Individual Differences in the Activity of Dominant Forearm Muscles during VDT Work

1995 ◽  
Vol 39 (13) ◽  
pp. 926-930 ◽  
Author(s):  
Rajendra D Paul ◽  
Krishna Menon ◽  
Chandra Nair
Keyword(s):  
Muscle Activity ◽  
Role Play ◽  
Employee Training ◽  
Extensor Muscle ◽  
Flexor Muscle ◽  
Work Activity ◽  
Forearm Muscles ◽  
Analysis Of Results ◽  
Forearm Muscle ◽  
Subject Differences

In two studies on VDT work, activity of dominant forearm muscles was measured using surface electromyography. In the first study (n = 12), subjects used only a keyboard; whereas in the second study (n = 8), subjects used both keyboard and mouse. In both studies, analysis of results indicated that inter-subject differences in forearm muscle effort were significantly different (p < 0.05). In the first study, the minimum-to-maximum ratio for average extensor muscle activity was 1:3.7. In the second study, the minimum-to-maximum ratio was 1:2.2 for the flexor muscle activity and 1:3.7 for the extensor muscle activity. These results support the notion of differences in individual workstyles proposed by Feuerstein (1995). Individual typing styles play an important role play an important role in the stress on forearm muscles during VDT work and should be included in employee training protocols.

scholarly journals Back-Support Exoskeleton Control Strategy for Pulling Activities: Design and Preliminary Evaluation

Designs ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 39
Author(s):  
Maria Lazzaroni ◽  
Tommaso Poliero ◽  
Matteo Sposito ◽  
Stefano Toxiri ◽  
Darwin G. Caldwell ◽  
...  
Keyword(s):  
Control Strategy ◽  
Muscle Activity ◽  
Material Handling ◽  
Ease Of Use ◽  
Biomechanical Analysis ◽  
Perceived Support ◽  
Preliminary Evaluation ◽  
Subjective Measurements ◽  
Spinal Muscles ◽  
Forearm Muscle

The execution of manual material handling activities in the workplace exposes workers to large lumbar loads that increase the risk of musculoskeletal disorders and low back pain. In particular, the redesign of the workplace is making the execution of pulling activities more common, as an alternative to lifting and carrying tasks. The biomechanical analysis of the task revealed a substantial activation of the spinal muscles. This suggests that the user may benefit from the assistance of a back-support exoskeleton that reduces the spinal muscle activity and their contribution to lumbar compression. This work addresses this challenge by exploiting the versatility of an active back-support exoskeleton. A control strategy was specifically designed for assisting pulling that modulates the assistive torques using the forearm muscle activity. These torques are expected to adapt to the user’s assistance needs and the pulled object mass, as forearm muscle activity is considered an indicator of grip strength. We devised laboratory experiments to assess the feasibility and effectiveness of the proposed strategy. We found that, for the majority of the subjects, back muscle activity reductions were associated with the exoskeleton use. Furthermore, subjective measurements reveal advantages in terms of perceived support, comfort, ease of use, and intuitiveness.

Intersegmental reflex actions from a joint sensory organ (CB) to a muscle receptor (MCO) in decapod crustacean limbs

1978 ◽  
Vol 73 (1) ◽  
pp. 47-63 ◽  
Author(s):  
B. M. Bush ◽  
J. P. Vedel ◽  
F. Clarac
Keyword(s):  
Decapod Crustacean ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Flexor Muscle ◽  
Proprioceptive Reflexes ◽  
Co Activation ◽  
Extensor Muscles ◽  
Motor Activities ◽  
Central Excitability ◽  
Reflex Discharge

In the walking legs of decapod crustaceans, intersegmental reflex actions originate from various joint proprioceptors. The activity of the ‘accessory flexor’ (AF) muscle, which with the myochordotonal organ (MCO) constitutes a muscle proprioceptor for the mero-carpopodite (M-C) joint, is modulated by the sensory discharge of a joint receptor (CB chordotonal organ) for the more proximal, coxo-basal (C-B) joint. Selective mechanical stimulation of the CB organ also reflexly modifies the motor activities of the main M-C flexor and extensor muscles (recorded as EMGs). 1. Dynamic CB stretch (as would occur during a dorso-ventral C-B movement - i.e. ‘depression’ of the limb) stimulates motor discharge to the M-C extensor muscle, while dynamic release of CB (as during a ventrodorsal C-B movement - or leg ‘elevation’) excites the accessory flexor as well as the main flexor muscle. 2. Successive M-C muscle responses to repetitive sinusoidal changes of CB length differ quantitatively according to the direction (stretch or release) of the first CB movement, in some cases increasing but more commonly ‘adapting’ with repetition. 3. Reflex discharge frequencies of the extensor, flexor and accessory flexor motoneurones increase with velocity of CB movement. 4. Eye illumination, and spontaneous or other sources of increased central excitability, generally increase the CB reflex drive to the flexor and accessory flexor muscles and, in parallel, decrease the reflex action on the extensor muscle. The results are discussed in terms of the role of proprioceptive reflexes in intersegmental co-ordination of the leg joints. In particular the significance of the reflex regulation of the myochordotonal receptors, and thereby the gain of the M-C resistance reflexes, is considered in the light of the observed ‘co-activation’ of main flexor and receptor muscle motoneurones.

New Pistol Grip Control for an Electric Utility Aerial Bucket Reduces Risk of Forearm Muscle Fatigue

2018 ◽  
Vol 62 (1) ◽  
pp. 888-892
Author(s):  
Richard W. Marklin ◽  
Jonathon E. Slightam ◽  
Mark L. Nagurka ◽  
Casey D. Garces ◽  
Lovely Krishen ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Muscular Activity ◽  
Electric Utility ◽  
Scale Model ◽  
Overhead Line ◽  
Endurance Time ◽  
Forearm Muscles ◽  
Actual Equipment ◽  
Forearm Muscle ◽  
Semg Activity

Overhead line workers have anecdotally reported elevated levels of fatigue in forearm muscles when operating the pistol grip control that maneuvers an aerial bucket on a utility truck. Previous research with surface electromyographic (sEMG) recordings of forearm muscles corroborated these reports of muscle fatigue. A new pistol grip was designed that reduces the applied force by 50% in all directions of movement. In laboratory testing, sEMG signals were recorded from the upper extremity muscles of twenty subjects, who operated a conventional-force pistol grip and the 50% reduced-force control to move a 1/15 scale model of an aerial truck boom. The muscle that resulted in the greatest sEMG activity (extensor digitorum communis (EDC)) was the muscle that workers typically pointed to when they reported forearm muscle fatigue from using the control. The reduced-forced pistol grip decreased EDC sEMG by an average of 5.6%, compared to the conventional control, increasing the maximum endurance time by 38% according to muscle fatigue models. This study was the first to quantify muscular activity of a new aerial bucket pistol grip control and the results show promise for improving the occupational health of electric utility overhead line workers, specifically reducing muscle fatigue. Before the new design of the pistol grip can be commercialized, it must be tested in the field on actual equipment.

Evaluation of an adjustable support shoulder exoskeleton on static and dynamic overhead tasks

2018 ◽  
Vol 62 (1) ◽  
pp. 804-808 ◽  
Author(s):  
Logan Van Engelhoven ◽  
Nathan Poon ◽  
Homayoon Kazerooni ◽  
Alan Barr ◽  
David Rempel ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Peak Torque ◽  
Industrial Workers ◽  
Human Engineering ◽  
Shoulder Injuries ◽  
Flexor Muscle ◽  
Work Related ◽  
Upper Trapezius ◽  
Shoulder Complex

Introduction: Overhead tasks increase the risk of work related musculoskeletal disorders to industrial workers. A shoulder supporting exoskeleton with adjustable and angle dependent torque (referred to as shoulderX in this paper for brevity) was designed and built at the University of California Berkeley Human Engineering and Robotics Laboratory for workers performing overhead tasks. shoulderX was designed specifically to reduce the exposure to large muscle exertion forces on the shoulder complex from overhead work. Methods: We evaluated shoulderX by measuring the muscle activation of the upper trapezius (UT), anterior deltoid (AD), triceps long head (TR), and infraspinatus (IF) during static and dynamic overhead tasks. Thirteen male subjects with experience in the construction or manufacturing industries were recruited to perform overhead tasks using light (.45 kg) and heavy (2.25 kg) weight tools with four exoskeleton support levels (0, 8.5, 13.0, 20.0 Nm peak torque). Results: During all conditions, the wearer’s shoulder flexor muscle activity of UT, AD were reduced with increasing strength of shoulderX by up to 80%. Subjects unanimously preferred the use of shoulderX over the unassisted condition for all task types (static and dynamic overhead tasks) and tool weights (.45 kg and 2.25 kg). Conclusion: shoulderX reduces the wearer’s primary muscle activity in overhead static and dynamic work and results in a more desirable and balanced pattern of shoulder complex activation. This investigation indicates that shoulderX reduces the risk of work related shoulder injuries during overhead tasks.

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