Participants assigned to this arm will undergo a sham procedure designed to mimic the experimental intervention. The procedure includes the same positioning, ultrasound guidance, needle insertion, and duration as the experimental arm; however, no electrical current will be delivered. Blood samples will be collected at the same pre- and post-procedure time points as in the experimental arm. This control condition is used to account for nonspecific effects related to needling and the procedural context.

Participants assigned to this arm will receive ultrasound-guided percutaneous electrolysis applied to the lumbar multifidus muscle. After baseline blood sample collection, a fine needle will be inserted into the target muscle under ultrasound guidance and connected to a medical device delivering a low-intensity galvanic current. The intervention consists of multiple stimulation cycles separated by short rest periods. A post-treatment blood sample will be collected after a predefined time interval to assess biochemical changes induced by the intervention.

Participants assigned to this arm will receive ultrasound-guided percutaneous electrolysis applied to the lumbar multifidus muscle. After baseline blood sample collection, a fine needle will be inserted into the target muscle under ultrasound guidance and connected to a medical device delivering a low-intensity galvanic current. The intervention consists of multiple stimulation cycles separated by short rest periods. A post-treatment blood sample will be collected after a predefined time interval to assess biochemical changes induced by the intervention.

The Blood Proteomic Profile is measured by collecting blood samples at two time points: pre-intervention (T1) and post-intervention (T2). The blood samples are processed to extract serum, which is then subjected to proteomic analysis using mass spectrometry (LC-MS/MS). Proteins are first depleted of abundant proteins using a specific depletion kit. The remaining proteins are digested and analyzed using an Orbitrap Fusion Lumos mass spectrometer coupled with a nano-UHPLC system. Protein identification and quantification are performed using Proteome Discoverer software, and the data are analyzed statistically to identify proteins with significant changes in concentration between pre- and post-treatment samples.

The Blood Lipidomic Profile is measured by collecting blood samples at two time points: pre-intervention (T1) and post-intervention (T2). Plasma lipids are extracted using a biphasic method and analyzed by liquid chromatography coupled with mass spectrometry (UHPLC-Orbitrap). The lipidomic analysis involves a detailed quantification of lipid species, including the measurement of lipid classes and their associated metabolites. Data are processed using MS-DIAL for peak detection and alignment, followed by normalization with internal standards. The relative concentrations of lipids are compared between pre- and post-treatment samples to identify significant changes in lipid profiles associated with the intervention.