Meta-analysis of Anthropometric Outcomes of Supervised Exercise Interventions in Healthy Adults Vicki Conn PhD RN FAAN Todd Ruppar PhD RN Lorraine Phillips PhD RN Jo-Ana Chase MSN RN M ETA -A NALYSIS R ESEARCH C ENTER U NIVERSITY OF M ISSOURI S CHOOL OF N URSING

Parent Study: Meta-Analysis of Physical Activity Interventions in Healthy People Funding: Meta-analysis of interventions to increase exercise & physical activity (R01NR07870) Vicki Conn, principal investigator Grant co-investigators: Adam Hafdahl PhD David Mehr MD MS Diane Johnson MS

Extant Research Evidence mixed about effects of PA on anthropometric outcomes Limited previous meta-analyses: Focused on clinical populations Did not report findings separately for exercise and diet changes Did not separate supervised exercise and motivational interventions 1991 last semi-comprehensive meta-analysis No previous moderator analyses

What is the overall effect of supervised exercise interventions on anthropometric outcomes? How do the anthropometric effects of supervised exercise vary depending on sample, design, or intervention characteristics? Research Questions

Inclusion Criteria ‘Healthy’ adult sample Samples included regardless of anthropometric status at entry Supervised exercise with verified exercise dose Adequate data to calculate effect size for body mass index (BMI), weight, percent body fat, or central obesity (abdominal girth, waist-to-hip ratio)

Search Strategies (1) Searched 14 computerized databases –MEDLINE & PsycINFO –EMBASE –Cochrane Controlled Trials Register –Database of Abstracts of Reviews of Effectiveness –Healthstar –Combined Health Information Database –Educational Resources Information Center –Sport Discus –Dissertation Abstracts International

Search Strategies (2) Ancestry searches Author searches from all primary studies Hand searches of 114 journals Conference abstracts (e.g. ACSM, APHA, AHA, MNRS, SBM) Research registers (e.g. CRISP [RePORT]) Reviewed 54,642 studies for potential eligibility

Coding Data Categories Source characteristics Published vs. unpublished Year of distribution Participant attributes Ages Gender/minority distribution Methodological features Supervised exercise intervention characteristics Effect size information

Calculating Effect Sizes Basic conceptual definition of standardized mean difference (d): X 1 – X 2 d = SD 1 + SD 2 2 Meta-analysis equations convert to d index from : Change scores Comparison of unadjusted means by t statistic Two group F statistic P values for t statistic Proportions (success rates) Correlations

Analyses Random effect model Assumes heterogeneity beyond sampling error Appropriate with variations in research methods (interventions, measures, samples) Effect sizes weighted by inverse of variance Effect sizes adjusted for bias Q & I 2 statistics to examine heterogeneity Moderator analyses: Dichotomous: meta-analysis analogue of ANOVA Continuous: meta-analysis analog of regression

Study Characteristics Two-group comparisons: treatment vs. control 316 comparisons 24,689 people Single-group comparisons: treatment baseline vs. treatment outcome 794 comparisons 20,335 people

Sample Characteristics Sample sizes: Two group: median 23 subjects Single group: median 17 subjects Modest attrition: median 7% Age: median 38 years Percent female: median 55% Percent minority: median 13% (poorly reported) Baseline BMI: median 27 – 28 kg/m2

Typical Intervention Characteristics Supervised exercise interventions: 47 minutes per session 3 sessions per week 42 total sessions

Anthropometric Outcomes Comparisons kESpI2I2 Treatment vs. control post-intervention316.21< Treatment vs. control pre-post303.18<.0010 Treatment pre- vs. post-intervention794.20< Control group pre- vs. post-intervention <.0010 k = number of comparisons ES = effect size (d index) p = test of statistical significance of effect size I 2 = index of heterogeneity beyond within-study sampling error

Effect Size Meaning Converted effect size (treatment vs. control at outcome) to original metric of BMI Effect size * BMI SD = difference in original metric (.21 * 4.6 =.97) At outcome: Treatment subjects BMI = 27.0 Control subjects BMI = 28.0 Mean difference 2.3 kg between treatment and control subjects

Significant Moderators Previous exercise: studies of people with existing exercise behavior reported lower ES (.11) than studies of sedentary subjects (ES =.24) Lower effect size for studies with more minority subjects (B = -.26) Larger exercise dose associated with better anthropometric outcomes: Studies with more total number of exercise sessions reported larger effect sizes (B =.29): remained important in multivariate analyses Studies with more total minutes of supervised exercise reported larger effect sizes (B =.29): total number of exercise sessions more important

Potential Moderators Which Were Not Significant Publication year Published vs. unpublished report Presence of funding Sample characteristics: gender, age, BMI Random vs. non-random assignment Behavioral target (exclusively PA vs. PA plus diet) Fitness testing present vs. absent Aerobic exercise only vs. aerobic plus resistance Individual components of exercise dose: Minutes of exercise per session Frequency of sessions per week

Limitations Primary studies often poorly report interventions, minority participants, and statistical outcomes Anthropometric outcomes may have measurement error Need research with documented exercise dose over years to determine health outcomes Future meta-analyses focus on overweight/obese adults

Discussion Clinically important improvement in BMI following interventions (BMI = 28 vs. 27; Kg = 2.3 difference) Important health benefit across years of exercise Exercise may be more effective in preventing gain Exercise confers benefits beyond anthropometric outcomes Minority subjects may experience less improvement Dose matters: total number of sessions most important (but few studies with brief or infrequent sessions)