Effects of fractionized and continuous exercise on 24-h ambulatory blood pressure

PURPOSE

The objective of this study is to compare the effects of fractionized aerobic exercise (three 10-min exercise sessions) and continuous exercise (one 30-min exercise session) on 24-h ambulatory blood pressure (ABP).

METHODS

Eleven healthy prehypertensive subjects (28.3 ± 8.0 (SD) yr) completed three randomly assigned conditions: 1) three 10-min sessions of aerobic exercise (3 × 10 min), 2) one continuous 30-min session of aerobic exercise (1 × 30 min), and 3) a nonexercise control trial (control). The mode of exercise was walking on a motor-driven treadmill at 75%-79% of maximum heart rate (HRmax) (60%-65% V˙O2peak). Twenty-four-hour ABP was monitored with an automated ABP device (Oscar 2™; SunTech Medical, Morrisville, NC). Linear mixed models were used to compare 24-h ABP responses between trials.

RESULTS

The mean ± SD 24-h systolic blood pressure (SBP) was significantly lower during the 3 × 10-min trial (127 ± 15 mm Hg) compared with control (130 ± 15 mm Hg) (P < 0.001). Although both 3 × 10-min and 1 × 30-min trials reduced SBP compared with control during daytime/evening (1300-2300 h), only the 3 × 10-min trial reduced SBP during nighttime (2300-0800 h, 118 ± 16 vs 122 ± 14 mm Hg, P = 0.024) and the following morning (0800-1200 h, 127 ± 15 vs 131 ± 15 mm Hg, P = 0.016). For 24 h, 26.7% of SBP values during 3 × 10 min were normal (i.e., <120 mm Hg) compared with 18.3% for 1 × 30 min and 19.4% for control (P < 0.001).

CONCLUSIONS

In prehypertensive individuals, fractionized exercise (e.g., three 10-min aerobic exercise sessions spread and effective exercise alternative to continuous exercise for cardiovascular risk reduction in this population.

Evaluation of racial differences in resting and postprandial endothelial function in postmenopausal women matched for age, fitness and body composition

OBJECTIVE

We investigated endothelial function at rest and after a high-fat meal challenge in African American (AA) and Caucasian postmenopausal women matched for age, body mass index, percent fat and fitness level.

DESIGN

Pilot study.

SETTING

University of Virginia General Clinical Research Center.

PARTICIPANTS

Eight AA and 8 Caucasian postmenopausal women.

INTERVENTION

PARTICIPANTS underwent a VO2 peak treadmill protocol, percent fat assessment, and brachial artery flow-mediated dilation measurements (baseline and 4 hours following a high-fat meal).

MAIN OUTCOMES MEASURES

Baseline and postprandial flow mediated dilation (FMD) following a high-fat meal.

RESULTS

FMD values were similar in AA (5.4%, 95% CI: 3.3, 7.4) and Caucasian women (4.0%, 95% CI: 2.0, 6.1). There was no significant change in FMD from baseline to four hours following the meal challenge within groups (AA: .9%, P = .397, Caucasian: 2.3%, P = .063) or between groups (P = .449), despite a significant increase in triglycerides (AA: 81.8 mg/dL, P < .001, Caucasian: 99.7 mg/dL, P = .004).

CONCLUSIONS

The present pilot study found that when postmenopausal AA and Caucasian women are matched for age, fitness and body composition, reported racial differences in resting endothelial function were not observed. Additionally, there were no racial differences in postprandial endothelial function or metabolism following a high-fat meal.

Lifestyle Measures to Reduce Inflammation

Chronic low-grade inflammation associated with cardiovascular disease and type 2 diabetes (T2D) may be ameliorated with exercise and/or diet. High levels of physical activity and/or cardiorespiratory fitness are associated with reduced risk of low-grade inflammation. Both aerobic and resistance exercise have been found to improve inflammatory status, with the majority of evidence suggesting that aerobic exercise may have broader anti-inflammatory effects. In particular, aerobic exercise appears to improve the balance between pro- and anti-inflammatory markers. Improvement in inflammatory status is most likely to occur in persons with elevated levels of pro-inflammatory markers prior to intervention. A number of dietary factors, including fiber-rich foods, whole grains, fruits (especially berries), omega-3 fatty acids, antioxidant vitamins (eg, C and E), and certain trace minerals (eg, zinc) have been documented to reduce blood concentrations of inflammatory markers. Anti-inflammatory foods may also help mitigate the pro-inflammatory postprandial state that is particularly evident after ingestion of meals high in saturated fat. Intensive lifestyle interventions involving both exercise and diet appear to be most effective. For the most part, anti-inflammatory effects of exercise and diet are independent of weight loss. Thus overweight and obese men and women, who are most likely to have a pro-inflammatory profile, do not necessarily have to normalize body mass index to improve inflammatory status and reduce risk of type 2 diabetes and cardiovascular disease.

Exercise and diet, independent of weight loss, improve cardiometabolic risk profile in overweight and obese individuals

Diet and/or exercise are routinely advised as methods for weight loss in overweight/obese individuals, particularly those who are at high risk for cardiovascular disease and type 2 diabetes mellitus. However, physical activity and structured exercise programs rarely result in significant loss of body weight or body fat, and weight-loss diets have extraordinarily high recidivism rates. Despite only modest effects on body weight, exercise and ad libitum nutrient-dense diets for overweight/obese individuals have many health benefits, including skeletal muscle adaptations that improve fat and glucose metabolism, and insulin action; enhance endothelial function; have favorable changes in blood lipids, lipoproteins, and hemostatic factors; and reduce blood pressure, postprandial lipemia and glycemia, and proinflammatory markers. These lifestyle-induced adaptations occur independently of changes in body weight or body fat. Thus, overweight/obese men and women who are at increased risk for cardiovascular disease and type 2 diabetes as a result of sedentary lifestyle, poor diet, and excess body weight should be encouraged to engage in regular physical activity and improve their diet, regardless of whether the healthier lifestyle leads to weight loss.

Walking and running economy: inverse association with peak oxygen uptake

PURPOSE

The purpose of this study was to test the hypothesis that V˙O2peak is positively correlated with the regression coefficients of the curve-linear relationship between V˙O2 and speed during a protocol consisting of submaximal walking and running.

METHODS

Nineteen healthy men (mean ± SD: age = 26.4 ± 6.4 yr, height = 179.9 ± 7.2 cm, weight = 77.7 ± 8.7 kg, % fat = 16.3 ± 7.3) and 21 healthy women (age = 25.6 ± 4.9 yr, height = 167.2 ± 5.4 cm, weight = 61.6 ± 7.7 kg, % fat = 24.0 ± 6.8) underwent an incremental treadmill test to determine VO2peak and on two separate days performed an exercise protocol consisting of treadmill walking on a level grade at 2.0 mph (54 m·min−¹), 3.0 mph (80 m·min−¹), and 4.0 mph (107 m·min−¹) and running at 6.0 mph (161 m·min−¹). Subjects exercised for 5 min at each velocity, with 3 min of rest in between each exercise bout. Pulmonary ventilation (VE) and gas exchange were measured breath-by-breath each minute. The average of VO2 values obtained during the last 2 min of exercise for both exercise sessions was used in polynomial random coefficient regression analysis.

RESULTS

In the polynomial random coefficient regression analysis for walking speeds only, both linear (r = 0.31, P = 0.053) and quadratic (r = 0.35, P = 0.029) coefficients were modestly correlated with VO2peak. Steady-state VO2 during walking at 3.0 and 4.0 mph and running at 6.0 mph was also modestly correlated with VO2peak (r = 0.30-0.48).

CONCLUSIONS

The results confirm our hypothesis and suggest that, as walking speed increases, the increase in VO2 is positively correlated with the VO2peak. Our findings are consistent with the notion that cardiorespiratory fitness and exercise economy are inversely related.

Perception of exercise difficulty predicts weight regain in formerly overweight women

It has been previously reported that overweight and obese individuals perceive exercise as more difficult than their lean counterparts, and this difference may not be solely attributed to physiological differences. Therefore, we tested the hypothesis that individual differences in the perception of exercise difficulty during exercise, independent of concurrently measured physiological markers of exertion, are predictive of weight regain, after completion of a weight loss program. A total of 113 formerly overweight women who had previously completed a weight-loss program to achieve a normal body weight (BMI <25 kg/m(2)) underwent a submaximal aerobic exercise task while measures of physiological and perceived exertion (rating of perceived exertion (RPE)) were recorded. Weight gain was assessed following a subsequent 1-year free-living period. Average weight regain 1 year following the intervention was 5.46 +/- 3.95 kg. In regression modeling, RPE (beta = 0.21, P = 0.01), but not physiological exertion (beta = 0.02, P = 0.81), during the submaximal exercise task was positively associated with 1-year weight regain following weight loss in premenopausal women, independent of measured confounding variables. The association between RPE and weight regain suggests that perception of exercise difficulty is an important predictor of weight regain following a weight-loss intervention.

Pre-exercise cardiology screening guidelines for asymptomatic patients with diabetes

Coronary heart disease is a major cause of morbidity and mortality in persons with diabetes mellitus. Exercise is an important cornerstone in the treatment and management of diabetes but is also associated with a heightened risk of sudden cardiac death in those with occult coronary heart disease. Before beginning a physical activity program that involves anything greater than moderate intensity exercise, consideration should be given to screening asymptomatic persons with diabetes for silent myocardial ischemia.

Effect of exercise training intensity on abdominal visceral fat and body composition

The metabolic syndrome is a complex clustering of metabolic defects associated with physical inactivity, abdominal adiposity, and aging.

PURPOSE

To examine the effects of exercise training intensity on abdominal visceral fat (AVF) and body composition in obese women with the metabolic syndrome.

METHODS

Twenty-seven middle-aged obese women (mean +/- SD; age = 51 +/- 9 yr and body mass index = 34 +/- 6 kg x m(-2)) with the metabolic syndrome completed one of three 16-wk aerobic exercise interventions: (i) no-exercise training (Control): seven participants maintained their existing levels of physical activity; (ii) low-intensity exercise training (LIET): 11 participants exercised 5 d x wk(-1) at an intensity < or = lactate threshold (LT); and (iii) high-intensity exercise training (HIET): nine participants exercised 3 d x wk(-1) at an intensity > LT and 2 d x wk(-1) < or = LT. Exercise time was adjusted to maintain caloric expenditure (400 kcal per session). Single-slice computed tomography scans obtained at the L4-L5 disc space and midthigh were used to determine abdominal fat and thigh muscle cross-sectional areas. Percent body fat was assessed by air displacement plethysmography.

RESULTS

HIET significantly reduced total abdominal fat (P < 0.001), abdominal subcutaneous fat (P = 0.034), and AVF (P = 0.010). There were no significant changes observed in any of these parameters within the Control or the LIET conditions.

CONCLUSIONS

The present data indicate that body composition changes are affected by the intensity of exercise training with HIET more effectively for reducing total abdominal fat, subcutaneous abdominal fat, and AVF in obese women with the metabolic syndrome.

Effects of exercise training intensity on nocturnal growth hormone secretion in obese adults with the metabolic syndrome

CONTEXT

Abdominal adiposity is associated with reduced spontaneous GH secretion, and an increased incidence of the metabolic syndrome, type 2 diabetes, and cardiovascular disease. Exercise training increases GH secretion, induces abdominal visceral fat loss, and has been shown to improve the cardiometabolic risk factor profile. However, little is known about the effects of endurance training intensity on spontaneous GH release in obese individuals.

OBJECTIVE

Our objective was to examine the effects of 16 wk endurance training on spontaneous 12-h overnight GH secretion in adults with the metabolic syndrome.

DESIGN AND SETTING

This randomized, controlled exercise intervention was conducted at the University of Virginia.

PARTICIPANTS

A total of 34 adults with the metabolic syndrome (mean +/- sem: age: 49.1 +/- 1.8 yr) participated.

INTERVENTION

Participants were randomized to one of three groups for 16 wk: no exercise training (control), low-intensity exercise training, or high-intensity training.

MAIN OUTCOME MEASURE

Change in nocturnal integrated GH area under the curve (AUC) was calculated.

RESULTS

Both exercise training conditions augmented within-group nocturnal GH AUC pretrain to post-training (low-intensity exercise training approximately (upward arrow) 49%, P < 0.05; and high-intensity training approximately (upward arrow) 65%, P < 0.01), and these changes were also greater than the changes in the control group (P < 0.01). The change in nocturnal GH AUC was inversely associated with the change in fat mass across the entire sample (r = -0.34; P = 0.051; n=34) but was not significantly associated with the change in abdominal visceral fat (r = 0.02; P = 0.920; n = 34).

CONCLUSIONS

Sixteen wk of supervised exercise training in adults with the metabolic syndrome increases spontaneous nocturnal GH secretion independent of exercise training intensity.