Date of Award
Doctor of Physical Therapy (DPT)
Anterior Cruciate Ligament Injuries -- etiology; Risk Factors
Being that the anterior cruciate ligament (ACL) is the most commonly torn ligament, much research has been performed regarding this matter. Females have been found to be more likely to tear their ACL. This may be due to strength, structural (anatomical), hormonal, and neuromuscular differences compared to men. Several studies have also been conducted to help improve preventative measures with using strengthening and neuromuscular training programs. Many speculations have been made about the precipitating factors of an ACL injury. The general consensus in regard to foot placement is that the foot is usually placed in pronation during an ACL tear.
This research study was conducted to determine if differing foot placements made a difference in muscle activity of the tibialis anterior, lateral gastrocnemius, biceps femoris, rectus femoris, gluteus medius, and gluteus maximus muscles. Participants performed a single leg squat on 5 different angled surfaces while electromyographic (EMG) electrodes recorded muscle activity data. The different surfaces included 5° and 10° of pronation, 5° and 10° of supination, and neutral.
The results showed a significant difference in muscle activity of the lateral gastrocnemius, gluteus maximus, and biceps femoris. All 3 muscles showed the highest mean activity during pronation. These findings support the research hypothesis that there is a difference in muscle activity in the lateral gastrocnemius, biceps femoris, and gluteus maximus muscles during pronation.
Large standard deviations were found during statistical analysis of all 5 foot positions. The large standard deviations can be attributed to the following: decreased balance and unsteadiness of the participants during squats; not having time to practice squats prior to participating in the study; prior pronation tendencies were not screened prior to the study; measuring the degree of knee flexion during the squat was not done (some participants may have squatted deeper than others); and a low sample size of participants was used. Because a significant difference was found among muscle activity, there may be a connection with ACL injuries and foot positions.
Letvin, Hayley J., "Influence of Foot Position on Lower Extremity Muscle Activity" (2012). Physical Therapy Scholarly Projects. 625.