Trunk Neuromuscular Control is Associated with ACL Loading Mechanisms During an Athletic Cutting Task

Abstract

Trunk position and postural control influence lower extremity biomechanics during athletic tasks. Triplanar loading of the knee results in high levels of stress in the anterior cruciate ligament (ACL). Excessive trunk motion has been reported during movements resulting in ACL injury. However, the relationship between trunk neuromuscular control (NMC) and triplanar knee loads during an athletic cutting task (ACT) has not been examined. PURPOSE: To investigate the relationship between a laboratory measure of trunk NMC during unstable-sitting (UST) and triplanar knee loads during an ACT. METHODS: 30 physically active subjects (15 male, 15 female, age: 20.5 ± 2.5 yrs, mass: 67.50 ± 11.39 Kg, height: 173.78 ± 9.28 cm) from the university setting participated in this study. During each 1-minute UST trial subjects were required to maintain balance atop a rigid hemisphere with their arms crossed at the chest and with their feet in contact with a footrest fixed to the unstable-sitting device. Center of pressure (CoP) sway data were collected during the UST using a forceplate. For the ACT subjects were instructed to take 3 running steps, jump over a 17 cm hurdle, and cut at 60° in the opposite direction of their dominant plant leg. Peak triplanar trunk angles and knee loads were collected using an infrared motion capture system and forceplate during the first 50% of stance time during the side-step ACT. Pearson product-moment correlation coefficients were calculated among CoP sway data and external knee loads. RESULTS: CoP sway velocity (1.34 ± 0.23 cm/s) was directly associated with anterior tibial shear force (0.114 ± 0.092) (r = 0.382, p = 0.049), and tibial external rotation moment (0.032 ±.013) (r = 0.451, p = 0.018). CoP sway area (50.29 ± 18.50 cm2) was positively associated (r = 0.548, p = 0.006) with knee flexion moment (0.115 ± 0.032). CoP sway path (81.02 ± 14.44 cm) was positively associated with knee flexion moment (r = 0.407, p = 0.032) and tibial external rotation moment (r = 0.474, p = 0.011). CONCLUSION: The results of this study provide evidence of a relationship between trunk NMC and triplanar knee loading associated with ACL injury. These relationships suggest that poor NMC of the trunk is associated with increased triplanar loading at the knee joint. Interventions with a focus on improving trunk NMC may decrease ACL injury risk.