Papers by Nicholas Stergiou
Motor control, 2012
Postural disturbances are one of the first reported symptoms in patients with Multiple Sclerosis ... more Postural disturbances are one of the first reported symptoms in patients with Multiple Sclerosis (MS). The purpose of this study was to investigate the effect of supervised resistance training on postural control in MS patients. Postural control was assessed using amount of sway variability [Root Mean Square (RMS)] and temporal structure of sway variability [Lyapunov Exponent (LyE)] from 15 MS patients. Posture was evaluated before and after completion of three months of resistance training. There were significant differences between MS patients pretraining and healthy controls for both LyE (p = .000) and RMS (p = .002), but no differences between groups after training. There was a significant decrease in RMS (p = .025) and a significant increase in LyE (p = .049) for MS patients pre- to posttraining. The findings suggested that postural control of MS patients could be affected by a supervised resistance training intervention.
Journal of applied biomechanics, 2012
Peripheral arterial disease (PAD) is a manifestation of atherosclerosis resulting in intermittent... more Peripheral arterial disease (PAD) is a manifestation of atherosclerosis resulting in intermittent claudication (IC) or leg pain during physical activity. Two drugs (cilostazol and pentoxifylline) are approved for treatment of IC. Our previous work has reported no significant differences in gait biomechanics before and after drug interventions when PAD patients walked without pain. However, it is possible that the drugs are more efficacious during gait with pain. Our aim was to use advanced biomechanical analysis to evaluate the effectiveness of these drugs while walking with pain. Initial and absolute claudication distances, joint kinematics, torques, powers, and gait velocity during the presence of pain were measured from 24 patients before and after 12 weeks of treatment with either cilostazol or pentoxifylline. We found no significant improvements after 12 weeks of treatment with either cilostazol or pentoxifylline on the gait biomechanics of PAD patients during pain. Our finding...
Journal of applied biomechanics, 2013
Multiple sclerosis (MS) causes severe gait problems in relatively young individuals, yet there ha... more Multiple sclerosis (MS) causes severe gait problems in relatively young individuals, yet there have been limited studies to quantitatively identify the specific gait parameters that are affected. The purpose of this study was to define any differences in biomechanical gait parameters between patients with MS and healthy controls. A total of 31 MS patients and 31 healthy controls were evaluated: joint torques and joint powers were calculated at the ankle, knee, and hip during the stance phase of gait. The self-selected walking velocity was used as a covariate in the analysis to ensure that group differences were not due to differences in walking velocity between the MS and healthy control groups. Reduced angular range, less joint torque, and reduced joint power were seen in patients with MS. We also found significant correlations between biomechanical gait parameters and EDSS score, which provides a clinical rating of disease severity. Our findings provide a quantitative assessment o...
Archives of Physical Medicine and Rehabilitation, 2011
Journal of applied biomechanics, 2010
Pharmacological treatment has been used to alleviate the claudication symptoms and improve walkin... more Pharmacological treatment has been used to alleviate the claudication symptoms and improve walking performance in peripheral arterial disease (PAD) patients. However, the effects of claudication treatments on gait mechanics have not been objectively identified with biomechanical techniques. For this study, 20 PAD patients were assigned to take either pentoxifylline (n=11) or cilostazol (n=9), the two FDA-approved pharmacological therapies used to treat intermittent claudication symptoms. All patients completed a gait evaluation protocol that involved the acquisition of kinematic and kinetic gait data before use of the medication and after 12 weeks of treatment. Results showed that treatment with either pentoxifylline or cilostazol resulted in limited overall improvement in gait parameters including joint angles and joint moments. Walking speed was unchanged, in either treatment group, as a result of the medication. These results suggest that to improve biomechanical walking paramete...
Pediatric Physical Therapy, 2009
Functional Reach Test scores were examined for the effects of traditional and alternate methods a... more Functional Reach Test scores were examined for the effects of traditional and alternate methods and subject characteristics. Eighty subjects aged 7 to 16 years were tested. Effects of measurement method (from finger-to-finger or from toe-to-finger) and style of reach (1 or 2 arms) were investigated. Five subject variables were analyzed for interactions among the methods and groups defined by subject characteristics. Measurement method and style of reach showed a significant interaction. Interaction of method with subject characteristics was significant for age, height, and base of support only. Height groups by quartile were significantly different and scores increased with height, especially in toes-to-finger methods. Functional Reach Test scores were affected by method of reach and method of measurement. Height categories may be more useful when using the test for discriminative purposes, especially with toes-to-finger methods.
Perceptual and Motor Skills, 2002
Purpose: Functional Reach Test scores were examined for the effects of traditional and alternate ... more Purpose: Functional Reach Test scores were examined for the effects of traditional and alternate methods and subject characteristics. Methods: Eighty subjects aged 7 to 16 years were tested. Effects of measurement method (from finger-to-finger or from toe-to-finger) and style of reach (1 or 2 arms) were investigated. Five subject variables were analyzed for interactions among the methods and groups defined
Pediatric Physical Therapy, 2006
This investigation quantitatively characterized the certainty of the aging neuromuscular system i... more This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty
The purpose,of this investigation was to determine,if phase plot normalization,and phase angle de... more The purpose,of this investigation was to determine,if phase plot normalization,and phase angle definitions would,have an affect on continuous,relative phase calculations. A subject ran on a treadmill while sagittal plane kinematic,data were collected with a high- speed(180 Hz) camera. Segmental angular d isplacements andvelocities were usedto create phase plots, andexamine the coordination,between,the leg and,thigh. Continuous,relative phase was,calculated with a combination,of
PloS one, 2015
Variability is an inherent and important feature of human movement. This variability has form exh... more Variability is an inherent and important feature of human movement. This variability has form exhibiting a chaotic structure. Visual feedback training using regular predictive visual target motions does not take into account this essential characteristic of the human movement, and may result in task specific learning and loss of visuo-motor adaptability. In this study, we asked how well healthy young adults can track visual target cues of varying degree of complexity during whole-body swaying in the Anterior-Posterior (AP) and Medio-Lateral (ML) direction. Participants were asked to track three visual target motions: a complex (Lorenz attractor), a noise (brown) and a periodic (sine) moving target while receiving online visual feedback about their performance. Postural sway, gaze and target motion were synchronously recorded and the degree of force-target and gaze-target coupling was quantified using spectral coherence and Cross-Approximate entropy. Analysis revealed that both force...
Journal of neurologic physical therapy : JNPT, 2006
Variability is a natural and important feature of human movement. Using existing theoretical fram... more Variability is a natural and important feature of human movement. Using existing theoretical frameworks as a foundation, we propose a new model to explain movement variability as it relates to motor learning and health. We contend that mature motor skills and healthy states are associated with an optimal amount of movement variability. This variability also has form and is characterized by a chaotic structure. Less than optimal movement variability characterizes biological systems that are overly rigid and unchanging, whereas greater than optimal variability characterizes systems that are noisy and unstable. Both situations characterize systems that are less adaptable to perturbations, such as those associated with abnormal motor development or unhealthy states. From our perspective, the goal of neurologic physical therapy should be to foster the development of this optimal amount of movement variability by incorporating a rich repertoire of movement strategies. The development of s...
Surgical Innovation, 2008
Frontiers in Psychology, 2015
The American journal of sports medicine
It is possible that gait abnormalities may play a role in the pathogenesis of meniscal or chondra... more It is possible that gait abnormalities may play a role in the pathogenesis of meniscal or chondral injury as well as osteoarthritis of the knee in patients with anterior cruciate ligament deficiency. The three-dimensional kinematics of anterior cruciate ligament-deficient knees are changed even during low-stress activities, such as walking, but can be restored by reconstruction. Case control study. Using a three-dimensional optoelectronic gait analysis system, we examined 13 patients with anterior cruciate ligament-deficient knees, 21 patients with anterior cruciate ligament-reconstructed knees, and 10 control subjects with uninjured knees during walking. Normal patterns of knee flexion-extension, abduction-adduction, and internal-external rotation during the gait cycle were maintained by all subjects. A significant difference in tibial rotation angle during the initial swing phase was found in anterior cruciate ligament-deficient knees compared with reconstructed and control knees....
Journal of Biomechanics, 2015
Journal of athletic training
The return-to-play decision after sport-related cerebral concussion depends in part on knowing wh... more The return-to-play decision after sport-related cerebral concussion depends in part on knowing when an athlete has fully recovered postural control after injury. To describe the postconcussion recovery of postural control using approximate entropy (ApEn), a regularity statistic from nonlinear dynamics. Retrospective case series analysis. Sports medicine research laboratory. Collegiate athletes from whom center-of-pressure and symptom data were collected at preseason, less than 48 hours after injury, and 48 to 96 hours after injury. Approximate entropy values reflecting the amount of randomness contained in center-of-pressure oscillations were calculated for anterior-posterior (AP) and medial-lateral (ML) time series. Equilibrium scores reflecting the amplitude of center-of-pressure AP oscillations were used to indicate postural stability. The number and severity of symptoms were described. Compared with the healthy preseason state, ApEn values for the AP and ML time series generally...
Scientific Reports, 2014
Humans exhibit an innate ability to synchronize their movements to music. The field of gait rehab... more Humans exhibit an innate ability to synchronize their movements to music. The field of gait rehabilitation has sought to capitalize on this phenomenon by invoking patients to walk in time to rhythmic auditory cues with a view to improving pathological gait. However, the temporal structure of the auditory cue, and hence the temporal structure of the target behavior has not been sufficiently explored. This study reveals the plasticity of auditory-motor coupling in human walking in relation to 'complex' auditory cues. The authors demonstrate that auditory-motor coupling can be driven by different coloured auditory noise signals (e.g. white, brown), shifting the fractal temporal structure of gait dynamics towards the statistical properties of the signals used. This adaptive capability observed in whole-body movement, could potentially be harnessed for targeted neuromuscular rehabilitation in patient groups, depending on the specific treatment goal.
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Papers by Nicholas Stergiou