Angle-Matched Isometric and Isokinetic Hamstring-to-Quadriceps Ratios Are Not Directly Interchangeable: An...

Area of Science:

• Biomechanics
• Sports Medicine
• Human Movement Science

Background:

• Hamstring-to-quadriceps (H/Q) strength ratios are crucial for assessing knee flexor-to-extensor torque balance.
• Interpretation of H/Q ratios can be affected by joint angle, contraction mode, and the stability of the denominator used.
• Understanding the interchangeability of H/Q ratios from different testing methods is vital for accurate clinical and athletic assessments.

Purpose of the Study:

• To investigate whether angle-matched hamstring-to-quadriceps (H/Q) strength ratios derived from isometric and isokinetic dynamometry are directly interchangeable.
• To explore the influence of joint angle and contraction mode on H/Q ratios.
• To provide a basis for hypothesis generation regarding H/Q ratio interpretation.

Main Methods:

• An exploratory, repeated-measures study involving fourteen healthy young adults.
• Maximal knee extension and flexion torque measurements using a Biodex System 4 Pro.
• Isometric testing at multiple joint angles (10°, 30°, 60°, 90°, 110°) and isokinetic testing at various speeds (60°/s, 150°/s, 300°/s), with torque extracted at matched angles.

Main Results:

• Significant effects of joint angle, limb, and interactions between angle and mode on log-transformed H/Q ratios were observed.
• The angle × mode interaction remained significant even after excluding endpoint angles, indicating mode-dependent angle effects.
• These findings suggest that H/Q ratios are influenced by both joint position and the testing dynamometry mode.

Conclusions:

• Angle-specific hamstring-to-quadriceps (H/Q) strength ratios are significantly influenced by joint angle and the testing mode (isometric vs. isokinetic).
• Isometric and isokinetic H/Q ratios should not be considered directly interchangeable due to these observed differences.
• Endpoint H/Q ratios require careful interpretation alongside the underlying flexor and extensor torque values, especially given the exploratory nature and small sample size of this study.