Objective measurement of knee extension force based on computer adaptive testing

Methods for Dynamic Characterization of the Major Muscles Activating the Lower Limb Joints in Cycling Motion

The functional activation, through electrical stimulation, of the lower limb consisting of several deficient muscles requires well-patterned and coordinated activation of these muscles. This study presents a method for characterizing the parameters of the major muscle groups controlling the ankle and knee joints in cycling motion, the latter having particular significance in the rehabilitation of locomotion. To lower mechanical indeterminacy in the joints the system is reduced by grouping the muscles acting in synergism. The joint torques were calculated by inverse dynamics methods from cycling motion data, including kinematics and foot/pedal reaction loads (forces, moments). The mechanical indeterminacy was resolved by applying optimization criteria and the individual muscle torques were parceled-out from the joint torques. System identification of the individual muscles, part of which being bi-articular, in this non-isometric condition was performed from the relationship between the evaluated force and the measured EMG of each the muscles, using both first and second order linear transfer functions. Feasibility of the presented method was demonstrated through the computation of the coefficients of the muscles involved and validating the results on the experimental data obtained from one subject.

Letting the CAT out of the bag: comparing computer adaptive tests and an 11-item short form of the Roland-Morris Disability Questionnaire

STUDY DESIGN

A post hoc simulation of a computer adaptive administration of the items of a modified version of the Roland-Morris Disability Questionnaire.

OBJECTIVE

To evaluate the effectiveness of adaptive administration of back pain-related disability items compared with a fixed 11-item short form.

SUMMARY OF BACKGROUND DATA

Short form versions of the Roland-Morris Disability Questionnaire have been developed. An alternative to paper-and-pencil short forms is to administer items adaptively so that items are presented based on a person's responses to previous items. Theoretically, this allows precise estimation of back pain disability with administration of only a few items.

MATERIALS AND METHODS

Data were gathered from 2 previously conducted studies of persons with back pain. An item response theory model was used to calibrate scores based on all items, items of a paper-and-pencil short form, and several computer adaptive tests (CATs).

RESULTS

Correlations between each CAT condition and scores based on a 23-item version of the Roland-Morris Disability Questionnaire ranged from 0.93 to 0.98. Compared with an 11-item short form, an 11-item CAT produced scores that were significantly more highly correlated with scores based on the 23-item scale. CATs with even fewer items also produced scores that were highly correlated with scores based on all items. For example, scores from a 5-item CAT had a correlation of 0.93 with full scale scores. Seven- and 9-item CATs correlated at 0.95 and 0.97, respectively. A CAT with a standard-error-based stopping rule produced scores that correlated at 0.95 with full scale scores.

CONCLUSION

A CAT-based back pain-related disability measure may be a valuable tool for use in clinical and research contexts. Use of CAT for other common measures in back pain research, such as other functional scales or measures of psychological distress, may offer similar advantages.