Felix Huang - Academia.edu (original) (raw)

Papers by Felix Huang

Research paper thumbnail of Perception of Stiffness in Laparoscopy - the Fulcrum Effect

We explored how the perception of stiffness can be distorted in Minimally Invasive Surgery. We co... more We explored how the perception of stiffness can be distorted in Minimally Invasive Surgery. We combined a mechanical simulator with a haptic device, and implemented linear springs at the tip of the simulated laparoscopic device. To explore the influence of mechanical advantage on perception, we set different values of the ratio between internal and external length of the tool. We found that a nonsymmetrical ratio causes bias in the perceived stiffness when novice tangential probing is compared to radial probing. In contrast, haptic experts did not show similar perceptual bias.

Research paper thumbnail of Key components of mechanical work predict outcomes in robotic stroke therapy

Journal of NeuroEngineering and Rehabilitation, 2020

Research paper thumbnail of Sensors and Psychomotor Metrics: A Unique Opportunity to Close the Gap on Surgical Processes and Outcomes

ACS Biomaterials Science & Engineering, 2020

The surgical process remains elusive to many. This paper presents two independent empirical inves... more The surgical process remains elusive to many. This paper presents two independent empirical investigations where psychomotor skill metrics were used to quantify elements of the surgical process in a procedural context during surgical tasks in a simulated environment. The overarching goal of both investigations was to address the following hypothesis: Basic motion metrics can be used to quantify specific aspects of the surgical process including instrument autonomy, psychomotor efficiency, procedural readiness, and clinical errors. Electromagnetic motion tracking sensors were secured to surgical trainees' (N = 64) hands for both studies, and several motion metrics were investigated as a measure of surgical skill. The first study assessed performance during a bowel repair and laparoscopic ventral hernia (LVH) repair in comparison to a suturing board task. The second study assessed performance in a VR task in comparison to placement of a subclavian central line. The findings of the first study support our subhypothesis that motion metrics have a generalizable application to surgical skill by showing significant correlations in instrument autonomy and psychomotor efficiency during the suturing task and bowel repair (idle time: r = 0.46, p < 0.05; average velocity: r = 0.57, p < 0.05) and the suturing task and LVH repair (jerk magnitude: r = 0.36, p < 0.05; bimanual dexterity: r = 0.35, p < 0.05). In the second study, performance in VR (steering and jerkiness) correlated to clinical errors (r = 0.58, p < 0.05) and insertion time (r = 0.55, p < 0.05) in placement of a subclavian central line. Both gross (dexterity) and fine motor skills (steering) were found to be important as well as efficiency (i.e., idle time, duration, velocity) when seeking to understand the quality of surgical performance. Both studies support our hypotheses that basic motion metrics can be used to quantify specific aspects of the surgical process and that the use of different technologies and metrics are important for comprehensive investigations of surgical skill.

Research paper thumbnail of Robot training with vector fields based on stroke survivors' individual movement statistics

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, Feb 16, 2017

The wide variation in upper extremity motor impairments among stroke survivors necessitates more ... more The wide variation in upper extremity motor impairments among stroke survivors necessitates more intelligent methods of customized therapy. However, current strategies for characterizing individual motor impairments are limited by the use of traditional clinical assessments (e.g. Fugl-Meyer) and simple engineering metrics (e.g. goal-directed performance). Our overall approach is to statistically identify the range of volitional movement capabilities, and then apply a robot-applied force vector field intervention that encourages under-expressed movements. We investigated whether explorative training with such customized force fields would improve stroke survivors' (n = 11) movement patterns in comparison to a control group that trained without forces (n = 11). Force and Control groups increased Fugl-Meyer UE scores (average of 1.0 and 1.1, respectively), which is not considered clinically meaningful. Interestingly, participants from both groups demonstrated dramatic increases in ...

Research paper thumbnail of Movement distributions of stroke survivors exhibit distinct patterns that evolve with training

Journal of NeuroEngineering and Rehabilitation, 2016

Research paper thumbnail of Distributions in the error space: goal-directed movements described in time and state-space representations

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2014

Manipulation of error feedback has been of great interest to recent studies in motor control and ... more Manipulation of error feedback has been of great interest to recent studies in motor control and rehabilitation. Typically, motor adaptation is shown as a change in performance with a single scalar metric for each trial, yet such an approach might overlook details about how error evolves through the movement. We believe that statistical distributions of movement error through the extent of the trajectory can reveal unique patterns of adaption and possibly reveal clues to how the motor system processes information about error. This paper describes different possible ordinate domains, focusing on representations in time and state-space, used to quantify reaching errors. We hypothesized that the domain with the lowest amount of variability would lead to a predictive model of reaching error with the highest accuracy. Here we showed that errors represented in a time domain demonstrate the least variance and allow for the highest predictive model of reaching errors. These predictive model...

Research paper thumbnail of Data sample size needed for prediction of movement distributions

2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2014

Human movement ability should be described not only by its typical behavior, but also by the wide... more Human movement ability should be described not only by its typical behavior, but also by the wide variation in capabilities. This would mean that subjects that are encouraged to move throughout their workspace but otherwise free to move any way they like might reveal their unique movement tendencies. In this study, we investigate how much information (data) is needed to reliably construct a movement distribution that predicts an individual&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s movement tendencies. We analyzed the distributions of position, velocity and acceleration data derived during self-directed motor exploration by stroke survivors (n=10 from a previous study) and healthy individuals (n=5). We examined whether these simple kinematic variables differed in terms of the amount of data required. We found a trend of decreasing time needed for characterization with the order of kinematic variable, for position, velocity, and acceleration, respectively. In addition, we investigated whether data requirements differ between stroke survivors and healthy. Our results suggest that healthy individuals may require more data samples (time for characterization), though the trend was only significant for position data. Our results provide an important step towards using statistical distributions to describe movement tendencies. Our findings could serve as more comprehensive tools to track recovery in or design more focused training intervention in neurorehabiliation applications.

Research paper thumbnail of Individual patterns of motor deficits evident in movement distribution analysis

2013 IEEE 13th International Conference on Rehabilitation Robotics (ICORR), 2013

Research paper thumbnail of Error Augmentation and the Role of Sensory Feedback

Neurorehabilitation Technology, 2011

Research paper thumbnail of Visual and haptic feedback enable on-line tuning to resonant dynamics

Research paper thumbnail of Human adaptation to dynamic interaction forces during learning of a visuo-motor task

Research paper thumbnail of Learning Kinematic Constraints in Laparoscopic Surgery

IEEE Transactions on Haptics, 2012

Research paper thumbnail of Evidence of multiple coordinate representations during generalization of motor learning

Experimental Brain Research, 2014

Research paper thumbnail of Manual Skill Generalization Enhanced by Negative Viscosity

Journal of Neurophysiology, 2010

Recent human-machine interaction studies have suggested that movement augmented with negative vis... more Recent human-machine interaction studies have suggested that movement augmented with negative viscosity can enhance performance and can even promote better motor learning. To test this, we investigated how negative viscosity influences motor adaptation to an environment where forces acted only in one axis of motion. Using a force-feedback device, subjects performed free exploratory movements with a purely inertia generating forces proportional to hand acceleration, negative viscosity generating destabilizing forces proportional to hand velocity, or a combination of the acceleration and velocity fields. After training, we evaluated each subject's ability to perform circular movements in only the inertial field. Combined training resulted in lowest error and revealed similar responses as inertia training in catch trials. These findings are remarkable because negative viscosity, available only during training, evidently enhanced learning when combined with inertia. This success in ...

Research paper thumbnail of Augmented Dynamics and Motor Exploration as Training for Stroke

IEEE Transactions on Biomedical Engineering, 2013

With chronic stroke survivors (n = 30), we investigated how upper extremity training with negativ... more With chronic stroke survivors (n = 30), we investigated how upper extremity training with negative viscosity affects coordination under unperturbed conditions. Subjects trained with a planar robotic interface simulating 1) negative viscosity augmented to elbow and shoulder joints; 2) negative viscosity combined with inertia; or 3) a null-field condition. Two treatment groups practiced with both force conditions (cross-over design), while a control group practiced with a null-field condition. Training (exploratory movement) and evaluations (prescribed circular movement) alternated in several phases to facilitate transfer from forces to the null field. Negative viscosity expanded exploration especially in the sagittal axis, and resulted in significant within-day improvements. Both treatment groups exhibited next day retention unobserved in the control. Our results suggest enhanced learning from forces that induce a broader range of kinematics. This study supports the use of robot-assisted training that encourages active patient involvement by preserving efferent commands for driving movement.

Research paper thumbnail of Learning kinematic mappings in laparoscopic surgery

Research paper thumbnail of Visual error augmentation enhances learning in three dimensions

Research paper thumbnail of Evaluation of negative viscosity as upper extremity training for stroke survivors

With stroke survivors (n=30) as the test population, we investigated how upper extremity training... more With stroke survivors (n=30) as the test population, we investigated how upper extremity training with negative viscosity affects coordination in unassisted conditions. Using a planar force-feedback device, subjects performed exploratory movements within an environment that simulated 1) negative viscosity added to elbow and shoulder joints 2) augmented inertia to the upper and lower arm combined with negative viscosity, or 3) a null force field (control). After training, we evaluated each subject&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s ability to perform circular movements in the null field. Negative viscosity training resulted in greater within-day reductions in error compared with the combined field training. Negative viscosity promoted greater distributions of accelerations during free exploration, especially in the sagittal axis, while combined field training diminished overall activity. Both force field training groups exhibited next day retention, while this was not observed for the control group. The improvement in performance suggests that greater range of kinematic experiences contribute to learning, even despite novel force field environments. These findings provide support for the use of movement amplifying environments for upper extremity rehabilitation, allowing greater access to training while maintaining user engagement.

Research paper thumbnail of Interactive priming enhanced by negative damping aids learning of an object manipulation task

We investigated how free interaction with an object influences the formation of motor planning. S... more We investigated how free interaction with an object influences the formation of motor planning. Subjects controlled a force-feedback planar manipulandum that presented simulated anisotropic inertial forces. As a performance evaluation, subjects made circular movements about a prescribed track. In order to investigate potential enhancement of motor planning, we introduced negative damping during an ldquointeractive primingrdquo phase prior to task performance. As a control, we presented a second subject group with normal interactive priming. Our results showed significantly greater reduction in maximum curvature error for the subject group that received enhanced priming (two-tailed T-test, p=1.86e-6) compared to the control group. Group-I demonstrated a 34.8% reduction in error while Group-II achieved 5.78% reduction. We also observed that the presentation of enhanced priming evidently caused a greater sensitivity to catch trials compared to the control. Group-I demonstrated a larger increase (92.0%) in maximum curvature error in catch- trials (with respect to baseline), compared to Group-II (50.8%) during early training (two-tailed T-test, p=1.9e-3). These results suggest that some forms of augmentation to task dynamics - leading to the exploration of a broader state space -can help the accelerate the learning of control strategies suitable for an unassisted environment. The finding is also consistent with the hypothesis that subjects can decompose the environment impedance into acceleration and velocity dependent elements.

Research paper thumbnail of Negative viscosity can enhance learning of inertial dynamics

We investigated how learning of inertial load manipulation is influenced by movement amplificatio... more We investigated how learning of inertial load manipulation is influenced by movement amplification with negative viscosity. Using a force-feedback device, subjects trained on anisotropic loads (5 orientations) with free movements in one of three conditions (inertia only, negative viscosity only, or combined), prior to common evaluation conditions (prescribed circular pattern with inertia only). Training with combined-load resulted in lower error (6.89 plusmn 3.25%) compared to inertia-only (8.40 plusmn 4.32%) and viscosity-only (8.17 plusmn 4.13%) according to radial deviation analysis (% of trial mean radius). Combined-Load and inertia-only groups exhibited similar unexpected no-load trials (8.38 plusmn 4.31% versus 8.91 plusmn 4.70% of trial mean radius), which suggests comparable low-impedance strategies. These findings are remarkable since negative viscosity, only available during training, evidently enhanced learning when combined with inertia. Modeling analysis suggests that a feedforward after-effect of negative viscosity cannot predict such performance gains. Instead, results from combined-load training are consistent with greater feedforward inertia compensation along with a small increase in impedance control. The capability of the nervous system to generalize learning from negative viscosity suggests an intriguing new method for enhancing sensorimotor adaptation.

Research paper thumbnail of Perception of Stiffness in Laparoscopy - the Fulcrum Effect

We explored how the perception of stiffness can be distorted in Minimally Invasive Surgery. We co... more We explored how the perception of stiffness can be distorted in Minimally Invasive Surgery. We combined a mechanical simulator with a haptic device, and implemented linear springs at the tip of the simulated laparoscopic device. To explore the influence of mechanical advantage on perception, we set different values of the ratio between internal and external length of the tool. We found that a nonsymmetrical ratio causes bias in the perceived stiffness when novice tangential probing is compared to radial probing. In contrast, haptic experts did not show similar perceptual bias.

Research paper thumbnail of Key components of mechanical work predict outcomes in robotic stroke therapy

Journal of NeuroEngineering and Rehabilitation, 2020

Research paper thumbnail of Sensors and Psychomotor Metrics: A Unique Opportunity to Close the Gap on Surgical Processes and Outcomes

ACS Biomaterials Science & Engineering, 2020

The surgical process remains elusive to many. This paper presents two independent empirical inves... more The surgical process remains elusive to many. This paper presents two independent empirical investigations where psychomotor skill metrics were used to quantify elements of the surgical process in a procedural context during surgical tasks in a simulated environment. The overarching goal of both investigations was to address the following hypothesis: Basic motion metrics can be used to quantify specific aspects of the surgical process including instrument autonomy, psychomotor efficiency, procedural readiness, and clinical errors. Electromagnetic motion tracking sensors were secured to surgical trainees' (N = 64) hands for both studies, and several motion metrics were investigated as a measure of surgical skill. The first study assessed performance during a bowel repair and laparoscopic ventral hernia (LVH) repair in comparison to a suturing board task. The second study assessed performance in a VR task in comparison to placement of a subclavian central line. The findings of the first study support our subhypothesis that motion metrics have a generalizable application to surgical skill by showing significant correlations in instrument autonomy and psychomotor efficiency during the suturing task and bowel repair (idle time: r = 0.46, p < 0.05; average velocity: r = 0.57, p < 0.05) and the suturing task and LVH repair (jerk magnitude: r = 0.36, p < 0.05; bimanual dexterity: r = 0.35, p < 0.05). In the second study, performance in VR (steering and jerkiness) correlated to clinical errors (r = 0.58, p < 0.05) and insertion time (r = 0.55, p < 0.05) in placement of a subclavian central line. Both gross (dexterity) and fine motor skills (steering) were found to be important as well as efficiency (i.e., idle time, duration, velocity) when seeking to understand the quality of surgical performance. Both studies support our hypotheses that basic motion metrics can be used to quantify specific aspects of the surgical process and that the use of different technologies and metrics are important for comprehensive investigations of surgical skill.

Research paper thumbnail of Robot training with vector fields based on stroke survivors' individual movement statistics

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, Feb 16, 2017

The wide variation in upper extremity motor impairments among stroke survivors necessitates more ... more The wide variation in upper extremity motor impairments among stroke survivors necessitates more intelligent methods of customized therapy. However, current strategies for characterizing individual motor impairments are limited by the use of traditional clinical assessments (e.g. Fugl-Meyer) and simple engineering metrics (e.g. goal-directed performance). Our overall approach is to statistically identify the range of volitional movement capabilities, and then apply a robot-applied force vector field intervention that encourages under-expressed movements. We investigated whether explorative training with such customized force fields would improve stroke survivors' (n = 11) movement patterns in comparison to a control group that trained without forces (n = 11). Force and Control groups increased Fugl-Meyer UE scores (average of 1.0 and 1.1, respectively), which is not considered clinically meaningful. Interestingly, participants from both groups demonstrated dramatic increases in ...

Research paper thumbnail of Movement distributions of stroke survivors exhibit distinct patterns that evolve with training

Journal of NeuroEngineering and Rehabilitation, 2016

Research paper thumbnail of Distributions in the error space: goal-directed movements described in time and state-space representations

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2014

Manipulation of error feedback has been of great interest to recent studies in motor control and ... more Manipulation of error feedback has been of great interest to recent studies in motor control and rehabilitation. Typically, motor adaptation is shown as a change in performance with a single scalar metric for each trial, yet such an approach might overlook details about how error evolves through the movement. We believe that statistical distributions of movement error through the extent of the trajectory can reveal unique patterns of adaption and possibly reveal clues to how the motor system processes information about error. This paper describes different possible ordinate domains, focusing on representations in time and state-space, used to quantify reaching errors. We hypothesized that the domain with the lowest amount of variability would lead to a predictive model of reaching error with the highest accuracy. Here we showed that errors represented in a time domain demonstrate the least variance and allow for the highest predictive model of reaching errors. These predictive model...

Research paper thumbnail of Data sample size needed for prediction of movement distributions

2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2014

Human movement ability should be described not only by its typical behavior, but also by the wide... more Human movement ability should be described not only by its typical behavior, but also by the wide variation in capabilities. This would mean that subjects that are encouraged to move throughout their workspace but otherwise free to move any way they like might reveal their unique movement tendencies. In this study, we investigate how much information (data) is needed to reliably construct a movement distribution that predicts an individual&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s movement tendencies. We analyzed the distributions of position, velocity and acceleration data derived during self-directed motor exploration by stroke survivors (n=10 from a previous study) and healthy individuals (n=5). We examined whether these simple kinematic variables differed in terms of the amount of data required. We found a trend of decreasing time needed for characterization with the order of kinematic variable, for position, velocity, and acceleration, respectively. In addition, we investigated whether data requirements differ between stroke survivors and healthy. Our results suggest that healthy individuals may require more data samples (time for characterization), though the trend was only significant for position data. Our results provide an important step towards using statistical distributions to describe movement tendencies. Our findings could serve as more comprehensive tools to track recovery in or design more focused training intervention in neurorehabiliation applications.

Research paper thumbnail of Individual patterns of motor deficits evident in movement distribution analysis

2013 IEEE 13th International Conference on Rehabilitation Robotics (ICORR), 2013

Research paper thumbnail of Error Augmentation and the Role of Sensory Feedback

Neurorehabilitation Technology, 2011

Research paper thumbnail of Visual and haptic feedback enable on-line tuning to resonant dynamics

Research paper thumbnail of Human adaptation to dynamic interaction forces during learning of a visuo-motor task

Research paper thumbnail of Learning Kinematic Constraints in Laparoscopic Surgery

IEEE Transactions on Haptics, 2012

Research paper thumbnail of Evidence of multiple coordinate representations during generalization of motor learning

Experimental Brain Research, 2014

Research paper thumbnail of Manual Skill Generalization Enhanced by Negative Viscosity

Journal of Neurophysiology, 2010

Recent human-machine interaction studies have suggested that movement augmented with negative vis... more Recent human-machine interaction studies have suggested that movement augmented with negative viscosity can enhance performance and can even promote better motor learning. To test this, we investigated how negative viscosity influences motor adaptation to an environment where forces acted only in one axis of motion. Using a force-feedback device, subjects performed free exploratory movements with a purely inertia generating forces proportional to hand acceleration, negative viscosity generating destabilizing forces proportional to hand velocity, or a combination of the acceleration and velocity fields. After training, we evaluated each subject's ability to perform circular movements in only the inertial field. Combined training resulted in lowest error and revealed similar responses as inertia training in catch trials. These findings are remarkable because negative viscosity, available only during training, evidently enhanced learning when combined with inertia. This success in ...

Research paper thumbnail of Augmented Dynamics and Motor Exploration as Training for Stroke

IEEE Transactions on Biomedical Engineering, 2013

With chronic stroke survivors (n = 30), we investigated how upper extremity training with negativ... more With chronic stroke survivors (n = 30), we investigated how upper extremity training with negative viscosity affects coordination under unperturbed conditions. Subjects trained with a planar robotic interface simulating 1) negative viscosity augmented to elbow and shoulder joints; 2) negative viscosity combined with inertia; or 3) a null-field condition. Two treatment groups practiced with both force conditions (cross-over design), while a control group practiced with a null-field condition. Training (exploratory movement) and evaluations (prescribed circular movement) alternated in several phases to facilitate transfer from forces to the null field. Negative viscosity expanded exploration especially in the sagittal axis, and resulted in significant within-day improvements. Both treatment groups exhibited next day retention unobserved in the control. Our results suggest enhanced learning from forces that induce a broader range of kinematics. This study supports the use of robot-assisted training that encourages active patient involvement by preserving efferent commands for driving movement.

Research paper thumbnail of Learning kinematic mappings in laparoscopic surgery

Research paper thumbnail of Visual error augmentation enhances learning in three dimensions

Research paper thumbnail of Evaluation of negative viscosity as upper extremity training for stroke survivors

With stroke survivors (n=30) as the test population, we investigated how upper extremity training... more With stroke survivors (n=30) as the test population, we investigated how upper extremity training with negative viscosity affects coordination in unassisted conditions. Using a planar force-feedback device, subjects performed exploratory movements within an environment that simulated 1) negative viscosity added to elbow and shoulder joints 2) augmented inertia to the upper and lower arm combined with negative viscosity, or 3) a null force field (control). After training, we evaluated each subject&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s ability to perform circular movements in the null field. Negative viscosity training resulted in greater within-day reductions in error compared with the combined field training. Negative viscosity promoted greater distributions of accelerations during free exploration, especially in the sagittal axis, while combined field training diminished overall activity. Both force field training groups exhibited next day retention, while this was not observed for the control group. The improvement in performance suggests that greater range of kinematic experiences contribute to learning, even despite novel force field environments. These findings provide support for the use of movement amplifying environments for upper extremity rehabilitation, allowing greater access to training while maintaining user engagement.

Research paper thumbnail of Interactive priming enhanced by negative damping aids learning of an object manipulation task

We investigated how free interaction with an object influences the formation of motor planning. S... more We investigated how free interaction with an object influences the formation of motor planning. Subjects controlled a force-feedback planar manipulandum that presented simulated anisotropic inertial forces. As a performance evaluation, subjects made circular movements about a prescribed track. In order to investigate potential enhancement of motor planning, we introduced negative damping during an ldquointeractive primingrdquo phase prior to task performance. As a control, we presented a second subject group with normal interactive priming. Our results showed significantly greater reduction in maximum curvature error for the subject group that received enhanced priming (two-tailed T-test, p=1.86e-6) compared to the control group. Group-I demonstrated a 34.8% reduction in error while Group-II achieved 5.78% reduction. We also observed that the presentation of enhanced priming evidently caused a greater sensitivity to catch trials compared to the control. Group-I demonstrated a larger increase (92.0%) in maximum curvature error in catch- trials (with respect to baseline), compared to Group-II (50.8%) during early training (two-tailed T-test, p=1.9e-3). These results suggest that some forms of augmentation to task dynamics - leading to the exploration of a broader state space -can help the accelerate the learning of control strategies suitable for an unassisted environment. The finding is also consistent with the hypothesis that subjects can decompose the environment impedance into acceleration and velocity dependent elements.

Research paper thumbnail of Negative viscosity can enhance learning of inertial dynamics

We investigated how learning of inertial load manipulation is influenced by movement amplificatio... more We investigated how learning of inertial load manipulation is influenced by movement amplification with negative viscosity. Using a force-feedback device, subjects trained on anisotropic loads (5 orientations) with free movements in one of three conditions (inertia only, negative viscosity only, or combined), prior to common evaluation conditions (prescribed circular pattern with inertia only). Training with combined-load resulted in lower error (6.89 plusmn 3.25%) compared to inertia-only (8.40 plusmn 4.32%) and viscosity-only (8.17 plusmn 4.13%) according to radial deviation analysis (% of trial mean radius). Combined-Load and inertia-only groups exhibited similar unexpected no-load trials (8.38 plusmn 4.31% versus 8.91 plusmn 4.70% of trial mean radius), which suggests comparable low-impedance strategies. These findings are remarkable since negative viscosity, only available during training, evidently enhanced learning when combined with inertia. Modeling analysis suggests that a feedforward after-effect of negative viscosity cannot predict such performance gains. Instead, results from combined-load training are consistent with greater feedforward inertia compensation along with a small increase in impedance control. The capability of the nervous system to generalize learning from negative viscosity suggests an intriguing new method for enhancing sensorimotor adaptation.