Laurie's Blogs.

In last week’s blog, we looked at defining and understanding the mechanisms behind arthrogenic muscle inhibition (AMI).  Find it at:   https://www.fourleg.com/Blog?b=584 

This week, we go back to the literature to give us some ideas on how to best address AMI.

Authors of the paper used for this discussion (Norte et al 2021) start out by acknowledging that specific interventions need to be anchored to a clinical goal(s), and while not ‘time-based in nature, are likely to fall into acute or subacute phases of recovery.  In other words – Patient Specific.

Although theoretical, there is evidence to suggest that failure to resolve AMI during the early phases of recovery from injury may promote maladaptive neural plasticity, contributing to persistent muscular impairments and compensatory movement patterns (Figure 1)

Figure 1

—Natural progression and theoretical development of maladaptive motor neuron behavior in the context of clinical manifestations. Healthy individuals are able to recruit motor neurons within a given motor neuron pool (eg, quadriceps) with high variability. Patients begin rehabilitation following joint injury (eg, anterior cruciate ligament reconstruction) with a limited proportion of their motor neuron pool available for use. Although the availability of motor neurons returns to normal over time, traditional rehabilitation does not always restore the ability to voluntarily recruit newly available motor neurons (ie, central activation failure). This theoretical maladaptive strategy has low variability, which may fatigue a smaller proportion of motor neurons and increase joint loading. This deficiency may allow for effective compensation in a low-demand environment yet may fail under higher demands once the patient returns to their sport. As new motor neurons become available, specific rehabilitation strategies may be used to optimize voluntary recruitment (Italics = Theory).

Citation: Journal of Sport Rehabilitation 31, 6; 10.1123/jsr.2021-0139

Following, the authors present a series of interventions with empirical and/or theoretical support for their ability to reduce the immediate effects, or potential sequelae, of AMI (Figure 2).

Figure 2

—Summary of interventions with evidence to support use in treating arthrogenic muscle inhibition. Acute and subacute recovery phases are presented with their associated clinical goals for context. There is likely considerable overlap between the interventions used in each phase, and the decision for use should be anchored to an individualized clinical goal. Emerging interventions are presented for a broad range of recovery. Green boxes represent evidence from individuals with joint or simulated joint injury. Yellow boxes represent evidence from healthy individuals only. Colored boxes do not reflect the strength or quality of evidence. NMES indicates neuromuscular electrical stimulation; TENS, transcutaneous electrical nerve stimulation.

Citation: Journal of Sport Rehabilitation 31, 6; 10.1123/jsr.2021-0139

The chart above is fairly self-explanatory.  One could argue that certain interventions are missing from the ‘Acute Phase’ options (such as laser therapy which is commonly used in our animal patients more so than ultrasound).  To note, in the ‘Subacute phase’ it appears important to adopt eccentric cross-exercises (i.e. of the other limb) and eccentric exercises (to the affected limb) as well as whole body vibration as ways to enhance cortical neural excitability.  Where we will struggle with our animal caseload is in the ‘Emerging interventions’ category.  

Let’s look at some emerging interventions for AMI that might be able to cross over for our animal patients.

Motor skill training: Neural plasticity underlying motor skills acquisition through practice should be considered to guide patients in motor skill (re)learning following injury.  Promoting differential learning by manipulating the environment, utilizing random practice schedules, and ensuring patient motivation.  What does this mean in clinical terms for our canine patient?  I see this as the ‘boot camp’ phase, where you take an animal through a variety of land based exercises that incorporate functional activities and challenge the body from a strength perspective, complexity perspective, learning perspective, fatigue perspective, acceleration – deceleration perspective, reaction-time perspective, coordination perspective, and so on!

Visual occlusion:  Put a blindfold on the dog and then have them perform a safe task.  Here you could use a land treadmill, moving at a predictable safe rate of speed, while holding the dog in place or enticing the dog with treats to continue to walk (forwards, backwards, or sideways).  Note: I would only do this after acclimatizing the dog to the task.  You might also try luring the blindfolded dog over a series of soft or inflatable ground level objects (i.e. folded yoga mat, foam, baby mattress, air mattress, etc.) as a way of accomplishing visual occlusion training.

Beyond these two categories, the animal physiotherapy / canine rehabilitation practitioner has a greater challenge in alleviating AMI.  However, a greater focus on these two categories, and in particular motor skill training, has the best potential for addressing arthrogeneic muscle inhibition.   

If I’ve said it once, I’ve said it a million times, you need to get the dog out of the UWT or Pool and into dry-land training if you want your canine patient to fully recover!  You need to prescribe home exercises, beyond leash walks, that serve to challenge the neuromusculoskeletal system.  If you don’t, you set the dog up for reinjury or new-injury down the road!

How’s that for pressure?

Until next time… Cheers!

Laurie

Reference:

Norte G, Rush J, Sherman D. Arthrogenic Muscle Inhibition: Best Evidence, Mechanisms, and Theory for Treating the Unseen in Clinical Rehabilitation. J Sport Rehabil. 2021 Dec 9;31(6):717-735. doi: 10.1123/jsr.2021-0139. PMID: 34883466.