Title

Changes in corticospinal motor excitability following ankle joint manipulation

ORCiD

0000-0001-5772-7727

Document Type

Poster

Conference Title/Conference Publication

Annual Meeting of the Society for Neuroscience

Organization

Society for Neuroscience

Location

New Orleans, LA

Conference Dates

October 13, 2012, October 17, 2012

Date of Presentation

10-13-2012

ISSN

2572-6803

Abstract

Background: Recent research aimed at determining the neural mechanisms underlying manual intervention (such as massage or joint manipulation) serve to strengthen the clinical decision making for patient care. Ankle sprain, which affects millions of people each year, has been managed by improving dorsiflexion (DF) range through a quick end-range thrust of the talus(joint manipulation) or a slow stretch of the talocrural joint. Evidence suggests that better outcomes in DF range occur with the faster compared to the slower intervention. We hypothesized that this functional benefit may in part be explained by central neuroplastic modifications. Therefore, the purpose of this preliminary study is to determine if speed of stretch differentially alters central changes, as measured by corticospinal motor excitability using transcranial magnetic stimulation (TMS).

Methods: Fifteen young adults post ankle sprain participated in this study. Input-output (I/O) curves for both the tibialis anterior (TA) and the gastrocnemius (GAS) were derived from motor evoked potential (MEP) amplitudes obtained across eight TMS stimulation intensities. After baseline I/O assessment, the participants were randomly assigned to receive either a quick end-range thrust (n = 6), a slow stretch (n = 6), or a sham stretch (n = 3) of the talus. A second set of I/O curves for TA and GAS were obtained post intervention. The main outcome measures were pre/post values (mean ± SEM) of maximal MEP amplitudes and the slope of the I/O curves for each muscle.

Results: On average, the quick thrust group demonstrated an increase in the maximal MEP amplitude from 306.7 ± 123.1μV to 672.3 ± 167.2μV for the TA and from 178.8 ± 36.4μV to 476.4 ± 204.2μV for the GAS. On the other hand, the slow stretch and the sham stretch groups both demonstrated decreased maximal MEP amplitudes for the TA and the GAS. Consistent with the MEP results, the quick thrust group demonstrated an increase in the slope of I/O curves from 16.6 ± 7.0 to 40.6 ± 15.9 for the TA and from 11.9 ± 4.0 to 23.6 ± 12.3 for the GAS. Conversely, both slow stretch and the sham stretch groups showed a flattening of the slope post intervention for TA and GAS.

Summary: Based on our pilot data, a quick thrust of the talus appeared to increase corticospinal motor excitability of the TA and GAS muscles, while slow and sham stretch did not. While preliminary, this data may provide an understanding of the differential effect of speed of stretch on central nervous system modification and potentially an explanation for the superior outcomes observed with a quick end-range thrust compared to slow stretch.

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