Weak hip muscle strength and excessive hip motion during running have been suggested as potential risk factors for developing patellofemoral pain syndrome (PFPS) in females, but not males. There is conflicting evidence on the relationship between hip strength and hip kinematics, which may be partly due to sex differences in the relationship between these parameters. Hip, pelvis, and trunk kinematics were collected while 60 healthy, habitual runners (23 females, 37 males) ran overground, and isometric hip abduction and external rotation strengths were measured bilaterally. Pearson correlation coefficients quantified sex-specific correlations between hip strength and kinematics, and unpaired t tests assessed sex differences in hip strength and kinematics. Hip abduction strength was moderately and inversely correlated to hip adduction excursion in females, and pelvic internal rotation excursion in males. Hip external rotation strength was moderately and inversely correlated to trunk flexion excursion in females. Finally, females displayed less hip external rotation strength and greater excursion at the hip and trunk during running compared to males. Despite the significant correlations, the relatively low r2 values suggest that additional factors outside of strength contribute to a substantial portion of the variance in trunk, pelvis, and hip kinematics.
James J. Hannigan, Louis R. Osternig and Li-Shan Chou
Reed Ferber, Denise C. Gravelle and Louis R. Osternig
The effects of proprioceptive neuromuscular facilitation (PNF) on joint range of motion (ROM) for older adults are unknown, and few studies have investigated changes in joint ROM associated with age. This study examined PNF stretch techniques' effects on knee-joint ROM in trained (T) and untrained (UT) older adults. Knee-joint ROM was tested in T and UT adults age 45–55 and 65–75 years using 3 PNF stretch techniques: static stretch (SS), contract-relax (CR). and agonist contract-relax (ACR). The 45–55 UT group achieved significantly more ROM than did the 65–75 UT group, suggesting an age-related decline in ROM. The 65–75 T group achieved significantly greater knee-extension ROM than did their UT counterparts, indicating a training-related response to PNF stretch techniques and that lifetime training might counteract age-related declines in joint ROM. The ACR-PNF stretch condition produced 4–6° more ROM than did CR and SS for all groups except the 65–75 UT group, possibly as a result of lack of neuromuscular control or muscle strength.