Muscle strength improves independently of kinesiophobia in breast cancer patients undergoing neoadjuvant chemotherapy: a secondary analysis of a randomized trial

Abstract

Introduction: Exercise improves physical and psychosocial outcomes in breast cancer patients. However, kinesiophobia remains a potential barrier to engagement. It is unclear whether fear of movement modulates physiological adaptations to exercise during neoadjuvant chemotherapy. Methods: This secondary analysis of an ongoing randomized controlled trial included women with stage II–III breast cancer undergoing neoadjuvant chemotherapy. Participants were allocated to a resistance training group (RT; n=9), a combined training group (CT; n=8), or a control group (CG; n=7). RT and CT performed once-weekly supervised resistance training for 12 weeks; CT additionally performed aerobic exercise immediately after resistance training. Peak isometric muscle strength (PIMS) was assessed via knee extensor dynamometry, and kinesiophobia via the Tampa Scale of Kinesiophobia (TSK). A two-way analysis of variance (Group × Time) with Tukey post hoc was applied. Pearson correlations were assessed between ΔPIMS and ΔTSK, and between values at baseline and post-intervention. Analyses followed the intention-to-treat principles with expectation-maximization data imputation. Results: A significant group × time interaction was observed for PIMS (F=4.49; p=0.017; ηp²=0.176, ω²=0.102, indicating a large effect size), with higher values in RT (254.2, standard deviation ±84.79 N) and CT (236.2±81.56 N) compared to CG (124.3±26.84 N) at 12 weeks, with no difference between exercise groups. No significant effects were found for TSK (p>0.05). No correlations were observed between ΔTSK and ΔPIMS (r= −0.138; p=0.349), nor between TSK and PIMS at baseline (r= −0.062; p=0.775) or post-intervention (r=0.238; p=0.263). Conclusion: Supervised resistance and combined training improved muscle strength but did not affect kinesiophobia. The absence of association suggests that neuromuscular adaptations occur independently of fear-related psychological factors. However, the small sample and preliminary results from ongoing research limit inference.