Moving in pain - A preliminary study evaluating the immediate effects of experimental knee pain on locomotor biomechanics.

Pain changes how we move, but it is often confounded by other factors due to disease or injury. Experimental pain offers an opportunity to isolate the independent effect of pain on movement. We used cutaneous electrical stimulation to induce experimental knee pain during locomotion to study the short-term motor adaptions to pain. While other models of experimental pain have been used in locomotion, they lack the ability to modulate pain in real-time. Twelve healthy adults completed the single data collection session where they experienced six pain intensity conditions (0.5, 1, 2, 3, 4, 5 out of 10) and two pain delivery modes (tonic and phasic). Electrodes were placed over the lateral infrapatellar fat pad and medial tibial condyle to deliver the 10 Hz pure sinusoid via a constant current electrical stimulator. Pain intensity was calibrated prior to each walking bout based on the target intensity and was recorded using an 11-point numerical rating scale. Knee joint angles and moments were recorded over the walking bouts and summarized in waveform and discrete outcomes to be compared with baseline walking. Knee joint angles changed during the swing phase of gait, with higher pain intensities resulting in greater knee flexion angles. Minimal changes in joint moments were observed but there was a consistent pattern of decreasing joint stiffness with increasing pain intensity. Habituation was limited across the 30-90 second walking bouts and the electrical current needed to deliver the target pain intensities showed a positive linear relationship. Experimental knee pain shows subtle biomechanical changes and favourable habituation patterns over short walking bouts. Further exploration of this model is needed in real-world walking conditions and over longer timeframes to quantify motor adaptations.

Evaluating visuomotor coordination in children with amblyopia.

Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in children-specifically, for complex tasks that require movement sequencing. This study therefore compared the visuomotor performance in 21 children with abnormal binocular vision (patient group) due to amblyopia and/or strabismus to that of 236 children with normal binocular vision development (control group) ages 5-14 years. Visual acuity, stereoacuity, and hand-movement kinematics on a bead-threading task were assessed. The patient group showed significantly longer durations than the control group on grasp, thread, and total movement durations. Both groups of participants were then split into immature (ages 5-9 years) and mature (ages 10-14 years) groups based on the maturation age for these parameters in control children. Grasp duration was longer in both mature and immature patient groups; thread and total movement durations were longer in the mature patient group only. Grasp duration was the most disrupted kinematic parameter in children with disrupted binocular vision due to amblyopia and/or strabismus, regardless of age. The level of stereoacuity loss rather than the depth of visual acuity loss was associated with the severity of visuomotor deficits.