Muscle Balance between Hamstrings and Quadriceps during Isokinetic Exercise

Area of Science:

• Biomechanics
• Human Physiology
• Sports Science

Background:

• Assessing knee joint strength is vital in sports and rehabilitation.
• Muscle torque ratios, particularly hamstrings to quadriceps, indicate joint function.
• Previous studies have not fully accounted for gravitational effects on torque measurements.

Purpose of the Study:

• To determine the influence of angular velocity on knee flexor and extensor peak torques.
• To evaluate the effect of gravity on the hamstring to quadriceps torque ratio.
• To highlight the importance of gravity correction in isokinetic strength testing.

Main Methods:

• Maximum flexor and extensor peak torques of 34 subjects (17 male, 17 female) were measured using a CYBEX isokinetic dynamometer.
• The ratio of peak hamstrings torque to peak quadriceps torque was calculated.
• Measurements were analyzed with and without gravity correction at various angular velocities.

Main Results:

• The flexion-extension torque ratio, when corrected for gravity, showed no significant difference across tested angular velocities.
• The uncorrected torque ratio demonstrated significant differences at increasing joint angular velocities.
• Gravitational influence was found to be a significant factor in torque ratio calculations.

Conclusions:

• Physiotherapists must recognize and account for gravity's influence when measuring vertical plane forces.
• Gravity correction is essential for accurate hamstring to quadriceps torque ratio assessment, especially at higher velocities.
• Standardized protocols for isokinetic testing should incorporate gravity correction for reliable strength evaluations.