Effect Of Exercise-induced Dehydration Research Articles

Discussion of "Effect of exercise-induced dehydration on circulatory markers of oxidative damage and antioxidant capacity".

We read with great interest a recent article by Georgescu et al. (2017) entitled “Effect of exercise-induced dehydration on circulatory markers of oxidative damage and antioxidant capacity”. The authors aimed to investigate effects of hydration and rehydration by using sensitive indirect measures of oxidative stress and the antioxidant capacity response. In this study, they evaluated concentrations of plasma osmolality, Trolax equivalent antioxidant capacity (TEAC), and ferric reducing ability of plasma (FRAP) in a sample of athletes during pre-exercise, immediately postexercise, and 1 h after full rehydration. As stated in statistical analysis and also abstract of the article, the authors used 1-way ANOVA to compare differences in means of numerical variables (i.e., concentrations of plasma osmolality, TEAC, and FRAP) of different time-points of measurement. Since they investigated the same sample of participants in each group during different time-points (i.e., pre-exercise, immediately postexercise, and 1 h after full rehydration), their measurements are completely dependent (Farrokhi and Peykanpour 2017a; Farrokhi and Shirian 2017; Farrokhi et al. 2017). ANOVA and Kruskal–Wallis test are used for comparison of the means of more than 2 independent groups (Gaddis 1998; Farrokhi 2017b; Farrokhi and Arjaki 2017; Farrokhi and Peykanpour 2017b). Therefore, after assessment of the normal distribution of studied quantitative variables, including concentrations of plasma osmolality, TEAC, and FRAP, the authors must use repeated-measures ANOVA or Friedman test for comparison of the means of each variable at pre-exercise, immediately postexercise, and 1 h after full rehydration (Farrokhi 2017a; Farrokhi and Amani-Beni 2017). Furthermore, they must use Wilcoxon test and paired t test for comparison of concentrations of plasma osmolality, TEAC, and FRAP between 2 time-points of measurement.

Effect of exercise-induced dehydration on circulatory markers of oxidative damage and antioxidant capacity.

Dehydration is a common event associated with exercise. However, few studies have examined the effects of dehydration on plasma redox status in humans. Eighty-two athletes were recruited and baseline anthropometrics and blood samples were obtained. Athletes then engaged in a dehydration protocol, training until 3% of preweight body mass was lost. Athletes returned to the lab and had postdehydration blood collected. Athletes then consumed an isotonic drink until pre-exercise body weight was reestablished. Blood was then recollected (1 h post full rehydration (PFR)). Samples were centrifuged and the plasma snap frozen in liquid nitrogen and stored at -80 °C. Lipid and protein oxidative stress was determined by measuring F2-isoprostanes and protein carbonyls (PC), respectively. Antioxidant capacity was determined by the ferric reducing ability of plasma (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays. Plasma osmolality was determined using an osmometer. Statistical analysis utilized a 1-way ANOVA with posthoc testing. Values are reported as mean ± SD. Plasma osmolality was significantly elevated immediately postdehydration (p ≤ 0.001) but decreased to baseline at PFR. Plasma TEAC increased immediately postdehydration and at PFR (p ≤ 0.001). FRAP increased immediately postdehydration (p ≤ 0.001) and decreased to below baseline at PFR (p ≤ 0.05). Conversely, F2-isoprostanes declined significantly from baseline to immediately postdehydration and then significantly rose at PFR (p ≤ 0.001), whereas PC declined at PFR (p ≤ 0.01). This study indicates that dehydration and exercise cause a significant increase in plasma osmolality and antioxidant potential immediately postexercise. We propose dehydration significantly elevates antioxidant concentration which suppresses F2-isoprostanes and PC.

The Effect of Exercise-Induced Dehydration on Neuropsychological Performance and Postural Stability.

The Effect of Exercise-Induced Dehydration on Neuropsychological Performance and Postural Stability.

Effect Of Exercise-induced Dehydration And Subsequent Overnight Fluid Restriction On Immunity At The Ocular Surface

Effect Of Exercise-induced Dehydration And Subsequent Overnight Fluid Restriction On Immunity At The Ocular Surface

Meta-Analysis of the Effect of Exercise-Induced Dehydration on Endurance Performance

Meta-Analysis of the Effect of Exercise-Induced Dehydration on Endurance Performance

Effects of Dehydration and Fluid Ingestion on Cognition

The effects of exercise-induced dehydration and fluid ingestion on men's cognitive performance were assessed. Eleven young men attended separate sessions in which each individual cycled in a controlled environment at 60 % of V.O (2max) for periods of 15, 60, or 120 min without fluid replacement or 120 min with fluid replacement. Immediately following the assigned submaximal exercise period, the participant completed a graded exercise test to voluntary exhaustion. An executive processing test and a short-term memory test were performed prior to and immediately following exercise. Choice-response times during the executive processing test decreased following exercise, regardless of the level of dehydration. Choice-response errors increased following exercise, but only on trials requiring set shifting. Short-term memory performance improved following exercise, regardless of the level of dehydration. Changes in cognitive performance following exercise are hypothesized to be related to metabolic arousal following strenuous physical activity.

Effects Of Exercise-induced Dehydration On Thermoregulation And Cycling Hill-climbing Performance

Effects Of Exercise-induced Dehydration On Thermoregulation And Cycling Hill-climbing Performance

Effect of Exercise-Induced Dehydration on Lactate Parameters During Incremental Exercise

Cyclists often use heart rate limits or power output zones, obtained from lactate parameters during incremental exercise testing, to control training intensity. However, the relationship between heart rate or power output, and blood lactate can be changed by several factors including dehydration. Therefore, in the current study we investigated the impact of exercise-induced dehydration on lactate parameters during graded exercise. Nine triathletes completed two test sessions in random order, with a 1-week interval. Each session consisted of 2 graded cycling tests to exhaustion (pretest, posttest), interspersed by a 2-h endurance exercise bout. In one session the cyclists received adequate fluid replacement (EH, 1350 ml . h (-1)) whilst in the other session dehydration was not prevented (DH, 225 ml . h (-1)). Subjects received equal amounts of carbohydrates (150 g) during either condition. The 4-mmol lactate threshold (OBLA) and the d (max) lactate threshold (TH-Dm) were calculated from the power : lactate curves. Weight loss was 0.5 +/- 0.3 kg in EH versus 2.5 +/- 0.2 kg in DH (p < 0.05). Heart rate (HR) at TH-Dm remained unchanged in all test occasions. Conversely, HR at OBLA increased by approximately 10 beats . min (-1) from the pretest to the posttest (p < 0.05), in both EH and DH. Compared to the pretest, in the posttest power output at TH-Dm was reduced (minus approximately 12 %, p < 0.05) in DH, but not in EH. Gross mechanical efficiency at TH-Dm was 20.7 +/- 1 % in the pretest in EH and was not different from the pretest value in DH (21.4 +/- 0.7 %, n.s.). Gross efficiency decreased in the posttest in DH (18.4 +/- 0.6 %, p < 0.05), but not in EH (20.2 +/- 0.8 %, n.s.). It is concluded that heart rate rather than power output should be used to monitor training load in cyclists exercising in environmental conditions predisposing to dehydration. Furthermore, in the latter condition, adequate rehydration is essential to preserve optimal mechanical efficiency.