Decreased muscle strength following management of breast cancer

To assess whether muscle strength, power and endurance at the affected shoulder were reduced in women treated for breast cancer. Secondly, we assessed whether muscle performance was explained by management or other symptoms.

Participants were 40 women (mean +/- SD: 56.7 +/- 11.6 yr) who had completed all treatments for breast cancer at least 6 m previously. We measured dynamic concentric strength at one repetition maximum (1RM), endurance at 90% 1RM, and power through a range of 40-100% 1RM for shoulder protractors, extensors and retractors. Strength and endurance, but not power, were measured for shoulder flexors. Additionally, maximal grip strength, passive shoulder range of motion and arm circumference were measured. Self-reported symptoms were recorded using a questionnaire.

Shoulder protractors (p = 0.011), retractors (p = 0.007), and extensors (p = 0.009), but not flexors, were significantly weaker on the affected side compared to the unaffected side. Muscle power and endurance at the shoulder and grip strength were not impaired. Inter-limb differences in muscle strength were not explained by the surgical and medical management of the cancer. Self-reported weakness correlated poorly with our measures of muscle strength.

Long-term weakness occurs about the shoulder secondary to treatment for breast cancer. Strategies to prevent weakness need to be considered.