Effect of fatigue on knee kinetics and kinematics in stop-jump tasks.
BACKGROUND
Altered motor control strategies in landing and jumping maneuvers are a potential mechanism of noncontact anterior cruciate ligament injury. There are biomechanical differences between male and female athletes in the landing phase of stop-jump tasks. Fatigue is a risk factor in musculoskeletal injuries.


OBJECTIVE
Lower extremity muscle fatigue alters the knee kinetics and kinematics during the landing phase of 3 stop-jump tasks and increases an athlete's risk of anterior cruciate ligament injury.


METHODS
Controlled laboratory study.


METHODS
Three-dimensional videography and force plate data were collected for 20 recreational athletes (10 male and 10 female athletes) performing 3 stop-jump tasks before and after completing a fatigue exercise. Knee joint angles and resultant forces and moments were calculated.


RESULTS
Both male and female subjects had significantly increased peak proximal tibial anterior shear forces (P = .01), increased valgus moments (P = .03), and decreased knee flexion angles (P = .03) during landings of all 3 stop-jump tasks when fatigued. Fatigue did not significantly affect the peak knee extension moment for male or female athletes.


CONCLUSIONS
Fatigued recreational athletes demonstrate altered motor control strategies, which may increase anterior tibial shear force, strain on the anterior cruciate ligament, and risk of injury for both female and male subjects. CLINIC RELEVANCE: Fatigued athletes may have an increased risk of noncontact anterior cruciate ligament injury.
Center for Human Movement Science, Division of Physical Therapy, CB 7135 Medical School Wing E, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7136, USA.
Jonathan D
JD
Chappell
Daniel C
DC
Herman
Bradford S
BS
Knight
Donald T
DT
Kirkendall
William E
WE
Garrett
Bing
B
Yu
D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D013177:Sports / Q000502:physiology*