Author(s): ÖLMEZ, C., ACAR, S.T., YÜCELSOY, B., Institution: ORDU UNIVERSITY, Country: TURKEY, Abstract-ID: 447

INTRODUCTION:
Mobility of the spine and hip may actively modulate torque generation and temporal control within the kinetic chain. The neuromechanical contribution of regional flexibility to hip torque performance remains unclear. The purpose of this study was to determine whether lumbar, thoracic, and hip flexibility predict torque magnitude and timing during isokinetic testing in recreationally active women.
METHODS:
Twenty-two females completed standing isokinetic hip flexion–extension and abduction–adduction testing. Peak torque (PT), time to peak torque (TPT), joint angle at peak torque (JAP), and explosive torque index (PT/TPT) were normalized to body mass. Multi-planar trunk and hip flexibility were assessed using an IMU-based 3D motion capture system. Lumbar, thoracic, and hip composite flexibility indices were derived from standardized range-of-motion values. Associations were examined using Spearman correlations and multiple regression analyses.
RESULTS:
Greater total lumbopelvic–hip flexibility was moderately to strongly associated with higher PT and explosive torque outputs during flexion and adduction (ρ = 0.43–0.58, p < 0.05). Lumbar flexibility showed the strongest relationship with torque magnitude, predicting dominant adduction PT (β = 0.57, R² = 0.33, p = 0.005) and non-dominant flexion PT (β = 0.54, R² = 0.29, p = 0.010). Thoracic mobility primarily influenced temporal characteristics, with greater flexibility associated with shorter or optimized TPT values (ρ ≈ 0.52, p < 0.01) and contributing to up to 24% of the variance in timing outcomes. Hip abduction range demonstrated a negative association with JAP during adduction (β = −0.46, p = 0.032), indicating that higher lateral mobility enabled peak torque to occur at more mechanically efficient joint angles. Collectively, regional flexibility variables independently explained meaningful proportions of both torque magnitude and timing variance.
CONCLUSION:
The findings suggest that flexibility functions as an active neuromechanical resource rather than a passive range-of-motion trait. Lumbar mobility showed the strongest association with torque magnitude, likely facilitating proximal stability and more effective force transfer along the kinetic chain. In contrast, thoracic mobility primarily influenced temporal parameters, indicating a role in intersegmental sequencing and the timing of torque development. Hip mobility contributed to improved mechanical efficiency by enabling peak torque to occur at more favorable joint angles. Together, these region-specific contributions support a distributed control strategy in which spinal and hip segments cooperatively regulate both the magnitude and timing of torque production. From a practical perspective, integrating targeted multi-segmental flexibility training into strength and rehabilitation programs may enhance force transmission, coordination, and postural control, thereby improving overall movement efficiency within the lumbopelvic–hip complex.