Reliability of manual versus automated techniques for assessing passive stiffness of the posterior muscles of the hip and thigh

The purpose of this study was to compare the reliability of passive stiffness, passive torque, range of motion (ROM), and electromyography (EMG) of the biceps femoris during passive thigh flexion motions intended to assess the ROM of the posterior muscles of the hip and thigh during manual versus automated assessment techniques. Eleven healthy men (mean ± s age = 22 ± 4 years; mass = 85 ± 12 kg; and height = 178 ± 4 cm) and nine healthy women (age = 19 ± 1 years; mass = 66 ± 15 kg; and height = 164 ± 5 cm) completed four randomly ordered passive straight-legged ROM assessments. Two ROM assessments were performed using a manual technique, which consisted of the primary investigator applying slow passive resistance against a load cell attached to the heel while the foot was moved toward the head. Two automated ROM assessments were also performed using a Biodex System 3 isokinetic dynamometer programmed in passive mode to move the foot toward the head at 0.087 rad · s^-1. The intraclass correlation coefficients (ICCs) for passive stiffness measured with the manual technique ranged from 0.81-0.86, while for the automated technique they were 0.72-0.92. Standard error of measurement (SEM) values for passive stiffness expressed as a percentage of the mean ranged from 15.5-21.7% for the manual and 17.8-23.7% for the automated technique. Both techniques (manual and automated) were comparably reliable across the three trials, which suggested that the manual technique could be applied outside the laboratory.