The effect of upper-limb motion on lower-limb muscle synchrony - Implications for anterior cruciate ligament injury

Background: A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely , abrupt decelerative landings. Methods: Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catc hing. Ground-reaction force and electromyographic data for six lower-limb m uscles were sampled while the subjects' landing technique was filmed. The j oint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the tim e of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force. Results: When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial f oot-ground contact and of the peak tibiofemoral shear force, and they showe d delayed biceps femoris onset relative to the timing of the peak tibiofemo ral shear force compared with the findings in the trials without catching. Conclusions: We concluded that catching a ball during an abrupt landing cou ld increase the potential for an anterior cruciate ligament injury by limit ing the time available for the hamstring muscles to generate posterior tibi al-drawer force before the onset of the quadriceps-induced anterior tibial translation. Clinical Relevance: The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, partic ularly the quadriceps and the hamstrings. The present study demonstrated th at motion of the upper-limbs may interfere with recruitment of these muscle s, thereby predisposing the anterior cruciate ligament to injury.