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Gait Posture. 2016 Jan;43:182-6. doi: 10.1016/j.gaitpost.2015.09.020. Epub 2015 Sep 30.

Reliability of the Achilles tendon tap reflex evoked during stance using a pendulum hammer.

Author information

1
Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada. Electronic address: robyn.mildren@alumni.ubc.ca.
2
Department of Kinesiology, Brock University, Saint Catharines, ON, Canada. Electronic address: m.zaback@alumni.ubc.ca.
3
Department of Kinesiology, Brock University, Saint Catharines, ON, Canada. Electronic address: aadkin@brocku.ca.
4
Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada. Electronic address: frank@uwaterloo.ca.
5
Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada. Electronic address: lbent@uoguelph.ca.

Abstract

The tendon tap reflex (T-reflex) is often evoked in relaxed muscles to assess spinal reflex circuitry. Factors contributing to reflex excitability are modulated to accommodate specific postural demands. Thus, there is a need to be able to assess this reflex in a state where spinal reflex circuitry is engaged in maintaining posture. The aim of this study was to determine whether a pendulum hammer could provide controlled stimuli to the Achilles tendon and evoke reliable muscle responses during normal stance. A second aim was to establish appropriate stimulus parameters for experimental use. Fifteen healthy young adults stood on a forceplate while taps were applied to the Achilles tendon under conditions in which postural sway was constrained (by providing centre of pressure feedback) or unconstrained (no feedback) from an invariant release angle (50°). Twelve participants repeated this testing approximately six months later. Within one experimental session, tap force and T-reflex amplitude were found to be reliable regardless of whether postural sway was constrained (tap force ICC=0.982; T-reflex ICC=0.979) or unconstrained (tap force ICC=0.968; T-reflex ICC=0.964). T-reflex amplitude was also reliable between experimental sessions (constrained ICC=0.894; unconstrained ICC=0.890). When a T-reflex recruitment curve was constructed, optimal mid-range responses were observed using a 50° release angle. These results demonstrate that reliable Achilles T-reflexes can be evoked in standing participants without the need to constrain posture. The pendulum hammer provides a simple method to allow researchers and clinicians to gather information about reflex circuitry in a state where it is involved in postural control.

KEYWORDS:

Achilles tendon reflex; Reliability; Soleus; Spinal reflex; Standing

PMID:
26454702
DOI:
10.1016/j.gaitpost.2015.09.020
[Indexed for MEDLINE]

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