Publications

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    Circulation 09/2014; 130(12):1014-27. · 15.20 Impact Factor
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    ABSTRACT: This study seeks to determine the risks for obstructive sleep apnea (OSA) and cardiometabolic disease (CMR) in elderly patients with mild-moderate abdominal aortic aneurysms (AAA).
    09/2014;
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    ABSTRACT: Current research is inconclusive as to whether obstructive sleep apnea severity directly limits exercise capacity and lowers health-related quality of life (HRQoL). The aim of this study was to evaluate the association of obstructive sleep apnea severity with determinants of exercise capacity and HRQoL. Subjects were evaluated by home somnography and classified as no obstructive sleep apnea (n = 43) or as having mild (n = 27), moderate or severe obstructive sleep apnea (n = 21). Exercise capacity was assessed by a ramping cycle ergometer test, and HRQoL was assessed with the SF-36 questionnaire. Greater obstructive sleep apnea severity was associated with older age, higher body weight, higher body mass index, lower peak aerobic capacity, a higher percentage of peak aerobic capacity at a submaximal exercise intensity of 55 watts, and lower physical component summary score from the SF-36. None of these variables were statistically different among obstructive sleep apnea severity groups after controlling for age and body weight. Obstructive sleep apnea severity was not associated with any cardiorespiratory fitness or HRQoL parameter. Obstructive sleep apnea severity has no independent association with exercise capacity or HRQoL.
    North American journal of medical sciences. 06/2013; 5(6):362-6.
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    ABSTRACT: PURPOSE: Obstructive sleep apnea (OSA) increases the risk for insulin resistance (IR). The mechanisms that link the two are not clear and are frequently confounded by obesity. OSA is associated with alterations in adipose-derived hormones (adipokines) that increase IR; however, previous studies have focused on middle-aged and older adults. The objective of this study was to determine if IR and alterations in adipokines exist in young men with OSA, independent of obesity. METHODS: Subjects were assigned into the following groups based on body mass index and presence of OSA: obese with OSA (OSA, n = 12), obese without OSA (NOSA, n = 18), and normal weight without OSA (CON, n = 15). Fasting blood was obtained for batch analysis of biomarkers of IR. The homeostasis model assessment (HOMA) method was used to assess IR. RESULTS: HOMA and leptin were higher in the OSA group than the CON group. There were no differences in insulin, tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) between the OSA and NOSA groups. Adiponectin was lower in the OSA group vs. NOSA and CON; however, when controlled for central abdominal fat (CAF), the difference was nullified. When controlled for total body adiposity, however, CAF was 24 % higher in the subjects with OSA vs. subjects without OSA. CONCLUSIONS: These findings suggest that excess CAF in young men with OSA may contribute to risk for type 2 diabetes indirectly by a degree that would otherwise not be reached through obesity, although further research is needed.
    Sleep And Breathing 03/2013; 17(1):403-409. · 2.26 Impact Factor
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    ABSTRACT: Abstract Prediction of osteoporotic fractures is currently an imperfect science and new tools are desperately needed to identify at-risk patients at an earlier stage in the disease process. The mechanical response tissue analyser (MRTA) is a novel, non-invasive, radiation-free device that measures the bending stiffness of long bones in vivo, an indicator of a bone's ability to resist deformation under a given load and a strong predictor of long bone structural integrity and strength. Bone bending stiffness measured with the MRTA has been consistently shown to be a stronger predictor of post-mortem and ex vivo bone breaking strength compared to bone mineral measured with dual-energy X-ray absorptiometry. Bone bending stiffness measured with MRTA also decreases with advanced age and disease states and increases with chronic physical activity, independent of bone mineral changes. The MRTA measures different parameters than DXA (bone quality vs bone mineral content and density) and may be a more robust tool for identifying those at risk for fracture. Research initiatives focused on improving long-term repeatability and optimizing the signal-to-noise ratio of the measurement are currently underway to further advance the clinical usefulness of this technology.
    Journal of Medical Engineering & Technology 01/2013; 37(2):144-9.
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    ABSTRACT: The aim of this study was to compare and determine the repeatability of foreleg and forearm muscle and fat indices evaluated by the peripheral quantitative computed tomography (pQCT). Effects of habitual physical activity and associated health risk of type 2 diabetes were examined within the interrelations of intermuscular adipose tissue (IMAT) and muscle density. Eighty-two premenopausal women (mean age ± standard deviation: 38.6 ± 4.7 yr) underwent dual-energy X-ray absorptiometry scans and pQCT of foreleg and forearm scans to assess muscle and fat parameters. Physical activity status was based on 4-d self-reported log and pedometer step counts. Fat and muscle distribution between the foreleg and forearm were similar and highly correlated to total body adiposity. The pQCT device reliably measured muscle density in the foreleg and forearm; coefficients of variation were 0.8% and 2.1%, which was therefore used to reflect IMAT status. Muscle density was positively related to physical activity and negatively associated with markers of fat distribution and risk for type 2 diabetes. The pQCT is a novel, noninvasive tool to assess IMAT and muscle density in the foreleg and forearm. Additional research is necessary to understand the biology of IMAT and its relations with physical activity and potentially, with risks for cardiometabolic disease.
    Journal of Clinical Densitometry 04/2012; 15(3):355-61. · 1.71 Impact Factor
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    ABSTRACT: Endothelial dysfunction has an important role in genesis of atherosclerosis and is depicted by a series of inflammatory and endothelial biomarkers. Shear stress arising from repeated episodes of increased blood flow with physical activity (PA) is a possible mechanism that improves vascular endothelial function. Our purpose was to examine whether inflammatory markers mediate the association between PA and endothelial function. Subjects were young, healthy men recruited according to recreational PA habits: highactive (n=21) vs. sedentary (n=17). Active subjects reported >45 min/day of moderate-vigorous physical activities, >4 days/week over 6 months, while sedentary subjects reported no recreational physical activity. Fasting serum samples were analyzed for C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). Endothelial function was determined using flow-mediated dilation of the brachial artery induced by post ischemic reactive hyperemia. Hyperemia response was greater in the high-active than in sedentary men (30.2±8.2 vs. 24.3±5.2 mL/min/100mL; P<0.001). There were no differences between the groups with respect to CRP, TNF-α, or IL-6. Concentrations of these inflammatory biomarkers were unrelated to reactive hyperemia differences attributable to PA. Improved hyperemic response seen in young physically active subjects may be influenced by factors beyond the inflammatory factors, e.g., enhanced nitric oxide production. Physical activity was associated with an increased vascular function in young adults, although a diminished inflammatory state was no revealed. Additional research is needed to clarify the role of PA on cytokine indicators of inflammation and how this relates to endothelial function.
    Journal of Human Sport and Exercise 04/2012; 7(2):581.
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    Obesity Surgery 09/2010; · 3.10 Impact Factor
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    ABSTRACT: Bariatric surgery is a common procedure often used to ameliorate comorbidities associated with obesity, including type 2 diabetes. Substantial weight loss leads to alterations in inflammation and insulin sensitivity as well as numerous metabolic and physiologic pathways. Several inflammatory markers have been evaluated, yet adiponectin, an anti-inflammatory adipokine, has not been fully investigated. Adiponectin may play a key role as a mediator between obesity and inflammation, as lower blood levels are more commonly associated with obesity and type 2 diabetes and because adiponectin lessens insulin resistance. This review evaluates outcome variables from patients who underwent Roux-en-Y gastric bypass (RYGB) or restrictive bariatric surgery to compare and contrast any differential surgical impacts on weight loss, adiponectin, and insulin. A systematic literature review was conducted using a PubMed search. Published studies from 1999 to 2009 that measured blood levels of adiponectin and insulin in bariatric surgery patients prior to and at least 6 months after surgery were included. Eighteen studies met inclusion criteria for evaluation. RYGB surgery compared to restrictive surgery led to significantly greater weight loss and improvements in adiponectin and insulin sensitivity. Despite significant weight loss, many patients did not achieve "healthy" body mass index or normalization of inflammatory markers. While RYGB surgery appears to more favorably influence body weight and inflammatory markers, data are insufficient to fully understand the impact of bariatric surgery on changes in adiponectin and insulin and related health implications. Long-term research is needed to more thoroughly evaluate inflammatory outcomes following these two bariatric surgery procedures.
    Obesity Surgery 02/2010; 20(5):559-68. · 3.10 Impact Factor
  • Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2010; 42:724-725.
  • Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2010; 42.
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    ABSTRACT: Obstructive sleep apnea (OSA) is characterized by a repetitive collapse of the upper airway during sleep and may affect as many as 1 in 5 adults. Although OSA appears to increase risk for metabolic syndrome in middle-aged adults, no data currently exist in a younger, preclinical cohort. Forty-five sedentary young men: 12 overweight with OSA (OSA), 18 overweight without OSA (NOSA), and 15 normal-weight without OSA (CON). Respiratory distress index (RDI) was determined using an at-home, unsupervised, portable polygraphy device. Total and subcutaneous abdominal fat (SAF) were quantified using dual-energy X-ray absorptiometry (DXA). Blood pressure was obtained manually via auscultation. Fasting triglycerides, glucose, and high-density lipoprotein cholesterol (HDL-C) concentrations were analyzed from whole blood using a commercial lipid profile kit. The OSA group had 25% more SAF than the NOSA group (P < 0.05) and higher triglycerides (136.7 +/- 21.3 mg/dL versus 92.2 +/- 7.5, P < 0.05). RDI was directly related to fasting triglycerides (R = 0.32, P < 0.05) after controlling for SAF. The number of metabolic syndrome components was directly correlated to indices of adiposity, but not RDI. Using multiple linear regression analysis, triglycerides were the only independent predictor of RDI. Results from this study demonstrate that unique physiologic and anthropometric abnormalities exist in young men with occult OSA, beyond those that are seen in uncomplicated obesity. These findings may indicate early pathogenesis of metabolic syndrome in these young men.
    Metabolic syndrome and related disorders 11/2009; 8(1):33-8.
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    ABSTRACT: Dairy calcium may help prevent excess weight gain and obesity when consumed in adequate amounts (three or more servings per day) and combined with energy balance. This prospective cohort study was conducted to evaluate dairy intake and examine the association between low-fat dairy intake and body weight and composition changes in college students. Seventy-six college students (65 women and 11 men; mean age+/-standard error [SE]=19.2+/-0.2 years) completed 7-day food records, body height (cm), weight (kg), and waist circumference (cm) measurements twice (September 2004 and April 2005). Percentage of truncal fat and percentage of total body fat were measured by dual-energy x-ray absorptiometry. One-way multivariate analysis of covariance was conducted. Overall (mean+/-SE) total dairy (1.4+/-0.1 servings/day), low-fat dairy (0.5+/-0.1 servings/day), and calcium (815+/-41 mg/day) intakes were low. Subjects who consumed a higher amount of low-fat dairy products (mean+/-SE=0.8+/-0.1 servings/day) had better diet quality, gained less body weight, and had reductions in waist circumference, percentage truncal fat, and percentage total body fat compared to those with lower intake (mean+/-SE=0.1+/-0.0 servings/day). Low-fat dairy intake may be associated with better diet quality and weight management in college students. Nutrition interventions in young adults should promote low-fat dairy intake as part of an overall healthful lifestyle.
    Journal of the American Dietetic Association 09/2009; 109(8):1433-8. · 3.80 Impact Factor
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    ABSTRACT: This study assessed the influence of age on the predictors of bone mineral in men. Middle-age (n = 41, 54 +/- 4 yrs) and older (n = 40, 69 +/- 5 yrs) men underwent grip and knee extensor strength tests, total body dual-energy X-ray absorptiometry with regional analyses and a graded exercise treadmill test. Bone-free lean mass (BFLM) and, to a lesser extent, fat mass (FM) were correlated with bone mineral variables in middle-age men. In older men, BFLM and, to a lesser extent, FM were related to bone mineral content (BMC) at most sites, but inconsistently to bone mineral density (BMD). Knee extensor strength related to bone mineral (BMC and BMD) at most sites in middle-age men, but none in older men. Grip strength inconsistently related to bone mineral in both groups. Aerobic capacity related to bone mineral in middle-age men, but none in older men. In multiple regression, body weight or BFLM predicted bone mineral in middle-age men (R2 = 0.33-0.68) and BMC in older men (R2 = 0.33-0.50). Predictors of BMD were inconsistent in older men. Relationships of body composition, muscular strength and aerobic capacity to bone mineral are stronger in middle-age versus older men.
    The Aging Male 07/2009; 12(2-3):47-53. · 1.71 Impact Factor
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    ABSTRACT: Bone mineral content (BMC) and bone mineral density (BMD) are common but imperfect surrogate measures of bone strength. The mechanical response tissue analyzer is a device that measures long bone bending stiffness (EI), which strongly predicts bone breaking strength. We hypothesized that isokinetic resistance training of the knee flexor and extensor muscles would increase tibial EI, BMC, and BMD in young women. Fifty-two women, aged 18-26 years, performed concentric (CON, n = 30) or eccentric (ECC, n = 22) isokinetic resistance training with the nondominant leg three times per week for 20 weeks. Before and after the training period, subjects were tested for CON and ECC peak torque of the knee flexor and extensor muscles with isokinetic dynamometry, tibial BMC and BMD using dual-energy X-ray absorptiometry, and tibial EI using mechanical response tissue analysis. Both training groups increased CON (15-21%) and ECC (17-31%) peak torque vs. the untrained leg. Tibial EI increased in the entire cohort (26%) and in each training group (CON 34%, ECC 16%) vs. the untrained tibia. Tibial BMC and BMD increased in the trained and untrained tibiae, with no significant differences between limbs. No differential tibial EI or bone mineral outcomes were observed between the CON and ECC training groups. In summary, CON and ECC isokinetic resistance training increased tibial EI, but not BMC or BMD, in young women.
    Calcified Tissue International 06/2009; 84(6):446-52. · 2.50 Impact Factor
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    ABSTRACT: Obstructive sleep apnea (OSA) is a disorder characterized by repetitive obstructions of the upper airway. Individuals with OSA experience intermittent hypoxia, hypercapnia, and arousals during sleep, resulting in increased sympathetic activation. Chemoreflex activation, arising from the resultant oscillatory disturbances in blood gases from OSA, exerts control over ventilation, and may induce increases in sympathetic vasoconstriction, contributing to increased long-term risks for hypertension (HTN) and cardiovascular disease (CVD). To evaluate whether OSA elicits exaggerated ventilatory responses to exercise in young men, 14 overweight men with OSA and 16 overweight men without OSA performed maximal ramping cycle ergometer exercise tests. Oxygen consumption (VO(2)), ventilation, (V(E)), ventilatory equivalents for oxygen (V(E)/VO(2)) and carbon dioxide (V(E)/VCO(2)), and V(E)/VCO(2) slope were measured. The VO(2) response to exercise did not differ between groups. The V(E), V(E)/VCO(2), V(E)/VO(2) were higher (p< 0.05, 0.002, and p<0.02, respectively) in the OSA group across all workloads. The V(E)/VCO(2) slope was greater in the OSA group (p<0.05). The V(E)/VCO(2) slope and AHI were significantly correlated (r=0.56, p<0.03). Thus, young, overweight men with OSA exhibit increased ventilatory responses to exercise when compared to overweight controls. This may reflect alterations in chemoreflex sensitivity, and contribute to increased sympathetic drive and HTN risk.
    Respiratory medicine 02/2009; 103(7):1063-9. · 2.33 Impact Factor
  • Laura J. Newsome, Adrian Aron, William G. Herbert
    Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41:329-330.
  • Katrina L. Butner, Kyle W. Creamer, William G. Herbert
    Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41.
  • Adrian Aron, William G. Herbert
    Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41:226-227.
  • Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41.

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