Effect of fluid replacement with green tea on body fluid balance and renal responses under mild thermal hypohydration: a randomized crossover study.

PURPOSE: Maintaining an appropriate hydration level by ingesting fluid in a hot environment is a measure to prevent heat-related illness. Caffeine-containing beverages, including green tea (GT), have been avoided as inappropriate rehydration beverages to prevent heat-related illness because caffeine has been assumed to exert diuretic/natriuretic action. However, the influence of caffeine intake on urine output in dehydrated individuals is not well documented. The aim of the present study was to examine the effect of fluid replacement with GT on body fluid balance and renal water and electrolyte handling in mildly dehydrated individuals. METHODS: Subjects were dehydrated by performing three bouts of stepping exercise for 20 min separated by 10 min of rest. They were asked to ingest an amount of water (H2O), GT, or caffeinated H2O (20 mg/100 ml; Caf-H2O) that was equal to the volume of fluid loss during the dehydration protocol; fluid balance was measured for 2 h after fluid ingestion. RESULTS: The dehydration protocol induced hypohydration by ~ 10 g/kg body weight (~ 1% of body weight). Fluid balance 2 h after fluid ingestion was significantly less negative in all trials, and the fluid retention ratio was 52.2 ± 4.2% with H2O, 51.0 ± 5.0% with GT, and 47.9 ± 6.2% with Caf-H2O; those values did not differ among the trials. After rehydration, urine output, urine osmolality, and urinary excretions of osmotically active substances, sodium, potassium and chloride were not different among the trials. CONCLUSION: The data indicate that ingestion of GT or an equivalent caffeine amount does not worsen the hydration level 2 h after ingestion and can be effective in reducing the negative fluid balance for acute recovery from mild hypohydration. TRIAL REGISTRATION: ISRCTN53057185; retrospectively registered.

Effects of 6-(Methylsulfinyl)hexyl Isothiocyanate Ingestion on Muscle Damage after Eccentric Exercise in Healthy Males: A Pilot Placebo-Controlled Double-Blind Crossover Study.

An animal study demonstrated that 6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC), a major bioactive compound in Japanese pungent spice wasabi, has an action of inhibiting the activation of calpain-1 (a protease). Increases in calpain activity can cause continual strength loss after eccentric exercise. It remains to be determined in humans whether 6-MSITC intake would modulate calpain and/or muscle damage responses after eccentric exercise. We performed a randomized, double-blind, crossover design study wherein eight healthy young males were randomly assigned to ingest 9 mg/day of 6-MSITC or placebo from 1 day before exercise to 4 days after exercise (30 maximal isokinetic eccentric contractions of the elbow flexors using an isokinetic dynamometer). Calpain-1 concentration, inflammatory and muscle damage markers (creatine kinase activity, urinary titin concentration, muscle strength, range of motion, muscle soreness and transverse relaxation time) were assessed. Plasma calpain-1 concentration after eccentric exercise was similar between the placebo- and 6-MSITC-treated conditions. All muscle damage and inflammatory markers were not affected by 6-MSITC relative to those in the placebo-treated condition. Our results suggest that 6-MSITC has no effect on plasma calpain-1 concentration and muscle damage and inflammatory markers measured after eccentric exercise.

The link between the range of rapid weight loss and physical conditions of elite wrestlers during competition under the morning weigh-in rule.

BACKGROUND: Amateur wrestlers have often undergone rapid weight loss (RWL) to win their matches. On January 1, 2018, the rule of weigh-in was changed and weight category increased. The study aimed to determine the prevalence of wrestlers undergoing RWL under the new rule of morning weigh-in before the tournament and examine the relationship between the range of RWL and physical conditions. METHODS: Male (N.=204) and female (N.=50) wrestlers participating in the National Wrestling Championship completed a questionnaire about weight reduction methods and their physical condition. RESULTS: Among 159 participants exceeding their weight class one-week before competition, 36% of males and 44% of females exceeded their weight class by 0.0-4.9% (requiring small RWL); 30% of males and 6% of females exceeded by 5.0-10.0% (requiring large RWL), but neither males nor females were over 10.0% above required weight. In males, there was a moderate negative correlation between excess rates of body mass one-week before competition and their physical condition (r=-0.330 to -0.467, P<0.05) on the first day of the competition; however, no significant correlation was found in the females. Comparing physical condition according to the range of RWL, there were significantly lower scores in the large RWL group (≥4.9%) than the small RWL group (<4.9%) in males. CONCLUSIONS: We found that RWL≤5% is most appropriate to ensure better physical condition of wrestlers on competition day.

When and How Should Chinese Pregnant Women Exercise? A Longitudinal Study in China.

This study aimed to examine when and how physical activity (PA) influences gestational weight gain (GWG) and infant birthweight (BW) by considering the PA's total volume, timing, intensity, and type, controlling for the influence of energy intake. A total of 1272 participants in different stages of pregnancy were recruited from hospital. The associations between PA and GWG or BW in the latter half of pregnancy were significant. Women with the highest PA volume in the third trimester had significantly lower risks of inadequate and excessive GWG by 69% (OR = 0.31, 95%CI: 0.10-0.91) and 67% (OR = 0.33, 95% CI: 0.12-0.91), respectively, compared to women in the lowest quartile. Women who achieved the recommended moderate intensity of PA during their second and third trimesters, independent of total volume of PA, had infants with significantly lower BWs compared to those who did not (ß = -0.15, SE = 66.33, p = 0.04; ß = -0.20, SE = 64.54, p = 0.01, respectively). Therefore, the effects of total volume and intensity of PA on GWG and BW were different. Interventions to prevent inappropriate GWG and macrosomia may need to set different priorities and timing regarding total volume or intensity of PA.

Physical activity and dietary intake among Chinese pregnant women: an observational study.

BACKGROUND: Physical activity (PA) and dietary intake are important modifiable factors associated with health outcomes. However, Chinese pregnant women's PA and dietary intake are only vaguely understood. The aim of this study was to reveal the characteristics of PA and dietary intake of Chinese women in different trimesters as well as the associations between PA and dietary intake. METHODS: This is a cross-sectional observational study. PA, dietary intake, and demographics of 1077 Chinese pregnant women were measured. The Chi-square test, Kruskal-Wallis test, multiple logistic regression, and multiple linear regression were used for data analysis. RESULTS: About 57.1% of the participants met the international guideline for PA. Household activity and occupational activity contributed the most to the total PA, while sports/exercise contributed little. The mean energy intake of the participants was 2008 ± 748.0 kcal. Most participants had normal energy intake, but they obtained excessive energy from fat (mean = 41.7 ± 8.7%). PA was not found to be significantly associated with dietary intake. Further, the participants who were unemployed during pregnancy (OR = 0.72, 95% CI: 0.55-0.95; p < 0.05) or had no exercise habits before pregnancy (OR = 0.62, 95% CI: 0.47-0.80; p < 0.01) were less likely to meet the PA guideline. The participants in the third trimester (OR = 1.43, 95% CI: 1.03-1.99; p < 0.05) were more likely to meet the PA guideline compared to those in the first trimester. The older participants (> 30 years) showed higher dietary intake than the younger (< 25 years) participants (p < 0.01). CONCLUSIONS: The total PA of Chinese women during pregnancy mostly consists of household and occupational activities, but little sports/exercise. Starting exercise before pregnancy may help women achieve adequate PA during pregnancy. Moreover, these women consumed an excessive amount of fat and their diet intake varies by age.

Effects of Chios mastic gum and exercise on physical characteristics, blood lipid markers, insulin resistance, and hepatic function in healthy Japanese men.

The effects of Chios mastic gum (Pistacia lentiscus var. Chia) and exercise on physical characteristics, blood lipid markers, insulin resistance, and hepatic function were investigated in healthy, non-smoking Japanese men aged ≥ 40 years. Participants were allocated to control (C, 5 g/day placebo powder, n = 7), mastic (M, 5 g/day mastic powder, n = 7), or mastic plus physical activity groups (M + PA, 5 g/day mastic powder and 30-min exercise three times/week, n = 7), and measurements were taken at baseline, 3 and 6 months. Serum triglycerides were significantly reduced at 3 months in M and M + PA compared with C (P < 0.05). Serum insulin and homeostatic model assessment of insulin resistance values were significantly reduced at 3 and 6 months in M + PA, and at 6 months in M, compared with C (P < 0.05). These results indicate that Chios mastic gum intake for 6 months reduced serum triglyceride and insulin concentrations, and additional exercise enhanced the effect on insulin.

Effects of Different Intensities of Endurance Exercise in Morning and Evening on the Lipid Metabolism Response.

To study the effects of different exercise intensity performed at different exercise times on lipid metabolism response during prolonged exercise. Nine young men performed endurance exercise at different exercise intensities (60%VO2max or Fatmax) in the morning (9 am to 10 am) or evening (5 pm to 6 pm); blood samples were collected before exercise and immediately and one and two hours after exercise completion. Expired gas was analyzed from the start of exercise until two hours after exercise completion. There were no significant changes in catecholamine (adrenaline and noradrenaline) and free fatty acid levels between morning and evening trials for each endurance exercise intensity. However, the morning and evening trials both exhibited significantly higher lipid oxidation at Fatmax than that at 60%VO2max. These results suggest that exercise at Fatmax offers greater lipid oxidation than that at 60%VO2max, regardless of exercise timing.

Reliability and Validity of a Chinese-Translated Version of a Pregnancy Physical Activity Questionnaire.

Objectives The objectives of the present study were to translate the English version of the Pregnancy Physical Activity Questionnaire into Chinese (PPAQ-C) and to determine its reliability and validity for use by pregnant Chinese women. Methods The study included 224 pregnant women during their first, second, or third trimesters of pregnancy who completed the PPAQ-C on their first visit and wore a uniaxial accelerometer (Lifecorder; Suzuken Co. Ltd) for 7 days. One week after the first visit, we collected the data from the uniaxial accelerometer records, and the women were asked to complete the PPAQ-C again. Results We used intraclass correlation coefficients to determine the reliability of the PPAQ-C. The intraclass correlation coefficients were 0.77 for total activity (light and above), 0.76 for sedentary activity, 0.75 for light activity, 0.59 for moderate activity, and 0.28 for vigorous activity. The intraclass correlation coefficients were 0.74 for "household and caregiving", 0.75 for "occupational" activities, and 0.34 for "sports/exercise". Validity between the PPAQ-C and accelerometer data was determined by Spearman correlation coefficients. Although there were no significant correlations for moderate activity (r = 0.19, P > 0.05) or vigorous activity (r = 0.15, P > 0.05), there were significant correlations for total activity [light and above; r = 0.35, P < 0.01)] and for light activity (r = 0.33, P < 0.01). Conclusions for Practice The PPAQ-C is reliable and moderately accurate for measuring physical activity in pregnant Chinese women.

Diurnal variation in the diving bradycardia response in young men.

PURPOSE: The present study aimed to examine diurnal variation of the diving bradycardia responses on the same day. METHODS: Eighteen young men (age 26 ± 2 years; height 174.2 ± 6.0 cm; body mass 70.2 ± 8.1 kg; body fat 18.0 ± 3.8 %; mean ± standard deviation) participated in this study. Oral temperature, heart rate variability (HRV) from 5-min of electrocardiogram data, and diving bradycardia responses were measured at 0900, 1300, and 1700 hours daily. All participants performed diving reflex tests twice in the sitting position with the face immersed in cold water (1.9-3.1 °C) and apnea at midinspiration for a minimum of 30 s and as long as possible, in consecutive order. RESULTS: Oral temperature was found to be less in the morning (0900) than in the afternoon (1300) and evening (1700). In the frequency domain parameters of heart rate variability, the natural logarithms of high-frequency power were higher in the morning than in the evening. All participants showed bradycardia response to the two diving reflex tests. The peak values of R-R interval during the diving reflex test both for as long as possible and 30 s were longer in the morning than in the afternoon and evening. CONCLUSION: Our results indicated that the maximal bradycardia during the diving reflex test exhibits a diurnal variation, with peak levels at morning and gradual decrease towards the evening. The HRV indexes show the same variation.