Cross talk in surface electromyograms of human hamstring muscles

Area of Science:

• Biomedical Engineering
• Neuroscience
• Sports Science

Background:

• Surface electromyograms (EMGs) are crucial for assessing muscle activity.
• Interference from adjacent muscles, known as cross talk, can compromise EMG signal accuracy.
• Accurate hamstring muscle activity assessment is vital in biomechanics and rehabilitation.

Purpose of the Study:

• To quantify cross talk in hamstring surface EMGs.
• To compare the efficacy of the double differential technique versus conventional bipolar recordings in reducing cross talk.
• To evaluate the utility of software simulations for the double differential technique.

Main Methods:

• Electrical stimulation of the quadriceps femoris via the femoral nerve to induce cross talk.
• Recording EMGs from vastus lateralis, medial, and lateral hamstring muscles.
• Analysis of EMG signals using power density spectrum and median frequency, comparing bipolar and double differential techniques.

Main Results:

• Cross talk in lateral hamstrings averaged 17.1% and medial hamstrings 11.3% with bipolar recordings.
• The double differential technique reduced cross talk to 7.6% (lateral) and 4.2% (medial) MVE.
• Median frequencies of electrically stimulated and maximum voluntary effort signals were not significantly different.

Conclusions:

• The double differential technique is more selective than bipolar recordings for hamstring EMGs, particularly with active neighbors.
• This technique improves the accuracy of surface EMG interpretation in challenging recording scenarios.
• Software simulations of the double differential technique offer a viable alternative when amplifier availability is limited.