Angle-Matched Isometric and Isokinetic Hamstring-to-Quadriceps Ratios Are Not Directly Interchangeable: An Exploratory Multi-Angle Dynamometry Study

Hamstring-to-quadriceps (H/Q) strength ratios describe knee flexor-to-extensor torque balance, but their interpretation may depend on joint angle, contraction mode, and denominator stability. This exploratory repeated-measures study examined whether angle-matched H/Q ratios obtained from isometric and isokinetic dynamometry are directly interchangeable. Fourteen healthy young adults performed maximal knee extension and flexion using a Biodex System 4 Pro. Isometric testing was conducted at 10°, 30°, 60°, 90°, and 110° of knee flexion; isokinetic testing was performed at 60°/s, 150°/s, and 300°/s, with torque extracted at matched angles. H/Q ratios were calculated as flexor torque divided by extensor torque for each angle, limb, and mode and analyzed after log transformation. In the all-angle model, log-transformed H/Q ratio showed a significant angle effect (F(4,52) = 14.60, p < 0.001, partial η2 = 0.529), limb effect (F(1,13) = 5.54, p = 0.035, partial η2 = 0.299), angle × mode interaction (F(12,156) = 2.78, p = 0.002, partial η2 = 0.176), and angle × mode × limb interaction (F(12,156) = 2.60, p = 0.004, partial η2 = 0.167). After excluding endpoint angles, the angle × mode interaction remained significant (F(6,78) = 8.60, p < 0.001, partial η2 = 0.398). These findings suggest that angle-specific H/Q ratios are influenced by joint position and testing mode. Because of the small sample and absence of protocol-specific test-retest reliability, the results should be interpreted as exploratory and hypothesis-generating. Isometric and isokinetic H/Q ratios should not be treated as directly interchangeable, and endpoint ratios should be interpreted together with the underlying flexor and extensor torque values.