Relationship between hip strength and trunk motion in college cross-country runners. (2013)

Abstract
PURPOSE:
Hip strength may directly relate to abnormal running mechanics and contribute to the high incidence of overuse injuries in distance runners. The purpose of this study was to determine the relationship between hip isokinetic strength and thorax and pelvic motion during treadmill running.

METHODS:
Isokinetic hip strength and treadmill running kinematics were collected on 24 collegiate cross-country runners (14 males and 10 females). Each subject completed a running protocol on a treadmill at a self-selected speed (3.58 ± 0.26 m·s) and prescribed speed (3.58 ± 0.0 m·s). Kinematic data were collected with retroreflective markers attached to the thorax, pelvis, and each lower extremity segment (thigh, shank, and foot). Thorax and pelvis range of motion (ROM) were calculated from initial ground contact to toe-off. Pearson correlation coefficients were used to determine the relationship between strength and ROM (P < 0.05). Differences between male and female athletes were tested with mixed-design ANOVAs (P < 0.05).

RESULTS:
Isokinetic hip extension and abduction torque had significant inverse correlations to thorax axial rotation ROM during stance phase of running (r = -0.60 and r = -0.53) at self-selected speed. Frontal plane pelvic obliquity ROM was also significantly correlated to hip strength (extension r = -0.49; abduction r = -0.44). Similar correlations were found during the prescribed speed condition. Female runners had significantly decreased normalized strength (hip extension 1.8 ± 0.4 N·m·kg, P < 0.05; hip abduction 1.0 ± 0.2 N·m·kg, P < 0.05), increased pelvic obliquity (13.1° ± 2.6°, P < 0.05), and thorax axial rotation (34.5° ± 7.0°, P < 0.05) ROM compared to males (hip extension 2.5 ± 0.5 N·m·kg; hip abduction 1.3 ± 0.2 N·m·kg; pelvic obliquity 8.9° ± 1.9°; thorax axial rotation 22.6° ± 3.5°).

CONCLUSIONS:
Moderate correlations were found in hip extensor and hip abductor strength and pelvic and thorax motion during running in collegiate runners.

My comments:
This is a good recent paper that I think relates to both back pain sufferers who run and those that don’t.  I’ve done a number of recent blogs on running injuries that show hip strength relates to knee, shin, foot and ankle pain.  This study didn’t look at low back pain per se, but increased spine motion with every step in a run I expect is some kind of risk factor.

Also for non-runners with low back pain, where the hip muscles are weaker still, I would expect increased spine motion with normal walking.  I often see  that clinically in my physical therapy office when patients with hip and back pain walk on a treadmill.  As such I think it very prudent to include all around hip extensor strengthening for runners to include hip abduction exercises and my favorites for hip extensors being Romanian Deadlifts (RDLs).