Estimation of sweat rates during cycling exercise by means of the closed chamber condenser technology.

BACKGROUND/AIM: Knowledge of local sweating patterns is of importance in occupational and exercise physiology settings. The recently developed closed chamber condenser technology (Biox Aquaflux® ) allows the measurement of evaporative skin water loss with a greater measurement capacity (up to 1325 g/h/m2 ) compared to traditional evaporimeters. The aim of this study was to evaluate the applicability of the Biox Aquaflux® to estimate sweat production during exercise. METHODS: Fourteen healthy subjects performed a 20-min cycle ergometer trial at respectively 55% heart rate (HRreserve and 75% HRreserve . Sweat production was estimated by measuring body weight before and after exercise, by calculating the amount of sweat collected in a patch, and by measuring the water flux (in g/h/m2 ) with the Biox Aquaflux® instrument. RESULTS: The Biox Aquaflux® instrument allowed the follow up of sweat kinetics at both intensities. Correlations between the measurement methods were all significant for the 75% HRreserve trial (with r ranging from 0.68 to 0.76) whilst for the 55% HRreserve a significant relation was detected between the patch method and the Biox Aquaflux® only (with r ranging from 0.41 to 0.79). CONCLUSION: The Biox Aquaflux® instrument is a practical and direct method for the estimation of local sweat rates under field conditions.

Influence of physical development on start and countermovement jump performance in adolescent sprint athletes.

AIM: The aim of the present study was to describe the effect of physical changes during adolescence on sprint start and countermovement jump (CMJ) performance. METHODS: Twenty-eight girls and 25 boys (15.0±1.6 and 14.7±1.9 years at start respectively) were measured twice with a one year interval. Anthropometric data allowed skeletal muscle mass (SMM) estimation. Athletes performed a 10m sprint tracked from behind by a laser sensor, with starting blocks measuring propulsion forces. CMJ's were performed on a Kistler force plate. RESULTS: Between the two measurement occasions both genders increased in body height, weight and SMM. In girls and boys, impulse during the push-off, block leaving velocity and times at 5 and 10 m improved significantly. In both genders CMJ absolute power increased but not power.kg-1. Only in boys a higher CMJ was registered on occasion 2. For both genders on both occasions, impulse during the push-off correlated with body weight, SMM and CMJ power (r from .46 to .84), and in boys also with CMJ height and CMJ power.kg-1 (r from 0.43 to 0.76). Boys showed CMJ height and power to correlate with 5 and 10 m times (r from -0.42 to -0.79) and with block leaving velocity, however only on the first data collection (r=0.61 and 0.59, respectively). CONCLUSION: Sprint start performance is only partly related to muscular development and CMJ could predict start performance in boys only. Sprint start and CMJ rely on technical skills and, therefore, increasing muscularity should be accompanied with sufficient specific training to allow an optimal transfer to start performance.

The influence of stratum corneum hydration on body fat determination by bioelectrical impedance analysis.

BACKGROUND/AIMS: Bioelectrical impedance analysis (BIA) is used for the estimation of the amount of body fat. We evaluated the influence of the stratum corneum hydration at the contact areas used for BIA on the body fat estimation. METHODS: Stratum corneum hydration was measured at the sole of the right foot and the palm of the right hand before and after contact with the Tanita Body Composition Analyzer TBF 410(®) and the Omron Body Fat Analyzer(®) , (n=128 females and 126 males), respectively. Changes in stratum corneum hydration during the contact time were calculated (ΔHYD). As a gold standard for body fat estimation, the underwater weighing method (UWW) was used and the deviation of this standard was calculated for the Tanita (DT) and the Omron (DO) measurement. RESULTS: During contact with the Tanita, stratum corneum hydration increased significantly at the foot. Neither stratum corneum hydration measured at the respective contact sites before BIA nor ΔHYD at the respective skin sites was related to DT or with DO. CONCLUSION: The BIA measuring procedure using the Tanita instrument leads to an occlusive effect at the contact site. BIA for the determination of body composition is not influenced by stratum corneum hydration.

Demographic, socioeconomic and nutritional determinants of daily versus non-daily sugar-sweetened and artificially sweetened beverage consumption.

OBJECTIVE: The aim of this study was to determine the impact of demographic, socioeconomic and nutritional determinants on daily versus non-daily sugar-sweetened and artificially sweetened beverage consumption. METHODS: Cross-sectional design in 1852 military men. Using mailed questionnaires, sugar-sweetened and artificially sweetened beverage consumption was recorded. Principal component analysis was used for dietary pattern analysis. RESULTS: Sugar-sweetened and artificially sweetened beverages were consumed daily by 36.3% and 33.2% of the participants, respectively. Age, body mass index (BMI), non-smoking and income were negatively related to sugar-sweetened beverage consumption. High BMI and trying to lose weight were related to artificially sweetened beverages consumption. Three major patterns were obtained from principal component analysis: first, the 'meat pattern', was loaded for red meats and processed meats; second, the 'healthy pattern', was loaded for tomatoes, fruit, whole grain, vegetables, fruit, fish, tea and nuts; finally, the 'sweet pattern' was loaded for sweets, desserts, snacks, high-energy drinks, high-fat dairy products and refined grains. The sugar-sweetened beverage consumption was strongly related with both the meat and sweet dietary patterns and inversely related to the healthy dietary pattern. The artificially sweetened beverage consumption was strongly related with the sweet and healthy dietary pattern. CONCLUSIONS: Daily consumption of sugar-sweetened beverages was inversely associated with a healthy dietary pattern. Daily consumption of artificially sweetened beverages was clearly associated with weight-loss intention.