The Effects of Whole Body Vibration Therapy on Increasing Quadriceps Strength Prior to Anterior Cruciate Ligament Reconstruction

The effect of whole body vibration therapy on increasing quadriceps strength prior to anterior cruciate ligament reconstruction

1. Introduction:

Anterior cruciate ligament (ACL) injury is a common knee injury in orthopaedic and sports medicine. It is estimated that there are 200000 ACL injuries annually in US. According to the ACL injury registry system of Scandinavia, the incidence of ACL injury was about 32-38/10000 people per year. ACL reconstruction (ACLR) has been recommended as the optimal treatment to restore knee passive laxity in patients with ACL injury who have desire to return to sports. However, a recent meta-analysis showed that only 42% of elite athletes are able to return to non-elite competitive sports following a successful reconstruction and rehabilitation. About 50% of them cannot return to sports at 1 year and one-third cannot return at 2 years post-operatively.

Until now, the reason why some patients can have good functional recovery following surgery while the others cannot is still unknown. Since the ultimate goal of ACL reconstruction is to help patients return to pre-injury activity without high re-injury risk, identifying those who are at high risk of poor recovery following surgery is extremely essential. Some previous studies concluded that pre-operative quadriceps strength is a key predictor for functional recovery post-operatively. Therefore, increasing pre-operative quadriceps strength is very important. Several studies implemented pre-operative rehabilitation found that part of patients still could not achieve symmetrical quadriceps strength, which mainly because of injury-induced arthrogenic inhibition and increased atrophy-related biomarkers makes those patients have low response to traditional strength training.

It has been demonstrated that whole body vibration is an effective way in decreasing AMI due to increase corticomotor excitability. Whole body vibration becomes more and more popular as an additional program of physiotherapy for diverse disorders. For patients with ACL injury, previous studies indicate that whole body vibration is effective in improving quadriceps function, neuromuscular control and balance. There are several mechanisms can explain the benefits whole body vibration therapy brought to ACLD patients. Firstly, vibratory stimuli can increase the excitability of type Ia afferent neuron via muscle spindles, resulting in tonic vibration reflex and enlargement of type I and type II muscle fibers. Secondly, whole body vibration can decrease fast-twitch motor unit recruitment thresholds immediately, leading to higher activation of muscles. Thirdly, vibratory stimuli may activate proprioceptive receptors of lower limbs. On molecular level, Low-amplitude high frequency vibration can down regulate Atrogin-1 mRNA and myostatin expression. In addition, it also was found effective in increasing circulating irisin which is a recently identified myokine levels acutely after vibration exercises. Several studies also reported that whole body vibration training can reduce blood concentration of TNF-αreceptors, TNF-α, IL-6 in elderly population and healthy people after exercise. Based on the above, whole body vibration maybe a more efficient and effective way to improve quadriceps strength prior to surgery.