Isokinetic Shoulder and Knee Strength in Female Breakers: Associations with Training Habits

Literature review: Breaking combines dance and acrobatics, making it a physically demanding discipline. Limited evidence suggests muscular imbalances in isometric shoulder strength and jump performance. To date, research has primarily focused on male participants and has not included isokinetic dynamometry assessments. Objective: To analyze the isokinetic strength of the shoulder internal and external rotators and the knee flexors and extensors in female breakers, and to explore their association with training habits. Methods: A retrospective cross-sectional analysis was conducted on eight women with over 5 years of breaking experience. Concentric isokinetic strength tests were performed for shoulder rotators (at 90°/s and 240°/s) and knee flexors and extensors (at 60°/s and 180°/s). Peak torque, Inter-Limb Asymmetry Index (IAI), hamstring-to-quadriceps (H:Q) ratio, and external-to-internal shoulder rotation (ER:IR) ratio were calculated. Spearman’s rank correlation coefficient (ρ) assessed relationships between training habits and isokinetic strength measures. Results: In the shoulder test at 90°/s, the median IAI for internal rotator peak torque was 14.0% (7.7-17.0). The ER:IR ratio showed median values of 38.0% (36.7-44.0) in the right arm and 32.5% (29.2-42.7) in the left. A positive correlation was found between ER:IR ratio and weekly resistance training hours (ρ = .709; P = .049). In the knee test at 60°/s, a positive correlation was observed between extensor torque IAI and weekly breaking hours (ρ = .70; P = .049). At 180°/s, flexor torque IAI was positively correlated with years of breaking practice (ρ = .929; P < .001). Conclusion: Female breakers exhibit shoulder and knee muscle imbalances associated with training duration and volume. These findings support the relevance of targeted strength assessments and preventive strategies in this population.