Feedback control of heart rate during treadmill exercise based on a two-phase response model

Area of Science:

• Biomedical Engineering
• Control Systems Engineering
• Exercise Physiology

Background:

• Automatic control of physiological parameters during exercise is crucial for research and training.
• Accurate heart rate (HR) tracking during exercise requires robust control system design.
• Previous studies have explored HR control using cycle ergometers, with limited data on treadmill-based systems.

Purpose of the Study:

• To theoretically derive a generic feedback design strategy for constant input sensitivity function in linear, time-invariant models.
• To empirically compare the dynamic performance and tracking accuracy of a second-order compensator (C2) against a first-order compensator (C1) for HR control during treadmill exercise.

Main Methods:

• Twenty-three healthy participants engaged in 35-minute treadmill running sessions.
• Heart rate was automatically controlled using two compensators: C1 (first-order model) and C2 (second-order model).
• Performance was evaluated based on tracking error and control signal power.

Main Results:

• Compensator C2 exhibited significantly higher accuracy, with 7% lower mean root-mean-square tracking error (1.98 vs. 2.13 bpm, p=0.026).
• Compensator C2 demonstrated significantly greater dynamism, with 17% higher mean control signal power (23.4 × 10-4 m²/s² vs. 20.0 × 10-4 m²/s², p=0.011).
• The enhanced performance of C2 is attributed to the superior fidelity of second-order models in capturing cardiac responses to exercise.

Conclusions:

• Second-order models provide a more accurate representation of the cardiac response to exercise compared to first-order models.
• Compensator C2, based on a second-order model, is recommended for applications prioritizing heart rate tracking accuracy and dynamic control during treadmill exercise.
• The findings are consistent with previous research using cycle ergometers, suggesting generalizability across exercise modalities.