Muscle force as affected by fatigue: mathematical model and experimental verification

Area of Science:

• Biomechanics
• Muscle Physiology
• Computational Modeling

Background:

• Muscle fatigue significantly impacts force generation during physical activities.
• Existing muscle models often lack comprehensive fatigue integration.
• Understanding fatigue mechanisms is crucial for performance analysis and injury prevention.

Purpose of the Study:

• To derive and present indices of muscle fatigue for a fiber-based muscle model.
• To validate the developed muscle model's ability to predict forces during fatiguing contractions.
• To assess the model's accuracy in both isometric and dynamic conditions.

Main Methods:

• Developed a fiber-based muscle model calculating force from individual fiber contributions.
• Derived fatigue indices based on experimental data for three distinct fiber types.
• Validated the model using an elbow extension study involving maximal effort isometric and dynamic fatigue tests.
• Compared model-predicted forces with those derived from rigid-body dynamics.

Main Results:

• The muscle model successfully incorporated fatigue effects across different fiber types.
• Model-predicted forces showed no significant difference compared to rigid-body dynamics for specific time intervals (isometric < 50s, dynamic > 40s).
• Statistical analysis confirmed the validity and utility of the developed muscle fatigue modeling approach.

Conclusions:

• The presented fiber-based muscle model provides a robust framework for simulating muscle fatigue.
• The derived fatigue indices and model validation demonstrate its applicability to maximal effort activities.
• This modeling approach offers a valuable tool for biomechanical research and performance analysis.