R. Speers - Academia.edu (original) (raw)

Papers by R. Speers

Research paper thumbnail of Multivariate changes in coordination of postural control following spaceflight

Journal of Biomechanics, 1998

Research paper thumbnail of Performance of young and old women on graded difficulty tests of tandem stand and tandem walk

Research paper thumbnail of Age differences in abilities to perform tandem stand and walk tasks of graded difficulty

Gait & Posture, 1998

We quantified the abilities of 12 young (mean age 23.3 years) and 12 old (mean age 72.0 years) he... more We quantified the abilities of 12 young (mean age 23.3 years) and 12 old (mean age 72.0 years) healthy women to tandem stand and tandem walk on a set of six beams, ranging from 15 cm down to 2.5 cm in width. Tandem stand tasks were conducted with eyes both open ...

Research paper thumbnail of D. Usaha Scientific Papers

ONE HUNDRED …, 2005

The Animal and Plant Health Inspection Service, Veterinary Services (APHIS-VS) within the US Depa... more The Animal and Plant Health Inspection Service, Veterinary Services (APHIS-VS) within the US Department of Agriculture (USDA) asked the CNA Corporation to conduct a reconstruction and analysis of eradication efforts during the 2002-03 outbreak of exotic ...

Research paper thumbnail of Reconstruction of Response Operations to Eradicate Exotic Newcastle Disease in 2002–2003

Alexandria, VA: The CNA …, 2004

Research paper thumbnail of Analysis and Recommendations from Operation" Aphtosa

California Department of …, 2004

Research paper thumbnail of Labyrinthectomy versus Vestibular Neurectomy: Long-term Physiologic and Clinical Outcomes

Otology & Neurotology, 2001

To determine whether long-term vestibular compensation (VC) and clinical outcomes differ after tr... more To determine whether long-term vestibular compensation (VC) and clinical outcomes differ after transmastoid labyrinthectomy (TML) versus retrolabyrinthine vestibular neurectomy (RVNS). Prospective, observational study. Tertiary care, university hospital. Twenty-one subjects were studied several years after they were relieved of spontaneous episodic vertigo caused by peripheral vestibular disease by TML or RVNS. All patients had undergone TML or RVNS more than 2.5 years before the study and returned for physiologic and functional studies of vestibular compensation. Completeness of physiologic VC, as assessed by electronystagmography and rotational chair testing; performance on computerized dynamic posturography; pure-tone and speech audiometry; self-assessment of balance and hearing function with validated survey instruments. There were no differences in the incidence of physiologic VC or functional recovery between the TML and RVNS subjects. Although a majority of subjects in each group had evidence of incomplete vestibular compensation, there was no difference in self-assessment of balance or hearing handicap at long-term follow-up. Long-term clinical balance and hearing outcomes are equivalent when TML and RVNS successfully cure spontaneous, episodic vertigo. There is a high incidence of incomplete VC after both procedures, though this does not usually produce a significant balance handicap.

Research paper thumbnail of Hamstrings and psoas lengths during normal and crouch gait: Implications for muscle-tendon surgery

Journal of Orthopaedic Research, 1996

Research paper thumbnail of Effect of altered sensory conditions on multivariate descriptors of human postural sway

Experimental Brain Research, 1998

to posture control. Descending postural commands are multivariate in nature, and the motion at ea... more to posture control. Descending postural commands are multivariate in nature, and the motion at each joint is affected uniquely by input from multiple sensors.

Research paper thumbnail of Head Shake Computerized Dynamic Posturography in Peripheral Vestibular Lesions

American Journal of Audiology, 2009

To determine the sensitivity of a head shake modification to the Sensory Organization Test (SOT) ... more To determine the sensitivity of a head shake modification to the Sensory Organization Test (SOT) of dynamic posturography in identifying (a) those patients with unilateral, peripheral vestibular hypofunction as indicated by caloric irrigation findings and (b) those patients who report that head movements provoke disruption in postural control. A prospective, single-blinded, random selection methodology was used with 91 patients stratified by the presence or absence of a significant caloric asymmetry and by the presence or absence of head movement provoked symptoms (independent variables). Postural control performance, as measured by EquiTest during the standard test and a head shake modification, served as the dependent variables. Receiver operating characteristic curves demonstrated only minor improvement in sensitivity (a) with the head shake modification for unilateral peripheral asymmetry and (b) for identification of those with complaints of head movement provoked imbalance. The head shake modification to standard SOT increased the test sensitivity to identification of patients with unilateral, peripheral vestibular hypofunction and those with head movement provoked symptoms. However, this occurred with low specificity, resulting in no significant improvement in overall performance with this head shake protocol. Suggestions for further research to improve the performance of the head shake modification of SOT for clinical application are discussed.

Research paper thumbnail of Multivariate changes in coordination of postural control following spaceflight

Journal of Biomechanics, 1998

Postural and gait instabilities in astronauts returning from spaceflight are thought to result fr... more Postural and gait instabilities in astronauts returning from spaceflight are thought to result from in-flight adaptation of central nervous system processing of sensory inputs from the vestibular, proprioceptive, and visual systems. We hypothesized that reorganization of posture control relying on these multiple inputs would result in not only greater amounts of sway, but also changes in interjoint coordination. We tested this hypothesis by examining the multivariate characteristics of postural sway and comparing the postural control gain used for maintenance of upright stance during the altered sensory conditions of the Sensory Organization Test (EquiTest, Neurocom Intl.). We used the covariance of hip and ankle kinematics as a measure of joint motion and interjoint coordination, and then utilized discriminant analysis to further examine these characteristics in a group of 10 first-time astronauts. In five of the six conditions, the most important difference was an increased relative utilization of the hip strategy, which would not be evident using conventional balance measures such as peak or root-mean-square sway. This finding was supported by indications of increased hip torque gains relative to lower extremity and neck motion in at least four conditions (p(0.05). In contrast, ankle torque gains to these motions did not appear to change. These results suggest that after spaceflight, astronauts exhibit significant multivariate changes in multijoint coordination, of which increased sway is only one component. These changes are consistent with reweighting of vestibular inputs and changes in control strategy in a multivariable control system. : S 0 0 2 1 -9 2 9 0 ( 9 8 ) 0 0 0 6 5 -7

Research paper thumbnail of Multivariate changes in coordination of postural control following spaceflight

Journal of Biomechanics, 1998

Research paper thumbnail of Performance of young and old women on graded difficulty tests of tandem stand and tandem walk

Research paper thumbnail of Age differences in abilities to perform tandem stand and walk tasks of graded difficulty

Gait & Posture, 1998

We quantified the abilities of 12 young (mean age 23.3 years) and 12 old (mean age 72.0 years) he... more We quantified the abilities of 12 young (mean age 23.3 years) and 12 old (mean age 72.0 years) healthy women to tandem stand and tandem walk on a set of six beams, ranging from 15 cm down to 2.5 cm in width. Tandem stand tasks were conducted with eyes both open ...

Research paper thumbnail of D. Usaha Scientific Papers

ONE HUNDRED …, 2005

The Animal and Plant Health Inspection Service, Veterinary Services (APHIS-VS) within the US Depa... more The Animal and Plant Health Inspection Service, Veterinary Services (APHIS-VS) within the US Department of Agriculture (USDA) asked the CNA Corporation to conduct a reconstruction and analysis of eradication efforts during the 2002-03 outbreak of exotic ...

Research paper thumbnail of Reconstruction of Response Operations to Eradicate Exotic Newcastle Disease in 2002–2003

Alexandria, VA: The CNA …, 2004

Research paper thumbnail of Analysis and Recommendations from Operation" Aphtosa

California Department of …, 2004

Research paper thumbnail of Labyrinthectomy versus Vestibular Neurectomy: Long-term Physiologic and Clinical Outcomes

Otology & Neurotology, 2001

To determine whether long-term vestibular compensation (VC) and clinical outcomes differ after tr... more To determine whether long-term vestibular compensation (VC) and clinical outcomes differ after transmastoid labyrinthectomy (TML) versus retrolabyrinthine vestibular neurectomy (RVNS). Prospective, observational study. Tertiary care, university hospital. Twenty-one subjects were studied several years after they were relieved of spontaneous episodic vertigo caused by peripheral vestibular disease by TML or RVNS. All patients had undergone TML or RVNS more than 2.5 years before the study and returned for physiologic and functional studies of vestibular compensation. Completeness of physiologic VC, as assessed by electronystagmography and rotational chair testing; performance on computerized dynamic posturography; pure-tone and speech audiometry; self-assessment of balance and hearing function with validated survey instruments. There were no differences in the incidence of physiologic VC or functional recovery between the TML and RVNS subjects. Although a majority of subjects in each group had evidence of incomplete vestibular compensation, there was no difference in self-assessment of balance or hearing handicap at long-term follow-up. Long-term clinical balance and hearing outcomes are equivalent when TML and RVNS successfully cure spontaneous, episodic vertigo. There is a high incidence of incomplete VC after both procedures, though this does not usually produce a significant balance handicap.

Research paper thumbnail of Hamstrings and psoas lengths during normal and crouch gait: Implications for muscle-tendon surgery

Journal of Orthopaedic Research, 1996

Research paper thumbnail of Effect of altered sensory conditions on multivariate descriptors of human postural sway

Experimental Brain Research, 1998

to posture control. Descending postural commands are multivariate in nature, and the motion at ea... more to posture control. Descending postural commands are multivariate in nature, and the motion at each joint is affected uniquely by input from multiple sensors.

Research paper thumbnail of Head Shake Computerized Dynamic Posturography in Peripheral Vestibular Lesions

American Journal of Audiology, 2009

To determine the sensitivity of a head shake modification to the Sensory Organization Test (SOT) ... more To determine the sensitivity of a head shake modification to the Sensory Organization Test (SOT) of dynamic posturography in identifying (a) those patients with unilateral, peripheral vestibular hypofunction as indicated by caloric irrigation findings and (b) those patients who report that head movements provoke disruption in postural control. A prospective, single-blinded, random selection methodology was used with 91 patients stratified by the presence or absence of a significant caloric asymmetry and by the presence or absence of head movement provoked symptoms (independent variables). Postural control performance, as measured by EquiTest during the standard test and a head shake modification, served as the dependent variables. Receiver operating characteristic curves demonstrated only minor improvement in sensitivity (a) with the head shake modification for unilateral peripheral asymmetry and (b) for identification of those with complaints of head movement provoked imbalance. The head shake modification to standard SOT increased the test sensitivity to identification of patients with unilateral, peripheral vestibular hypofunction and those with head movement provoked symptoms. However, this occurred with low specificity, resulting in no significant improvement in overall performance with this head shake protocol. Suggestions for further research to improve the performance of the head shake modification of SOT for clinical application are discussed.

Research paper thumbnail of Multivariate changes in coordination of postural control following spaceflight

Journal of Biomechanics, 1998

Postural and gait instabilities in astronauts returning from spaceflight are thought to result fr... more Postural and gait instabilities in astronauts returning from spaceflight are thought to result from in-flight adaptation of central nervous system processing of sensory inputs from the vestibular, proprioceptive, and visual systems. We hypothesized that reorganization of posture control relying on these multiple inputs would result in not only greater amounts of sway, but also changes in interjoint coordination. We tested this hypothesis by examining the multivariate characteristics of postural sway and comparing the postural control gain used for maintenance of upright stance during the altered sensory conditions of the Sensory Organization Test (EquiTest, Neurocom Intl.). We used the covariance of hip and ankle kinematics as a measure of joint motion and interjoint coordination, and then utilized discriminant analysis to further examine these characteristics in a group of 10 first-time astronauts. In five of the six conditions, the most important difference was an increased relative utilization of the hip strategy, which would not be evident using conventional balance measures such as peak or root-mean-square sway. This finding was supported by indications of increased hip torque gains relative to lower extremity and neck motion in at least four conditions (p(0.05). In contrast, ankle torque gains to these motions did not appear to change. These results suggest that after spaceflight, astronauts exhibit significant multivariate changes in multijoint coordination, of which increased sway is only one component. These changes are consistent with reweighting of vestibular inputs and changes in control strategy in a multivariable control system. : S 0 0 2 1 -9 2 9 0 ( 9 8 ) 0 0 0 6 5 -7