Women’s Improvements in Cardiorespiratory Fitness Following Cardiac Rehabilitation Differ by Body Mass Index Category

Abstract Background Improving women's cardiovascular outcomes requires optimizing cardiorespiratory fitness (CRF), as higher CRF predicts improved mortality in people with cardiovascular disease (CVD). As such, increasing CRF is a key goal of cardiac rehabilitation (CR). This study assesses the potential influence of body habitus, assessed by body mass index (BMI), on improvements in CRF in women with CVD. Methods Women (18+ years) diagnosed with CVD who completed a 12-week exercise-based CR program between 1996 and 2016 were included in this retrospective analysis. Women completed a symptom-limited graded exercise test before CR and at CR completion to determine CRF via peak metabolic equivalents (METs). Women were categorized by baseline BMI: normal = 18.5 to 24.9 kg/m², overweight = 25.0 to 29.9 kg/m², and obese ≥ 30 kg/m². Mixed analysis of covariance (ANCOVA) was performed to evaluate the impact of BMI classification on ΔMETs at 12 weeks. Results Data from 1313 women (mean age = 62 ± 11 years) were analyzed. Results from mixed ANCOVA indicated a significant time (pre-CR, 12 weeks) by BMI category interaction (F [2,1307] = 3.20, P = 0.041, ƞp² = 0.005). Follow-up analyses of variance (ANOVAs) showed significant improvements in ΔMETs in women with normal and overweight BMI categories (standard mean difference =1.03, n = 454 and 0.92, n = 461, respectively, P < 0.001). However, ΔMETs among women classified as obese was nonsignificant using a Bonferroni-adjusted alpha of 0.017 (standardized mean difference [SMD] = 0.79, P = 0.028; n = 398). Conclusions A 12-week exercise-based CR program increased CRF in women classified as normal or overweight by BMI, whereas those with obesity did not realize similar improvements. Women with obesity may need tailored strategies to increase their improvements in CRF in CR. Clinical Trial Registration REB18-0083.