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

Study Design and Rationale This is a prospective, observational biomechanical and neuromuscular study evaluating the effect of external upper-limb loading (unilateral, dominant and non-dominant side, and bilateral) on gait parameters and the activity of selected trunk- and pelvis-stabilizing muscles in patients undergoing cardiac rehabilitation. Existing literature on muscle activity during loaded walking is limited, and the extent and pattern of these changes are not yet well characterized. This study aims to address that gap and provide data relevant to rehabilitation practice, including load standardization in physiotherapy.

Participants 50-60 adults (18-80 years) referred to cardiac rehabilitation following a cardiac event or procedure (including patients several years post-event), medically stable and classified as NYHA class I-II. Recruitment uses stratified random sampling, with strata based on sex and age to ensure balanced representation. Exclusion criteria include unstable coronary artery disease, recent myocardial infarction (<4 weeks), NYHA class III-IV heart failure, uncontrolled hypertension, cardiac arrhythmias, neurological or neurodegenerative disease, acute lower-limb or spinal injury, gait pathology, poorly controlled diabetes with hypoglycemia risk, pregnancy, BMI >35 kg/m², and lack of consent.

Procedures Participants complete a health/medical history questionnaire followed by a preliminary diagnostic assessment of physical capacity. During the main protocol, participants walk on a treadmill at 1 km/h, 3 km/h and 5 km/h under three loading conditions (no load, unilateral, bilateral), while sEMG records activity of the erector spinae, gluteus medius, tensor fasciae latae, and external oblique muscles, and baropodometry (integrated into the treadmill) simultaneously records plantar pressure and gait parameters.

Additionally, exercise stress test results obtained by the participant's physician before and after cardiac rehabilitation - performed independently of this study as part of routine clinical care - are retrieved from medical records by a research team member with institutional authorization to access patient data, and compared with the sEMG/gait findings. No stress testing is performed by the research team as part of this protocol.

Ethical and Regulatory Compliance The protocol has been reviewed and approved by the relevant bioethics committee. Written informed consent is obtained from all participants prior to participation. Access to participants' medical records (stress test results) is conducted under existing institutional authorization held by a research team member.

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 (<4 weeks), or recent revascularization (<4 weeks)
• Heart failure NYHA class III-IV
• Uncontrolled hypertension
• Cardiac arrhythmias
• Neurological or neurodegenerative disease
• Acute lower-limb or spinal injury, musculoskeletal deformity, or significant pain affecting gait
• Diabetes mellitus with hypoglycemia tendency
• Pregnancy
• BMI >35 kg/m²
• Lack of informed consent