Each year the Department of Exercise and Sport Science recognizes three different masters students, one from each specialization area, for their outstanding thesis project. This week we highlight the outstanding work of Kerry Peterson, MA, ATC (class of 2015 in the Athletic Training specialization area), who conducted her thesis under the direction of Dr. Bill Prentice and committee members Tim Mauntel and Darin Padua. Many thanks to Kerry and Dr. Prentice for providing this week’s EXSS Impact content.
Stay tuned for future EXSS Impact posts where we will recognize our other outstanding thesis award recipients and highlight their research findings.
Why did you do this study?
Clinical movement screenings such as the overhead squat have been developed to identify individuals who display dysfunctional movement patterns. Previous research has identified abnormal muscular activation patterns and lower extremity range of motion differences which contribute to faulty movement patterns that may increase injury risk. Dynamic knee valgus motion is a commonly identified faulty movement pattern and a primary predictor of lower extremity injuries. Dynamic knee valgus angle combines the motions of hip and knee rotation and hip adduction on a fixed foot. Greater hip adduction motion has been linked to ACL injuries, osteoarthritis, iliotibial band syndrome, and tibial stress fractures. Similarly, greater hip adduction and internal rotation, and less dorsiflexion ranges of motion have been found in individuals with patellofemoral pain syndrome.
Previous research has established relationships between neuromuscular control, passive range of motion measurements, and dysfunctional movement patterns. Proximal lower extremity muscular activation patterns have been theorized to affect distal joint positioning. Individuals who display knee valgus during squatting tasks display smaller gluteal to hip adductor co-activation ratios compared to those who maintain a neutral knee alignment. Similarly, greater hip adductor activation has been linked to greater hip adduction motion. Hip adduction has also been linked to less dorsiflexion and greater hip internal rotation motion during squat and step-down tasks. However, additional research is needed to better establish the relationships between muscle activation patterns, lower extremity ranges of motion, and dysfunctional movement patterns.
Therefore, the purpose of this study was to determine hip muscular activation and lower extremity range of motion patterns that contribute to lateral hip shift during the overhead squat. Once the contributing factors are identified, clinicians will be better able to develop intervention programs and improve movement quality. Correction of dysfunctional movement patterns may result in a decreased occurrence of injuries.
What did you do and what did you find in this study?
Forty subjects were assigned to a hip shift or control groups based on observations during performance of an overhead squat (Figures 1 and 2). EMG data for the gluteals and hip adductors was sampled during the overhead squat. Hip internal and external rotation, hip abduction, knee extension, and dorsiflexion range of motion were assessed. The hip shift group had less hip abduction and dorsiflexion range of motion in the limb shifted toward compared to the limb shifted away from. The results of this study suggest that individuals displaying a hip shift during an overhead squat have less dorsiflexion, less hip abduction range of motion, and greater hip internal rotation range of motion on the limb being shifted toward. The findings also suggest that hip shift subjects may have decreased gluteus medius activation compared to the control group.
How do these findings impact the public?
Sports medicine clinicians utilize clinical movement screenings to visually observe lower extremity kinematics during functional tasks. These screenings can identify individuals at high risk of non-contact injury and the underlying elements that contribute to the dysfunctional movement patterns. It can also detect asymmetrical imbalances specific to each athlete, which may be predisposing factors in their own right.
These findings can help guide lower extremity injury prevention and rehabilitation programs. Individuals displaying a hip shift may benefit from rehabilitation focused on increasing femoral internal rotation of the contralateral limb and dorsiflexion of the ipsilateral limb. Individuals may also benefit from inhibiting and stretching the hip adductors on the ipsilateral limb.