Regression Equations for Femoral Neck Loading Assessment During Hip-Targeted Resistance Training.

Abstract

To develop regression equations predicting femoral neck (FN) strains during hip-targeted resistance training in elderly women, enabling individualized exercise prescription for osteoporosis prevention. Twelve community-dwelling postmenopausal women (69.4±3.4 years) performed four resistance exercises (hip abduction, adduction, flexion, extension) at 40%, 60%, and 80% of one-repetition maximum (1RM). Three-dimensional motion capture combined with musculoskeletal modeling calculated hip contact forces (HCFs). Finite element analysis determined tensile and compressive strains in superior and inferior FN regions. Forward stepwise linear mixed models examined relationships between external loading parameters (weight lifted, leg length) and FN strain magnitudes. Hip abduction generated the highest HCFs (4.14 body weights at 80% 1RM), followed by hip extension (3.08 BW), hip flexion (2.58 BW), and hip adduction (1.89 BW). Two-way repeated measures ANOVA revealed significant effects of exercise type and intensity on all outcomes (p<0.001). Weight lifted alone adequately predicted most strain metrics (R²=0.354-0.764), with leg length significantly improving prediction only for tensile superior strain during hip extension (R²=0.586). Hip abduction and extension at 80% 1RM produced strain magnitudes exceeding osteogenic thresholds (>1500-2500 με), particularly in the superior FN region. Compressive superior strain during hip extension showed the strongest weight-strain relationship (R²=0.764). High-intensity hip abduction and extension exercises generate substantial FN loading that may stimulate bone formation. The developed regression equations provide practical tools for estimating individual strain responses based on weight lifted, supporting personalized exercise prescription. Only exercises performed at 80% 1RM consistently reached osteogenic strain thresholds, emphasizing the importance of high-load resistance training for bone health in elderly populations.