Janet P. Wallace

A Family Approach to Cardiovascular Risk Reduction: Results from The San Diego Family Health Project:

The effectiveness of a family-based cardiovascular disease risk reduction intervention was evaluated in two ethnic groups. Participants were 206 healthy, volunteer low-to-middle-income Mexican-American and non-Hispanic white (Anglo-American) families (623 individuals), each with a fifth or a sixth-grade child. Families were recruited through elementary schools. Half of the families were randomized to a year-long educational intervention designed to decrease the whole familys intake of high salt, high fat foods, and to increase their regular physical activity. Eighty-nine percent of the enrolled families were measured at the 24-month follow-up. Both Mexican- and Anglo-American families in the experimental groups gained significantly more knowledge of the skills required to change dietary and exercise habits than did those in the control groups. Experimental families in both ethnic groups reported improved eating habits on a food frequency index. Anglo families reported lower total fat and sodium intake. There were no significant group differences in reported physical activity or in tested cardiovascular fitness levels. Significant differences for Anglo-American experimental vs. control adult subjects were found for LDL cholesterol. Significant intervention-control differences ranging from 2.2 to 3.4 mmHg systolic and/or diastolic blood pressure were found in all subgroups. Direct observation of diet and physical activity behaviors in a structured environment suggested generalization of behavior changes. There was evidence that behavior change persisted one year beyond the completion of the intervention program. It is concluded that involvement of families utilizing school based resources is feasible and effective. Future studies should focus on the most cost-effective methods of family involvement, and the potential for additive effects when family strategies are combined with other school health education programs.

Effects of diet and exercise interventions on control and quality of life in non-insulin-dependent diabetes mellitus

Evidence suggests that diet and exercise are associated with improved glucose tolerance for patients with non-insulin-dependent diabetes mellitus (NIDDM). Seventy-six volunteer adult patients with NIDDM were each assigned to one of four programs: 1) diet, 2) exercise, 3) diet plus exercise, or 4) education (control). Each program required ten weekly meetings. Detailed evaluations were completed prior to the program and after three, six, 12, and 18 months. Evaluations included various psychosocial measures, measures of the quality of life, and fasting blood glucose, glycosylated hemoglobin, and relative weight determinations. Of the 76 original participants, 70 completed the 18-month follow-up study. At 18 months, the combination diet-and-exercise group had achieved the greatest reductions in glycosylated hemoglobin measures. In addition, this group showed significant improvements on a general quality of life measure. These improvements were largely uncorrelated with changes in weight. The authors conclude that the combination of dietary change and physical conditioning benefits NIDDM patients, and that the benefits may be independent of substantial weight loss.

Dietary fat, sugar, and fiber predict body fat content

OBJECTIVE This study was conducted to determine the relationships among the specific components of dietary fat and carbohydrate and body fatness in lean and obese adults. DESIGN Body composition determination was performed on each subject by hydrostatic weighing at residual volume. Subsequently, the individual components of dietary fat and carbohydrate were examined relative to body fatness using a 3-day food diary and a food frequency questionnaire. SUBJECTS Subjects were 23 lean (11.1 +/- 2.9% body fat) men, 23 obese (29.2 +/- 3.8% body fat) men, 17 lean (16.7 +/- 3.3% body fat) women, and 15 obese (42.7 +/- 3.9% body fat) women who volunteered for free diet and body composition analyses. Inclusion criteria were 15% body fat for lean men, 25% for obese men, 20% for lean women, and 35% for obese women. STATISTICAL ANALYSIS PERFORMED Group comparisons for dietary variables were made with a multivariate analysis of variance. RESULTS No differences were found between lean and obese subjects for energy intake or total sugar intake, but obese subjects derived a greater portion of their energy from fat (33.1 +/- 2.6% and 36.3 +/- 2.3% for obese men and women, respectively, vs 29.1 +/- 1.3% and 29.6 +/- 2.0%, lean men and women, respectively). Percent of fat intake for saturated, monounsaturated, and polyunsaturated fats was not different among groups. Obese subjects derived a greater percentage of their sugar intake from added sugars than lean subjects (38.0 +/- 3.5% vs 25.2 +/- 2.0%, respectively, for men; 47.9 +/- 8.0% vs 31.4 +/- 3.4%, respectively, for women). Dietary fiber was lower for obese men (20.9 +/- 1.8 g) and women (15.7 +/- 1.1 g) than for lean men (27.0 +/- 1.8 g) and women (22.7 +/- 2.1 g). APPLICATIONS/CONCLUSIONS Obesity is maintained primarily by a diet that is high in fat and added sugar and relatively low in fiber. Alterations in diet composition rather than energy intake may be a weight control strategy for overweight adults.

Health‐related fitness and physical activity in patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has been referred to as the hepatic manifestation of the metabolic syndrome. There is a lower prevalence of metabolic syndrome in individuals with higher health‐related fitness (HRF) and physical activity (PA) participation. The relationship between NAFLD severity and HRF or PA is unknown. Our aim was to compare measures of HRF and PA in patients with a histological spectrum of NAFLD severity. Thirty‐seven patients with liver biopsy–confirmed NAFLD (18 women/19 men; age = 45.9 ± 12.7 years) completed assessment of cardiorespiratory fitness (CRF, VO2peak), muscle strength (quadriceps peak torque), body composition (%fat), and PA (current and historical questionnaire). Liver histology was used to classify severity by steatosis (mild, moderate, severe), fibrosis stage (stage 1 versus stage 2/3), necroinflammatory activity (NAFLD Activity Score; ≤4 NAS1 versus ≥5 NAS2) and diagnosis of NASH by Brunt criteria (NASH versus NotNASH). Analysis of variance and independent t tests were used to determine the differences among groups. Fewer than 20% of patients met recommended guidelines for PA, and 97.3% were classified at increased risk of morbidity and mortality by %fat. No differences were detected in VO2peak (x = 26.8 ± 7.4 mL/g/min) or %fat (x = 38.6 ± 8.2%) among the steatosis or fibrosis groups. Peak VO2 was significantly higher in NAS1 versus NAS2 (30.4 ± 8.2 versus 24.4 ± 5.7 mL/kg/min, P = 0.013) and NotNASH versus NASH (34.0 ± 9.5 versus 25.1 ± 5.7 mL/kg/min, P = 0.048). Conclusion: Patients with NAFLD of differing histological severity have suboptimal HRF. Lifestyle interventions to improve HRF and PA may be beneficial in reducing the associated risk factors and preventing progression of NAFLD. (HEPATOLOGY 2008.)

Exercise in Hypertension A Clinical Review

The current exercise prescription for the treatment of hypertension is: cardiovascular mode, for 20–60 minutes, 3–5 days per week, at 40–70% of maximum oxygen uptake (V̇O2max). Cardiovascular exercise training is the most effective mode of exercise in the prevention and treatment of hypertension. Resistance exercise is not the preferred mode of exercise treatment, but can be incorporated into an exercise regime provided the diastolic blood pressure response is within safe limits. It is inconclusive whether durations longer than 30 minutes produce significantly greater reductions in blood pressure. A frequency of three exercise sessions per week has been considered to be the minimal frequency for blood pressure reduction. Higher frequencies tended to produce greater reductions, although not significantly different. Evidence still exists that high intensity exercise (>75% V̇O2max) may not be as effective as low intensity exercise (<70% V̇O2max) in reducing elevated blood pressures. Exercise can be effective without a change in bodyweight or body fat. Bodyweight or body fat loss and anti-hypertensive medications do not have an added effect on blood pressure reduction associated with exercise. β-blockade is not the recommended anti-hypertensive medication for effective exercise performance in non-cardiac patients. Not all hypertensive patients respond to exercise treatment. Differences in genetics and pathophysiology may be responsible for the inability of some hypertensive patients to respond to exercise. Ambulatory technology may allow advances in individualising a more effective exercise prescription for low-responders and non-responders.

Predicting max HR and the HR-VO2 relationship for exercise prescription in obesity.

This research derived regression equations for predicting maximal heart rate (MHR) and examined the relationship between relative oxygen consumption (VO2) and heart rate (HR) in obese (N = 86, body fat > 30%, hydrostatic weighing) compared with normal-weight (N = 51, body fat < or = 30%) adults. Simultaneous measurements of HR and VO2 were recorded at rest and every minute during a maximal graded exercise test. When MHR was regressed on age, two distinct equations for the obese and normalweights were generated. The relationship between %MHR and %max VO2 was similar between groups (r = 0.83, obese; r = 0.87 normalweights). Likewise, when %max VO2 was regressed on %max heart rate range similar equations were derived fro the obese (r = 0.81) and normalweights (r = 0.84). Correlation between Karvonens predicted HR at a submaximal VO2 and the true HR at that VO2 was 0.88, regardless of adiposity. These data indicate that when predicting MHR in normalweights the equation 220-Age can be used, but for obese individuals the equation 200-0.5 x Age is more accurate; each having 12 as a standard error of estimate. Once MHR is determined, either the straight percentage technique or Karvonens method would be appropriate for prescribing exercise intensity for both populations.

The Flow-mediated Dilation Response to Acute Exercise in Overweight Active and Inactive Men

Objective: Inflammation has been found to play a role in the etiology of cardiovascular disease as well as provoke endothelial dysfunction. Inflammatory cytokines associated with endothelial function are interleukin‐6 (IL‐6) and tumor necrosis factor‐α (TNF‐α). IL‐6 is exercise intensity dependent and has been shown to inhibit TNF‐α expression directly. The aim of this study was to investigate the interaction of IL‐6 and TNF‐α on endothelial function in response to acute exercise in overweight men exhibiting different physical activity profiles.

Mechanotransduction of shear in the endothelium: basic studies and clinical implications.

The endothelium plays an integral role in the development and progression of atherosclerosis. Hemodynamic forces, particularly shear stress, have a powerful influence on endothelial phenotype and function; however, there is no clear consensus on how endothelial cells sense shear. Nevertheless, multiple endothelial cell signal transduction pathways are activated when exposed to shear stress in vitro. The type of shear, laminar or oscillatory, impacts which signal transduction pathways are initiated as well as which subsequent genes are up- or down-regulated, thereby influencing endothelial phenotype and function. Recently, human studies have examined the impact of shear stress and different shear patterns at rest and during exercise on endothelial function. Current evidence supports the theory that augmented exercise-induced shear stress contributes to improved endothelial function following acute exercise and exercise training, whereas retrograde shear initiates vascular dysfunction. The purpose of this review is to examine the current theories on how endothelial cells sense shear stress, to provide an overview on shear stress-induced signal transduction pathways and subsequent gene expression, and to review the current literature pertaining to shear stress and shear patterns at rest as well as during exercise in humans and the related effects on endothelial function.

Normalization of flow-mediated dilation to shear stress area under the curve eliminates the impact of variable hyperemic stimulus

BackgroundNormalization of brachial artery flow-mediated dilation (FMD) to individual shear stress area under the curve (peak FMD:SSAUC ratio) has recently been proposed as an approach to control for the large inter-subject variability in reactive hyperemia-induced shear stress; however, the adoption of this approach among researchers has been slow. The present study was designed to further examine the efficacy of FMD normalization to shear stress in reducing measurement variability.MethodsFive different magnitudes of reactive hyperemia-induced shear stress were applied to 20 healthy, physically active young adults (25.3 ± 0. 6 yrs; 10 men, 10 women) by manipulating forearm cuff occlusion duration: 1, 2, 3, 4, and 5 min, in a randomized order. A venous blood draw was performed for determination of baseline whole blood viscosity and hematocrit. The magnitude of occlusion-induced forearm ischemia was quantified by dual-wavelength near-infrared spectrometry (NIRS). Brachial artery diameters and velocities were obtained via high-resolution ultrasound. The SSAUC was individually calculated for the duration of time-to-peak dilation.ResultsOne-way repeated measures ANOVA demonstrated distinct magnitudes of occlusion-induced ischemia (volume and peak), hyperemic shear stress, and peak FMD responses (all p < 0.0001) across forearm occlusion durations. Differences in peak FMD were abolished when normalizing FMD to SSAUC (p = 0.785).ConclusionOur data confirm that normalization of FMD to SSAUC eliminates the influences of variable shear stress and solidifies the utility of FMD:SSAUC ratio as an index of endothelial function.

Accumulation of physical activity leads to a greater blood pressure reduction than a single continuous session, in prehypertension.

Background Despite limited research, the accumulation of physical activity has been recommended for the treatment of prehypertension. Objectives To compare the duration and magnitude of blood pressure reduction after accumulated physical activity with that after a single session of continuous physical activity, and to investigate sympathetic modulation as a possible mechanism for the reduction in blood pressure after each acute session. Methods Prehypertensive adults (n = 21) participated in a randomized crossover design. Ambulatory blood pressure and heart rate variability (Holter monitoring) were measured for 12 h after accumulated physical activity (4 × 10-min walks (1/h for 4 h) at 50% of VO2peak), continuous physical activity (40-min walk at 50% of VO2peak) and control treatments. Blood pressure and heart rate variability after each activity treatment were compared with the respective periods from the control treatment. Heart rate variability was correlated with reduction in blood pressure. Results Systolic blood pressure (SBP) was reduced for 11 h after accumulated physical activity (P < 0.01), and for 7 h after continuous physical activity (P < 0.05). Diastolic blood pressure (DBP) was reduced for 10 h after accumulated physical activity (P < 0.05) and for 7 h after continuous physical activity (P < 0.05). With accumulated physical activity, the differences in normalized low-frequency (r = 0.517, P < 0.01) and high-frequency (r = −0.503, P < 0.05) power were correlated with reduction in SBP and the differences in normalized low-frequency (r = 0.745, P < 0.001), high-frequency (r = −0.738, P < 0.001) powers, and low frequency: high frequency ratio (r = 0.756, P < 0.001) were correlated with reduction in DBP. With continuous physical activity, the difference in low frequency: high frequency ratio (r = 0.543, P < 0.05) was correlated with reduction in DBP. Conclusion The accumulation of physical activity appears to be more effective than a single continuous session in the management of prehypertension. Sympathetic modulation was associated with reduced blood pressure after each session.