Quadriceps EMG frequency content following isometric lumbar extension exercise

Area of Science:

• Neuromuscular physiology
• Exercise science
• Biomedical engineering

Background:

• A known relationship exists between lumbar spine muscles and lower extremity function.
• Quadriceps muscles can become inhibited following lumbar paraspinal fatiguing exercise.

Purpose of the Study:

• To investigate the changes in surface electromyography (sEMG) total frequency content of the quadriceps following lumbar paraspinal fatiguing exercise.
• To compare the effects of lumbar fatiguing exercise on quadriceps neuromuscular activity.

Main Methods:

• Fifty subjects performed fatiguing lumbar extension exercise, monitored by lumbar paraspinal sEMG median frequency shifts.
• Maximal isometric knee extension torque and quadriceps central activation ratio (QI) were measured before and after exercise sets.
• Quadriceps vastus lateralis sEMG was recorded, and total frequency content (fEMG(TOTAL)) was calculated.

Main Results:

• Quadriceps fEMG(TOTAL) significantly decreased from baseline after the first and second exercise sets.
• No significant changes were observed in quadriceps sEMG median frequency.
• The decrease in fEMG(TOTAL) correlated with changes in quadriceps QI.

Conclusions:

• Fatiguing lumbar extension exercise leads to a reduction in quadriceps fEMG(TOTAL).
• This reduction occurs without significant alterations in quadriceps median frequency, suggesting a specific neuromuscular response.