Neuromechanical coupling in the regulation of muscle tone and joint stiffness

Abstract

The ability of the nervous system to accommodate changes to joint mechanics is crucial in the maintenance of joint stability and the prevention of injury. This neuromechanical coupling is achieved through several mechanisms such as the central and peripheral regulation of muscle tone and subsequent alterations to joint stiffness. Following joint injury, such as a ligamentous sprains, some patients develop functional instability or require surgery to stabilize the joint, while others are able to cope and display limited impairments. Several researchers have attempted to explain these divergent outcomes, although research using proprioceptive tasks and quantifying reaction times has led to equivocal results. Recent innovations have allowed for the simultaneous measurement of mechanical and nervous system function among these subsets. The intent of this review was to explore the relationships between joint stiffness and nervous system function, and how it changes following injury. By better understanding these mechanisms, researchers and clinicians may better develop and implement rehabilitation protocols to target individual deficits among injured populations.

Lower extremity muscle activation onset times during the transition from double-leg stance to single-leg stance in anterior cruciate ligament injured subjects

“…Furthermore, a standardized speed of movement was used. These task constraints may have led to a neurocognitive overload during the transition from DLS to SLS for the ACLI subjects, hereby exceeding the capability of their compensatory attentional and motor planning resources, resulting in delayed muscle activation onset times (Grooms et al, 2015;Needle et al, 2014;Ward et al, 2015). The fact that differences between groups were also apparent during the eyes open condition, and not only during the eyes closed condition, does not support the compensatory increased need for visualization (Kapreli et al, 2009) which was previously demonstrated in ACLI subjects when evaluating center of pressure outcomes during the SLS phase of the transition task from DLS to SLS (Dingenen et al, 2015a).…”

“…In this perspective, it is important to know that the acquisition of peripheral proprioceptive information reflects only one aspect of a long and complex sensorimotor pathway. During recent years, evidence is emerging that a decreased ability of the CNS to reorganize the integration and interpretation of the altered proprioceptive afferent information and plan the motor commands may be the underlying mechanism of altered neuromuscular control patterns after ACL injury (Baumeister et al, 2008(Baumeister et al, , 2011Grooms et al, 2015;Kapreli et al, 2009;Needle et al, 2014;Ward et al, 2015). Using functional magnetic resonance imaging of the brain while performing flexion and extension of the knee while lying supine, an increased activation of specific brain areas including the pre-supplementary motor area and the posterior inferior temporal gyrus was found in ACLI subjects compared to matched controls (Kapreli et al, 2009).…”

Graft tensioning in anterior cruciate ligament reconstruction

“…Other studies suggest that function is only affected once laxity becomes excessive (Ageberg, Roberts, Holmstrom, & Friden, 2005;Sernert et al, 2002). A possible explanation for such a variation in the literature may be related to the proposed difference between the term laxity and instability (Needle et al, 2014;Schmitt, Fitzgerald, Reisman, & Rudolph, 2008).…”

“…In addition to laxity, it is hypothesised that, under dynamic functional conditions, impaired muscle strength, neuromuscular control, proprioception and psychological factors all contribute to a sense of instability and, hence, a loss of function (Eastlack et al, 1999;Needle et al, 2014;Schmitt et al, 2008). Sernert et al (2002) found that, when STSD in anterior tibial translation was greater than 6mm a significantly poorer outcome resulted based on the IKDC, Lysholm, Tegner and hop test.…”

“…Commonly, laxity infers a STSD in anterior tibial translation as opposed to instability, which refers more specifically to the patient's experience of 'giving way' during functional activities (Needle et al, 2014). In addition to laxity, it is hypothesised that, under dynamic functional conditions, impaired muscle strength, neuromuscular control, proprioception and psychological factors all contribute to a sense of instability and, hence, a loss of function (Eastlack et al, 1999;Needle et al, 2014;Schmitt et al, 2008).…”