The influence of hamstring musculo-articular stiffness on biomechanical factors indicative of anterior cruciate ligament loading

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Justin Phillip Waxman (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Advisor
Sandra Shultz

Abstract: Noncontact anterior cruciate ligament (ACL) injuries commonly occur upon initial foot contact (IC) with the ground during single-leg cutting or jump-landing maneuvers. Because these injuries occur in the absence of physical contact with another player or object, it is believed that some of these injuries may be avoided through intervention strategies aimed to target modifiable injury risk factors. In this regard, hamstring musculo-articular stiffness (KHAM) may play a critical role in protecting the ACL during functional athletic movements by helping resist biomechanical characteristics indicative of ACL loading, such as proximal tibia anterior shear force (PTASF), anterior tibial translation (ATT), and anterior tibial acceleration (ATA). However, current evidence regarding the influence of KHAM on knee joint biomechanics is limited to studies of non-weight bearing perturbations and double-leg landing tasks, which may not adequately represent the single-leg landing situations in which noncontact injuries commonly occur. Additionally, males and females have been included in the same analyses without accounting for between-sex differences that may confound reported relationships. Thus, the purposes of this study were to: 1) compare the neuromuscular and biomechanical demands of a double-leg stop-jump (DLSJ) task to that of a single-leg stop-jump (SLSJ) task in males and females; 2) determine, within each sex, the extent to which KHAM predicts ACL-loading characteristics during a SLSJ, after controlling for initial body positioning (i.e. trunk center-of-mass position and hip and knee flexion angles at IC); and 3) examine the extent to which a select group of anatomical, neuromuscular, and biomechanical characteristics collectively predict ACL-loading characteristics during a SLSJ. Eighty healthy, physically-active, males (n = 40) and females (n = 40) completed a 5-min warm-up, were measured for anterior knee laxity (AKL), quadriceps and hamstring maximal voluntary isometric contractions (MVIC), and KHAM, and then performed the DLSJ and SLSJ tasks, during which biomechanical and neuromuscular activation data were collected. Compared to the DLSJ, males and females performed the SLSJ with a more posterior trunk center-of-mass position (P < .001) and smaller knee-flexion angles (P < .001) at IC, less knee-flexion excursion (P = .038), greater ground reaction forces (P < .001), knee-extension moments (P = .033), and PTASF (P < .001), and less ATT (P = .007). Compared to men, women performed both tasks with smaller knee-flexion angles at IC (P = .047), less hip-flexion excursion (P = .006), slower hip-flexion velocities (P = .040), smaller hip-extension moments (P < .001), and greater ATT (P = .006); however, compared to the DLSJ, females performed the SLSJ with a greater reduction in hip-flexion velocity (P < .001) and a smaller increase in hip-extension moment (P < .001) than males. Irrespective of sex, individuals with greater amounts of AKL performed the SLSJ with a greater increase in PTASF compared to individuals with lesser AKL (P < .001). After controlling for initial body positioning, KHAM was not a predictor of ACL-loading characteristics during the SLSJ in either sex. These results indicate that performing a stop-jump task on a single leg elicits characteristics associated with increased ligamentous loading and a landing posture that is more representative of what has been observed during injurious situations, and that the demands placed on the body during the SLSJ are greater for females compared to males. Thus, researchers are encouraged to use tasks that more closely mimic the conditions in which noncontact ACL injuries commonly occur, and employ sex-specific analyses, in future work. Additionally, although individuals with greater KHAM have previously been reported to display biomechanical characteristics indicative of lesser ACL loading during non-weight bearing perturbations and double-leg jump-landings, KHAM was not found to be a significant predictor of ACL-loading characteristics in either sex during the SLSJ in the current study. While these conflicting findings may indicate that the hamstrings ability to resist sagittal-plane ACL loading characteristics is negated when landing on a single leg, due to a more upright landing style, future studies are needed to further elucidate the functional role of the hamstrings in resisting sagittal-place ACL loading characteristics when landing on a single leg in a more upright position.

Additional Information

Publication
Dissertation
Language: English
Date: 2017
Keywords
Anterior crudiate ligament, Hamstrings, Injury, Lower extremity, Neuromuscular, Stiffness
Subjects
Anterior cruciate ligament $x Wounds and injuries $x Prevention
Hamstring muscle $x Mechanical properties

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