Potential recovery of arm strength capability in a post-breast cancer treatment population: A simulation analysis

Arm dysfunction often follows breast cancer treatments. Diversity in treatment makes it challenging to explore how exercise impacts dysfunction in survivors. This study computationally simulated treatment scenarios to identify a theoretical maximal producible force (aided by muscular training) and the internal muscle forces required to produce that force in a compromised system. An existing shoulder model was modified to reduce the capacity of certain muscles to mimic lower-functioning breast cancer populations. Capacity of muscles were increased to emulate training, with maximums dictated based on damage from treatment-specific scenarios (radiation, chemotherapy, combination treatment). Maximum force, torque, and muscle forces were extracted for each treatment scenario, a maximum (unaltered) non-cancer reference, and baseline (breast cancer survivor) force, across 2 maximum isometric force exertions (adduction and internal rotation). Overall, 70-80 % of strength was recoverable with successful retraining. Specifically, for both exertions' recruitment of primary movers (adductors or internal rotators) and scapular and glenohumeral stabilizers, increased from the baseline level in each scenario, with highest recruitment at the non-cancer reference force level. Although no post-training scenario reached non-cancer reference control population force levels, achieving 70-80 % of force could enable more successful daily task performance, return to work and enhance overall physical self-efficacy.