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The free testosterone to cortisol ratio (fTC) and heart rate variability (HRV) indices have been independently proposed as objective biomarkers of physiological resilience and readiness, respectively. It is hypothesized that individuals that enter a training period with high resilience and readiness would have a greater positive response to the training. PURPOSE: Therefore, the purpose of this study was to investigate the association between fTC and HRV with fitness changes in division I male college soccer players. METHODS: Two division I teams were recruited to participate in this study. Participants completed an orthostatic HRV challenge (supine, sitting, standing) and provided blood samples prior to the 6-week Spring training period. The HRV indices of root mean square of successive differences (RMSSD) and high frequency power (autoregressive, normalized; HF) were calculated in all postural conditions. Blood samples were assayed for free testosterone and cortisol using competitive binding ELISAs. Participants completed the yo-yo intermittent recovery test (YYIR) before and after the 6-week training period and the absolute increase in distance (m) achieved during the YYIR represented the change in fitness (YYIRΔ). Separate linear regression models tested the association of fTC and all HRV indices and their interactions with YYIRΔ. All predictors were first centered and scaled and alpha level was set at p < 0.05 for all models. RESULTS: Participants (n = 21, age = 19.5±1.0 years, height = 179.0±6.4 cm, weight = 76.9±9.4 kg, body fat = 12.6±4.3 %) from the two teams did not differ in YYIRΔ (mean±SD = 438±212, p = 0.64). A significant association with YYIRΔ was observed for the interaction between fTC and HFsitting (F(3,17) = 4.31, β = 4.92,p = 0.02, R² = 0.33). No other indices or interactions were significantly associated with YYIRΔ. CONCLUSIONS: These results suggest that HRV and fTC represent potential objective pre-training biomarkers capable of identifying athletes that will be most responsive to individualized fitness and conditioning programs. Further research is necessary to confirm the utility of these specific objective biomarkers in larger cohorts and across multiple training situations. [ABSTRACT FROM AUTHOR]

PURPOSE: Animal research suggests that variations in daily dietary macronutrient distribution may impact fluid consumption. However, this has not been fully investigated in humans. Thus, the purpose of this study was to determine the impact of dietary intake on fluid intake, thirst, and urinary hydration biomarkers. METHODS: Thirty-four participants (44% female; age: 23±4 years; height: 172.9±10.3cm; body mass: 77.2±18.1kg; body fat: 18.4± 8.4%) recorded their food and fluid intake, and provided a 24h urine sample over seven consecutive days. Urinary hydration biomarkers included urine volume (UVOL), urine osmolality (UOSM), urine specific gravity (USG), and urine color (UCOL). Each morning, participants completed two subjective ratings of perceived thirst; a 9-point Likert scale, and 100mm visual analog scales comprised of six indices (thirstiness, pleasantness, dryness, taste, fullness, sickness). RESULTS: Mean weekly macronutrient percentages and total calorie intake were used in multiple regression models as predictors of average total fluid intake, thirst, and urinary hydration markers. Throughout the week, participants reported consuming, on average, 1945±429 calories (36.5±4.4% fat, 44.3±6.3% carbohydrate, 18.5±4.5% protein) and 2508±1122mL fluid per day. Mean 7-day 24h urinary hydration markers were UVOL:1724±850mL, USG :1.017±0.005, UOSM: 565±212, UCOL: 3.89±0.99. Dietary intake that was higher in percentage of fat consumed was associated with higher ratings of "fullness" on morning thirst scale sub ratings (adj R² = 0.1181, p =0.0167). Consuming a greater proportion of calories from protein was associated with increased UVOL (adj R² = 0.1370, p = 0.0340). However, protein intake was not significantly associated with fluid intake (adj R2 = 0.0569, p = 0.2516), regardless of the type of fluid consumed (p > 0.05). UOSM, USG, UCOL and the other indices of thirst were not associated with macronutrient consumption (p>0.05). CONCLUSION: These results suggest increased consumption of dietary protein intake is associated with improved hydration status based on increased 24h urine volume, with the maintenance of other urinary hydration indices. Grant or Funding Information: This study was funded by a University of North Carolina at Greensboro Office of Research Engagement New Faculty Grant. [ABSTRACT FROM AUTHOR]

PURPOSE: Appropriate fluid intake is important to offset water losses induced by physical activity. However, limited research has investigated the relationships between physical activity and fluid intake in free living individuals. To assess the associations between objective and subjective measures of physical activity, reported fluid intake, and urinary hydration biomarkers in free living emerging adults. METHODS: Thirty-four participants (44% female; age, 23±4 years; height, 172.9±10.3cm; body mass, 77.2±18.1kg; body fat, 18.4± 8.4%) provided a 24h urine sample across seven consecutive days for measures of urine volume (UVOL), urine osmolality (UOSMO), urine specific gravity (USG) and urine color (UCOL). A validated fluid log was used to record fluid intake each day, where fluid intake was segmented into morning (waking - noon), afternoon (noon - 5pm) and evening (5pm - sleep). Physical activity was objectively assessed using wrist-worn actigraphy and analyzed using standard cutoffs. Subjective assessment of physical activity quantified day-level physical activity and was measured by MET-minutes. RESULTS: Over 7 consecutive days, participants participated in 16.97±23.42 minutes of moderate-to-vigorous physical activity (MVPA) and 677.89±702.62 MET-minutes of activity per day. Mean 7-day fluid consumption was 2551±1056mL and corresponding mean 7-day UVOL, UOSMO, USG, and UCOL was 1699±865mL, 567±210 mOsm/kg, 1.020±0.010 AU, and 3.9±1.0 AU, respectively. Increased MVPA (adj R² = 0.114, p = 0.044) and increased total MET-minutes (adj R² = 0.192, p = 0.005) was associated with decreased 24 h USG. Greater morning and evening fluid consumption was associated with increased 24h UVOL (adj R² = 0.589, P = 0.02; P < 0.0001). Greater evening fluid intake was associated with lower 24h UOSMO (adj R² = 0.331, P = 0.01). CONCLUSIONS: Increasing day-level physical activity in addition to consuming a greater volume of fluids in the morning and evening improved hydration status as reflected by 24h urinary hydration variables. Further work is needed to explore the associations between physical activity and timing of the fluids consumed. Grant or Funding Information: This study was funded by a University of North Carolina at Greensboro Office of Research Engagement New Faculty Grant. [ABSTRACT FROM AUTHOR]

Limited evidence exists examining the manipulation of total body water on inflammatory biomarkers in free-living emerging adults. PURPOSE: The purpose of this study was to investigate the acute effects of partial and full fluid restriction on inflammatory biomarkers in males and females. METHODS: Thirty-one participants (42% female; age, 23±4 y; mass, 78.2±17.3 kg; height, 173.2±9.9 cm; body fat, 18.2±8.7%) provided a 24 h measure of urine volume (UVOL) and urine osmolality (UOSM), 24 h dietary and fluid intake record, and fasted blood draw for two consecutive days. Following measure of nude body mass (NBM) and blood draw on day 1, participants underwent a 2 h sauna exposure (41°C, 50% RH) and were randomly assigned to one of three groups; control (CON) where females and males consumed 2.0 and 2.5L of water, respectively, partial fluid restriction (PART) where water consumption matched sauna sweat losses, and full fluid restriction (FULL) where participants were restricted from consuming fluids prior to day 2. Blood samples were analyzed for c-reactive protein (CRP), interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 10 (IL-10), interferon gamma (IFN-y), tumor necrosis factor alpha (TNF-a) and copeptin, a surrogate for arginine vasopressin. RESULTS: On day 2, percent body mass loss in PART (MD [95%CI]; 1.2% [0.2, 2.1], p=0.013) and FULL (1.4% [0.45, 2.5], p=0.004) were significantly greater than CON (0.0±0.5%). Higher UOSM (p=0.001) and copeptin (p<0.001), and lower UVOL(P=0.008) were observed in PART and FULL compared to CON. CRP was significantly lower in CON (estimate [95%CI]; - 7.35 pg/mL [-4.81, -13.13], p=0.011) than PART, however there were no differences between CON (1.82±1.55 pg/mL) and FULL (3.93±6.17 pg/mL, p>005). IL-8 was significantly greater in FULL (estimate, 3.12 pg/mL [0.49, 5.72], p=0.021) than PART. There were no differences in IL-6, IL-10, IFN-y, or TNF-a between groups (p>0.05). CONCLUSIONS: Partial and full fluid restriction over 24 h produced significant changes in circulating concentrations of CRP and IL-8, however, these differences were not consistent between hydration groups. Twenty-four-hour changes in total fluid intake eliciting mild hypohydration (<1.5% body mass loss) may be insufficient to cause a sustained systemic inflammatory response in free-living emerging adults. [ABSTRACT FROM AUTHOR]