Background: The plank exercise is widely used in rehabilitation to enhance core muscle activation, spinal stability, and reduce the risk of lower back injuries. Objectives: This study investigated the effects of exercise complexity and instability on core muscle activation, with a particular focus on using a sling suspension system during prone bridge exercises. Design: Cross-sectional study. Methods: Twenty healthy adults performed three variations of prone bridge exercises: Both Limb Prone Bridge (BLPB), Single Limb Prone Bridge (SLPB), and Single Limb Prone Bridge with Hip Abduction (SLPBHA). Electromyography (EMG) was used to measure muscle activation in the erector spinae (ES), multifidus (MF), and internal oblique (IO) muscles. Results: Significant increases in ES muscle activation were observed during SLPBHA compared to BLPB and SLPB (P<.05), indicating that exercise complexity and the introduction of instability significantly enhanced ES activation. However, no significant differences were found in MF and IO activation across the exercise variations (P>.05). Conclusion: This study underscores the importance of exercise complexity and instability, particularly SLPBHA, in enhancing ES muscle activation. The findings support the inclusion of these exercises in core stability training programs aimed at improving spinal stability and preventing lower back injuries.

INTRODUCTION
SUBJECTS AND METHODS
    Subjects
    Experimental Procedures
    Statistical Analysis
RESULTS
DISCUSSION
CONCLUSION
ACKNOWLEDGMENT
REFERENCES

• Taeseok Choi(Department of Physical Therapy, Daewon University, Jecheon, Republic of Korea)
• Okkon Moon(Department of Physical Therapy, Howon University, Gunsan, Republic of Korea) Corresponding author