Effect of Breast Cancer Surgery on Upper-Limb Muscle Activation

Area of Science:

• Biomechanics
• Rehabilitation Science
• Oncology

Background:

• Breast cancer surgery, including mastectomies and lumpectomies, can impact upper-limb function.
• Understanding muscle activation patterns is crucial for effective rehabilitation strategies.

Purpose of the Study:

• To compare upper-limb muscle activation between the affected and non-affected sides after unilateral breast cancer surgery.
• To evaluate the influence of different fatigue levels on muscle activation.
• To identify the most reliable method for normalizing muscle activation data.

Main Methods:

• A two-step design involving unilateral bench press exercises.
• Comparison of three normalization methods: isometric (ISO_Norm), repetition maximum (1RM_Norm), and Max80%_Norm.
• Electromyography (EMG) to measure muscle activation in twelve women post-surgery.
• Testing at 60% and 80% of 1RM until 40% velocity loss, divided into low and moderate fatigue groups.

Main Results:

• Max80%_Norm exhibited the lowest inter-subject variability (12.9%) for muscle activation normalization.
• The affected side showed higher deltoid and triceps activation but lower pectoralis activation at 60% 1RM.
• Differences in muscle activation between sides were minimal and inconsistent at 80% 1RM and not statistically significant.

Conclusions:

• The Max80%_Norm method is recommended for normalizing muscle activation data in similar studies.
• No significant or clinically meaningful differences in upper-limb muscle activation were found between the affected and non-affected sides.
• Findings suggest upper-limb muscle activation is largely preserved following breast cancer surgery, though caution is advised due to sample limitations.