<p>Preserving lumbar lordotic curvature (LLC) is considered an important strategy for both managing low back pain (LBP) and preventing its exacerbation; however, this approach has traditionally been limited to postural education. This study aimed to evaluate the effectiveness of a real-time biofeedback system that uses inertial sensors, and to compare its impact across various activities. Ten male participants with LBP wore sensor-equipped clothing while performing four daily activities commonly associated with an increased risk of LBP, under varying conditions of auditory feedback and postural education. The relative angles from the sensors were monitored in real-time as lumbar lordotic angle (LLA), with alarms triggered when LLA values dropped below a preset threshold. The impact of increasing LLA was assessed through regression analysis. For continuous flexion activities, such as sitting and mopping, auditory feedback significantly increased LLA by 10.2° and 10.5°, respectively (<i>p</i> &lt; 0.001 for both). For repeated flexion tasks, such as picking-up and squatting, auditory feedback showed less or no effect compared with postural education. The feedback increased LLA by 5.8° in the picking-up task (<i>p</i> &lt; 0.001), but was ineffective in squatting. These findings suggest that real-time biofeedback may be more effective in continuous flexion, whereas it appears to be limited in repetitive flexion.</p>