Lower-limb muscle function is a determinant of exercise tolerance after lung resection surgery in patients with lung cancer.

BACKGROUND AND OBJECTIVE: This study aims to investigate the association between exercise tolerance, pulmonary function and lower-limb muscle function in patients with lung cancer who underwent lung resection surgery in the previous year.

METHODS: Sixty-four patients (age: 67 ± 11 years, 66% males) performed a symptom-limited incremental cycle test to define peak oxygen consumption (VO2 peak) and peak workload (Wpeak). The best of two 6-min walking distance (6MWD) tests was also included. Isometric quadriceps strength and isokinetic quadriceps endurance were measured. Post-bronchodilator spirometry, lung volumes and diffusing capacity of the lung for carbon monoxide (DLCO ) measurements were assessed. Univariate correlation analysis and multiple regression analyses were performed.

RESULTS: VO2 peak, W peak and 6MWD showed moderate to strong correlations with quadriceps strength/endurance and DLCO while weak to moderate correlations were found with forced expiratory volume in 1 s (FEV1 ) , functional residual capacity (FRC) and body weight. Multiple regression showed that peak isometric quadriceps strength (P < 0.001) and DLCO (P < 0.001) were significant predictors of VO2 peak (explained variance R2  = 0.67), while quadriceps endurance (P = 0.0015) and DLCO (P < 0.0001) were significant predictors of W peak (R2  = 0.61). Quadriceps endurance capacity (P = 0.013), but not DLCO , significantly contributed to the 6MWD model (R2  = 0.29).

CONCLUSION: We identified a strong significant relationship between peak aerobic capacity and quadriceps muscle function and lung diffusing capacity. 6MWD was significantly related to quadriceps muscle function but not to pulmonary function. These findings suggest that accurate assessment of lower-limb muscle strength has a role in the accurate interpretation of exercise tests and in selecting optimal candidates for resistance training interventions targeting the lower-limb muscles after resection surgery.