The Balance Recovery Mechanism Following a Sudden External Anterior- Posterior Perturbation in Individuals with Kyphosis



The purpose of this study was to determine the balance recovery mechanism
following a sudden external perturbation in kyphotic individuals in comparison
with normal individuals (control). For this purpose, ten males (mean age:
21.5+1.6 years) with increased thoracic kyphosis>40 degrees and 15 individuals
(mean age: 22.1+1.19) without thoracic kyphosis (control) were selected to
participate in the study. Six reflective markers were attached to the right side of the
acromion, greater trochanter, lateral femoral epicondyle, external malleolus,
calcaneus and fifth metatarsal and a 4-segment 2-dimension model was defined.
Kinematic data were collected using three high-speed cameras at 120 Hz. Each
subject conducted six 5-second trials including three quite standing trials and three
unexpected anterior-posterior perturbed trials triggered by a weight equivalent to
10% of the subjects’ body weight. The change in range of motion and torque
deviation of the hip, knee and ankle joints were calculated with Eva software.
Statistical data were analyzed by analysis of variance with repeated measures
(p=0.05). The results showed that kyphotic subjects had a greater significant
change and deviation in their range of motion after perturbation in their hip
(p=0.000) and ankle (p=0.000) joints compared with control subjects. There was a
relative similarity in joint torque deviation pattern in response to a balance
perturbation between the two groups. But this torque deviation fluctuated with
greater amplitude in kyphotic group. These findings illustrated that postural
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Journal of Faculty of 13 Physical Education, University of Tehran
strategy and responses employed by kyphotic individuals to recover upright
posture following forward balance perturbation is different from those in control
group. Consequently, kyphosis can influence postural reaction strategy in response
to a balance perturbation.