Effects of an Acute Strength and Conditioning Bout on Dual Energy X-ray Absorptiometry Results

Dual Energy X-ray Absorptiometry (DXA) scans to assess body composition have become increasingly popular, especially in athletic populations. Acute factors, such as hydration status and food intake have been shown to alter DXA results (Tinsley, MSSE 2016). It is currently not known if prior strength and conditioning bouts may alter fat mass, lean mass, and bone density results. PURPOSE: To determine if a strength and conditioning (S&C) bout, similar to what athletes regularly engage in, will alter the fat mass, lean mass, and bone content results of a DXA scan. METHODS: Fourteen strength-trained subjects (10 men, 4 women, age 24 ± 2 yrs, height 176.7 ± 8.1 cm, weight 88.8 ± 14.7 kg) who were enrolled in an athletic strength and conditioning course volunteered to participate in this study. Each subject underwent two DXA scans on the same day. The first scan was performed prior to the S&C bout. The second scan was completed within 45 minutes after completion of the S&C bout. Participants were instructed to consume their normal, free living breakfast prior to scan one. A food and water log was distributed during the informed consent process and was maintained by the participants for 24 hours prior to all DXA scans. Nutritional information was analyzed via a commercial nutrition software for macronutrients, micronutrients, and hydration status. All DXA scans were performed and analyzed by the same trained technician. After the first scan, subjects were instructed to avoid all food intake until completion of the second scan. Subjects were encouraged to drink water ad libitum during the S&C bout from individually assigned 1-liter bottles; the volume consumed during the bout was measured by weight. RESULTS: No significant difference was found (correlated t-test a = 0.05) on any of the body composition measures between pre and post DXA body composition measurements after a S&C bout (changes pre to post: fat mass 46.5-46.0 kg, lean mass 64.8-64.9 kg, bone content 3.3-3.3 kg). CONCLUSION: Based on the results of the present study, S&C bouts do not need to be considered to ensure accuracy when performing DXA scans. The physiological changes that occur in response to a single S&C bout do not affect body composition analysis of DXA scans

Significant Predictors of Nonalcoholic Fatty Liver Disease in Texas Firefighters

Risk factors for Nonalcoholic Fatty Liver Disease (NAFLD) include obesity, hypertension, dyslipidemia, and diabetes mellitus. Not only are these prevalent in the general US population, but they are also present at high rates in a specific subset responsible for public safety – firefighters. PURPOSE: The aim of the present study is to use logistic regression to predict the likelihood of occurrence of NAFLD in firefighters using a subset of health-related factors associated with common cardiometabolic risk factors. METHODS: Data were collected on 136 firefighters (128 males, 8 females; 36.3 ± 9.0 yrs; 95.7 ± 17.0 kg; 178.9 ± 7.4 cm; 29.8 ± 4.2 kg/m2) participating in FITLIFE, a university-based fitness program at Texas A&M University. Nominal logistic regression with stepwise removal was used to estimate the best model to predict fatty liver disease. Stepwise removal identified resting systolic blood pressure (RSBP, mm HG), Body Mass Index (BMI, kg/m2), visceral adipose tissue (VAT, cm2), whether or not has hypertension or is on medication (HTNMED; 0=No,1=Yes), and plasma triglyceride concentrations (TG, mg/dL) as independent predictors (p\u3c0.05). Odds ratios (OR) were calculated to determine the change in the odds of NAFLD per unit increase in each predictor. RESULTS: Logistic regression yielded the following equation to predict the probability of developing NAFLD: Logit = -22.5176 + 0.0918(RSBP) + 0.2154(BMI) + 0.0065(TG) + 0.0161(VAT) + 1.830(HTNMED) (R2 = 0.4655, p \u3c 0.001). Of the predictors, the ORs from largest to smallest were 6.235, 1.240, 1.096, 1.016, and 1.002 for HTNMED, BMI, RSBP, VAT, and TG, respectively. CONCLUSION: Using RSBP, BMI, VAT, TG, and HTNMED as predictors, this study demonstrates that the probability of developing NAFLD in Texas firefighters can be reasonably predicted. This regression model and individual predictors may be used by health practitioners as a cost-effective screening tool to identify those at higher risk for NAFLD

Wearable Positive End-Expiratory Pressure Valve Improves Exercise Performance

Positive end-expiratory pressure (PEEP) provides benefits to pulmonary patients, yet effects in healthy, exercising adults are unknown. PURPOSE: We designed two experiments (EXP) to test a novel PEEP (4.2 cmH2O PEEP) mouthpiece (PMP) on maximal cycling performance of physically active volunteers. METHODS: EXP-1 PMP vs. control (CON) mouthpiece (N=9, Age=30±2 yr, Weight=72.2±3.7 kg, BMI=24.4±1.2, 5♂); and EXP-2 PMP vs. no mouthpiece (NMP) (N=10, Age=27±1 yr, Weight=76.7±3.6 kg, BMI=23.9±0.8, ♂). Exercise test procedures for both experiments were identical. On Day 1, under the first mouthpiece condition assigned at random subjects performed graded exercise cycling testing (GXT) (Corival®) for VO2peak (ml*kg*min-1), oxygen pulse (mlO2*bt) (O2pulse), GXT endurance time (s) (GXT-T), and VO2(ml*kg*min-1)-at-ventilatory-threshold (VO2 @VT). Subjects returned 72 h later (Day 2), to complete an endurance ride timed (s)to exhaustion (VTER) at an intensity equivalent to their VO2 @VT power (W). One week later, subjects repeated exercise testing protocols (Days 3 & 4, time-of-day controlled) under the alternate mouthpiece condition. RESULTS: Selected outcomes were as follows (paired T-test, *PMP vs. CON, respectively: VO2peak=45.2±2.4* vs. 42.4±2.3; VO2@VT=33.7±2.0 vs. 32.3±1.6; GXT-T=521.7±73.4* vs. 495.3±72.8; VTER=846.2±166.0 vs. 743.1±124.7; O2pulse=24.5±1.4* vs. 23.1±1.3. PMP vs. NMP, respectively: VO2peak=43.3±1.6* vs. 41.7±1.6; VO2@AT=31.1±1.2* vs. 29.1±1.3; GXT-T=511.7*±49.6 vs. 486.4±49.6; VTER 872.4±134.0 vs. 792.9 ± 122.4; O2pulse=24.1±0.9* vs. 23.4±0.9. CONCLUSION: These results demonstrate that the novel PEEP mouthpiece we tested confers a significant performance benefit to cyclists completing high intensity exercise. By extension, it is likely to be an advantage in any physical activity having an aerobic component

High Fat Relative to Low Fat Ground Beef Consumption Lowers Blood Pressure and Does Not Negatively Alter Arterial Stiffness

Beef consumption has been stigmatized as an unhealthy dietary choice. However, randomized control trials to support this claim are lacking. PURPOSE: To examine the effect of low-fat (5%) and high-fat (25%) ground beef consumption on blood pressure (BP) and carotid-femoral pulse wave velocity (PWV).METHODS: Twenty-three male subjects (age 40±11 yrs, height 177.4±6.7 cm, weight 97.3±25.0 kg, lean mass 64.5±9.5 kg, fat mass 30.6±19.1 kg) volunteered to participate in this cross-over design study. Each participant completed two, 5-week ground beef interventions in a randomized order with a 4-week washout period in-between. All participants visited the lab four times after an overnight fast. Each visit to the lab consisted of supine BP, dual energy x-ray absorptiometry (DXA) scan to assess body composition, and PWV analysis. The PWV recording was assessed on the right carotid and femoral arteries. The distance used for the PWV calculation was 80% of the actual distance between carotid and femoral sites. All PWV measures were completed according to previously published procedures (Van Bortel, 2011). BP and PWV results were analyzed separately via 2x2 repeated measures ANOVA. RESULTS: Our results indicate there was a significant decrease in systolic BP (p=0.01) following the high-fat ground beef intervention compared to the low-fat. The BP values for low-fat beef and high-fat beef are 120/74 and 116/73 mmHg, respectively. Further, there were no significant differences between the PWV measures. CONCLUSION: Based on our results, high fat ground beef favorably alters systolic BP and does not negatively affect PWV measures

Consuming High-Fat and Low-Fat Ground Beef Depresses High-Density and Low-Density Lipoprotein Cholesterol Concentrations, and Reduces Small, Dense Low-Density Lipoprotein Particle Abundance

We hypothesized that consumption of high-fat (HF) ground beef (24% fat) would not affect plasma concentrations of high-density lipoprotein cholesterol (HDL-C) or low-density lipoprotein (LDL-C), whereas low-fat (LF) ground beef (5% fat) would decrease HDL-C and LDL-C concentrations. In a randomized 2-period crossover, controlled feeding trial, 25 men (mean age and body mass index, 40 years and 31.2) consumed 115-g HF or LF patties, 5/week for 5 weeks with a 4-week washout. The HF treatment increased % energy from fat (p = 0.006) and saturated fat (p = 0.004) and tended (p = 0.060) to depress % energy from carbohydrates. The HF and LF treatments decreased the plasma concentrations of HDL-C (p = 0.001) and LDL-C (p = 0.011). Both ground beef treatments decreased the abundance of HDL3a and increased the abundance of HDL3 (p ≤ 0.003); the LF treatment also decreased the abundance of HDL2b and HDL2a (p ≤ 0.012). The HF and LF treatments decreased the abundance of LDL3 and LDL4 (p ≤ 0.024) and the HF treatment also decreased LDL5 (p = 0.041). Contrary to our hypothesis, the HF treatment decreased plasma HDL-C and LDL-C concentrations despite increased saturated fat intake, and both treatments decreased the abundance of smaller, denser LDL subfractions

Cardiovascular Responses to Mild Lower Body Negative Pressure during Spaceflight

INTRODUCTION: Weightlessness during spaceflight causes a chronic cephalad fluid shift that has been hypothesized to underlie numerous risks associated with spaceflight, including the development of ocular structural and functional changes and in rare cases venous thrombosis. Acute use of 25 mmHg lower body negative pressure (LBNP) during spaceflight can partially reverse this headward fluid shift and thus, may represent a promising countermeasure. However, there are limited data on how the cardiovascular system responds to sustained use of mild LBNP during spaceflight when cardiovascular deconditioning and adaptation may cause crewmembers to be more susceptible to orthostatic stressors than they would have been on Earth. PURPOSE: The purpose of this study was to quantify the heart rate (HR) and blood pressure response throughout ~60 minutes of exposure to 25 mmHg LBNP during spaceflight and determine if this response was augmented at later time points during 6-month spaceflight missions. HYPOTHESIS: We hypothesized that crewmembers would experience an increase in HR during LBNP that would be sufficient to maintain mean arterial pressure (MAP) and this would not be augmented later in spaceflight. METHODS: Brachial arterial pressure and HR were measured before and throughout ~60 min of 25 mmHg LBNP after ~45 days (FD45) and ~150 days (FD150) of spaceflight in 12 crewmembers. Total LBNP session times varied slightly due to logistical constraints. MAP and HR changes from baseline with LBNP exposure were analyzed with splines models. Marginal means were used for estimation and statistical comparisons across time and between flight days. RESULTS: Before LBNP use, HR was 59 beats per min (BPM 95% CI: 56 - 62) and MAP was 93 mmHg (95% CI: 90 - 96). During LBNP exposure on FD45, HR increased by 9 BPM (95% CI: +7 - +10) at 15 min of exposure, and increased further to +10 BPM (95% CI: +8 - +12) at 30 min, and +11 BPM (95% CI: +9 - +14) at 45 min. On FD150, HR increased by 8 BPM (95% CI: +5 - +11) at 15 min of exposure but plateaued thereafter. MAP decreased by 5 mmHg (95% CI: -8 - -2) at 15 min and remained lower thereafter. MAP responses during ~60 min of LBNP exposure were not statistically different between FD45 and FD150. A total of 46 sessions of LBNP were successfully completed, and only a single case of mild hypotensive symptoms was reported, and this session was completed. CONCLUSION: These data suggest that the cardiovascular system can accommodate up to 60 min of sustained use of mild levels of LBNP during long-duration spaceflight. There was a single report of mild hypotensive symptoms during use of LBNP by an individual who had low blood pressure prior to the start of the LBNP session. Thus, the absolute arterial blood pressure should be taken into consideration when determining if an LBNP session will be a potential challenge to the cardiovascular system during spaceflight

Detection of a Specular Reflection on Titan by Cassini-VIMS

We present the detection of a specularly reflected signal from Titan's surface associated with Kraken Mare, which indicates a liquid surface that is smooth on the scale of the observed VIMS signal at 5 µm