Thirty‐one (boys: 13, girls: 18) children served as the control group (CON) and 61 (boys: 30, girls: 31) as the intervention (INT). Volunteers had free access to fluids. Hydration was assessed on the basis of first morning urine. A series of field tests were used to evaluate exercise performance. All tests occurred outdoors in the morning (mean ambient temperature=28 °C). After baseline testing, INT attended a lecture on hydration, and urine color charts were mounted in all bathrooms. Additionally, water accessibility was facilitated in training, dining and resting areas. Hydration status was improved significantly in the INT [USG: pre=1.031 ± 0.09, post=1.023 ± 0.012, P<0.05; urine osmolality (mOsm/kg water): pre=941 ± 30, post=782 ± 34, P<0.05], while no statistically significant changes were found in the CON [USG: pre=1.033 ± 0.011, post=1.032 ± 0.013, P>0.05; urine osmolality (mOsm/kg water) 970 ± 38 vs 961 ± 38, P>0.05]. Performance in an endurance run was improved significantly only in INT (time for 600 m: pre=189 ± 5 s, post=167 ± 4 s, P<0.05). Improving hydration status by ad libitum consumption of water can enhance performance in young children exercising in the heat.

Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss

CONTEXT Sodium replacement during prolonged exercise in the heat may be critically important to maintaining fluid and electrolyte balance and muscle contractility. OBJECTIVE To examine the effectiveness of sodium-containing sports drinks in preventing hyponatremia and muscle cramping during prolonged exercise in the heat. DESIGN Randomized crossover study. PATIENTS OR OTHER PARTICIPANTS Thirteen active men. INTERVENTION(S) Participants completed 4 trials of an exercise protocol in the heat (30 degrees C) consisting of 3 hours of exercise (alternating 30 minutes of walking and cycling at a heart rate of 130 and 140 beats per minute, respectively); a set of standing calf raises (8 sets of 30 repetitions); and 45 minutes of steep, brisk walking (5.5 km x h(-1) on a 12% grade). During exercise, participants consumed fluids to match body mass loss. A different drink was consumed for each trial: carbohydrate-electrolyte drink containing 36.2 mmol/L sodium (HNa), carbohydrate-electrolyte drink containing 19.9 mmol/L sodium (LNa), mineral water (W), and colored and flavored distilled water (PL). MAIN OUTCOME MEASURE(S) Serum sodium, plasma osmolality, plasma volume changes, and muscle cramping frequency. RESULTS During both HNa and LNa trials, serum sodium remained relatively constant (serum sodium concentration at the end of the protocol was 137.3 mmol/L and 136.7 mmol/L, respectively). However, a clear decrease was observed in W (134.5 +/- 0.8 mmol/L) and PL (134.4 +/- 0.8 mmol/L) trials compared with HNa and LNa trials (P < .05). The same trends were observed for plasma osmolality (P < .05). Albeit not significant, plasma volume was preserved during the HNa and LNa trials, but a reduction of 2.5% was observed in the W and PL trials. None of the volunteers experienced cramping. CONCLUSIONS The data suggest that sodium intake during prolonged exercise in the heat plays a significant role in preventing sodium losses that may lead to hyponatremia when fluid intake matches sweat losses.

Water Ingestion Improves Performance Compared with Mouth Rinse in Dehydrated Subjects

UNLABELLED It has been suggested that mouth rinse and/or ingestion of fluids during exercise may have a beneficial effect on performance. However, the existing results are controversial. PURPOSE We hypothesized that pharyngeal receptor activation through ingestion of a small amount of water could enhance performance better than mouth rinse in dehydrated subjects. METHODS Ten healthy trained male cyclists (weight = 78.2 ± 2.2 kg, age = 25.9 ± 1.0 yr, body fat = 15.6% ± 1.6%, VO2max = 53.8 ± 4.8 mL · kg(-1) · min(-1)) completed three time-to-exhaustion cycling tests at 75% of their maximum power output after being dehydrated by 2% of their total body weight. Dehydration was induced by a 2-h moderate-intensity exercise (70% of maximum HR), which included 30-min intervals alternating between jogging and cycling in the heat (31 °C). All subjects repeated the protocol in random order on three separate occasions: a) mouth rinse with 25 mL of plain water before and every 5 min of the trial (MR), b) ingestion of 25 mL of plain water before and every 5 min (DR), and c) control (CON), where no fluids were provided. Blood and urine samples were collected at the beginning of the dehydration phase, before the performance test, and at the end of the experimental protocol. RESULTS A significantly greater time to exhaustion was recorded in the DR trial compared with MR and CON trials (21.9 ± 1.2 vs 18.7 ± 1.3 and 17.7 ± 1.1 min, respectively, P < 0.05). There were no differences in mean HR, maximum lactate concentration, or RPE between the three trials (P > 0.05). CONCLUSIONS The results demonstrated that ingestion of even a small amount of water increased exercise time in dehydrated subjects possibly through activation of pharyngeal receptors.

Mild Dehydration and Cycling Performance During 5-Kilometer Hill Climbing

CONTEXT Hydration has been shown to be an important factor in performance; however, the effects of mild dehydration during intense cycling are not clear. OBJECTIVE To determine the influence of mild dehydration on cycling performance during an outdoor climbing trial in the heat (ambient temperature = 29.0°C ± 2.2°C). DESIGN Crossover study. SETTING Outdoor. PATIENTS OR OTHER PARTICIPANTS Ten well-trained, male endurance cyclists (age = 28 ± 5 years, height = 182 ± 0.4 cm, mass = 73 ± 4 kg, maximal oxygen uptake = 56 ± 9 mL·min(-1)·kg(-1), body fat = 23% ± 2%, maximal power = 354 ± 48 W). INTERVENTION(S) Participants completed 1 hour of steady-state cycling with or without drinking to achieve the desired pre-exercise hydration level before 5-km hill-climbing cycling. Participants started the 5-km ride either euhydrated (EUH) or dehydrated by -1% of body mass (DEH). MAIN OUTCOME MEASURE(S) Performance time, core temperature, sweat rate, sweat sensitivity, and rating of perceived exertion (RPE). RESULTS Participants completed the 5-km ride 5.8% faster in the EUH (16.6 ± 2.3 minutes) than DEH (17.6 ± 2.9 minutes) trial (t1 = 10.221, P = .001). Postexercise body mass was -1.4% ± 0.3% for the EUH trial and -2.2% ± 0.2% for the DEH trial (t1 = 191.384, P < .001). Core temperature after the climb was greater during the DEH (39.2°C ± 0.3°C) than EUH (38.8°C ± 0.2°C) trial (t1 = 8.04, P = .005). Sweat rate was lower during the DEH (0.44 ± 0.16 mg·m(-2)·s(-1)) than EUH (0.51 ± 0.16 mg·m(-2)·s(-1)) trial (t8 = 2.703, P = .03). Sweat sensitivity was lower during the DEH (72.6 ± 32 g·°C(-1)·min(-1)) than EUH (102.6 ± 54.2 g·°C(-1)·min(-1)) trial (t8 = 3.072, P = .02). Lastly, RPE after the exercise performance test was higher for the DEH (19.0 ± 1.0) than EUH (17.0 ± 1.0) participants (t9 = -3.36, P = .008). CONCLUSIONS We found mild dehydration decreased cycling performance during a 5-km outdoor hill course, probably due to greater heat strain and greater perceived intensity.

Physical Activity and Adherence to Mediterranean Diet Increase Total Antioxidant Capacity: The ATTICA Study

We studied the association of physical activity and adherence to the Mediterranean diet, in total antioxidant capacity (TAC). A random sample of 1514 men and 1528 women was selected from Attica region. Physical activity was assessed with a translated version of the validated “International Physical Activity Questionnaire” (iPAQ), and dietary intake through a validated Food Frequency Questionnaire (FFQ). Adherence to the Mediterranean diet was assessed by the MedDietScore that incorporated the inherent characteristics of this diet. TAC was positively correlated with the degree of physical activity (P < .05). TAC was also positively correlated with MedDietScore (r = 0.24, P < .001). Stratified analysis by diet status revealed that the most beneficial results were observed to highly active people as compared to inactive, who also followed the Mediterranean diet (288 ± 70 μmol/L, 230 ± 50 μmol/L, resp.), after adjusting for various confounders. Increased physical activity and greater adherence to the Mediterranean diet were associated with increased total antioxidant capacity.

FLUID BALANCE DURING TRAINING IN ELITE YOUNG ATHLETES OF DIFFERENT SPORTS

Abstract Arnaoutis, G, Kavouras, SA, Angelopoulou, A, Skoulariki, C, Bismpikou, S, Mourtakos, S, and Sidossis, LS. Fluid balance during training in elite young athletes of different sports. J Strength Cond Res 29(12): 3447–3452, 2015—Although there are many studies demonstrating a high percentage of adult athletes who start exercise in suboptimal hydration state, limited data concerning hydration levels in athletic youth exist. The purpose of this study was to identify the hydration status of elite young athletes of different sports, during a typical day of training. Fifty-nine young elite male athletes from different sports (basketball, gymnastics, swimming, running, and canoeing) participated in the study (age: 15.2 ± 1.3 years; years of training: 7.7 ± 2.0). Hydration status was assessed in the morning, before and immediately after practice. Data collection took place at the same time of the day, with mean environmental temperature and humidity at the time of the measurements at 27.6 ± 0.9° C and 58 ± 8%, respectively. All athletes trained for approximately 90 minutes, and they were consuming fluids ad libitum throughout their practice. Over 89% of the athletes were hypohydrated (urine specific gravity [USG] ≥1.020 mg·dl−1) based on their first morning urine sample. Pretraining urine samples revealed that 76.3% of the athletes were hypohydrated, whereas a significant high percent remained hypohydrated even after training according to USG values ≥1.020 mg·dl−1 (74.5%) and urine color scale: 5–6 (76.3%). Mean body weight loss during training was −1.1 ± 0.07%. We concluded that the prevalence of hypohydration among elite young athletes is very high, as indicated by the USG and urine color values. The majority of the athletes was hypohydrated throughout the day and dehydrated even more during practice despite fluid availability.

Fluid consumption pattern and hydration among 8–14 years-old children

Background/objectivesChildren consume various fluids to meet dietary water intake needs. However, the contribution of different fluid types on hydration is unclear. The purpose of this study was to develop fluid intake patterns and examine their association with hydration, as indicated by 24-h urine osmolality.Subjects/methodsTwo hundred ten (105 girls) healthy children (height: 1.49 ± 0.13 m, weight: 43.4 ± 12.6 kg, body fat: 25.2 ± 7.8%) recorded their fluid intake for two consecutive days, and collected their urine for 24-h during the 2nd day, while conducting their normal daily activities. Urine samples were analyzed for specific gravity and osmolality. Factor analysis with principal components method was applied to extract dietary patterns from six fluid groups. Linear regression analysis evaluated the associations between the extracted dietary patterns and hydration based on 24-h urine osmolality.ResultsThe analysis revealed the following six components: 1, characterized by consumption of milk and fresh juice, but not packaged juice; 2, by regular soda and other drinks, but not water; 3, by fresh juice and other drinks; 4, by packaged juice, but not regular soda; 5, by water and milk; and 6, by fresh juice. Component 5 was negatively correlated with urine osmolality (P = 0.001) indicating better hydration, whereas component 2 was positively correlated with urine osmolality (P = 0.001).ConclusionsA drinking pattern based on water and milk was associated with better hydration, as indicated by lower urine osmolality, whereas drinking regular soda and other drinks but not water was associated with inferior hydration.

Association of Anthropometric and Lifestyle Parameters with Fitness Levels in Greek Schoolchildren: Results from the EYZHN Program

Objective The aim of the study was to evaluate physical fitness (PF) and identify its anthropometric and lifestyle determinants in a sample of Greek schoolchildren. Methods The study sample consisted of 335,810 schoolchildren (♂: 51.3%, 6–18 years old). Students’ anthropometric parameters and PF levels—assessed via the Eurofit test battery—were measured by trained physical education teachers and evaluated according to the available norms, while their lifestyle habits were assessed through a questionnaire. Results In all applied PF tests, students’ performance was negatively associated with the presence of obesity and central obesity, defined through international criteria for body mass index and waist to height ratio, respectively. According to multiple logistic regression analysis, the presence of overweight/obesity [odds ratio (OR): 4.43, 95% confidence interval (CI): 3.98–4.93], low adherence to the MD (KIDMED ≤ 3) (OR: 1.27, 95% CI: 1.09–1.48), and increased time spent in sedentary activities (>2 h per day) (OR: 1.16, 95% CI: 1.03–1.29) were positively associated with poor PF, after adjusting for age and sex. In contrast, for every 1 day increase in the weekly frequency of engagement in athletic activity, the probability of poor PF decreased by 26% (OR: 0.74, 95% CI: 0.72–0.77). In a similar model, the presence of central obesity emerged as an even stronger possible predictor of poor PF (OR: 5.20, 95% CI: 4.66–5.78), compared to the presence of general obesity. Conclusion Higher general or abdominal adiposity, as well as the adoption of a low-quality diet and a sedentary lifestyle, is strongly associated with low PF levels during childhood.

Water intake and urinary hydration biomarkers in children

Background/Objectives:The aims of the study were as follows: (1) examine fluid intake and urinary hydration markers of children in Greece, (2) determine the calculated relative risk of hypohydration in children who did not meet the recommendations for daily water intake provided by the Institute of Medicine and the European Food Safety Authority compared with those who did and (3) analyze the efficacy of the recommendations as a method to achieve euhydration in children.Subjects/Methods:One hundred and fifty Greek boys and girls (age 9–13) recorded their fluid intake for 2 consecutive days. A 24-h urine collection was obtained during the second day. Fluid intake records were analyzed for total water intake from fluids (TWI-F), and urine samples were analyzed for osmolality, color, specific gravity and volume. Urine osmolality ⩾800 mmol/kg H2O was defined as hypohydration.Results:Water intake from fluids was 1729 (1555–1905) and 1550 (1406–1686) ml/d for boys and girls, respectively. Prevalence of hypohydration was 33% (44% of boys, 23% of girls). Children who failed to meet TWI-F recommendations demonstrated a risk of hypohydration that was 1.99–2.12 times higher than those who met recommendations (P⩽0.01). Boys between 9 and 13 years displayed urine osmolality of 777 (725–830) mmol/kg, and urine specific gravity of 1.021 (1.019–1.022), which was higher than those in girls between 9–13 years (P⩽0.015), and >27% were classified as hypohydrated despite meeting water intake recommendations.Conclusions:Failure to meet TWI-F guidelines increased calculated relative risk of hypohydration in children. Boys between 9 and 13 years are at greater hazard regardless of meeting guidelines and may require greater water intake to avoid elevated urine concentration and ensure adequate hydration.

Coffee with High but Not Low Caffeine Content Augments Fluid and Electrolyte Excretion at Rest

Background Low levels of caffeine ingestion do not induce dehydration at rest, while it is not clear if larger doses do have an acute diuretic effect. The aim of the present investigation was to examine the acute effect of low and high levels of caffeine, via coffee, on fluid balance in habitual coffee drinkers (at least one per day) at rest. Methods Ten healthy adults (eight males and two females; age: 27 ± 5 years, weight: 89.5 ± 14.8 kg, height: 1.75 ± 0.08 m, and body mass index: 29.1 ± 4.4 kg m−2) ingested 200 mL of water (W), coffee with low caffeine (3 mg kg−1, LCAF), or coffee with high caffeine (6 mg kg−1, HCAF) on three respective separate occasions. All sessions were performed at 09:00 in the morning in a counterbalanced, crossover manner, at least 5 days apart. Subjects remained in the laboratory while urine samples were collected every 60 min for 3 h post ingestion. Results Absolute caffeine consumption was 269 ± 45 and 537 ± 89 mg for the LCAF and HCAF, respectively. Coffee ingestion at the HCAF trial induced greater diuresis during the 3-h period (613 ± 101 mL, P < 0.05), when compared to W (356 ± 53 mL) and LCAF (316 ± 38 mL). In addition, cumulative urinary osmotic excretion was significantly greater in the HCAF (425 ± 92 mmol, P < 0.05), as compared to the W (249 ± 36 mmol) and LCAF (177 ± 16 mmol) trials. Conclusion The data indicate that caffeine intake of 6 mg kg−1 in the form of coffee can induce an acute diuretic effect, while 3 mg kg−1 do not disturb fluid balance in healthy casual coffee drinking adults at rest.