The biological plausibility that physical activity could improve CV outcomes by positively altering lipid profiles is well established. Although not included in this evidence review, cross-sectional and observational data have demonstrated an association between regular physical activity and reductions in TC and LDL.[143-146] A structured, exercise-based cardiac rehabilitation program in patients recently diagnosed with CHD has been found to improve CV mortality, all-cause mortality, and non-fatal MI. Based on the systematic review and meta-regression analysis of 69 RCTs by Abell et al. (2017), structured cardiac rehabilitation programs with detailed exercise prescription (i.e., frequency, duration, intensity) and follow-up assessments were associated with a 26% reduction (NNT=31) in CV mortality over an average follow-up period of 10 years (range 3 19 years).[147] This benefit does not apply to unstructured interventions, such as providing general exercise advice (e.g., exercise for 150 minutes per week, walk daily), which were excluded from Abell et al. (2017). As is typical for complex interventions, the formats of the 72 individual exercise programs were highly heterogeneous. There was variability in supervision (supervised versus unsupervised programs), setting (community based, residential, clinic), additional risk factor counseling, individual exercise components (i.e., frequency, intensity, type, duration), and adherence. The meta-regression analysis by Abell et al. (2017) found the abovementioned co-variates did not affect any of the CV outcomes with rare exception, such as high adherence.[147] Therefore, the Work Group determined the available evidence base does not support a specific cardiac rehabilitation program or exercise component type. Structured programs of variable format have been shown to reduce critical CV outcomes. Of note, reviewed studies included only patients with CHD (MI event, diagnosis of CAD, CABG, or PCI), most of whom began the exercise intervention between 2 8 weeks after the event. 