Exploring the Links Between Human Movement, Biomechanics & Gait
Yay for the lift, spread and reach exercise!
Toe spreads and squeezes are aimed at strengthening specific intrinsic foot muscles—the dorsal and plantar interrosei, according to Irene S. Davis, PhD, PT, director of the Spaulding National Running Center and a professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School in Boston. Doming or foot shortening exercises contract most of the muscles on the plantar side of the foot, and help to strengthen the abductor hallucis muscle
Treat the paraspinals in addition to the peripheral muscle
As people who treat a wide variety of gait related disorders we often emphasize needling the paraspinal muscles associated with the segemental innervation of the peripheral muscle you are treating. For example, you may facilitate or needle the L2-L4 paraspinals (ie: femoral nerve distribution) along with the quads, or perhaps the C5-C6 PPD’s along with the shoulder muscles for the deltiods or rotator cuff for arm swiing. We do this to get more temporal and spacial summation at a spinal cord level, to hopefully get better clinical results.
White and Panjabi described clinical instability as the loss of the ability of the spine, under physiologic loads, to maintain relationships between vertebrae in such a way that there is neither damage nor subsequent irritation to the spinal cord or nerve roots, and, in addition there is no development of incapacitating deformity or pain due to structural changes.
Increased movement between vertebrae (antero or retrolisthesis) of > 3.5 mm (or 25% of the saggital body diameter) during flexion and/or extension suggests clinical instability. This often leads to intersegmental dysfunction and subsequent neurological sequelae which could be explained through the following mechanisms:
Recall that the spinal nerve, formed from the union of the ventral (motor) and dorsal (sensory) rami, when exiting the IVF splits into an anterior and posterior division, supplying the structures anterior and posterior to the IVF respectively. The posterior division has 3 branches: a lateral branch that supplies the axial muscles such as the iliocostalis and quadratus; an intermediate branch, which innervates the medial muscles, such as the longissimus, spinalis and semispinalis; and a medial branch, which innervates the segmental muscles, (multifidus and rotatores) as well as the joint capsule. Inappropriate intersegmental motion has 2 probable neurological sequelae: I) alteration of afferentation from that level having segmental (reflexogenic muscle spasm or vasoconstrictive/vasodilatory changes from excitation of primary afferents and gamma motoneurons) and suprasegmental (less cerebellar afferentation, less cortical stimulation) effects and II) compression or traction of the medial branch of the PPD, causing, over time, demyelination and resultant denervation, of the intrinsic muscles, resulting in impaired motor control both segmentally and suprasegmentally. The segmental effects are directly measurable with needle EMG. This is a form of paraspinal mapping, which has also been explored by Haig et al. So, in short, instability can lead to denervation and denervation can lead to instability.
We often see clinically that treating a trigger point (needling, dry needling, acupuncture, manual pressure) can alter the function of the associated muscle . Improvements in muscle strength and changes in proprioception are not uncommon. Needling also seems to increase fibroblastic activty through the local inflammation it causes. Wouldn’t better muscle function and some scar tissue be a beneficial thing to someone with instability?
The next time you have a patient with instability, make sure to include the paraspinals in your quest for better outcomes.
Does variability in muscle activity reflect a preferred way of moving or just reflect what they’ve always done? In this study it was found that there isn’t always this tight relationship between activity in the muscles and the movement we’re seeing. “Clearly, locomotion is not as simple as we thought it was,” Foster said. “This decoupling – big changes in movement without corresponding changes in muscle activity – suggests there are other important factors going on and we need to better understand them if we want to reproduce these movements in prosthetics or robotics.” Hmmmm. thoughts. this makes everything more interesting doesn’t it ?!
“We expected to see a one-to-one correlation between the muscle activity and movements because motion is generally driven by muscles,” Higham said, “but as we changed the structure of their habitat and they changed their motions, we were surprised to find very few accompanying changes in muscle activity.”
Lots of links available here with today’s blog post. please make sure to take your time and check out each one (underlined below)
As you remember, the peroneii (3 heads) are on the outside of the lower leg (in a nice, easy to remember order of longus, brevis and tertius, from top to bottom) and help to stabilize the lateral ankle. The peroneus brevis and tertius dorsiflex and evert the foot while the peroneus longus plantarflexes and everts the foot. We discuss the peroneii more in depth here in this post. It then is probably no surprise to you that people with ankle issues, probably have some degree of peroneal dysfunction. Over the years the literature has supported notable peroneal dysfunction following even a single inversion sprain event.
Functional ankle instability (FAI) is defined as ” the subjective feeling of ankle instability or recurrent, symptomatic ankle sprains (or both) due to proprioceptive and neuromuscular deficits.”
Arthrogenic muscle inhibition (AMI) is a neurological phenomenon where the muscles crossing a joint become “inhibited”, sometimes due to effusion (swelling) of the joint (as seen here) and that may or may not be the case with the ankle (see here), or it could be due to nociceptive input altering spindle output or possibly higher centers causing the decreased muscle activity.
This paper (see abstract below) merely exemplifies both the peroneals and FAI as well as AMI.
Take home message?
Keep the peroneals strong with lots of balance work!
The Gait Guys: bringing you the meat, without the filler!
Am J Sports Med. 2009 May;37(5):982-8. doi: 10.1177/0363546508330147. Epub 2009 Mar 6.
Peroneal activation deficits in persons with functional ankle instability.
School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109, USA. firstname.lastname@example.org
Functional ankle instability (FAI) may be prevalent in as many as 40% of patients after acute lateral ankle sprain. Altered afference resulting from damaged mechanoreceptors after an ankle sprain may lead to reflex inhibition of surrounding joint musculature. This activation deficit, referred to as arthrogenic muscle inhibition (AMI), may be the underlying cause of FAI. Incomplete activation could prevent adequate control of the ankle joint, leading to repeated episodes of instability.
Arthrogenic muscle inhibition is present in the peroneal musculature of functionally unstable ankles and is related to dynamic peroneal muscle activity.
Cross-sectional study; Level of evidence, 3.
Twenty-one (18 female, 3 male) patients with unilateral FAI and 21 (18 female, 3 male) uninjured, matched controls participated in this study. Peroneal maximum H-reflexes and M-waves were recorded bilaterally to establish the presence or absence of AMI, while electromyography (EMG) recorded as patients underwent a sudden ankle inversion perturbation during walking was used to quantify dynamic activation. The H:M ratio and average EMG amplitudes were calculated and used in data analyses. Two-way analyses of variance were used to compare limbs and groups. A regression analysis was conducted to examine the association between the H:M ratio and the EMG amplitudes.
The FAI patients had larger peroneal H:M ratios in their nonpathological ankle (0.399 +/- 0.185) than in their pathological ankle (0.323 +/- 0.161) (P = .036), while no differences were noted between the ankles of the controls (0.442 +/- 0.176 and 0.425 +/- 0.180). The FAI patients also exhibited lower EMG after inversion perturbation in their pathological ankle (1.7 +/- 1.3) than in their uninjured ankle (EMG, 3.3 +/- 3.1) (P < .001), while no differences between legs were noted for controls (P > .05). No significant relationship was found between the peroneal H:M ratio and peroneal EMG (P > .05).
Arthrogenic muscle inhibition is present in the peroneal musculature of persons with FAI but is not related to dynamic muscle activation as measured by peroneal EMG amplitude. Reversing AMI may not assist in protecting the ankle from further episodes of instability; however dynamic muscle activation (as measured by peroneal EMG amplitude) should be restored to maximize ankle stabilization. Dynamic peroneal activity is impaired in functionally unstable ankles, which may contribute to recurrent joint instability and may leave the ankle vulnerable to injurious loads.
all material (except for the study); copyright 2013 The Gait Guys/ The Homunculus Group. All rights reserved. Please ask before you lift our stuff. If you are nice and give us credit, we will probably let you use it!