## 4 Discussion  
This study analyzes the bilateral activity of spine extensors and rotators during 12 distinct lumbar stabilization exercises resulting from 4 asymmetric limb elevation combinations (leg raise, arm raise, contralateral arm-leg rise, ipsilateral arm-leg rise) performed in 3 different body positions (prone, quadruped, and standing-prone position). This comprehensive dataset can provide deeper insights into the stabilizing function of the lumbar and oblique muscles during the execution of asymmetric tasks. The oblique muscles displayed characteristic activation patterns modulated by the different exercise conditions. In the prone position, a leg rise that brings the hip close to full hyperextension is naturally accompanied by a slight elevation from the ground of the ipsilateral pelvic side, indicating a small transversal pelvic rotation to the same side. With the chest in contact with the ground, this pelvic rotation triggers a compensatory spine rotation in the opposite direction. Maintaining this pelvic position against gravity requires an isometric effort involving closed-kinetic-chain spine rotation toward the side opposite the lifted leg. This is accomplished by pressing against the ground with the side of the chest ipsilateral to the lifted leg (the position cannot be sustained with the assistance of the upper limbs, which must remain relaxed in line with the body at the sides of the head throughout the entire exercise). The EO ipsilateral and the IO contralateral to the lifted leg generate the stabilizing effort. This explains the higher activation of these two muscles than the contralateral ones (Figure 1a). An arm rise from the prone position results in the opposite effect: a slight spine rotation towards the side of the lifted arm driven by the activation of the EO contralateral and the IO ipsilateral to the lifted arm, which exhibit higher activation compared to the contralateral muscles (Figure 2a). Hence, the elevation of a lower limb and the simultaneous elevation of the contralateral upper limb yield similar effects: a higher activation of the EO ipsilateral to the lifted leg and the IO ipsilateral to the lifted arm (Figure 3a). Conversely, the elevation of a lower limb and the simultaneous elevation of the ipsilateral upper limb yield contrasting effects on the oblique muscles, which display no significant difference in activation between the two sides of the body (Figure 4a). Similar patterns of oblique muscle activations are obtained in the quadruped position (Figures 1b, 2b and 3b), except for the ipsilateral arm-leg rise (Figure 4b). In this condition, the body zones in contact with the ground (ipsilateral forefoot, knee, and hand) are nearly aligned, posing a challenge to body equilibrium. To maintain balance, the body's center of mass should be shifted laterally towards the supporting side, reaching a position above the base of support. This was naturally achieved by participants through two rigid trunk displacements driven by closed-kinetic-chain (CKC) movements of the hip and shoulder of the supporting limbs: (1) a slight lateral trunk translation towards the supporting side, induced by transverse-plane CKC hip abduction and shoulder flexion; and (2) a slight trunk rotation that rises the non-supporting side of the trunk upwards and towards the supporting side, induced by transverse-plane CKC hip abduction and shoulder extension. These rigid trunk displacements maintain the spine in a neutral position; however, the rotated trunk and the weight of the raised limbs expose the spine to gravity-induced lateral flexion toward the supporting side. Counteracting this movement entails activating the ipsilateral external and internal oblique muscles on the non-supporting side of the body. The results confirm higher activation of these two muscles than the contralateral ones (Figure 4b).