Background: Abdominal bracing exercise (ABE) and abdominal hollowing exercise (AHE) improve the lumbar flexibility and pulmonary function in various patients, yet the efficacy of ABE or AHE have not yet been evaluated. Objects: The purpose of this study was to compare the lumbar flexibility and pulmonary function during both ABE and AHE in healthy adults. Methods: The study included 40 healthy adults, who were randomly divided into the experimental group and control group, each with 20 subjects. All subjects performed ABE (experimental group) and AHE (control group). The lumbar flexibility such as trunk flexion test (sitting and standing position) and schober test and pulmonary function such as the spirometer including forced vital capacity (FVC) and force expiratory volume in one second (FEV1) and chest circumference measurement (middle and lower chest) were measured, respectively. Two-way repeated analysis of variance was used to compare the lumbar flexibility and pulmonary function, respectively. Results: No significant effects of lumbar flexibility were observed on trunk flexion test from the sitting position (P=.478) and standing position (P=.096) in the ABE than in the AHE. However, the length of ABE was longer significantly than it of AHE (P=.024). No significant effects of lung function were observed on the FVC (P=.410) and FEV1 (P=.072) in the ABE group than in the AHE group. And also, no significant effects of chest circumference measurement were observed on the inspiration (P=.468) and expiration (P=.563) in middle chest circumference and inspiration (P=.104) and expiration (P=.346) in lower chest circumference. Conclusion: This study indicated that the ABE is only more effective in lumbar flexibility by lumbar length difference than AHE in healthy adults.

Introduction
 Methods
  Subjects
  Interventions
  Instruments
  Statistical analysis
 Results
 Discussion
 Conclusion
 References

• Kyung-bin Kim(Dept. of Physical Therapy, The Graduate School, Konyang University)
• Seung-chul Chon(Dept. of Physical Therapy, College of Medical Science, Konyang University) Corresponding author