Effects of External Upper Limb Loading on Gait and Trunk Muscle Activity in Cardiac Rehabilitation Patients

This study examines how external loading applied to the upper limbs affects gait parameters and the activity of selected trunk- and pelvis-stabilizing muscles (erector spinae, gluteus medius, tensor fasciae latae, external oblique) in patients undergoing cardiac rehabilitation. Participants are medically stable adults (18-80 years) referred to cardiac rehabilitation following a cardiac event or procedure, meeting NYHA class I-II criteria, with no unstable coronary disease, uncontrolled hypertension, neurological disease, or other exclusion criteria. Participants will walk on a treadmill at 1 km/h, 3 km/h and 5 km/h under three conditions: without load, with unilateral upper-limb loading, and with bilateral upper-limb loading. Muscle activity will be recorded using surface electromyography (sEMG), and plantar pressure/gait parameters will be recorded simultaneously using baropodometry integrated into the treadmill. The procedure is non-invasive, does not breach the skin, and does not involve any additional intervention beyond standard rehabilitation. To contextualize functional outcomes, previously collected exercise stress test results (performed independently by the treating physician before and after cardiac rehabilitation, as part of routine clinical care) will be retrieved from participants' medical records for comparison; this is a retrospective data comparison, not an additional study intervention. No financial compensation is provided. Each participant will receive an individual report of their sEMG and gait findings with professional interpretation. Risks are minimal and limited to transient skin irritation from electrodes and mild, temporary muscle fatigue or soreness typical of moderate exercise. Participants may withdraw at any time.

Inclusion Criteria: * Age ≥18 and ≤80 years * Referred to cardiac rehabilitation following a cardiac event or procedure * Medically stable, classified as NYHA class I-II * Able and willing to provide informed consent * Willing and able to complete the study procedures * Able to safely perform treadmill walking and exercise testing * No cardiological or pulmonological contraindications to exercise * No limb deformities or gait pathology identified on clinical interview Exclusion Criteria: * Unstable coronary artery disease, recent myocardial infarction (\