title: Reduced hamstring strength increases anterior cruciate ligament loading during anticipated sidestep cutting.
abstract: BACKGROUND
  Dynamic knee stability is considered a critical factor in reducing anterior cruciate ligament loads. While the relationships between hamstring force production and anterior cruciate ligament loading are well known in vitro, the influence of hamstring strength to anterior cruciate ligament loading during athletic maneuvers remains unknown. Therefore, the purpose of this study was to determine the influence of hamstring strength on anterior cruciate ligament loading during anticipated sidestep cut.
  
  
  METHODS
  Seventeen recreationally active females were recruited to perform sidestep cutting maneuvers pre/post an acute hamstring strength reduction protocol. Kinematics and kinetics were calculated during the cut and a musculoskeletal model was used to estimate muscle, joint, and anterior cruciate ligament loads. Dependent t-tests were conducted to investigate differences between the two cutting conditions.
  
  
  RESULTS
  Anterior cruciate ligament loading increased by 36% due to reduced hamstring strength. This was mostly due to a 44% increase in sagittal plane loading and a 24% increase in frontal plane loading. Post strength reduction sidestep cuts were also performed with decreased anterior tibiofemoral shear force, an outcome that would theoretically reduce anterior cruciate ligament loading. However, the overall decrease in hamstring force production coupled with a more axial hamstring line of action yielded a net increase in anterior cruciate ligament loading.
  
  
  CONCLUSIONS
  These results suggest that decreased hamstring strength significantly increases anterior cruciate ligament loading during anticipated sidestep cutting. Additionally, these results support the premise that preseason screening programs should monitor hamstring strength to identify female athletes with potential deficits and increased injury risk.
authors: Department of Human Movement Sciences, Old Dominion University, Norfolk, VA 23529, USA. Electronic address: jweinhan@odu.edu.
authors: Joshua T
authors: JT
authors: Weinhandl
authors: Department of Kinesiology, University of Wisconsin-Milwaukee, Milwaukee, WI 53202, USA.
authors: Jennifer E
authors: JE
authors: Earl-Boehm
authors: Department of Kinesiology, University of Wisconsin-Milwaukee, Milwaukee, WI 53202, USA.
authors: Kyle T
authors: KT
authors: Ebersole
authors: Department of Kinesiology, University of Wisconsin-Milwaukee, Milwaukee, WI 53202, USA.
authors: Wendy E
authors: WE
authors: Huddleston
authors: Department of Electrical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53202, USA.
authors: Brian S R
authors: BS
authors: Armstrong
authors: Department of Kinesiology, University of Wisconsin-Milwaukee, Milwaukee, WI 53202, USA.
authors: Kristian M
authors: KM
authors: O'Connor
mesh_terms: D000465:Algorithms; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D004576:Electromyography; D015444:Exercise; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000517:prevention & control; D007719:Knee Joint / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology*; D015203:Reproducibility of Results; D013177:Sports / Q000502:physiology; D013314:Stress, Mechanical; D013848:Thigh; D055815:Young Adult
keywords: Injury; Knee; Musculoskeletal modeling; Simulation