Purpose of this study was to investigate the effects of anterior cruciate ligament (ACL) repair on the gamma loop of the bilateral quadriceps femoris (QF). Maximal voluntary contraction (MVC) of knee extension and integrated electromyogram (I-EMG) of vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were examined in uninjured and injured limbs of 18 patients and 10 normal subjects, before and after 20-min vibration applied to the QF. Mean percentage changes were calculated as: (pre-vibration value-post-vibration value)/pre-vibration value x 100. Patients were divided into two groups: short-term-group (tested /=18 months after ACL repair, n=10). Mean percentage changes of the four groups were compared with those of controls. Results indicated that changes of MVC and I-EMG on the uninjured and injured sides in short-term-group in response to vibration were significantly different from those of controls. There were no significant differences between uninjured sides in long-term and control groups. MVC and I-EMG of VM and RF of injured side in patients in the long-term-group in response to vibration were not different from those of controls. From these results, we concluded that this abnormality of the gamma loop in both injured and uninjured sides did not recover despite ACL reconstruction. However, the abnormality in uninjured side might recover >/=18 months after repair.

This study was performed to obtain evidence regarding bilateral hindrance of motor unit (MU) recruitment in the quadriceps femoris (QF) of patients with anterior cruciate ligament (ACL) reconstruction. The subjects included 70 patients who underwent ACL reconstruction and 35 healthy subjects. To identify the muscle torque per unit volume (MTPUV), the peak torque of each velocity of isokinetic performance was divided by muscle volume of the QF measured by a series of cross-sectional images obtained by magnetic resonance imaging scans. Tests revealed that the mean MTPUV of the uninjured (0.113+/-0.03 N m/cm3 at 60 degrees /s, 0.081+/-0.02 N m/cm3 at 180 degrees /s) and injured sides (0.109+/-0.03 N m/cm3 at 60 degrees /s, 0.079+/-0.023 N m/cm3 at 180 degrees /s) were significantly lower than those of the control group (0.144+/-0.05 N m/cm3 at 60 degrees /s, 0.096+/-0.04 N m/cm3 at 180 degrees /s). Previous studies suggested that MU recruitment in the QF of patients with ACL injury was hindered bilaterally. However, the design of their studies could not provide evidence of bilateral hindrance of MU recruitment in the QF. The results of the present study demonstrated that the MTPUV of both injured and uninjured sides of patients were significantly lower than those of the control group.

To investigate the role of proprioceptors of different skeletal muscles in postural control, in normal subjects and patients with unilateral labyrinthine dysfunction (ULD), the effect of vibration on these muscles was studied by postulography. The subjects comprised 59 normal subjects and 12 patients with ULD due to resection of acoustic tumours. Sagittal body sway was observed during vibration to the triceps surae, tibialis anterior and upper dorsal neck muscles. No significant change in sway was observed in the frontal plane in normal subjects. Significant differences between normal subjects and patients were found on stimulation of the muscle groups of triceps surae and biceps femoris during vibration. In patients with ULD, vibration to the dorsal neck muscles caused a deviation towards the diseased side. It can be speculated that the upper dorsal neck muscle plays an important role in maintaining the body balance in the frontal plane in patients with ULD. On the other hand, the lower extremity muscles, especially the muscles on the dorsal side of the body, play a significant role in adjusting the standing posture in the sagittal plane.

No abstract