Pain, Low Muscle Mass, and Exercise Participation After Myocardial Infarction: Determinants of Initial Exercise Testing at a Tertiary Center Serving a Rural Region

Background/Objectives: Musculoskeletal pain and balance impairments are common in patients referred for cardiac rehabilitation (CR), but their influence on early exercise participation and aerobic capacity remains unclear. This study examined whether pain and muscle mass are associated with initial exercise tolerance test (ETT) participation and VO2 peak. Methods: This retrospective, single-center cohort included 162 of 189 patients referred to CR after percutaneous coronary intervention for acute myocardial infarction; 105 who completed a symptom-limited cardiopulmonary exercise test were analyzed for VO2 peak. Pain intensity was assessed using a visual analog scale (VAS 0–10), and the skeletal muscle index (SMI) was measured using a bioelectrical impedance analysis. Determinants of ETT participation and VO2 peak were evaluated using multivariable logistic and linear regressions, respectively, with pain analyzed as a binary, three-category, and continuous variable. Results: More than half the patients reported musculoskeletal pain during physical activity, and 24.7% had balance problems. Patients with pain (VAS 1–10) had lower appendicular skeletal muscle mass and poorer functional status than pain-free patients. Among the 105 who completed the ETT, the pain group showed significantly lower workload-estimated metabolic equivalents [METs (Q)], respiratory exchange ratios, and peak minute ventilation and a shorter exercise time, but VO2 peak did not differ between the groups. ETT participation rates were similar across pain categories (63.4%, 67.2%, and 63.0% for VAS 0, 1–5, and 6–10, respectively). In the multivariable logistic regression, older age, hypertension, and low SMI scores were independently associated with reduced ETT participation. In the linear regression, age was the only significant predictor of VO2 peak; the SMI score showed a borderline association (p = 0.065), but pain intensity was not independently associated with VO2 peak. Conclusions: Musculoskeletal pain is prevalent among patients entering CR after myocardial infarction, and it is accompanied by low muscle mass and functional limitations. However, after adjustment, pain itself was not an independent determinant of ETT participation or VO2 peak. Low SMI scores were independently associated with reduced test participation and showed only a borderline association with aerobic capacity. These cross-sectional findings should be regarded as hypothesis-generating.