@article{Forman2020b,

title = {Characterizing forearm muscle activity in university-aged males during dynamic radial-ulnar deviation of the wrist using a wrist robot},

author = {Davis A Forman and Garrick N Forman and Edwin Johnatan Avila-Mireles and Maddalena Mugnosso and Jacopo Zenzeri and Bernadette Murphy and Michael W R Holmes},

url = {https://linkinghub.elsevier.com/retrieve/pii/S0021929020303201},

doi = {10.1016/j.jbiomech.2020.109897},

issn = {18732380},

year  = {2020},

date = {2020-07-01},

journal = {Journal of Biomechanics},

volume = {108},

pages = {109897},

abstract = {Functioning as wrist stabilizers, the wrist extensor muscles exhibit higher levels of muscle activity than the flexors in most distal upper-limb tasks. However, this finding has been derived mostly from isometric or wrist flexion-extension protocols, with little consideration for wrist dynamics or radial-ulnar wrist deviations. The purpose of this study was to assess forearm muscle activity during the execution of dynamic wrist radial-ulnar deviation in various forearm orientations (pronation/supination). In 12 healthy university-aged males, surface electromyography (EMG) was recorded from eight muscles of the dominant arm: flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), extensor digitorum (ED), biceps brachii (BB) and triceps brachii (TB). While grasping a handle, participants performed dynamic radial-ulnar deviation using a three-degrees-of-freedom wrist manipulandum. The robotic device applied torque to the handle, in either a radial or ulnar direction, and in one of three forearm postures (30° supinated/neutral/30° pronated). Results indicated that forearm posture influenced the muscles acting upon the hand (FDS/ED), whereas movement phase (concentric-eccentric) and torque direction influenced nearly every muscle. The ECR demonstrated the greatest task-dependency of all forearm muscles, which is possibly reflective of forearm muscle lines of action. Co-contraction ratios were much higher in radial trials than ulnar (Radial: 1.20 ± 0.78, Ulnar: 0.28 ± 0.18, P textless 0.05), suggesting greater FCU and ECU contribution to wrist joint stability in radial-ulnar movement. These findings highlight a greater complexity of wrist extensor function than has previously been reported in isometric work.},

keywords = {Muscle Mechanics, Neuromusculoskeletal Modelling},

pubstate = {published},

tppubtype = {article}

}

@article{Forman2020,

title = {Characterizing forearm muscle activity in young adults during dynamic wrist flexion\textendashextension movement using a wrist robot},

author = {Davis A Forman and Garrick N Forman and Edwin Johnatan Avila-Mireles and Maddalena Mugnosso and Jacopo Zenzeri and Bernadette Murphy and Michael W R Holmes},

url = {https://doi.org/10.1016/j.jbiomech.2020.109908},

doi = {10.1016/j.jbiomech.2020.109908},

issn = {18732380},

year  = {2020},

date = {2020-01-01},

journal = {Journal of Biomechanics},

volume = {108},

pages = {109908},

publisher = {Elsevier Ltd},

abstract = {Current research suggests that the wrist extensor muscles function as the primary stabilizers of the wrist-joint complex. However, most investigations have utilized isometric study designs, with little consideration for wrist dynamics or changes in posture. The purpose of the present study was to assess forearm muscle activity during the execution of dynamic wrist flexion/extension in multiple forearm orientations (pronation/supination). In 12 young adult males, surface electromyography (EMG) was recorded from eight muscles of the dominant arm: flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), extensor digitorum (ED), biceps brachii (BB) and triceps brachii (TB). While grasping a handle, participants performed dynamic wrist flexion/extension using a three-degrees-of-freedom wrist manipulandum. The robotic device applied torque to the handle, in either a flexion or extension direction, and in one of three forearm postures (30° supinated/neutral/30° pronated). Results indicated that forearm posture had minimal influence on forearm muscle activity, but significantly altered the activity of the biceps and triceps brachii. Movement phase (concentric-eccentric) dictated muscle activity in every muscle. Interestingly, muscle activity in the eccentric phase was equal between the two applied handle torques, regardless of whether the muscle acted as the agonist or antagonist. Co-contraction ratios were higher in the flexion conditions (flexion: 2.28 ± 2.04, extension: 0.32 ± 0.27), suggesting significantly greater wrist extensor activity\textendashlikely a contribution to wrist joint stability. This highlights the vulnerability of the wrist extensor muscles to overuse injuries in settings requiring prolonged use of dynamic wrist exertions.},

keywords = {Muscle Mechanics, Neuromusculoskeletal Modelling},

pubstate = {published},

tppubtype = {article}

}

@article{Forman2020a,

title = {Investigating the Muscular and Kinematic Responses to Sudden Wrist Perturbations During a Dynamic Tracking Task},

author = {Garrick N Forman and Davis A Forman and Edwin Johnatan Avila-Mireles and Jacopo Zenzeri and Michael W R Holmes},

url = {http://dx.doi.org/10.1038/s41598-020-61117-9},

doi = {10.1038/s41598-020-61117-9},

issn = {20452322},

year  = {2020},

date = {2020-01-01},

journal = {Scientific Reports},

volume = {10},

number = {1},

pages = {1-13},

publisher = {Springer US},

abstract = {Sudden disturbances (perturbations) to the hand and wrist are commonplace in daily activities and workplaces when interacting with tools and the environment. It is important to understand how perturbations influence forearm musculature and task performance when identifying injury mechanisms. The purpose of this work was to evaluate changes in forearm muscle activity and co-contraction caused by wrist perturbations during a dynamic wrist tracking task. Surface electromyography was recorded from eight muscles of the upper-limb. Participants performed trials consisting of 17 repetitions of ±40° of wrist flexion/extension using a robotic device. During trials, participants received radial or ulnar perturbations that were delivered during flexion or extension, and with known or unknown timing. Co-contraction ratios for all muscle pairs showed significantly greater extensor activity across all experimental conditions. Of all antagonistic muscle pairs, the flexor carpi radialis (FCR)-extensor carpi radialis (ECR) muscle pair had the greatest change in co-contraction, producing 1602% greater co-contraction during flexion trials than during extensions trials. Expected perturbations produced greater anticipatory (immediately prior to the perturbation) muscle activity than unexpected, resulting in a 30% decrease in wrist displacement. While improving performance, this increase in anticipatory muscle activity may leave muscles susceptible to early-onset fatigue, which could lead to chronic overuse injuries in the workplace.},

keywords = {Muscle Mechanics, Neuromusculoskeletal Modelling},

pubstate = {published},

tppubtype = {article}

}

@article{Gorjan2019,

title = {Small, movement dependent perturbations substantially alter postural control strategy in healthy young adults},

author = {Da\v{s}a Gorjan and Jan Babi\v{c} and Nejc \v{S}arabon and Zrinka Potocanac},

url = {http://www.sciencedirect.com/science/article/pii/S0021929018307292},

doi = {10.1016/j.jbiomech.2018.09.008},

issn = {18732380},

year  = {2019},

date = {2019-01-01},

journal = {Journal of Biomechanics},

volume = {91},

pages = {1--6},

abstract = {Postural control is commonly investigated by observing responses to perturbations. We developed a perturbation paradigm mimicking self-generated errors in weight shifting, which are a common cause of falling among older adults. Our aim was to determine the effects of this small, but complex, perturbation on postural sway of healthy young adults and evaluate the role of vision and cognition during movement dependent perturbations. Fifteen participants stood hip-width apart with their eyes open, closed and while performing two different cognitive tasks. Participants were continuously perturbed by medial-lateral (ML) support surface translations corresponding to, and hence doubling, their own center of mass sway. We analyzed the standard deviation (SD), root mean square (RMS), range, and mean power frequency (MPF) of center of pressure displacements. ML postural sway increased due to the perturbation (SD p ≤ .001, range p \< .001, RMS p ≤ .001, MPF p \< .001). Cognitive load increased the ML sway range (p = .048). Lack of vision increased ML MPF (p = .001) and anterior-posterior (AP) range (p \< .001), SD (p \< .001), and RMS (p = .001). Significant interaction of vision with the perturbation was found for the ML range (p = .045) and AP SD (p = .018). The perturbation specifically affected ML postural sway. Increased MPF is indicative of a postural control strategy change, which was insufficient for fully controlling the increased sway. Despite being small, this type of perturbation appears to be challenging for young adults.},

keywords = {Kinematics, Muscle Mechanics, Postural Balance},

pubstate = {published},

tppubtype = {article}

}

@article{Sarabon2018,

title = {The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males},

author = {Nejc \v{S}arabon and Igor B Mekjavi\'{c} and Ola Eiken and Jan Babi\v{c}},

url = {http://journal.frontiersin.org/article/10.3389/fphys.2018.00027/full},

doi = {10.3389/fphys.2018.00027},

issn = {1664-042X},

year  = {2018},

date = {2018-01-01},

journal = {Frontiers in Physiology},

volume = {9},

pages = {27},

publisher = {Frontiers},

abstract = {Prolonged inactivity, such as bed rest induces several detrimental changes within a short timeframe. Impaired postural balance and responses of trunk muscles to (un)expected perturbations were both shown to be impaired after bed rest. Certain populations (e.g. astronauts) are exposed to hypoxic environment in addition to inactivity, similar to bed rest. While the isolated negative effects of hypoxia on postural balance have been observed before, no study to date has examined the combined effects of hypoxia and bed rest on postural balance or trunk muscle responses. In this study, we examined the effects of 21-day exposure to three conditions: (i) bed rest in hypoxic environment (HBR), (ii) bed rest in normoxic environment (NBR), and (iii) ambulatory hypoxic environment (HAMB). Fourteen healthy male subjects crossed over between conditions in a randomized order, with a 4 month break between conditions to ensure full recovery. Most body sway parameters indicated a similar deterioration of postural balance following both HBR and NBR. Similarly, both anticipatory and reactive responses of the trunk muscles (m. erector spinae and m. multifidus) were impaired after HBR and NBR to a similar degree and mostly unchanged after HAMB. Certain body sway parameters were impaired after HAMB, confirming that hypoxia alone can undermine postural balance. On the other hand, some trunk responses were improved after HAMB. In conclusion, the results of our study confirmed previous findings on negative effects of bed rest, but showed little or no additional effect of hypoxia during bed rest. Physical activity during bed rest is encouraged to preserve neuromuscular functions of the trunk. While the HBR condition in our study resembled conditions during space missions, our results could be relevant to other populations, such as patients with pulmonary diseases exposed to bed rest.},

keywords = {Muscle Mechanics, Postural Balance},

pubstate = {published},

tppubtype = {article}

}

@article{Peternel2016b,

title = {Adaptive Control of Exoskeleton Robots for Periodic Assistive Behaviours Based on EMG Feedback Minimisation},

author = {Luka Peternel and Tomoyuki Noda and Tadej Petri\v{c} and Ale\v{s} Ude and Jun Morimoto and Jan Babi\v{c}},

editor = {Dingguo Zhang},

url = {http://dx.plos.org/10.1371/journal.pone.0148942},

doi = {10.1371/journal.pone.0148942},

issn = {1932-6203},

year  = {2016},

date = {2016-02-01},

journal = {PLOS ONE},

volume = {11},

number = {2},

pages = {e0148942},

abstract = {In this paper we propose an exoskeleton control method for adaptive learning of assistive joint torque profiles in periodic tasks. We use human muscle activity as feedback to adapt the assistive joint torque behaviour in a way that the muscle activity is minimised. The user can then relax while the exoskeleton takes over the task execution. If the task is altered and the existing assistive behaviour becomes inadequate, the exoskeleton gradually adapts to the new task execution so that the increased muscle activity caused by the new desired task can be reduced. The advantage of the proposed method is that it does not require biomechanical or dynamical models. Our proposed learning system uses Dynamical Movement Primitives (DMPs) as a trajectory generator and parameters of DMPs are modulated using Locally Weighted Regression. Then, the learning system is combined with adaptive oscillators that determine the phase and frequency of motion according to measured Electromyography (EMG) signals. We tested the method with real robot experiments where subjects wearing an elbow exoskeleton had to move an object of an unknown mass according to a predefined reference motion. We further evaluated the proposed approach on a whole-arm exoskeleton to show that it is able to adaptively derive assistive torques even for multiple-joint motion.},

keywords = {Exoskeleton Design and Control, Human Performance Augmentation, Muscle Mechanics},

pubstate = {published},

tppubtype = {article}

}

@article{Babic2004,

title = {In vivo determination of triceps surae muscle-tendon complex viscoelastic properties},

author = {Jan Babi\v{c} and Jadran Lenar\v{c}i\v{c}},

url = {http://link.springer.com/10.1007/s00421-004-1107-4},

doi = {10.1007/s00421-004-1107-4},

issn = {1439-6319},

year  = {2004},

date = {2004-01-01},

journal = {European Journal of Applied Physiology},

volume = {92},

number = {4-5},

pages = {477--84},

abstract = {Viscoelastic properties of muscles and tendons have an important influence on human motion performance. Proper determination of these properties is essential in the analysis and modelling of human motion dynamics. The purpose of our study was to develop a method for in vivo determination of the viscoelastic properties of the entire triceps surae muscle-tendon complex (MTC) including the gastrocnemius. Ten trained male subjects participated in this study. The measurement procedure consisted of two parts: soleus and Achilles tendon stiffness and viscosity were determined in the first part while the gastrocnemius stiffness and viscosity were determined in the second part. The measurement device and the procedure have been designed in such a manner that as few human body segments move as possible during the measurement. Thus, the measurement uncertainty due to the approximation of the properties of the human body segments was minimized. Triceps surae MTC viscoelastic properties of both legs were measured for each subject. There were no significant differences in viscoelastic coefficients for left and right lower extremities; however, there were noticeable differences between subjects. The soleus stiffness coefficient was greater than the gastrocnemius stiffness coefficient by 87.6 m(-1) in average. For all subjects, soleus viscosity was equal or greater than gastrocnemius viscosity. Values of viscoelastic parameters obtained by our method can be used in the analysis and modelling of human movement in situations where the knee joint is not necessarily flexed and there is coactivation of the soleus and the gastrocnemius.},

keywords = {Biarticular Muscle, Muscle Mechanics, Neuromusculoskeletal Modelling},

pubstate = {published},

tppubtype = {article}

}