Quantification of full-range-of-motion unilateral and bilateral knee flexion and extension torque ratios

To evaluate the reliability and variability of repeated measurements of isometric knee flexion and extension strength, to quantify the extent of measurement error that may occur due to gravity, and to quantify isometric knee flexion/extension torque ratios at multiple angles through a full range of motion.

Reliability assessment.

A university exercise center.

Seventy-seven healthy men and women recruited from a university and surrounding community.

Isometric knee flexion and extension strength tests.

Knee flexion/extension strength was measured at 6 degrees, 24 degrees, 42 degrees, 60 degrees, 78 degrees, 96 degrees, and 108 of knee flexion. Before each contraction, subjects were instructed to completely relax the limbs to measure the mass of the lower leg. Torque values obtained during relaxation at each angle were added to or subtracted from "Total Torque" (TTQ) at peak exertion. The adjusted value was recorded as "Net Muscular Torque" (NMT).

Reliability for the unilateral and bilateral tests was high (r =.88 to r=.98) and measurement variability low (SEM%=5.1% to 12.6%). There was a statistically significant difference at each angle of measurement between the TTQ and NMT values for both knee flexion and extension. Knee flexion/extension ratios were highly dependent on the angle tested, ranging from 1.30 (at 60) to .31 (at 1080).

Isometric testing, using standardized angles, can reliably quantify knee flexion/extension strength. Furthermore, these findings emphasize the importance of correcting for the mass of the lower leg when assessing muscle function. Angle-specific knee flexion/extension torque ratios should provide clinicians with a more precise method of evaluating muscular balance (imbalance) throughout the range of motion.