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A new concept for isokinetic hamstring: quadriceps muscle strength ratio
P Aagaard1, E B Simonsen, S P Magnusson
1Department of Neurophysiology, Institute of Medical Physiology, Copenhagen, Denmark.
The American Journal of Sports Medicine
|April 21, 1998
Summary
Functional hamstring:quadriceps strength ratios offer a more accurate assessment of knee joint function than conventional ratios. These functional ratios, particularly during fast knee extension, highlight the hamstring muscles
Area of Science:
- Biomechanics
- Kinesiology
- Sports Medicine
Background:
- The conventional hamstring:quadriceps strength ratio relies on maximal knee flexor (hamstring) and knee extensor (quadriceps) moments at identical angular velocities.
- Agonist-antagonist muscle relationships, crucial for joint stability, may be better represented by functional strength ratios involving eccentric and concentric contractions.
Purpose of the Study:
- To compare functional and conventional isokinetic hamstring:quadriceps strength ratios.
- To examine the influence of knee joint angle and angular velocity on these strength ratios.
Main Methods:
- Maximal concentric and eccentric knee flexor and extensor moments were measured using isokinetic dynamometry across various speeds (30 and 240 deg/sec) and joint angles.
- Functional ratios (eccentric hamstring:concentric quadriceps for extension; concentric hamstring:eccentric quadriceps for flexion) and conventional ratios were calculated.
- Angle-specific ratios at 50, 40, and 30 degrees of knee flexion were analyzed, alongside peak moments.
Main Results:
- Functional hamstring:quadriceps ratios varied significantly (0.3–1.4) across different moments, speeds, and joint angles, unlike conventional ratios (0.5–0.8).
- A 1:1 functional ratio was observed for fast knee extension, increasing with knee extension, suggesting robust hamstring contribution to dynamic knee stability.
- Conventional ratios showed less variability and did not fully capture the functional strength relationship.
Conclusions:
- Functional hamstring:quadriceps ratios provide a more comprehensive evaluation of knee joint function compared to conventional ratios.
- The hamstring muscles demonstrate significant capacity for dynamic knee joint stabilization, particularly during rapid knee extension movements.
- Isokinetic dynamometry assessments should include both functional and conventional hamstring:quadriceps ratios, alongside absolute muscle strength data, for a complete understanding of knee function.