The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein

The beverage hydration index (BHI) facilitates a comparison of relative hydration properties of beverages using water as the standard. The additive effects of electrolytes, carbohydrate, and protein on rehydration were assessed using BHI. Nineteen healthy young adults completed four test sessions in randomized order: deionized water (W), electrolytes only (E), carbohydrate-electrolytes (C + E), and 2 g/L dipeptide (alanyl-glutamine)-electrolytes (AG + E). One liter of beverage was consumed, after which urine and body mass were obtained every 60 min through 240 min. Compared to W, BHI was higher (p = 0.007) for C + E (1.15 ± 0.17) after 120 min and for AG + E (p = 0.021) at 240 min (1.15 ± 0.20). BHI did not differ (p > 0.05) among E, C + E, or AG + E; however, E contributed the greatest absolute net effect (>12%) on BHI relative to W. Net fluid balance was lower for W (p = 0.048) compared to C + E and AG + E after 120 min. AG + E and E elicited higher (p < 0.001) overall urine osmolality vs. W. W also elicited greater reports of stomach bloating (p = 0.02) compared to AG + E and C + E. The addition of electrolytes alone (in the range of sports drinks) did not consistently improve BHI versus water; however, the combination with carbohydrate or dipeptides increased fluid retention, although this occurred earlier for the sports drink than the dipeptide beverage. Electrolyte content appears to make the largest contribution in hydration properties of beverages for young adults when consumed at rest

Whole-Body Sweat Rate Prediction:Indoor Treadmill and Cycle Ergometer Exercise

This paper describes the development and validation of accurate whole-body sweat rate prediction equations for individuals performing indoor cycle ergometer and treadmill exercise, where power output can be measured or derived from simple inputs. For cycle ergometry, 112 trials (67 participants) were used for model development and another 56 trials (42 participants) for model validation. For treadmill exercise, 171 trials (67 participants) were used for model development and another 95 trials (63 participants) for model validation. Trials were conducted over a range of dry-bulb temperature (20˚C to 40˚C), relative humidity (14% to 60%) and exercise intensity (~40% to 85% of peak aerobic power) conditions, which were matched between model development and model validation. Whole-body sweat rates were measured, and proprietary prediction models were developed (accounting for all relevant biophysical factors) and then validated. For model validation, mean absolute error for predicted sweating rate was 0.01 and 0.02 L·h -1 for cycle and treadmill trials, respectively. The 95% confidence intervals were modest for cycle ergometer (+0.25 and -0.22 L·h -1) and treadmill exercise (+0.33 and -0.29 L·h -1). The accounted for variance between predicted and measured values was 92% and 78% for cycle and treadmill exercise, respectively. Bland-Altman analysis indicated that zero and one predicted value exceeded the a priori acceptable level of agreement (equivalent to ±2% of total body mass in 3 h) for cycle and treadmill exercise, respectively. There were fewer trials with female subjects, but their values did not differ from those expected for males. This is the foremost study to develop and validate whole-body sweat rate prediction equations for indoor treadmill and cycle ergometer exercise of moderate-to-high intensity. These prediction equations are publicly available for use (https://sweatratecalculator.com). </p

Whole-Body Sweat Rate Prediction:Outdoor Running and Cycling Exercise

Our aim was to develop and validate separate whole-body sweat rate prediction equations for moderate to high intensity outdoor cycling and running, using simple measured or estimated activity and environmental inputs. Across two collection sites in Australia, 182 outdoor running trials, and 158 outdoor cycling trials were completed at a wet-bulb globe temperature ranging from ~15 to ~29˚C, with ~60-min whole-body sweat rates measured in each trial. Data were randomly separated into model development (running: 120; cycling: 100 trials) and validation groups (running: 62; cycling: 58 trials), enabling proprietary prediction models to be developed and then validated. Running and cycling models were also developed and tested when locally measured environmental conditions were substituted with participant subjective ratings for black globe temperature, wind speed, and humidity. The mean absolute error for predicted sweating rate was 0.03 and 0.02 L·h -1 for running and cycling models, respectively. The 95% confidence intervals for running (+0.44 and -0.38 L·h -1) and cycling (+0.45 and -0.42 L·h -1) were within acceptable limits for an equivalent change in total body mass over 3 h of ±2%. The individual variance in observed sweating described by the predictive models was 77% and 60% for running and cycling, respectively. Substituting measured environmental variables with subjective assessments of climatic characteristics reduced the variation in observed sweating described by the running model by up to ~25%, but only by ~2% for the cycling model. These prediction models are publicly accessible (https://sweatratecalculator.com) and can guide individualized hydration management in advance of outdoor running and cycling. </p

Hypertonic Saline Infusion Acutely Degrades Mood in Healthy Volunteers (P23-014-19)

Objectives: Mild and moderate dehydration adversely affect mood and cognitive function. During dehydration, hypertonic hypovolemia activates both osmo- and baro-receptors but it is not known which physiological pathway is associated with degraded mood state. This study examined the acute effect of osmoreceptor stimulation on mood.Methods: Sixty healthy adults (50% females, 30 ± 1 y; BMI: 26.9 ± 4.0 kg·m-2) were infused intravenously with 3.0% (HYPER) or 0.9% (ISO) NaCl for 2 h (0.1 ml·kg-1·min-1) using a counterbalanced, crossover design. Blood samples were collected every 30 minutes to measure plasma osmolality (POsm), copeptin (a surrogate marker of vasopressin), and renin-angiotensin-aldosterone system (RAAS) hormones. Mood was assessed with the short version of Profile of Mood State (POMS) questionnaire before and after the infusion.Results: POsm and copeptin increased from 286 ± 3 mmol·kg-1 to 305 ± 4 mmol·kg-1 and from 4.5 ± 3.7 pmol·L-1 to 20.4 ± 12.8 pmol·L-1, respectively in HYPER (P 0.05). No hormonal differences were observed between trials for RAAS hormones (P > 0.05). During HYPER copeptin, following the 2-h infusion, was greater in females than in males (female: 23.4 ± 13.9 pmol·L-1, male: 17.4 ± 10.9 pmol·L-1; P 0.05). Among POMS subscales, depression-dejection and fatigue-inertia increased in HYPER compared to ISO (P 0.05). The confusion-bewilderment subscales and fatigue-inertia of the POMS were also elevated post HYPER in females (P 0.05) in either sex.Conclusions: Hypertonic saline infusion acutely degrades mood state, and women appear to have a more pronounced response. The underlying mechanisms remain to be determined but may be related to higher copeptin levels in women.The study was registered at ClinicalTrials.gov as NCT02761434.Funding Sources: Danone Research.Supporting Tables Images and/or Graphs

Hypertonic Saline Infusion Acutely Degrades Mood in Healthy Volunteers (P23-014-19)

Objectives: Mild and moderate dehydration adversely affect mood and cognitive function. During dehydration, hypertonic hypovolemia activates both osmo- and baro-receptors but it is not known which physiological pathway is associated with degraded mood state. This study examined the acute effect of osmoreceptor stimulation on mood.Methods: Sixty healthy adults (50% females, 30 ± 1 y; BMI: 26.9 ± 4.0 kg·m-2) were infused intravenously with 3.0% (HYPER) or 0.9% (ISO) NaCl for 2 h (0.1 ml·kg-1·min-1) using a counterbalanced, crossover design. Blood samples were collected every 30 minutes to measure plasma osmolality (POsm), copeptin (a surrogate marker of vasopressin), and renin-angiotensin-aldosterone system (RAAS) hormones. Mood was assessed with the short version of Profile of Mood State (POMS) questionnaire before and after the infusion.Results: POsm and copeptin increased from 286 ± 3 mmol·kg-1 to 305 ± 4 mmol·kg-1 and from 4.5 ± 3.7 pmol·L-1 to 20.4 ± 12.8 pmol·L-1, respectively in HYPER (P 0.05). No hormonal differences were observed between trials for RAAS hormones (P > 0.05). During HYPER copeptin, following the 2-h infusion, was greater in females than in males (female: 23.4 ± 13.9 pmol·L-1, male: 17.4 ± 10.9 pmol·L-1; P 0.05). Among POMS subscales, depression-dejection and fatigue-inertia increased in HYPER compared to ISO (P 0.05). The confusion-bewilderment subscales and fatigue-inertia of the POMS were also elevated post HYPER in females (P 0.05) in either sex.Conclusions: Hypertonic saline infusion acutely degrades mood state, and women appear to have a more pronounced response. The underlying mechanisms remain to be determined but may be related to higher copeptin levels in women.The study was registered at ClinicalTrials.gov as NCT02761434.Funding Sources: Danone Research.Supporting Tables Images and/or Graphs