Ankle bracing and the neuromuscular factors influencing joint stiffness.
BACKGROUND
Health care professionals commonly prescribe external stabilization to decrease the incidence and severity of ankle sprains. The mechanism for this decrease is not clearly understood. Examining the effects of ankle bracing on biomechanical stability and influencing factors may provide important information regarding the neuromuscular effects of bracing.


OBJECTIVE
To study the effects of 2 different ankle braces on the neuromuscular factors influencing ankle stiffness.


METHODS
Mixed-model repeated-measures design.


METHODS
Research laboratory.


METHODS
Twenty-eight physically active participants composing 2 groups: 14 with unilateral functional ankle instability (age = 26.19 +/- 6.46 years, height = 166.07 +/- 12.90 cm, mass = 69.90 +/- 13.46 kg) and 14 with bilaterally stable ankles (age = 23.76 +/- 5.82 years, height = 174.00 +/- 11.67 cm, mass = 68.60 +/- 13.12 kg).


METHODS
Participants were fitted with surface electromyography electrodes over the peroneus longus, peroneus brevis, tibialis anterior, and soleus muscles. Each participant received transient motion oscillations to his or her ankle on a custom-built medial-lateral swaying cradle in each of 3 conditions: no ankle brace (NB), lace-up brace (LU), and semirigid brace (SR).


METHODS
Ankle stiffness as measured by the cradle and preactivation levels (percentage of maximal voluntary isometric contraction) of the 4 test muscles.


RESULTS
Stiffness levels increased across brace conditions (NB = 24.79 +/- 6.59 Nm/rad, LU = 28.29 +/- 7.05 Nm/rad, SR = 33.22 +/- 8.78 Nm/rad; F(2,52) = 66.185, P < .001). No differences were found between groups for rotational stiffness (stable = 27.36 +/- 6.17 Nm/rad, unstable = 30.18 +/- 8.21 Nm/rad; F(1,26) = 1.084, P = .307). Preactivation levels did not change for any of the tested muscles with the application of an ankle brace (F(2,52) = 1.326, P = .275).


CONCLUSIONS
The increase in ankle rotational stiffness with the addition of an ankle brace and the lack of any demonstrable neuromuscular changes suggested ankle braces passively contributed to the stability of the system.
Zinder
Steven M
SM
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. szinder@unc.edu
Granata
Kevin P
KP
Shultz
Sandra J
SJ
Gansneder
Bruce M
BM
D000328:Adult; D000704:Analysis of Variance; D016512:Ankle Injuries / Q000209:etiology / Q000517:prevention & control*; D000843:Ankle Joint / Q000294:innervation* / Q000503:physiopathology; D001696:Biomechanical Phenomena; D001915:Braces; D016001:Confidence Intervals; D004576:Electromyography; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D015994:Incidence; D007537:Isometric Contraction; D008297:Male; D018482:Muscle, Skeletal; D012720:Severity of Illness Index