Modulation of the Hoffmann reflex in the tibialis anterior with a change in posture.

Authors

Janelle UngerFollow
Justin W Andrushko
Alison R Oates
Doug W Renshaw
Trevor S Barss
E Paul Zehr
Jonathan P Farthing

Document Type

Article

Publication Date

7-1-2019

Journal

Physiological Reports

Volume

7

Issue

14

First Page

1

Last Page

8

URL with Digital Object Identifier

https://doi.org/10.14814/phy2.14179

Abstract

Hoffmann (H-) reflex amplitudes in plantar flexor soleus muscle are modulated by posture, yet dorsiflexor tibialis anterior (TA) H-reflex parameters have sparingly been studied. The purpose was to investigate modulation of the TA H-reflex when postural demands are increased from sitting to standing. In this study, data from 18 participants (Age: 25 ± 4 years, Height: 170.9 ± 9.5 cm, Weight: 75.9 ± 17.2 kg) allowed comparison of two experimental conditions involving different postures (i.e. sitting and standing). Maximal amplitude of the TA H-reflex (H_max) as a percent of the maximal M-wave amplitude (M_max) (H_max (% M_max)) during sitting and standing was compared using ANOVA. Modulation of TA H-reflex amplitude was found: Eleven participants showed facilitation and seven showed no change of reflex amplitudes. Only participants in the facilitation group showed modulation related to changes in posture (sitting: 8.7 ± 2.9%; standing: 14.8 ± 6.7%, P = 0.005). These data provide evidence of the sensitivity to posture of TA H-reflexes. As with task-dependent changes in soleus H-reflexes, presynaptic regulation of Ia afferent transmission is a possible mechanism. Further investigations into causes of modulation are warranted.

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