This randomized controlled trial aims to investigate the effectiveness of respiratory and relaxation training added to standard complex decongestive therapy (CDT) on muscle oxygenation, functional capacity, and limb volume in patients with lower extremity lymphedema. Participants will be randomly assigned to receive either standard CDT alone or CDT combined with respiratory and relaxation exercises. Outcomes will be assessed before treatment, immediately after treatment, and two months after completion.

Lower extremity lymphedema is a chronic condition characterized by impaired lymphatic drainage, limb swelling, pain, reduced physical function, and decreased quality of life. Complex decongestive therapy (CDT) is considered the gold standard treatment; however, additional interventions that may improve physiological and functional outcomes remain under investigation.

Respiratory exercises may facilitate lymphatic return through changes in intrathoracic pressure, whereas relaxation training may reduce sympathetic activation and improve exercise tolerance. Despite these theoretical benefits, there is limited evidence regarding their combined effect on muscle oxygenation in patients with lower extremity lymphedema.

Therefore, this randomized controlled study will evaluate whether adding respiratory and relaxation training to CDT improves muscle oxygenation measured by wearable near-infrared spectroscopy (MOXY), functional capacity assessed with the Six-Minute Walk Test, and limb volume compared with CDT alone.

Inclusion Criteria:

• Female patients aged 18 years or older.
• Clinically diagnosed with secondary lower extremity lymphedema.
• Presence of lower extremity lymphedema for at least 3 months.
• Able to stand and walk independently to complete the Six-Minute Walk Test.
• Willing and able to provide written informed consent.

Exclusion Criteria:

• Acute cellulitis or other active infection within the previous 2-4 weeks.
• Current or recent deep vein thrombosis (DVT) or uncontrolled peripheral vascular disease.
• Severe cardiovascular, pulmonary, orthopedic, or neurological conditions that could interfere with participation or outcome assessments.
• Pregnancy.
• Skin lesions or irritation preventing placement of the near-infrared spectroscopy (MOXY) sensor.
• Inability to comply with the study protocol or follow-up assessments.

Participants and treating physiotherapists cannot be blinded because of the nature of the intervention. However, the outcome assessor responsible for collecting all outcome measures, including muscle oxygenation, functional capacity, and limb volume, will be blinded to group allocation. Participants will be instructed not to disclose their treatment assignment to the assessor. Data analysis will be performed using coded group assignments.