Effects of Heat Exposure on Body Water Assessed using Single-Frequency Bioelectrical Impedance Analysis and Bioimpedance Spectroscopy

International Journal of Exercise Science 10(7): 1085-1093, 2017. The purpose of this study was to determine if heat exposure alters the measures of total body water (TBW), extracellular water (ECW), and intracellular water (ICW) in both single-frequency bioelectrical impedance analysis (BIA) and bioimpedance spectroscopy (BIS). Additionally, we sought to determine if any differences exist between the BIA and BIS techniques before and after brief exposure to heat. Body water was evaluated for twenty men (age=24±4 years) in a thermoneutral environment (22°C) before (PRE) and immediately after (POST) 15 min of passive heating (35°C) in an environmental chamber. The mean difference and 95% limits of agreement at PRE demonstrated that BIS yielded significantly higher body water values than BIA (all p0.05; 0.2±1.5kg). Additionally, the ES of the mean differences at POST were trivial to small and the r-values were high (r≥0.96). When analyzing the changes in body water before and after heat exposure, POST values for BIS were significantly higher than PRE (all

Sport Locus of Control and Perceived Stress among College Student-Athletes

The purpose of the study was to analyze athletes’ motivation for sport participation as it related to their locus of control. Research was conducted at two Division I universities in the southeastern United States. Participants were given the Sport Locus of Control and Perceived Stress among College Athletes surveys. There were 126 participants with a mean age of 19.69 ± 1.32 years. A Pearson correlation (r) was performed to determine a significant relationship between perceived stress and locus of control. Results indicated a significant negative relationship between the two variables (r = −0.393 and p = 0.001) (a moderate relationship). As perceived stress scores increased, locus of control scores decreased. Correlations related to perceived stress were gender (r = 0.323, p = 0.000), and grade point average (GPA) (r = −0.213, p = 0.01). The only other independent variable that was significantly related to locus of control was being on an academic scholarship (r = −0.203, p = 0.025). Athletes who have an external locus of control feel that they have little control over their circumstances. Findings of this study give coaches another factor to consider in retaining and getting the most from their athletes

Ultra-shortened Time-domain HRV Parameters at Rest and Following Exercise in Athletes: An Alternative to Frequency Computation of Sympathovagal Balance

Purpose The primary purpose of this study was to determine the accuracy of the standard deviation of normal-to-normal intervals (SDNN) to root mean square of successive normal-to-normal interval differences (RMSSD) ratio from 1-min recordings (SDNN:RMSSD1−min) compared to criterion recordings, as well as its relationship to low-frequency-to-high-frequency ratio (LF:HF) at rest and following maximal exercise in a group of collegiate athletes. Method Twenty athletes participated in the study. Heart rate variability (HRV) data were measured for 5 min before and at 5–10 and 25–30 min following a maximal exercise test. From each 5-min segment, the frequency-domain measures of HF, LF, and LF:HF ratio were analyzed. Time-domain measures of SDNN, RMSSD, and SDNN:RMSSD ratio were also analyzed from each 5-min segment, as well as from randomly selected 1-min recordings. Result The 1-min values of SDNN, RMSSD, and SDNN:RMSSD provided no significant differences and nearly perfect intra-class correlations (ICCs ranged from 0.97 to 1.00, p \u3c 0.001 for all) to the criterion measures from 5-min recordings. In addition, SDNN, RMSSD, and SDNN:RMSSD from the 1-min segments provided very large to nearly perfect correlations (r values ranged from 0.71 to 0.97, p \u3c 0.001 for all) to LF, HF, and LF:HF, respectively, at each time point. Conclusion The findings of the study suggest that ultra-shortened time-domain markers may be useful surrogates of the frequency-domain parameters for tracking changes in sympathovagal activity in athletes

Crossvalidation of Two 20-M Shuttle-Run Tests for Predicting V̇O2max in Female Collegiate Soccer Players

The aim of this study was twofold: (a) to compare the maximal attained speed (MAS) from the 20-m shuttle (MST) and 20-m square-shuttle (SST) tests and (b) to crossvalidate 2 equations for predicting maximal oxygen consumption (V̇O2max) that were previously developed from MST and SST in a group of female collegiate soccer players. Thirty-nine subjects (age: 20.1 ± 1.5 years) participated in the study. A maximal graded exercise treadmill test was used to measure V̇O2max. In addition, V̇O2max was predicted from the MAS obtained during MST (predV̇O2maxMST) and SST (predV̇O2maxSST) using previously developed equations. Measured V̇O2max for the group was 44.2 ± 3.3 ml·kg−1·min−1. The MAS was 12.5 ± 0.6 km·h−1 for MST and 13.3 ± 0.8 km·h−1 for SST (p \u3c 0.05). The prediction methods yielded a predV̇O2maxMST of 49.6 ± 3.9 ml·kg−1·min−1 and predV̇O2maxSST of 41.8 ± 3.1 ml·kg−1·min−1, which were significantly different from measured V̇O2max (p \u3c 0.05). The validity statistics revealed the following constant error (CE), correlation coefficient (r), standard error of estimate (SEE), and total error (TE) for predV̇O2maxMST and predV̇O2maxSST: CE = 5.35 ± 3.83, r = 0.45 (p \u3c 0.05), SEE = 2.97 ml·kg−1·min−1, TE = 6.39 ml·kg−1·min−1; and CE = −2.43 ± 2.49, r = 0.69 (p \u3c 0.05), SEE = 2.39 ml·kg−1·min−1, TE = 3.43 ml·kg−1·min−1, respectively. Residual plots indicated no proportional bias for either prediction model. The results of this study suggest that female collegiate soccer players had a higher MAS from SST compared with that from MST. In addition, SST appeared to be a more accurate predictor of V̇O2max than MST in the group of athletes

Authors’ reply to Medeiros et al.: Make it easier! Evaluation of the ‘vagal-sympathetic effect’ in different conditions with R–R intervals monitoring

Work published in European Journal of Applied Physiology

Validity of four-compartment model body fat in physically active men and women when using DXA for body volume

The purpose of this study was twofold: 1) compare body volume (BV) estimated from dual energy X-ray absorptiometry (DXA) to BV from a criterion underwater weighing (UWW) with simultaneous residual lung volume (RLV), and 2) compare four-compartment (4C) model body fat percentage (BF%) values when deriving BV via DXA (4CDXA) and UWW (4CUWW) in physically active men and women. One hundred twenty-two adults (62 men and 60 women) who self-reported physical activity levels of at least 1,000 MET·min·wk-1 volunteered to participate (age = 22 ± 5 years). DXA BV was determined with the recent equation from Smith-Ryan et al. while criterion BV was determined from UWW with simultaneous RLV. The mean BV values for DXA were not significant compared with UWW in women (p = .80; constant error [CE] = 0.0L), but were significantly higher in the entire sample and men (both p \u3c .05; CE = 0.3 and 0.7L, respectively). The mean BF% values for 4CDXA were not significant for women (p = .56; CE = –0.3%), but were significantly higher in the entire sample and men (both p \u3c .05; CE = 0.9 and 2.0%, respectively). The standard error of estimate (SEE) ranged from 0.6–1.2L and 3.9–4.2% for BV and BF%, respectively, while the 95% limits of agreement (LOA) ranged from ±1.8–2.5L for BV and ±7.9–8.2% for BF%. 4CDXA can be used for determining group mean BF% in physically active men and women. However, due to the SEEs and 95% LOAs, the current study recommends using UWW with simultaneous RLV for BV in a criterion 4C model when high individual accuracy is desired

A highly predictive model for diagnosis of colorectal neoplasms using plasma microRNA: improving specificity and sensitivity

Objective: To develop a plasma-based microRNA (miRNA) diagnostic assay specific for colorectal neoplasms, building upon our prior work. Background: Colorectal neoplasms [colorectal cancer (CRC) and colorectal advanced adenoma (CAA)] frequently develop in individuals at ages when other common cancers also occur. Current screening methods lack sensitivity, specificity, and have poor patient compliance. Methods: Plasma was screened for 380 miRNAs using microfluidic array technology from a “Training” cohort of 60 patients, (10 each) control, CRC, CAA, breast cancer, pancreatic cancer, and lung cancer. We identified uniquely dysregulated miRNAs specific for colorectal neoplasia (P < 0.05, false discovery rate: 5%, adjusted α = 0.0038). These miRNAs were evaluated using single assays in a “Test” cohort of 120 patients. A mathematical model was developed to predict blinded sample identity in a 150 patient “Validation” cohort using repeat-sub-sampling validation of the testing dataset with 1000 iterations each to assess model detection accuracy. Results: Seven miRNAs (miR-21, miR-29c, miR-122, miR-192, miR-346, miR-372, and miR-374a) were selected based upon P value, area under the curve (AUC), fold change, and biological plausibility. Area under the curve (±95% confidence interval) for “Test” cohort comparisons were 0.91 (0.85–0.96) between all neoplasia and controls, 0.79 (0.70–0.88) between colorectal neoplasia and other cancers, and 0.98 (0.96–1.0) between CRC and colorectal adenomas. In our “Validation” cohort, our mathematical model predicted blinded sample identity with 69% to 77% accuracy, 67% to 76% accuracy, and 86% to 90% accuracy for each comparison, respectively. Conclusions: Our plasma miRNA assay and prediction model differentiate colorectal neoplasia from patients with other neoplasms and from controls with higher sensitivity and specificity compared with current clinical standards