Enhance Sensory Input on Reversing the Quadriceps Inhibition in Individuals with Acl Deficiencies (II)

Anterior cruciate ligament (ACL) is vulnerable to injury. In individuals with ACL deficiency, quadriceps weakness and atrophy are very common. Following ACL deficiency, the voluntary activation level was found to be decreased which, thus, worsen the symptom of quadriceps weakness. In addition, the motor evoked potential elicited by transcranial magnetic stimulation was revealed to be decreased in ACL deficiency, but these changes were not significant. Part of the reasons might be due to the level of deficiencies were varied across subjects. Finding the correlation between the clinical symptoms and the excitability of motor pathways will be helpful to understand the contribution of neural factors to the quadriceps weakness in ACL deficiencies. The conventional training program for individuals with ACL deficiencies focused on the voluntary strength training. However, due to the neural inhibition, some muscular structure could not be activated. Training program focus on decreasing neural inhibition needed to be developed in individuals with ACL deficiencies. In reviewing of past researches, sensory level electrical stimulation at a intensity just above motor threshold found to be effective in enhancing the motor pathway excitability. Therefore, adding sensory stimulation to the conventional strength training program might be helpful to reverse the quadriceps weakness in individuals with ACL deficiencies. This research project contains a serial researches which are proposed to be completed within three years. The first part of this project is to investigate the deficits of the neural factors and the correlation of the clinical symptoms of quadriceps weakness to the neural factors in individuals with chronic ACL deficiencies. The first part of this project is ongoing. The pilot results supported the original hypotheses and showed that the ACL deficient legs exerted lower voluntary activation level during maximal voluntary contractions, persisted in a lower intracortical inhibition and higher intracortical facilitation status during resting in compared to the non-affected legs and to individuals without ACL deficiencies. These results suggested that neural deficits contributed to the deficits of muscle strength in individuals with ACL deficiencies. The second parts of this project will be completed in two years. The purpose of the first year’s study is to search the optimal sensory stimulation parameters to normalize the intracortical inhibition and facilitation and to investigate its short term adaptation on individuals with ACL deficiencies. The purpose of the second year’s study is to develop a training program which emphasizes on increasing motor pathway excitability and to compare the effect to that of conventional strength training program. The results of this project will help researchers, rehabilitation specialists, athlete trainers, and coaches to understand the neural factors that limit the quadriceps contraction performance in ACL deficiencies. In addition, this project will establish an effective training program to reverse the quadriceps weakness for ACL deficiencies.

Project ID:PC9807-0309
External Project ID:NSC98-2410-H182-021-MY2