Neuromuscular fatigue and tibiofemoral joint biomechanics when transitioning from non-weight bearing to weight bearing.
BACKGROUND
Fatigue is suggested to be a risk factor for anterior cruciate ligament injury. Fatiguing exercise can affect neuromuscular control and laxity of the knee joint, which may render the knee less able to resist externally applied loads. Few authors have examined the effects of fatiguing exercise on knee biomechanics during the in vivo transition of the knee from non-weight bearing to weight bearing, the time when anterior cruciate ligament injury likely occurs.


OBJECTIVE
To investigate the effect of fatiguing exercise on tibiofemoral joint biomechanics during the transition from non-weight bearing to early weight bearing.


METHODS
Cross-sectional study.


METHODS
Research laboratory.


METHODS
Ten participants (5 men and 5 women; age = 25.3 ± 4.0 years) with no previous history of knee-ligament injury to the dominant leg.


METHODS
Participants were tested before (preexercise) and after (postexercise) a protocol consisting of repeated leg presses (15 repetitions from 10°-40° of knee flexion, 10 seconds' rest) against a 60% body-weight load until they were unable to complete a full bout of repetitions.


METHODS
Electromagnetic sensors measured anterior tibial translation and knee-flexion excursion during the application of a 40% body-weight axial compressive load to the bottom of the foot, simulating weight acceptance. A force transducer recorded axial compressive force.


RESULTS
The axial compressive force (351.8 ± 44.3 N versus 374.0 ± 47.9 N; P = .018), knee-flexion excursion (8.0° ± 4.0° versus 10.2° ± 3.7°; P = .046), and anterior tibial translation (6.7 ± 1.7 mm versus 8.2 ± 1.9 mm; P < .001) increased from preexercise to postexercise. No significant correlations were noted.


CONCLUSIONS
Neuromuscular fatigue may impair initial knee-joint stabilization during weight acceptance, leading to greater accessory motion at the knee and the potential for greater anterior cruciate ligament loading.
Department of Kinesiology, University of North Carolina at Greensboro;
Randy J
RJ
Schmitz
Hyunsoo
H
Kim
Sandra J
SJ
Shultz
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007717:Knee; D007718:Knee Injuries / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D013977:Tibia; D016474:Weight-Bearing / Q000502:physiology*
anterior cruciate ligament; axial loading; knee