ASSESSMENT OF EXERCISE-INDUCED DEHYDRATION AND REHYDRATION: EFFECTIVENESS OF USING PREDICTION EQUATIONS FOR PLASMA OSMOLALITY

Chiagoziem K. Ohamadike, Lia Teng, HyunGyu Suh, Mindy L. Millard-Stafford, FACSM. Georgia Institute of Technology, Atlanta, GA. ASSESSMENT OF EXERCISE-INDUCED DEHYDRATION AND REHYDRATION: EFFECTIVENESS OF USING PREDICTION EQUATIONS FOR PLASMA OSMOLALITY BACKGROUND: Plasma osmolality (POsm) is a gold standard for assessing hydration status; however, osmometers are primarily found in research labs and therefore POsm is not typically measured in clinical or athletic settings. PURPOSE: To compare the accuracy in assessment of dehydration versus rehydration states following the ingestion of oral rehydration solution (ORS) between published equations estimating POsm from Na+, K+, glucose, and blood urea nitrogen (BUN) versus direct measured POsm. METHODS: Seventeen healthy men cycled 90 min in the heat losing ~2.5% body mass and then ingested Pedialyte ORS ([Na+] = 42.6 mmol/L; [K+] = 30.9 mmol/L) replacing 100% of sweat loss over 30 min (~2 liters). Blood samples were collected at dehydration, then 30, 60, and 90 min post rehydration. POsm was directly measured with 50 µl samples (Micro Osmette osmometer, Precision System Inc). These values were compared to three highly cited equations estimating POsm (mmol/L): 1) 2 x (Na++ K+) + BUN+ Glucose (Gerich, Diabetes, 1971); 2) 1.86 x (Na+ + K+) + (1.15 x Glucose) + BUN + 14 (Hooper, British Medical Journal Open, 2015); and 3) 2 x Na+ + Glucose + BUN (Worthley, Anaesthesia and Intensive Care, 1987). RESULTS: All estimation equations were significantly correlated with measured POsm (p \u3c 0.0001, R2ranging from 0.64-0.72). At dehydration and 90 min post-rehydration, measured POsm was 294.6 ± 3.4 and 285.0 ± 3.1 mosmol/L, respectively. At dehydration, Worthley was lower (p \u3c 0.05) than the other equations and measured POsm (mean osmole gap = -3.4 mosmol/L). Conversely, at 90 min post rehydration, Gerich and Hooper equations were higher than Worthley and measured POsm (mean osmol gaps = -4.9 and -3.7 mosmol/L). CONCLUSION: Dehydration due to sweat losses in the heat results in underestimation of POsm when using equations excluding plasma K+ (e.g. Worthley). However, rehydration is not accurately assessed with equations including K+(e.g. Hooper and Gerich) when ORS is ingested to fully restore fluid balance. Therefore, selection of an appropriate published equation to estimate POsm depends on the nature of dehydration and/or fluid replenishment. Supported by a grant from Einsof Biohealth, Miami, FL

METABOLIC AND CARDIAC AUTONOMIC RESPONSE TO A 1-HOUR CYCLING TIME TRIAL WITH CARBOHYDRATE RINSE

C.M. Williamson-Reisdorph1, E.E. Bechke2, C. McLester2, B. Buresh2, FASCM, M. L. Millard-Stafford3, FASCM, R. Rooks2, B. Nickerson4, B.M. Kliszczewicz, FASCM2 1 University of Montana, Missoula, MT; 2Kennesaw State University, Kennesaw, GA; 3Georgia Institute of Technology, Atlanta, GA; 4Texas A&M International University, Laredo, TX Carbohydrate (CHO) rinsing in the mouth (without ingestion) may improve endurance performance purportedly due to alterations in central command following detection of CHO at receptors in the oral cavity. PURPOSE: To examine the effect of CHO rinsing on autonomic and metabolic responses during the post-exercise recovery period to determine if rinsing could enhance post-exercise recovery. METHODS: Ten male recreational cyclists (age = 30 ± 6 years, VO2max= 54.5 ± 8.1 mL·kg-1·min-1) completed experimental trials in a randomized, double-blind, placebo-controlled, crossover design between CHO and placebo (PLA) rinse. The rinse was administered every 12.5% of prescribed work during a 1-hour cycling time trial at 75% Wmax. Heart rate variability (lnRMSSD), respiratory exchange ratio, and blood sampling for epinephrine, norepinephrine, insulin, glucose, free fatty acids, and lactate were completed pre- and post- exercise. RESULTS: CHO rinsing did not result in improvements in time trial performance (p = 0.545). A prolonged elevation of sympathetic nervous system (SNS) activity was observed at 30-minutes post-exercise in the CHO trial, as measured by lnRMSSD and epinephrine (p = 0.046, p = 0.022). Lactate remained elevated at 30-minutes post-exercise in the CHO rinse trial (p \u3c 0.001). A significant interaction was observed with higher free fatty acid concentrations occurring post-exercise in CHO trial (p = 0.024). A reduction in blood glucose concentrations occurred in the PLA trial (p = 0.021), but not in the CHO trial (p = 0.657). CONCLUSION: Periodic CHO mouth rinsing had no impact on 1-hour time trial performance in recreational cyclists. CHO rinsing resulted in prolonged elevation of SNS activity for up to 30-minutes post-exercise and altered metabolic activity as measured by epinephrine, free fatty acids, glucose, and lactate. Therefore, the use of a CHO rinse does not enhance post-exercise recovery. Supported by the Department of Exercise Science & Sport Management at Kennesaw State University

Measurement of longitudinal changes in body composition during weight loss and maintenance in overweight and obese subjects using air-displacement plethysmography in comparison with the deuterium dilution technique

Background: Air-displacement plethysmography (ADP) may be a valid and practical technique to assess body composition in a clinical setting. Objective: This study aimed to assess longitudinal changes in body composition using ADP and to compare it with the deuterium dilution technique. Design: The study was a 6-months dietary intervention, consisting of four phases. The first month, subjects were fed in energy balance (phase I). This was followed by 1 month with an energy intake of 33% of energy requirements (phase II), followed by 2 months at 67% of energy requirements (phase III) and 2 months of ad libitum intake (phase IV). Body composition was assessed using ADP (Bod Pod) and deuterium dilution at baseline and at the end of each phase. The baseline analysis included 111 subjects (88 female). Sixty-one subjects (50 female) completed all measurements and were included in the longitudinal analysis. Results: At baseline, the fat mass (FM) as assessed with the Bod Pod was on average 2.3±4.2 kg (mean±2 s.d.) higher than that assessed with deuterium dilution. The difference in FM between techniques increased significantly with increasing FM (R2=0.23; P<0.001). Both techniques showed significant changes in FM over time P<0.001). On average, FM as assessed with the Bod Pod was 2.0 kg higher than with deuterium dilution (P<0.001). During phase II, there was a significant interaction between time and method, meaning that the Bod Pod showed a larger decrease in FM than deuterium dilution. Conclusions: The Bod Pod was able to detect all changes in the body composition, but consistently measured a higher FM than deuterium dilution.G Plasqui, S Soenen, MS Westerterp-Plantenga and KR Westerter

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of −18%. There were no significant betweengroup differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo.</p