Kristi S. Kelley

Progressive Resistance Exercise and Resting Blood Pressure: A Meta-Analysis of Randomized Controlled Trials

Hypertension is a major public health problem affecting an estimated 43 million civilian, noninstitutionalized adults in the United States (24% of this population). The purpose of this study was to use the meta-analytic approach to examine the effects of progressive resistance exercise on resting systolic and diastolic blood pressure in adult humans. Studies were retrieved via (1) computerized literature searches, (2) cross-referencing from original and review articles, and (3) review of the reference list by 2 experts on exercise and blood pressure. Inclusion criteria were as follows: (1) trials that included a randomized nonexercise control group; (2) progressive resistance exercise as the only intervention; (3) adult humans; (4) journal articles, dissertations, and masters theses published in the English-language literature; (5) studies published and indexed between January 1966 and December 1998; (6) resting systolic and/or diastolic blood pressure assessed; and (7) training studies lasting a minimum of 4 weeks. Across all designs and categories, fixed-effects modeling yielded decreases of approximately 2% and 4% for resting systolic and diastolic blood pressure, respectively (mean+/-SD systolic, -3+/-3 mm Hg; 95% bootstrap CI, -4 to -1 mm Hg; mean+/-SD diastolic, -3+/-2 mm Hg; 95% bootstrap CI, -4 to -1 mm Hg). It was concluded that progressive resistance exercise is efficacious for reducing resting systolic and diastolic blood pressure in adults. However, a need exists for additional studies that limit enrollment to hypertensive subjects as well as analysis of data with an intention-to-treat approach before the effectiveness of progressive resistance exercise as a nonpharmacological intervention can be determined.

Resistance training and bone mineral density in women: a meta-analysis of controlled trials.

Kelley GA, Kelley KS, Tran ZV: Resistance training and bone mineral density in women: a meta-analysis of controlled trials. Am J Phys Med Rehabil 2001;80:65–77. The purpose of this study was to use meta-analysis to examine the effects of resistance training on bone mineral density at the femur, lumbar spine, and radius in pre- and postmenopausal women. Resistance training had a positive effect on bone mineral density at the lumbar spine of all women and at the femur and radius sites for postmenopausal women. It was concluded that resistance training has a positive effect on bone mineral density in women.

Aerobic exercise and lipids and lipoproteins in patients with cardiovascular disease : a meta-analysis of randomized controlled trials

PURPOSE Use the meta-analytic approach to examine the effects of aerobic exercise on lipids and lipoproteins in adults with cardiovascular disease (CVD). METHODS Studies were retrieved via electronic databases, review of reference lists from retrieved articles, including reviews, and hand searching. Inclusion criteria were: (1) randomized controlled trials, (2) aerobic exercise >or=4 weeks as an intervention, (3) studies published in English language only between January 1, 1955 and January 1, 2005, (4) studies published in journals or as dissertations or masters theses, (5) human subjects >or=18 years, (6) all subjects diagnosed with some type of CVD, and (7) pre and post data available for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and/or triglycerides (TG). Random-effects models were used for data analysis. RESULTS Of the more than 3,000 studies reviewed, a total of 10 representing 1,260 subjects (580 exercise, 680 control) were included in our analysis. There was a statistically significant increase of 9% in HDL-C (mean +/- SEM, 3.7 +/- 1.3 mg/dL; 95% CI, 1.2 to 6.1 mg/dL) and a statistically significant decrease of 11% in TG (-19.3 +/- 5.4 mg/dL; 95% CI, -30.1 to -8.5 mg/dL), but no statistically significant decreases in TC or LDL-C (TC, -8.8 +/- 6.8 mg/dL; 95% CI, -22.3 to 4.7 mg/dL; LDL-C, -7.7 +/- 6.0 mg/dL; 95% CI, -19.5 to 4.2 mg/dL). CONCLUSIONS The present findings suggest that chronic aerobic exercise increases HDL-C and decreases TG in adults, especially men, with CVD.

Efficacy of Resistance Exercise on Lumbar Spine and Femoral Neck Bone Mineral Density in Premenopausal Women: A Meta-Analysis of Individual Patient Data

BACKGROUND Osteoporosis and osteopenia are major public health problems. The purpose of this study was to conduct an individual patient data (IPD) meta-analysis to examine the efficacy of resistance exercise on lumbar spine and femoral neck bone mineral density (BMD) in premenopausal women. METHODS Studies were retrieved via (1). computerized literature searches, (2). review of reference lists from previous studies, (3). hand searching selected journals, and (4). expert review of the reference list. Two x two analysis of covariance (ANCOVA) tests with repeated measures on one factor (time) and study as a covariate were used to analyze changes in BMD. RESULTS One hundred forty-three subjects (74 exercise, 69 control) were included in the analysis. Changes in lumbar spine BMD averaged 0.006 +/- 0.035 g/cm(2) (0.64 +/- 2.99%) in the exercise group and 0.008 +/- 0.091 g/cm(2) (0.74 +/- 7.58%) in the control group, and changes in femoral neck BMD averaged 0.005 +/- 0.031 g/cm(2) (0.46 +/- 3.10%) in the exercise group and 0.003 +/- 0.031 g/cm(2) (0.31 +/- 2.97%) in the control group. No statistically significant differences in lumbar spine or femoral neck BMD were found within or between the exercise and control groups (p > 0.05). CONCLUSIONS Based on existing evidence, our results do not support the efficacy of resistance exercise for increasing or maintaining lumbar spine and femoral neck BMD in premenopausal women.

Isometric handgrip exercise and resting blood pressure: a meta-analysis of randomized controlled trials.

Objective : To examine the efficacy of isometric handgrip exercise for reducing resting SBP and DBP in adult humans. Methods : Meta-analysis of studies retrieved from five electronic databases as well as cross-referencing from identified articles. The criteria for inclusion were randomized controlled trials published in any language over an approximate 38-year period (1 January 1971 to 1 February 2009), isometric handgrip training of at least 4 weeks performed by adults of at least 18 years of age, and data for changes in resting SBP and DBP available. Dual coding of studies was performed by both investigators. Data were analyzed a priori using random-effects models and nonparametric 95% bootstrap percentile confidence intervals (BCIs, 5000 iterations). Because of the small sample size, analyses were also performed using fixed-effects models post hoc. Results : Eighty-one men and women (42 exercise and 39 control) from three of 287 reviewed studies were pooled for analysis. Using random-effects models, statistically significant exercise minus control group reductions of approximately 10% were observed for both resting SBP and DBP (SBP: Xd¯, −13.4 mmHg; 95% BCI, −15.3 to −11.0 mmHg and DBP: X¯, −7.8 mmHg; 95% BCI, −16.5 to −3.0 mmHg). Results were also statistically significant when fixed-effects models were used (SBP: X¯, −13.8 mmHg; 95% BCI, −15.3 to −11.0 mmHg and DBP: X¯, −6.1 mmHg; 95% BCI, −16.5 to −3.2 mmHg). Conclusion : Isometric handgrip exercise is efficacious for reducing resting SBP and DBP in adult humans. However, the generalizability of these findings is limited given the small number of studies included.

Statistical models for meta-analysis: A brief tutorial

Aggregate data meta-analysis is currently the most commonly used method for combining the results from different studies on the same outcome of interest. In this paper, we provide a brief introduction to meta-analysis, including a description of aggregate and individual participant data meta-analysis. We then focus the rest of the tutorial on aggregate data meta-analysis. We start by first describing the difference between fixed and random-effects meta-analysis, with particular attention devoted to the latter. This is followed by an example using the random-effects, method of moments approach and includes an intercept-only model as well as a model with one predictor. We then describe alternative random-effects approaches such as maximum likelihood, restricted maximum likelihood and profile likelihood as well as a non-parametric approach. A brief description of selected statistical programs available to conduct random-effects aggregate data meta-analysis, limited to those that allow both an intercept-only as well as at least one predictor in the model, is given. These descriptions include those found in an existing general statistics software package as well as one developed specifically for an aggregate data meta-analysis. Following this, some of the disadvantages of random-effects meta-analysis are described. We then describe recently proposed alternative models for conducting aggregate data meta-analysis, including the varying coefficient model. We conclude the paper with some recommendations and directions for future research. These recommendations include the continued use of the more commonly used random-effects models until newer models are more thoroughly tested as well as the timely integration of new and well-tested models into traditional as well as meta-analytic-specific software packages.

Exercise and Bone Mineral Density in Premenopausal Women: A Meta-Analysis of Randomized Controlled Trials

Objective. Examine the effects of exercise on femoral neck (FN) and lumbar spine (LS) bone mineral density (BMD) in premenopausal women. Methods. Meta-analysis of randomized controlled exercise trials ≥24 weeks in premenopausal women. Standardized effect sizes (g) were calculated for each result and pooled using random-effects models, Z score alpha values, 95% confidence intervals (CIs), and number needed to treat (NNT). Heterogeneity was examined using Q and I 2. Moderator and predictor analyses using mixed-effects ANOVA and simple metaregression were conducted. Statistical significance was set at P ≤ 0.05. Results. Statistically significant improvements were found for both FN (7gs, 466 participants, g = 0.342, 95%  CI = 0.132, 0.553, P = 0.001, Q = 10.8, P = 0.22, I 2 = 25.7%, NNT = 5) and LS (6gs, 402 participants, g = 0.201, 95%  CI = 0.009, 0.394, P = 0.04, Q = 3.3, P = 0.65, I 2 = 0%, NNT = 9) BMD. A trend for greater benefits in FN BMD was observed for studies published in countries other than the United States and for those who participated in home versus facility-based exercise. Statistically significant, or a trend for statistically significant, associations were observed for 7 different moderators and predictors, 6 for FN BMD and 1 for LS BMD. Conclusions. Exercise benefits FN and LS BMD in premenopausal women. The observed moderators and predictors deserve further investigation in well-designed randomized controlled trials.

Effects of Exercise in the Treatment of Overweight and Obese Children and Adolescents: A Systematic Review of Meta-Analyses

Purpose. Conduct a systematic review of previous meta-analyses addressing the effects of exercise in the treatment of overweight and obese children and adolescents. Methods. Previous meta-analyses of randomized controlled exercise trials that assessed adiposity in overweight and obese children and adolescents were included by searching nine electronic databases and cross-referencing from retrieved studies. Methodological quality was assessed using the Assessment of Multiple Systematic Reviews (AMSTAR) Instrument. The alpha level for statistical significance was set at P ≤ 0.05. Results. Of the 308 studies reviewed, two aggregate data meta-analyses representing 14 and 17 studies and 481 and 701 boys and girls met all eligibility criteria. Methodological quality was 64% and 73%. For both studies, statistically significant reductions in percent body fat were observed (P = 0.006 and P < 0.00001). The number-needed-to treat (NNT) was 4 and 3 with an estimated 24.5 and 31.5 million overweight and obese children in the world potentially benefitting, 2.8 and 3.6 million in the US. No other measures of adiposity (BMI-related measures, body weight, and central obesity) were statistically significant. Conclusions. Exercise is efficacious for reducing percent body fat in overweight and obese children and adolescents. Insufficient evidence exists to suggest that exercise reduces other measures of adiposity.

Aerobic Exercise and Resting Blood Pressure in Women: A Meta-Analytic Review of Controlled Clinical Trials

The purpose of this study was to use the meta-analytic approach to examine the effects of aerobic exercise on resting systolic and diastolic blood pressure in women. Twenty-one studies representing 1029 subjects (663 exercise, 366 controls) and 54 primary outcomes (28 systolic, 26 diastolic) met the criteria for inclusion. Across all designs and categories, statistically significant decreases in resting systolic (mean +/- SD, -2.03 +/- 2.87, 95% confidence interval [CI] -3.14 to -0.92 mm Hg) but not diastolic (mean +/- SD, -0.64 +/- 2.02, 95% CI -1.45 to 0.18 mm Hg) blood pressure were found. Changes in resting systolic blood pressure were correlated with initial systolic blood pressure, initial body mass index, initial resting heart rate, and rest period before assessment of blood pressure. Meta-analysis of included studies suggests that aerobic exercise causes small reductions in resting systolic blood pressure in women. However, a need exists for additional, well-designed studies on this topic, especially among hypertensive adult women.

Efficacy and Effectiveness of Exercise on Tender Points in Adults with Fibromyalgia: A Meta-Analysis of Randomized Controlled Trials

Fibromyalgia is a major public health problem affecting an estimated 200 to 400 million people worldwide. The purpose of this study was to use the meta-analytic approach to determine the efficacy and effectiveness of randomized controlled exercise intervention trials (aerobic, strength training, or both) on tender points (TPs) in adults with fibromyalgia. Using random effects models and 95% confidence intervals (CI), a statistically significant reduction in TPs was observed based on per-protocol analyses (8 studies representing 322 participants) but not intention-to-treat analyses (5 studies representing 338 participants) (per-protocol, g, −0.68, 95% CI, −1.16, −0.20; intention-to-treat, g, −0.24, 95% CI, −0.62, 0.15). Changes were equivalent to relative reductions of 10.9% and 6.9%, respectively, for per-protocol and intention-to-treat analyses. It was concluded that exercise is efficacious for reducing TPs in women with FM. However, a need exists for additional well-designed and reported studies on this topic.