Acute effects of core fatigue on thoracolumbar fascia mechanical and viscoelastic properties in healthy young adults: a cross-sectional study.

PURPOSE: This study investigated how acute fatigue of the rectus abdominis (RA) and erector spinae (ES) muscles affects the biomechanical and viscoelastic properties of the thoracolumbar fascia (TLF). METHODS: 45 healthy young men (18-30 years) participated. Two separate fatigue protocols were applied for RA and ES muscles. Fascia's stiffness, creep, and relaxation time were assessed before and after each protocol using the MyotonPRO™ device. The changes in fascial properties following RA fatigue were compared with those following ES fatigue. RESULTS: No significant changes were observed in any fascial parameter after RA fatigue. In contrast, ES fatigue resulted in significant decreases in stiffness and significant increases in creep and relaxation time (p < 0.05). Following ES fatigue, TLF stiffness decreased by 24.40 ± 37.25, while creep and relaxation time increased by 0.08 ± 0.19 and 1.75 ± 3.62, respectively. Post-fatigue comparisons revealed greater increases in creep (p = 0.01) and relaxation time (p = 0.02) in the ES group compared to the RA group. CONCLUSION: These findings highlight the different acute effects of RA and ES fatigue on the TLF and suggest that muscle-specific loading influences fascial responses. Clarifying these dynamics may enhance the application of fascial-targeted strategies not only for symptom management but also for preserving tissue health and optimizing physical performance. CLINICAL TRIAL REGISTRATION: This study has been registered in Clinical Trials under the number NCT06432062.