Influence of Deep Neck Flexor Activation on Transversus Abdominis and Internal Oblique Recruitment During Abdominal Drawing-in Maneuver: Ultrasound Imaging Study

Abstract Background/aim: Muscle activity in one region of the human body can influence muscle function in other regions, particularly between the cervical and lumbopelvic regions. The deep neck flexors (DNF) play a critical role in cervical spine stability and may have neuromuscular connections with deep core muscles. However, the impact of DNF activation on the transversus abdominis (TrA) and internal oblique (IO) muscles during the abdominal drawing-in maneuver (ADIM) remains unexplored. This study aimed to investigate the influence of DNF activation on TrA and IO muscle activity during the ADIM using ultrasound imaging (USI) to assess changes in muscle thickness and contraction ratio (CR). Materials and methods: Twentyseven healthy male participants (mean age: 34.24 ± 5.1 years, BMI: 23.66 ± 2.8 kg/m²) were recruited. Muscle thickness of the TrA and IO was measured at rest, during the ADIM, and during the ADIM with DNF activation. Contraction ratio (CR) was calculated as: CR = thickness during ADIM (with or without DNF activation) / resting thickness to assess relative changes in muscle activity. A paired t-test was used to compare muscle thickness and CR across conditions. Results: No significant changes were observed in TrA and IO muscle thickness with DNF activation (p > 0.05). However, a significant increase in TrA CR was observed bilaterally during DNF activation (right: t = 2.24, p = 0.03, Cohen’s d = 0.50; left: t = 2.04, p = 0.04, Cohen’s d = 0.50), while IO CR remained unchanged. Conclusion: The findings suggest that DNF activation selectively enhances TrA recruitment during the ADIM without affecting IO activation. This supports the hypothesis of neuromuscular interactions between the cervical and lumbopelvic regions, possibly mediated by myofascial and proprioceptive connections. Integrating DNF activation into core stabilization exercises may optimize deep core engagement, improve postural stability, and enhance neuromuscular control. Future research should investigate the long-term functional implications and include a broader participant demographic.