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AIM - To evaluate the relationship of abdominal muscle lean tissue and adipose tissue volumes with prediabetes and diabetes.
RESEARCH DESIGN AND METHODS - We measured abdominal muscle composition in 3170 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study who underwent computed tomography (CT) at Year 25 of follow-up (ages, 43-55 years). Multinomial regression analysis was used to evaluate the associations of CT-measured intermuscular adipose tissue (IMAT), lean muscle tissue (lean) and visceral adipose tissue (VAT) volumes with diabetes at any point during the CARDIA study, newly detected prediabetes, prior history of prediabetes, and normal glucose tolerance. Models were adjusted for potential confounding factors: age, sex, race, height, smoking status, hypertension, hyperlipidaemia, cardiorespiratory fitness and study centre.
RESULTS - Higher IMAT, lean and VAT volumes were all separately associated with a higher prevalence of prediabetes and diabetes. Inclusion of VAT volume in models with both IMAT volume and lean volume attenuated the association of IMAT with both prediabetes and diabetes, but higher lean volume retained its association with prediabetes and diabetes. Individuals in the highest IMAT quartile, coupled with VAT in its lower three quartiles, had a higher prevalence of diabetes, but not of prediabetes, than those with both IMAT and VAT in their respective lower three quartiles. Adjusting for cardiorespiratory fitness did not substantially change the findings.
CONCLUSION - Higher IMAT volume was associated with a higher prevalence of diabetes even after adjustment for VAT volume. However, further study is warranted to understand the complicated relationship between abdominal muscle and adipose tissues.
© 2018 John Wiley & Sons Ltd.
IMPORTANCE - Although cardiorespiratory fitness (CRF) is prognostic in older adults, the effect of CRF during early adulthood on long-term cardiovascular structure, function, and prognosis is less clear.
OBJECTIVE - To examine whether CRF in young adults is associated with long-term clinical outcome and subclinical cardiovascular disease (CVD).
DESIGN, SETTING, AND PARTICIPANTS - Prospective study of 4872 US adults aged 18 to 30 years who underwent treadmill exercise testing at a baseline study visit from March 25, 1985, to June 7, 1986, and 2472 individuals who underwent a second treadmill test 7 years later. Median follow-up was 26.9 years, with assessment of obesity, left ventricular mass and strain, coronary artery calcification (CAC), and vital status and incident CVD. Follow-up was complete on August 31, 2011, and data were analyzed from recruitment through the end of follow-up.
MAIN OUTCOMES AND MEASURES - The presence of CAC was assessed by computed tomography at years 15 (2000-2001), 20 (2005-2006), and 25 (2010-2011), and left ventricular mass was assessed at years 5 (1990-1991) and 25 (with global longitudinal strain). Incident CVD and all-cause mortality were adjudicated.
RESULTS - Of the 4872 individuals, 273 (5.6%) died and 193 (4.0%) experienced CVD events during follow-up. After comprehensive adjustment, each additional minute of baseline exercise test duration was associated with a 15% lower hazard of death (hazard ratio [HR], 0.85; 95% CI, 0.80-0.91; P < .001) and a 12% lower hazard of CVD (HR, 0.88; 95% CI, 0.81-0.96; P = .002). Higher levels of baseline CRF were associated with significantly lower left ventricular mass index (β = -0.24; 95% CI, -0.45 to -0.03; P = .02) and significantly better lobal longitudinal strain (β = -0.09; 95% CI, -0.14 to -0.05; P < .001) at year 25. Fitness was not associated with CAC. A 1-minute reduction in fitness by year 7 was associated with 21% and 20% increased hazards of death (HR, 1.21; 95% CI, 1.07-1.37; P = .002) and CVD (HR, 1.20; 95% CI, 1.06-1.37; P = .006), respectively, along with a more impaired strain (β = 0.15; 95% CI, 0.08-0.23; P < .001). No association between change in fitness and CAC was found.
CONCLUSIONS AND RELEVANCE - Higher levels of fitness at baseline and improvement in fitness early in adulthood are favorably associated with lower risks for CVD and mortality. Fitness and changes in fitness are associated with myocardial hypertrophy and dysfunction but not CAC. Regular efforts to ascertain and improve CRF in young adulthood may play a critical role in promoting cardiovascular health and interrupting early CVD pathogenesis.
Despite the important contribution increasing physical activity levels may play in reducing chronic disease morbidity and mortality, there is a paucity of interventions and research indicating how to improve physical activity levels in African American men. Men on the Move was a pilot study to increase African American men's levels of physical activity by improving access to age and ability-appropriate, male-focused physical activity opportunities and facilitating access to social support from male peers. Forty-one African American men ages 35 to 70 enrolled (mean age = 53.8). Groups of 5 to 10 men met once a week with a certified personal trainer for 10 weeks. Each meeting addressed barriers to physical activity, provided men with community resources, and incorporated activities that promoted flexibility, strength, balance, and conditioning. Improvements (p < .05) were detected for the following outcome measures: perceived self-efficacy to sustain physical activity, endurance, overall health status, and stress level. Physiological and fitness outcome measures improved, although not to significant levels. Whereas 40% of the men met the recommendation of 150 minutes of moderate or vigorous physical activity weekly at baseline, 68% of the men met this recommendation by the end of the project. These positive results attest to the feasibility of successfully engaging middle-aged and older African American men in a physical activity intervention, and our findings demonstrate the initial efficacy of this intervention approach. More research is needed that includes a more intensive intervention and one that helps motivate men to be physically active outside of the structured, small-group sessions.
Acute exercise results in transient change in redox balance. High concentrations of reactive oxygen species (ROS) can lead to oxidative damage to macromolecules. However, moderate periodic increases in ROS, such as experienced with habitual exercise, may activate signal transduction pathways which stimulate increases in endogenous antioxidant systems. This study tested the hypothesis that physically fit older adults would have less oxidative stress than unfit age-matched controls, due to greater circulating concentrations of non-enzymatic antioxidants and greater capacity to upregulate antioxidant enzymes. We compared 37 fit (mean age 65.2 ± 5 years) and 35 unfit (mean age 67.7 ± 4 years) men and women. Fitness status was classified by VO(2 max) and maximal leg power. Basal levels of oxidative stress were assessed by measuring urinary markers of nucleic acid damage and lipid peroxidation. Antioxidant status was assessed by measuring total antioxidant power and ratios of reduced to oxidized glutathione in plasma, at rest. The capacity to counteract an oxidative insult was assessed by measuring changes in plasma F(2)-isoprostanes in response to forearm ischemia-reperfusion. The fit individuals had significantly lower levels of urinary markers of oxidative damage (all P <0.05) and lower F(2)-isoprostane response to the oxidative challenge (P < 0.05), but there were no group differences in antioxidant status. The lower levels of oxidative stress in the fit individuals were not mediated by known effects of exercise training such as adiposity, HDL concentrations, or small molecular weight antioxidants. These data suggest that reduced oxidative stress associated with physical fitness results from differences in activity of antioxidant enzymes.
PURPOSES - To characterize the total hemoglobin concentration ([THb]) and oxyhemoglobin saturation (%HbO2) time courses after brief dorsiflexion maximal voluntary contractions (MVC) and to determine whether these responses varied by gender.
METHODS - Eighteen healthy, moderately physically active subjects (nine male) lay supine and performed two or more 3-s dorsiflexion MVC. [THb] and %HbO2 were measured continuously in the tibialis anterior muscle using near-infrared spectroscopy (NIRS). The data from 0 to 150 s postcontraction were analyzed using single- and multicomponent exponential models.
RESULTS - The mean (standard error) precontraction [THb] and %HbO2 values were 78.5 (7.3) microM and 65.0 (0.8) %, respectively, and decreased during the contraction. After the contraction, [THb] grew exponentially, characterized by amplitude (A), 8.7 (1.3) microM; time delay (TD), 0.2 (0.2) s, and time constant (tau), 5.9 (0.6) s. Fifteen subjects had a secondary decay phase characterized by A, 1.9 (0.7) microM; TD, 59.2 (6.4) s; and tau, 12.4 (2.3) s. Eight subjects experienced an initial decay in %HbO2, characterized by A, 1.8 (0.8) %; TD, 0.0 (0) s; and tau, 4.2 (0.3) s. Then, %HbO2 grew exponentially, being characterized by A, 7.9 (0.9) %; TD, 10.1 (1.0) s; and tau, 9.7 (2.0) s. Finally, in 16 subjects, there was a secondary decay phase, characterized by A, 2.6 (0.4) %; TD, 54.4 (7.5) s; and tau, 18.9 (2.6) s. There were no gender differences in any kinetic parameter.
CONCLUSIONS - There are three phases to the post-MVC oxygen supply-demand coupling: 1) rising oxygen demand relative to supply; 2) rising oxygen supply relative to demand; and 3) restoration of precontraction oxygen supply-demand matching. These processes are unaffected by gender.
OBJECTIVE - To investigate differences in associations between physical activity and overweight for students in two adjacent areas on the border between Mexico and the United States of America: students in the city of Matamoros, Mexico, and Mexican-American students in the Lower Rio Grande Valley (LRGV) area of southern Texas. Since the extremely high prevalence of overweight among Mexican-American adolescents is well-recognized, we wanted to determine whether overweight has become a problem among Mexican adolescents as well.
METHODS - Students from 6 schools (n = 653), representing 11% of the ninth-grade students in Matamoros during 2002-2003, and students from 13 high schools (n = 4,736), representing 22% of the ninth-grade students in the LRGV during 2000-2001, completed questionnaires. Polytomous logistic regression was performed to estimate the risk of being at risk for overweight (> or = 85th percentile to < 95th percentile of body mass index (BMI) for age and sex) and the risk of being overweight (> or = 95th percentile of BMI-for-age and sex) versus normal weight that were associated with measures of physical activity. For simplicity, the classification of normal weight also included underweight.
RESULTS - A higher percentage of adolescents in the LRGV were at risk of overweight (17%) in comparison with adolescents from Matamoros (15%). The percentages of LRGV and Matamoros adolescents who were overweight were identical (17%). LRGV adolescent boys (OR = 0.87, 95% CI = 0.77-0.98) who participated in team sports were less likely to be at or above the 85th percentile of BMI-for-age and sex. Although of borderline significance, Matamoros and LRGV adolescent boys who participated in physical education classes were less likely to be at risk for overweight. Among neither the Matamoros students nor the LRGV students were any of the various other physical activity categories or levels associated with being at risk for overweight or being overweight.
CONCLUSIONS - Nearly one-third of the students in both Matamoros and the LRGV are at risk for overweight or are overweight. Implementation of interventions on healthful dietary choices and participation in physical education classes and sports teams are essential for reducing the extremely high prevalence of overweight among students on both sides of the Texas/Mexico border.
STUDY DESIGN - Longitudinal.
OBJECTIVES - The purpose of this study was to evaluate the effect of lower extremity resistance training on quadriceps fatigability, femoral artery diameter, and femoral artery blood flow.
SETTING - Academic Institution.
METHODS - Five male chronic spinal cord injury (SCI) individuals (American Spinal Injury Association (ASIA): A complete; C5-T10; 36+/-5 years old) completed 18 weeks of home-based neuromuscular electrical stimulation (NMES) resistance training. Subjects trained the quadriceps muscle group twice a week with four sets of 10 dynamic knee extensions against resistance while in a seated position. All measurements were made before training and after 8, 12, and 18 weeks of training. Ultrasound was used to measure femoral artery diameter and blood flow. Blood flow was measured before and after 5 and 10 min of distal cuff occlusion, and during a 4-min isometric electrical stimulation fatigue protocol.
RESULTS - Training resulted in significant increases in weight lifted and muscle mass, as well as a 60% reduction in muscle fatigue (P = 0.001). However, femoral arterial diameter did not increase. The range was 0.44+/-0.03 to 0.46+/-0.05 cm over the four time points (P = 0.70). Resting, reactive hyperemic, and exercise blood flow did not appear to change with training.
CONCLUSION - NMES resistance training improved muscle size and fatigue despite an absence of response in the supplying vasculature. These results suggest that the decreases in arterial caliber and blood flow seen with SCI are not tightly linked to muscle mass and fatigue resistance. In addition, muscle fatigue in SCI patients can be improved without increases in arterial diameter or blood flow capacity.
Legumes may protect against myocardial infarction (MI). The objective of this study was to determine whether consumption of dried mature beans (referred to as beans), the main legume in Latin America, is associated with MI. The cases (n = 2119) were survivors of a first acute MI and were matched by age, sex, and area of residence to randomly selected population controls (n = 2119) in Costa Rica. Dietary intake was assessed with a validated FFQ. Of the population, 69% consumed > or = 1 serving of beans/d (1 serving = one-third cup of cooked beans, approximately 86 g). Consumption of > or = 1 serving/d was significantly higher (P < 0.001) in rural (81%) than in urban (65%) areas. Individuals who never eat dried beans or whose consumption was < 1 time/mo were classified as nonconsumers. Compared with nonconsumers, intake of 1 serving of beans/d was inversely associated with MI in analyses adjusted for smoking, history of diabetes, history of hypertension, abdominal obesity, physical activity, income, intake of alcohol, total energy, saturated fat, trans fat, polyunsaturated fat, and cholesterol [odds ratio (OR) = 0.62; 95% CI: 0.45-0.88]. No further protection was observed with increased number of servings/d (OR = 0.73; 95% CI: 0.52-1.03 for > 1 serving/d). In summary, we found that consumption of 1 serving of beans/d is associated with a 38% lower risk of MI. No additional protection was observed at intakes > 1 serving/d. These findings are timely given the trend toward increased obesity, cardiovascular disease, and a reduction in the intake of beans in Latin American countries.