Background: The presence of the lumbopelvic-hip neuromuscular chain is essential for dynamic spinal stabilization; its therapeutic effects on dynamic movements of the distal extremity segment and underpinning motor mechanism remain unknown and warrant further study on participants with low back pain (LBP).
Objects: We aim to compare the effects of the broken chain exercise (BCE) and connected chain exercise (CCE) on electromyography (EMG) amplitude and onset time in participants with and without LBP.
Methods: Randomized controlled clinical trial. A convenience sample of 40 nonathletic participants (mean age: 24.78 ± 1.70) with and without LBP participated in this study. All participants underwent CCE for 30 minutes, 30-minute daily. We measured EMG amplitude and onset times on bilateral erector spinae (ES), gluteus maximus (GM), hamstring (HAM), transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) during the prone hip extension (PHE) test before and after the BCE and CCE. We used multivariate analysis of variance (MANOVA) to analyze the amplitude and onset time difference between exercises (BCE and CCE) and Pearson’s correlations to determine any synergistic relationship among the HAM, GM, bilateral TrA/IO, and ES muscles. The statistical analyses were used at p < 0.05.
Results: MANOVA showed that CCE was more decreased on EMG amplitude in HAM and bilateral ES, while increased GM and contralateral TrA/IO than BCE (p < 0.05). MANOVA EMG onset time data analyses revealed that the main effect of the conditions was significant for all HAM, GM, and bilateral ES muscles, whereas the main effect for the group was significant only for GM and contralateral ES in healthy and LBP groups. Pearson’s correlation coefficient was computed to assess the relationship between BCE and CCE on dependent variables. In most of the muscles, there was a strong, positive correlation between the two variables, and there was a significant relationship (p < 0.001).
Conclusion: CCE produced more effective and coordinated core stabilization and motor control mechanism in the lumbopelvic-hip muscles in participants with and without LBP during PHE than BCE.

INTRODUCTION
MATERIALS AND METHODS
    1. Participants
    2. Electromyography Measurement
    3. Data Analysis
RESULTS
DISCUSSION
    1. EMG Amplitudes Between Normal and Low BackPain Groups
    2. Electromyography Onset Time and SequenceBetween Normal and Low Back Pain Groups
    3. Limitations
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
ORCID
REFERENCES

• Haeun Park(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Sports Movement Artificial- Intelligence Robotics Technology (SMART) Institute, Wonju, Korea)
• Chanhee Park(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Sports Movement Artificial- Intelligence Robotics Technology (SMART) Institute, Wonju, Korea)
• Joshua (Sung) Hyun You(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Sports Movement Artificial- Intelligence Robotics Technology (SMART) Institute, Wonju, Korea) Corresponding Author