It is well established that female runners are at a significantly increased risk of incurring injuries when compared to their male counterparts. Gender-specific factors such as anatomical, hormonal, and altered neuromuscular activation patterns have been implicated as causative factors. An association have been observed between hormonal fluctuation and ACL injury risk indicating potentially hormonal effect on both passive and dynamic knee stabilizer.

A growing contingency believes that we were designed with all we need in our feet to be able to run with minimal shoes that mimic barefoot running striking pattern. Habitual barefoot runners tend to FFS, compared to habitually shod populations who tend to RFS. Reduced collision forces generated with FFS patterns relative to RFS account for the reduced injuries.

The purpose of this study was to assess the effect of 6 weeks of a transition program of SBR on the pattern of muscle activation, spatiotemporal variables, and stance phase kinetics. These running parameters were compared and contrasted during the menstrual cycle to assess whether estrogen fluctuation has an effect on the pattern of muscle activation, and laxness of ACL.

Twenty four females runner were divided into two groups. First group was tested twice across a menstrual cycle for serum levels of E, KJL and EMG activity of the quadriceps and hamstrings muscles. Second group gradually experienced SBR over 6 weeks. Kinetic analysis of running was performed during shod running, habituated SBR conditions.

The results showed an observed increased in KJL in response to peak E during the ovulatory phase, which was associated with increased preactivity of the hamstring muscle. A consistent pattern was observed in the firing of the quadriceps muscle recruitment pattern throughout the follicular phase. The results of the second group indicated a significant decrease in the EMG activity of TA in the habituated SBR. A significant increase was observed in the preactivation of GAS between shod running, and habituated SBR.

In conclusion, changes in KJL in response to 17β-Estradiol fluctuations changes the neuromuscular control around the knee. Changes in motor patterns in previously habitually shod runners are possible and can be accomplished within 6 weeks.

LLU Discipline

Physical Therapy


Physical Therapy


School of Allied Health Professions

First Advisor

Petrofsky, Jerrold S.

Second Advisor

Daher, Noha S.

Third Advisor

Lohman III, Everett

Fourth Advisor

Mohamed, Olfat

Degree Name

Doctor of Science (DSc)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Running -- Physiological aspects; Foot -- Movements; Women; Sports Injuries; Athletic Injuries-Rehabilitation

Subject - Local

Estrogen Fluctuation



Page Count


Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives