The Journal of Korean Physical Therapy

The Korean Society of Physical Therapy (대한물리치료학회)
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Effects of Bulgarian Split Squat Exercise on Unstable Surface on Lower Extremity Strength and Balance Ability of University Students with Ankle Instability: A Pilot Study

  • Ji-Sung Yang (Department of Physical Therapy, Wonkwang University) ;
  • Yu-Rim Kang (Department of Physical Therapy, Wonkwang University) ;
  • Seo-Hee Kim (Department of Physical Therapy, Wonkwang University) ;
  • Sin-Yeong Kim (Department of Physical Therapy, Wonkwang University) ;
  • Min-Kyeong Yu (Department of Physical Therapy, Wonkwang University) ;
  • Yun-Jeong Lee (Department of Physical Therapy, Wonkwang University) ;
  • Ju-Heon Lee (Department of Physical Therapy, Wonkwang University) ;
  • Dong-Woon Lim (Department of Physical Therapy, Wonkwang University) ;
  • Ye-Jin Im (Department of Physical Therapy, Wonkwang University) ;
  • Dong-Hoo Choi (Department of Physical Therapy, Wonkwang University) ;
  • Min-Su Choi (Department of Physical Therapy, Wonkwang University) ;
  • Ui-Seung Hong (Department of Physical Therapy, Wonkwang University) ;
  • Jin Park (Department of Physical Therapy, Wonkwang University)
  • Received : 2026.03.17
  • Accepted : 2026.04.20
  • Published : 2026.04.30
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Abstract

Purpose: This study examined the effects of Bulgarian Split Squat (BSS) exercise performed on an unstable support surface on the muscle strength and balance ability in university students with ankle instability. Methods: Twelve university students with ankle instability participated in this study; they were assigned randomly to two groups. One group of subjects (n=6) performed the BSS on a stable support surface, and the other group (n=6) performed the exercise on an unstable support surface. The muscle strength was measured using a Commander Echo Muscle Tester, and the static and dynamic balance abilities were measured using a Balance Trainer 4 (BT4). Results: No significant between-group differences in static balance, dynamic balance, or muscle strength were found. On the other hand, within-group analysis indicated significant improvements in the hip flexor strength in the unstable group (p<0.05), whereas the stable group showed significant improvements in the knee extensor strength and in static balance (p<0.05). Conclusion: The results showed that no significant between-group differences were observed. By contrast, within-group changes suggested that BSS performed on an unstable surface may preferentially affect the hip flexor strength, whereas BSS performed on a stable surface may be associated with improvements in the knee extensor strength and static balance. Nevertheless, these findings should be interpreted with caution because of the pilot nature of the study and the small sample size.

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References

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