Abdominal hollowing and bracing strategies increase joint stability in the trunk region during sudden support surface translation but not in the lower extremities
Affiliations: [a] Department of Physical Therapy, College of Health Sciences, Korea University, Seoul, Korea | [b] Barunsesang Hospital, Bundang-gu, Seongnam-si, Gyeonggi-do, Korea | [c] Korea National Rehabilitation Research Institute, Seoul, Korea
Correspondence:
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Corresponding author: BumChul Yoon, Department of Physical Therapy, College of Health Sciences, Korea University Jeongneung 3-Dong, Sungbuk-Gu, Seoul 136-703, Korea. Tel.: +82 29402833; Fax: +82 29402830; E-mail:yoonbc@korea.ac.kr
Abstract: BACKGROUND AND OBJECTIVE: Application of hollowing and bracing,
abdominal activation strategies (AAS), has focused on improving trunk
stability. This study aimed to clarify the AAS effect on body sway during
support surface translation while standing. MATERIALS AND METHODS: Twenty healthy subjects (10 male, 10 female;
aged 25.45 ± 3.22 years) performed hollowing, bracing, and natural
strategies while standing, and exerted to maintain their balance during
forward and backward translation. Ultrasonography evaluations confirmed the
appropriate application of the 3 strategies by measuring abdominal muscle
thickness. Additionally, a motion analysis system was used to capture the
whole body sway along the sagittal plane. RESULTS: During backward translation, angular displacements of the
trunk were significantly different among the 3 strategies (upper thoracic: F
= 13.758, p < 0.001; lower thoracic: F = 8.477, p = 0.001; and lumbopelvis:
F = 8.651, p = 0.001). AAS significantly decreased the sway by 25-36% in
all inter-spinal segments compared with the natural strategy (p < 0.05).
During forward translation, only angular displacement of the lower thoracic
was significantly different among the 3 strategies (F = 7.640, p = 0.002),
and bracing decreased the sway by 33.48% compared with the natural
strategy (p = 0.003). No significant differences were seen between hollowing
and bracing during forward and backward translation. CONCLUSIONS: AAS increased joint stability only in the trunk where
joints are adjacent to abdominal muscles, but not in the lower extremities.
The low impact of AAS on the lower extremities might have important
implications on the paradigm of standing balance.
Keywords: Abdominal activation strategies, body sway, abdominal muscles, perturbation
