In this study, wearable multi-modal microsensors were deployed to simultaneously capture seismocardiography (SCG) and electrocardiography (ECG) signals, delineating the exercise-load-dependent responsiveness of SCG-ECG dynamic coupling during graded-speed treadmill protocols.

The heart adapts to varying exercise loads primarily by augmenting heart rate and contractility to achieve matching increases in cardiac output. However, whether there exists an intrinsic triaxial regulatory mechanism governing the interdependencies among 'exercise load - heart rate response - contractility response' remains unknown. In this study, participants performed treadmill exercise at multiple speed gradients (3-8 km/h). Seismocardiography (SCG) signals were captured via an inertial measurement unit (IMU) positioned on the precordium and were used to characterize mechanical cardiac contractility. Single-lead precordial ECG provided heart rate dynamics, while CPET-derived oxygen uptake (VO₂) indexed exercise intensity. The primary objectives were to delineate SCG-ECG responsivity patterns under graded exercise intensities and quantify potential intrinsic laws linking exercise load, heart rate adaptation, and contractility modulation.

Inclusion Criteria:

• Age 18-60 years
• Healthy individuals with no significant medical history
• Signed informed consent as an acceptance to participate to the trial

Exclusion Criteria:

• History of severe cardiovascular, cerebrovascular, pulmonary, hepatic, renal, psychiatric, or other critical systemic disorders
• Peripheral vascular diseases, musculoskeletal disorders, or other conditions limiting physical mobility
• Uncontrolled hypertension (systolic blood pressure >140 mmHg or diastolic blood pressure >90 mmHg)
• History of anemia
• Moderate to severe obesity (BMI ≥32.5 kg/m²)
• Pregnant or lactating women
• Any other conditions deemed ineligible for participation per investigator's discretion