Abstract Body (Do not enter title and authors here): Introduction: Peak oxygen uptake (VO₂ peak), standardized to total body mass (ml/kg/min) is a predictor of morbidity and mortality in cardiovascular disease patients. However, subsets of individuals undergoing exercise based cardiac rehabilitation (CR) show no improvement or reduction in VO₂ peak despite improvement in other functional measures.
Hypothesis: Change in peak VO₂ post-CR, adjusted for lean mass rather than total mass better reflects peak VO₂ improvements.
Aim: To assess the influence of CR on lean mass and the effect of lean mass compared to total body mass changes on peak VO₂ following CR.
Methods: This observational cohort study included adults >18 years old who completed CR between 2015-2022 at Mayo Clinic, Rochester. All patients completed both dual energy X-ray absorptiometry (DXA) and cardiopulmonary exercise testing (CPET) for measurement of body composition (total mass and lean mass) and VO₂ peak pre- and post-CR. Improvement in VO₂ peak was defined as >% increase. Paired t-tests, one-way ANOVA, and descriptive statistics were performed.
Results: Of 145 subjects, 81% were male and 63% Caucasian with a mean (SD) age of 62.8±12.6 years, BMI of 30.3±5.7, and 33.4±8.2 of 36 prescribed (92.8%) CR sessions completed. Pre-CR, patients demonstrated absolute VO₂ peak of 1,997.0±693.5 mL/min, relative of 22.1±6.2 mL/kg/min, and relative to lean mass of 35.2±9.6 mL/kg lean/min. After CR, patients demonstrated 1.2±3.1 kg reduction in total mass (p<0.05) and 0.4±1.7 kg increase in lean mass (p<0.05). Post-CR VO₂ peak increased by 17.1±117.0% absolute units (mL/min) (p<0.05), 9.0±16.1 % relative units (mL/kg/min) (p<0.05), and 15.9±111.9% units relative to lean mass (mL/kg lean/min) (p<0.05). Absolute and relative to lean mass units demonstrated greater improvements in VO₂ peak compared to relative units (p<0.05). Dependent on units, 70.3% of patients demonstrated an improvement in absolute VO₂, 75.2% patients improved relative VO₂, and 62.8% patients improved VO₂ relative to lean mass.
Conclusions: These data demonstrate significant increases in lean mass and VO₂ following CR, with larger improvements reflected in units adjusted for lean mass compared to traditional relative units. In contrast, the largest proportion of patients showed positive improvements in VO₂ peak relative units with the smallest proportion relative to lean mass. These data suggest the reporting methodology for change in VO₂ following CR may impact overall findings.