center of pressure

Immediate Effects of Vibrotactile Feedback on Postural Sway in Healthy Older Adults

Previous research has shown the utility of vibrotactile feedback to improve postural sway characteristics in persons with vestibular deficits. Tactile feedback given through vibration has been used more as a modality of training but immediate effects on postural control among older adults have not been investigated. PURPOSE: To compare the immediate effects of tactile vibration on postural sway in healthy older adults in challenging stance and sensory conditions. METHODS: 10 healthy older adults (76.4 ± 6.8years), performed five standing balance conditions on a AMTI forceplate for 30s each: feet together on firm surface eyes open (C1), eyes closed (C2); feet together on foam surface eyes open (C3), eyes closed (C4), and tandem stance on firm surface eyes open (C5). Participants did 2 trials of each condition both with and without vibrotactile feedback. The feedback was given using a waist belt with sensors that were activated when participants swayed in a particular direction as detected by an Xbox Kinect camera (Sensory Kinetics system; Engineering Acoustics, Casselberry, FL). Center of pressure sway area was compared within each condition using a paired samples t-test to estimate the effect of vibration. RESULTS: See Table 1. Since only 5 subjects could complete C4 data was not included in statistical analysis. CONCLUSION: Tactile vibration did not acutely effect postural sway in challenging stance conditions in healthy older adults. Long term effects of tactile vibration on postural sway in challenging stance conditions need to be investigated.
Listed In: Physical Therapy


The Effect of Work Boots on Center of Pressure Location at the Knee in Static Kneeling

INTRODUCTION: Workers in industry wear steel toe boots; however, these boots are inflexible and may restrict foot movement. Occupational kneeling is also associated with an increased risk of knee osteoarthritis. Examination of the effects of work boots in kneeling is needed to better understand potential injury risk. Therefore, the purpose of this study was to analyze the center of pressure (COP) at the knee during kneeling when shod and barefoot. METHODS: Fifteen, young, healthy males completed five 10-second static kneeling trials in each condition. Lower body kinematics were obtained using the Optotrak system (Certus and 3020, NDI, Waterloo, ON, CA). Force data were measured from a force plate under the knee of the dominant leg (OR6-7, AMTI, Watertown, MA, USA). The mean COP location was determined with respect to the medial tibial plateau (normalized to tibial width) and the tibial tuberosity (normalized to tibial length) for the medial/lateral and longitudinal directions, respectively. RESULTS: COP was located more medially in the shod condition (34% (±10.6%) tibial width) compared to the barefoot condition (40% (±11.9%) tibial width) (p=0.0485). COP was located above the tibial tuberosity, with no difference between conditions (shod 11% (±3.2%) tibial length, barefoot: (7%) (±8.8%) tibial length) (p=0.97). DISCUSSION: There is a difference in COP location in shod compared to barefoot kneeling. A COP location farther from the joint center of rotation, as occurred in the frontal plane of the shod condition, would increase the moment arm of the ground reaction force and thus the moment at the knee.
Listed In: Biomechanics