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Jim R. Potvin - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Functional Knee Braces on Muscular Contributions to Joint Rotational Stiffness in Anterior Cruciate Ligament-Deficient and -Reconstructed Patients.
Journal of Applied Biomechanics, 2019Co-Authors: Aaron J. Derouin, Jim R. PotvinAbstract:Functional knee braces are frequently prescribed by physicians to ameliorate the function of individuals with anterior cruciate ligament (ACL) injuries. These braces have been shown in the literature to potentially enhance knee stability by augmenting muscle activation patterns and the timing of muscle response to perturbations. However, very few techniques are available in the literature to quantify how those modifications in lower-limb muscle activity influence stability of the knee. The aim of the present study was to quantify the effect of an off-the-shelf functional knee brace on muscle contributions to knee joint Rotational Stiffness in ACL-deficient and ACL-reconstructed patients. Kinematic, electromyography, and kinetic data were incorporated into an electromyography-driven model of the lower extremity to calculate individual and total muscle contributions to knee joint Rotational Stiffness about the flexion-extension axis, for 4 independent variables: leg condition (contralateral uninjured, unbraced ACL injured, and braced ACL injured); knee flexion (5°-10°, 20°-25°, and 30°-35°); squat stability condition (stable and unstable); and injury status (ACL deficient and ACL reconstructed). Participants had significantly higher (P < .05, η2 = .018) total knee joint Rotational Stiffness values while wearing the brace compared with the control leg. A 2-way interaction effect between stability and knee flexion (P < .05, η2 = .040) for total joint Rotational Stiffness was also found.
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Trunk muscle contributions of to L4-5 joint Rotational Stiffness following sudden trunk lateral bend perturbations
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, 2013Co-Authors: Joel A. Cort, James P. Dickey, Jim R. PotvinAbstract:The purpose of this research was to investigate the contributions of individual muscles to joint Rotational Stiffness and total joint Rotational Stiffness about the lumbar spine's L(4-5) joint prior to, and following, sudden dynamic lateral perturbations to the trunk. Kinematic and surface EMG data were collected while subjects maintained a kneeling posture on a robotic platform, while restrained so that motions caused by the perturbation were transferred to the pelvis, causing motion of the trunk and head. The robotic platform caused sudden inertial trunk lateral perturbations to the right or left, with or without timing and direction knowledge. An EMG-driven model of the lumbar spine was used to calculate the muscle forces and contributions to joint Rotational Stiffness during the perturbations. Data showed 95% and 106% increases in total joint Rotational Stiffness, about the lateral bend and axial twist axes, when subjects had knowledge of the timing of the perturbation. Also, the contralateral muscles exhibited a significantly larger total joint Rotational Stiffness about the lateral bend axis, and earlier surface EMG responses, than the ipsilateral muscles. The results indicate that, when the timing of the perturbation was unknown, subjects relied more on delayed muscle forces following the perturbation to stiffen the L(4-5) joint.
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Muscle Contributions to L4-5 Joint Rotational Stiffness following Sudden Trunk Flexion and Extension Perturbations.
Journal of medical engineering, 2013Co-Authors: Joel A. Cort, James P. Dickey, Jim R. PotvinAbstract:The purpose of this study was to investigate the contribution of individual muscles (MJRSm) to total joint Rotational Stiffness (MJRST) about the lumbar spine's L4-5 joint prior to, and following, sudden dynamic flexion or extension perturbations to the trunk. We collected kinematic and surface electromyography (sEMG) data while subjects maintained a kneeling posture on a parallel robotic platform, with their pelvis constrained by a harness. The parallel robotic platform caused sudden inertial trunk flexion or extension perturbations, with and without the subjects being aware of the timing and direction. Prevoluntary muscle forces incorporating both short and medium latency neuromuscular responses contributed significantly to joint Rotational Stiffness, following both sudden trunk flexion and extension motions. MJRST did not change with perturbation direction awareness. The lumbar erector spinae were always the greatest contributor to MJRST. This indicates that the neuromuscular feedback system significantly contributed to MJRST, and this behaviour likely enhances joint stability following sudden trunk flexion and extension perturbations.
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knee muscle contributions to joint Rotational Stiffness
Human Movement Science, 2012Co-Authors: Joshua G. A. Cashaback, Jim R. PotvinAbstract:The purpose of this paper was to investigate total joint Rotational Stiffness (JRS) and relative muscle contributions to JRS with varying extensor moment demands. It was hypothesized that greater co-activation of the flexors at lower levels of moment would result in greater JRS, relative to moment demands. It was also hypothesized that the flexors would have greater relative JRS contributions at lower moment levels. Twelve male participants generated isometric extensor moments about the knee at varying intensities, during plateau and ramping (up and down) conditions. Electromyography was used to estimate individual muscle forces, which were used to calculate JRS about three orthogonal axes. Orthogonal trend analysis revealed a linear relationship (p<.001) between moment and JRS, about all axes. The vastus lateralis provided the greatest JRS about all axes. Of the flexors, the semimembranosis provided the most JRS about the flexion/extension (FE) and axial (AX) axes. However, while most muscle activity increased linearly, the gastrocnemious lateral (GL) had an interaction between condition and moment. Despite an extensor moment, the GL had minor contributions about the FE axis (1.2%), and it was postulated that this increase in activation was to stabilize about the VV axis, where its contribution was as high as 18.9%.
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Knee muscle contributions to joint Rotational Stiffness.
Human movement science, 2011Co-Authors: Joshua G. A. Cashaback, Jim R. PotvinAbstract:The purpose of this paper was to investigate total joint Rotational Stiffness (JRS) and relative muscle contributions to JRS with varying extensor moment demands. It was hypothesized that greater co-activation of the flexors at lower levels of moment would result in greater JRS, relative to moment demands. It was also hypothesized that the flexors would have greater relative JRS contributions at lower moment levels. Twelve male participants generated isometric extensor moments about the knee at varying intensities, during plateau and ramping (up and down) conditions. Electromyography was used to estimate individual muscle forces, which were used to calculate JRS about three orthogonal axes. Orthogonal trend analysis revealed a linear relationship (p
Stephen H M Brown - One of the best experts on this subject based on the ideXlab platform.
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the effects of experimentally induced low back pain on spine Rotational Stiffness and local dynamic stability
Annals of Biomedical Engineering, 2015Co-Authors: Ryan B Graham, Stephen H M Brown, Gwyneth B Ross, Matthew P MavorAbstract:Local dynamic stability, quantified using the maximum finite-time Lyapunov exponent (λ max), and the muscular contributions to spine Rotational Stiffness can provide pertinent information regarding the neuromuscular control of the spine during movement tasks. The primary goal of the present study was to assess if experimental capsaicin-induced low back pain (LBP) affects spine stability and the neuromuscular control of repetitive trunk movements in a group of healthy participants with no history of LBP. Fourteen healthy males were recruited for this investigation. Each participant was asked to complete three trials (baseline, in pain, and recovery) of 35 cycles of a repetitive trunk flexion/extension task at a rate of 0.25 Hz. Local dynamic stability and the muscular contributions to lumbar spine Rotational Stiffness were significantly impaired during the LBP trial compared to the baseline trial (p < 0.05); however, there was a trend for these measures to recover after a 1 h rest. This study provides evidence that capsaicin can effectively induce LBP, thereby altering spine Rotational Stiffness and local dynamic stability. Future research should directly compare the effects capsaicin-induced LBP and intramuscular/intraligamentous induced LBP on these same variables.
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The Effects of Experimentally Induced Low Back Pain on Spine Rotational Stiffness and Local Dynamic Stability
Annals of biomedical engineering, 2015Co-Authors: Gwyneth B Ross, Stephen H M Brown, Matthew P Mavor, Ryan B GrahamAbstract:Local dynamic stability, quantified using the maximum finite-time Lyapunov exponent (λ max), and the muscular contributions to spine Rotational Stiffness can provide pertinent information regarding the neuromuscular control of the spine during movement tasks. The primary goal of the present study was to assess if experimental capsaicin-induced low back pain (LBP) affects spine stability and the neuromuscular control of repetitive trunk movements in a group of healthy participants with no history of LBP. Fourteen healthy males were recruited for this investigation. Each participant was asked to complete three trials (baseline, in pain, and recovery) of 35 cycles of a repetitive trunk flexion/extension task at a rate of 0.25 Hz. Local dynamic stability and the muscular contributions to lumbar spine Rotational Stiffness were significantly impaired during the LBP trial compared to the baseline trial (p
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The effect of unstable loading versus unstable support conditions on spine Rotational Stiffness and spine stability during repetitive lifting
Journal of biomechanics, 2013Co-Authors: Shawn M. Beaudette, Ryan B Graham, Stephen H M BrownAbstract:Lumbar spine stability has been extensively researched due to its necessity to facilitate load-bearing human movements and prevent structural injury. The nature of certain human movement tasks are such that they are not equivalent in levels of task-stability (i.e. the stability of the external environment). The goal of the current study was to compare the effects of dynamic lift instability, administered through both the load and base of support, on the dynamic stability (maximal Lyapunov exponents) and Stiffness (EMG-driven model) of the lumbar spine during repeated sagittal lifts. Fifteen healthy males performed 23 repetitive lifts with varying conditions of instability at the loading and support interfaces. An increase in spine Rotational Stiffness occurred during unstable support scenarios resulting in an observed increase in mean and maximum Euclidean norm spine Rotational Stiffness (p=0.0011). Significant stiffening effects were observed in unstable support conditions about all lumbar spine axes with the exception of lateral bend. Relative to a stable control lifting trial, the addition of both an unstable load as well as an unstable support did not result in a significant change in the local dynamic stability of the lumbar spine (p=0.5592). The results suggest that local dynamic stability of the lumbar spine represents a conserved measure actively controlled, at least in part, by trunk muscle stiffening effects. It is evident therefore that local dynamic stability of the lumbar spine can be modulated effectively within a young-healthy population; however this may not be the case in a patient population.
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a direct comparison of spine Rotational Stiffness and dynamic spine stability during repetitive lifting tasks
Journal of Biomechanics, 2012Co-Authors: Ryan B Graham, Stephen H M BrownAbstract:Stability of the spinal column is critical to bear loads, allow movement, and at the same time avoid injury and pain. However, there has been a debate in recent years as to how best to define and quantify spine stability, with the outcome being that different methods are used without a clear understanding of how they relate to one another. Therefore, the goal of the present study was to directly compare lumbar spine Rotational Stiffness, calculated with an EMG-driven biomechanical model, to local dynamic spine stability calculated using Lyapunov analyses of kinematic data, during a series of continuous dynamic lifting challenges. Twelve healthy male subjects performed 30 repetitive lifts under three varying load and three varying rate conditions. With an increase in the load lifted (constant rate) there was a significant increase in mean, maximum, and minimum spine Rotational Stiffness (po 0.001) and a significant increase in local dynamic stability (po 0.05); both stability measures were moderately to strongly related to one another (r ¼� 0.55 to � 0.71). With an increase in lifting rate (constant load), there was also a significant increase in mean and maximum spine Rotational Stiffness (po 0.01); however, there was a non-significant decrease in the minimum Rotational Stiffness and a non-significant decrease in local dynamic stability (p40.05). Weak linear relationships were found for the varying rate conditions (r ¼� 0.02 to � 0.27). The results suggest that spine Rotational Stiffness and local dynamic stability are closely related to one another, as they provided similar information when movement rate was controlled. However, based on the results from the changing lifting rate conditions, it is evident that both models provide unique information and that future research is required to completely understand the relationship between the two models. Using both techniques concurrently may provide the best information regarding the true effects of (in) stability under different loading and movement scenarios, and in comparing healthy and clinical populations.
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A direct comparison of spine Rotational Stiffness and dynamic spine stability during repetitive lifting tasks.
Journal of biomechanics, 2012Co-Authors: Ryan B Graham, Stephen H M BrownAbstract:Stability of the spinal column is critical to bear loads, allow movement, and at the same time avoid injury and pain. However, there has been a debate in recent years as to how best to define and quantify spine stability, with the outcome being that different methods are used without a clear understanding of how they relate to one another. Therefore, the goal of the present study was to directly compare lumbar spine Rotational Stiffness, calculated with an EMG-driven biomechanical model, to local dynamic spine stability calculated using Lyapunov analyses of kinematic data, during a series of continuous dynamic lifting challenges. Twelve healthy male subjects performed 30 repetitive lifts under three varying load and three varying rate conditions. With an increase in the load lifted (constant rate) there was a significant increase in mean, maximum, and minimum spine Rotational Stiffness (p
Roger C. Haut - One of the best experts on this subject based on the ideXlab platform.
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The effect of Rotational Stiffness on ankle tibiocalcaneal motion and ligament strain during external rotation
Proceedings of the Institution of Mechanical Engineers Part P: Journal of Sports Engineering and Technology, 2016Co-Authors: Keith D. Button, Jerrod E. Braman, Feng Wei, Paige Thornton, Roger C. HautAbstract:The Rotational Stiffness of footwear has been previously shown to have an effect on ankle kinematics and injury risk, but this relationship has not yet been modeled. The aim of this study was to derive equations from experimental data that were able to predict ankle kinematics under various torsional Stiffness constraints and use these equations to estimate ligament strains. Three athletic tapes were tested for their ability to constrain the ankle during external rotation. Six subjects then performed a voluntary external foot rotation using the selected tape designs to constrain the ankle, as well as with no constraints. The motion of the calcaneus with respect to the tibia (tibiocalcaneal motion) from 0° to 15° of tibia rotation and predictive equations were determined to establish tibiocalcaneal rotation, eversion, and flexion as a function of gross tibia motion and tape Stiffness. These predictive equations were then used to drive a computational model in which ankle ligament strains were determined at 15° of tibia rotation and for ankle constraint Stiffness ranging from 0 to 30 N m/deg. The three tapes provided significantly different constraint Stiffnesses during external foot rotation. There was no statistical effect of ankle constraint on the dorsiflexion response of the ankle (p = 0.461). In contrast, there was an effect of constraint Stiffness on tibiocalcaneal external rotation (p < 0.001) and tibiocalcaneal eversion (p < 0.001). Results of the model simulation revealed the highest ligament strains in the anterior tibiotalar ligament and anterior tibiofibular ligament. Anterior tibiotalar ligament strain increased with increasing constraint Stiffness, while there was little effect of constraint Stiffness on anterior tibiofibular ligament strain. Results from this study could aid in the design of footwear, as well as the analysis of clinical injuries.
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the effect of Rotational Stiffness on ankle tibiocalcaneal motion and ligament strain during external rotation
Proceedings of the Institution of Mechanical Engineers Part P: Journal of Sports Engineering and Technology, 2016Co-Authors: Keith D. Button, Jerrod E. Braman, Feng Wei, Roger C. Haut, Paige ThorntonAbstract:The Rotational Stiffness of footwear has been previously shown to have an effect on ankle kinematics and injury risk, but this relationship has not yet been modeled. The aim of this study was to de...
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Rotational Stiffness of American football shoes affects ankle biomechanics and injury severity.
Journal of biomechanical engineering, 2015Co-Authors: Keith D. Button, Jerrod E. Braman, Mark A. Davison, Feng Wei, Maureen C. Schaeffer, Roger C. HautAbstract:While previous studies have investigated the effect of shoe-surface interaction on injury risk, few studies have examined the effect of Rotational Stiffness of the shoe. The hypothesis of the current study was that ankles externally rotated to failure in shoes with low Rotational Stiffness would allow more talus eversion than those in shoes with a higher Rotational Stiffness, resulting in less severe injury. Twelve (six pairs) cadaver lower extremities were externally rotated to gross failure while positioned in 20 deg of pre-eversion and 20 deg of predorsiflexion by fixing the distal end of the foot, axially loading the proximal tibia, and internally rotating the tibia. One ankle in each pair was constrained by an American football shoe with a stiff upper, while the other was constrained by an American football shoe with a flexible upper. Experimental bone motions were input into specimen-specific computational models to examine levels of ligament elongation to help understand mechanisms of ankle joint failure. Ankles in flexible shoes allowed 6.7±2.4 deg of talus eversion during rotation, significantly greater than the 1.7±1.0 deg for ankles in stiff shoes (p = 0.01). The significantly greater eversion in flexible shoes was potentially due to a more natural response of the ankle during rotation, possibly affecting the injuries that were produced. All ankles failed by either medial ankle injury or syndesmotic injury, or a combination of both. Complex (more than one ligament or bone) injuries were noted in 4 of 6 ankles in stiff shoes and 1 of 6 ankles in flexible shoes. Ligament elongations from the computational model validated the experimental injury data. The current study suggested flexibility (or Rotational Stiffness) of the shoe may play an important role in both the severity of ankle injuries for athletes.
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Rotational Stiffness of football shoes influences talus motion during external rotation of the foot.
Journal of biomechanical engineering, 2012Co-Authors: Feng Wei, Jerrod E. Braman, Eric G. Meyer, John W. Powell, Roger C. HautAbstract:Shoe-surface interface characteristics have been implicated in the high incidence of ankle injuries suffered by athletes. Yet, the differences in Rotational Stiffness among shoes may also influence injury risk. It was hypothesized that shoes with different Rotational Stiffness will generate different patterns of ankle ligament strain. Four football shoe designs were tested and compared in terms of Rotational Stiffness. Twelve (six pairs) male cadaveric lower extremity limbs were externally rotated 30 deg using two selected football shoe designs, i.e., a flexible shoe and a rigid shoe. Motion capture was performed to track the movement of the talus with a reflective marker array screwed into the bone. A computational ankle model was utilized to input talus motions for the estimation of ankle ligament strains. At 30 deg of rotation, the rigid shoe generated higher ankle joint torque at 46.2 ± 9.3 Nm than the flexible shoe at 35.4 ± 5.7 Nm. While talus rotation was greater in the rigid shoe (15.9 ± 1.6 deg versus 12.1 ± 1.0 deg), the flexible shoe generated more talus eversion (5.6 ± 1.5 deg versus 1.2± 0.8 deg). While these talus motions resulted in the same level of anterior deltoid ligament strain (approxiamtely 5%) between shoes, there was a significant increase of anterior tibiofibular ligament strain (4.5± 0.4% versus 2.3 ± 0.3%) for the flexible versus more rigid shoe design. The flexible shoe may provide less restraint to the subtalar and transverse tarsal joints, resulting in more eversion but less axial rotation of the talus during foot∕shoe rotation. The increase of strain in the anterior tibiofibular ligament may have been largely due to the increased level of talus eversion documented for the flexible shoe. There may be a direct correlation of ankle joint torque with axial talus rotation, and an inverse relationship between torque and talus eversion. The study may provide some insight into relationships between shoe design and ankle ligament strain patterns. In future studies, these data may be useful in characterizing shoe design parameters and balancing potential ankle injury risks with player performance.
Ryan B Graham - One of the best experts on this subject based on the ideXlab platform.
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the effects of experimentally induced low back pain on spine Rotational Stiffness and local dynamic stability
Annals of Biomedical Engineering, 2015Co-Authors: Ryan B Graham, Stephen H M Brown, Gwyneth B Ross, Matthew P MavorAbstract:Local dynamic stability, quantified using the maximum finite-time Lyapunov exponent (λ max), and the muscular contributions to spine Rotational Stiffness can provide pertinent information regarding the neuromuscular control of the spine during movement tasks. The primary goal of the present study was to assess if experimental capsaicin-induced low back pain (LBP) affects spine stability and the neuromuscular control of repetitive trunk movements in a group of healthy participants with no history of LBP. Fourteen healthy males were recruited for this investigation. Each participant was asked to complete three trials (baseline, in pain, and recovery) of 35 cycles of a repetitive trunk flexion/extension task at a rate of 0.25 Hz. Local dynamic stability and the muscular contributions to lumbar spine Rotational Stiffness were significantly impaired during the LBP trial compared to the baseline trial (p < 0.05); however, there was a trend for these measures to recover after a 1 h rest. This study provides evidence that capsaicin can effectively induce LBP, thereby altering spine Rotational Stiffness and local dynamic stability. Future research should directly compare the effects capsaicin-induced LBP and intramuscular/intraligamentous induced LBP on these same variables.
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The Effects of Experimentally Induced Low Back Pain on Spine Rotational Stiffness and Local Dynamic Stability
Annals of biomedical engineering, 2015Co-Authors: Gwyneth B Ross, Stephen H M Brown, Matthew P Mavor, Ryan B GrahamAbstract:Local dynamic stability, quantified using the maximum finite-time Lyapunov exponent (λ max), and the muscular contributions to spine Rotational Stiffness can provide pertinent information regarding the neuromuscular control of the spine during movement tasks. The primary goal of the present study was to assess if experimental capsaicin-induced low back pain (LBP) affects spine stability and the neuromuscular control of repetitive trunk movements in a group of healthy participants with no history of LBP. Fourteen healthy males were recruited for this investigation. Each participant was asked to complete three trials (baseline, in pain, and recovery) of 35 cycles of a repetitive trunk flexion/extension task at a rate of 0.25 Hz. Local dynamic stability and the muscular contributions to lumbar spine Rotational Stiffness were significantly impaired during the LBP trial compared to the baseline trial (p
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The effect of unstable loading versus unstable support conditions on spine Rotational Stiffness and spine stability during repetitive lifting
Journal of biomechanics, 2013Co-Authors: Shawn M. Beaudette, Ryan B Graham, Stephen H M BrownAbstract:Lumbar spine stability has been extensively researched due to its necessity to facilitate load-bearing human movements and prevent structural injury. The nature of certain human movement tasks are such that they are not equivalent in levels of task-stability (i.e. the stability of the external environment). The goal of the current study was to compare the effects of dynamic lift instability, administered through both the load and base of support, on the dynamic stability (maximal Lyapunov exponents) and Stiffness (EMG-driven model) of the lumbar spine during repeated sagittal lifts. Fifteen healthy males performed 23 repetitive lifts with varying conditions of instability at the loading and support interfaces. An increase in spine Rotational Stiffness occurred during unstable support scenarios resulting in an observed increase in mean and maximum Euclidean norm spine Rotational Stiffness (p=0.0011). Significant stiffening effects were observed in unstable support conditions about all lumbar spine axes with the exception of lateral bend. Relative to a stable control lifting trial, the addition of both an unstable load as well as an unstable support did not result in a significant change in the local dynamic stability of the lumbar spine (p=0.5592). The results suggest that local dynamic stability of the lumbar spine represents a conserved measure actively controlled, at least in part, by trunk muscle stiffening effects. It is evident therefore that local dynamic stability of the lumbar spine can be modulated effectively within a young-healthy population; however this may not be the case in a patient population.
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a direct comparison of spine Rotational Stiffness and dynamic spine stability during repetitive lifting tasks
Journal of Biomechanics, 2012Co-Authors: Ryan B Graham, Stephen H M BrownAbstract:Stability of the spinal column is critical to bear loads, allow movement, and at the same time avoid injury and pain. However, there has been a debate in recent years as to how best to define and quantify spine stability, with the outcome being that different methods are used without a clear understanding of how they relate to one another. Therefore, the goal of the present study was to directly compare lumbar spine Rotational Stiffness, calculated with an EMG-driven biomechanical model, to local dynamic spine stability calculated using Lyapunov analyses of kinematic data, during a series of continuous dynamic lifting challenges. Twelve healthy male subjects performed 30 repetitive lifts under three varying load and three varying rate conditions. With an increase in the load lifted (constant rate) there was a significant increase in mean, maximum, and minimum spine Rotational Stiffness (po 0.001) and a significant increase in local dynamic stability (po 0.05); both stability measures were moderately to strongly related to one another (r ¼� 0.55 to � 0.71). With an increase in lifting rate (constant load), there was also a significant increase in mean and maximum spine Rotational Stiffness (po 0.01); however, there was a non-significant decrease in the minimum Rotational Stiffness and a non-significant decrease in local dynamic stability (p40.05). Weak linear relationships were found for the varying rate conditions (r ¼� 0.02 to � 0.27). The results suggest that spine Rotational Stiffness and local dynamic stability are closely related to one another, as they provided similar information when movement rate was controlled. However, based on the results from the changing lifting rate conditions, it is evident that both models provide unique information and that future research is required to completely understand the relationship between the two models. Using both techniques concurrently may provide the best information regarding the true effects of (in) stability under different loading and movement scenarios, and in comparing healthy and clinical populations.
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A direct comparison of spine Rotational Stiffness and dynamic spine stability during repetitive lifting tasks.
Journal of biomechanics, 2012Co-Authors: Ryan B Graham, Stephen H M BrownAbstract:Stability of the spinal column is critical to bear loads, allow movement, and at the same time avoid injury and pain. However, there has been a debate in recent years as to how best to define and quantify spine stability, with the outcome being that different methods are used without a clear understanding of how they relate to one another. Therefore, the goal of the present study was to directly compare lumbar spine Rotational Stiffness, calculated with an EMG-driven biomechanical model, to local dynamic spine stability calculated using Lyapunov analyses of kinematic data, during a series of continuous dynamic lifting challenges. Twelve healthy male subjects performed 30 repetitive lifts under three varying load and three varying rate conditions. With an increase in the load lifted (constant rate) there was a significant increase in mean, maximum, and minimum spine Rotational Stiffness (p
Guojie Zhou - One of the best experts on this subject based on the ideXlab platform.
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analytical model for initial Rotational Stiffness of steel beam to concrete filled steel tube column connections with bidirectional bolts
Journal of Structural Engineering-asce, 2018Co-Authors: Guojie ZhouAbstract:AbstractThe initial Rotational Stiffness of connections is important for the design of semirigid frames. However, most current studies on steel beam to concrete-filled steel tube column connections...
