Relationship between the MRI and EMG measurements

Area of Science:

• Sports Medicine
• Exercise Physiology
• Biomedical Imaging

Background:

• Eccentric exercise is crucial for muscle strength and injury prevention.
• Understanding neuromuscular fatigue mechanisms is vital for optimizing training.
• Magnetic Resonance Imaging (MRI) offers non-invasive insights into muscle tissue changes.

Purpose of the Study:

• To investigate the effects of intensive eccentric exercise on hamstring muscles using MRI.
• To explore the relationship between electromyographic (EMG) changes and muscle tissue alterations (T2 relaxation time).
• To differentiate fatigue mechanisms in specific hamstring muscles (semitendinosus, biceps femoris, semimembranosus).

Main Methods:

• Seven male volunteers performed eccentric knee flexion exercises.
• Electromyographic (EMG) activity of hamstring muscles was recorded during exercise.
• Maximum isometric knee flexion torque was measured before and after exercise.
• Magnetic Resonance Imaging (MRI) was used to obtain T2 relaxation time values of hamstring muscles pre- and post-exercise.

Main Results:

• EMG activity significantly decreased across all hamstring muscles from the first to the fifth set.
• A significant correlation between changes in T2 relaxation time and EMG signals was found only in the semitendinosus muscle.
• No significant correlation was observed for the biceps femoris and semimembranosus muscles.

Conclusions:

• Reduced EMG activity in biceps femoris, semitendinosus, and semimembranosus muscles indicates neuromuscular fatigue.
• The semitendinosus muscle's response suggests impaired excitation-contraction coupling, likely due to excessive muscle fiber damage.
• MRI-derived T2 relaxation time can help differentiate fatigue mechanisms in specific muscles following eccentric exercise.