Push-pull Task Research Articles

Effect of Load on Upper Extremity Muscles of Agricultural Workers of West Bengal

Introduction: Agricultural fields like weed management and horticultural operations are the most common and labor-intensive. Most of these tasks are completed with the help of push-pull-type agricultural machinery. The push-pull tasks are mainly done using agricultural machinery (push-pull weeders, manually operated rice transplanters or seeders, long-handled agricultural tools, etc.) by farm workers. Since these are manually operated machinery, long working hours in awkward positions are expected, which causes physical stress and musculoskeletal disorders in the operators. An electromyography study for agricultural workers during push and pull operations was conducted in this study. Methods: To evaluate muscle activity, a laboratory test setup was developed based on the ergonomic criteria of the uniform force application. Four loads (50, 100, 150, and 200 N) and the four most used upper body muscles (middle deltoid MD, triceps brachii TR, brachioradialis BR, and biceps brachii BI) during push-pull operations were selected for an electromyographic study on twelve medically fit agricultural workers as subjects. This study attempted to minimize muscle activity, thereby reducing overexertion injuries. Results: The most activated muscles during the pushing and pulling operations were TR and BR, respectively. The muscle activity of the TR during the pushing task was found to be 109 µV, 135 µV, 178 µV and 195 µV at loads of 50 N, 100 N, 150 N, and 200 N, respectively. During the pulling task, the muscle activity of the BR was 51 µV, 66 µV, 80 µV, and 126 µV at loads of 50 N, 100 N, 150 N, and 200 N, respectively. Conclusion: For all subjects, a load of 200 N was found difficult to operate compared to other selected loads during push and pull operations. Muscle activation was found to increase with increasing load for each of the selected muscles.

Valence, arousal and appraisal of emotion influence the hand movement

<p id="C2">The positive-negative valence of emotion affecting hand movements toward or away from the body is known as the approach-avoidance effect. Previous studies have shown that the positive images elicit quicker reaction on approach movement while negative images are sensitive to the avoidance. However, few studies have focused on how emotion affects the complete process of the movement. In current research, the effects of valence, arousal and appraisal of emotion on the dragging movement were investigated. <br/><p id="C60">A push-pull task was performed on a touch screen to evaluate the ramifications which emotion holds for hand movement. Twenty-four right-handed participants volunteered in Experiments 1 and 2, and fifteen of these participants continued Experiment 3 two months later. In Experiments 1 and 3, emotional pictures with half positive and half negative valences included equal numbers of high-, medium- and low- arousal images. Participants were required to drag pictures upward or downward with their index finger. Experiment 1 and 3 differed in that only in Experiment 1 did the participants evaluate the valence of pictures. Neutral pictures as well as grey blank images were exploited in Experiment 2 to rule out the effects of other factors. <br/><p id="C61">Repeated-measured ANOVA and Paired t-tests were carried out. The results illustrate that (1) approaching (pulling) the positive pictures or avoiding (pushing) the negative ones yields faster dragging movement; (2) compared to medium and low arousal, high arousal enhances the emotional effect, especially in negative condition; (3) the emotional effect diminishes when participants did not evaluate the valence of images, and when neutral images (e.g., furniture) and grey blank images were displayed. <br/><p id="C62">In conclusion, this study indicates that the emotion does not only affect the reaction time of approach-avoidance movement, but also affects the latter hand movement. In addition, arousal and appraisal play an important role in this effect. This result suggests that the effects of emotion on the dragging movement might happen at the early stage and thus both movement programming and motor control are influenced by emotions.

Upper Extremity Muscular Strength in Push-Pull Tasks: Model Approach Towards Task Design.

Background:Pushing and pulling in workplaces are common actions. Repetitive forceful exertions in long-duration works lead to increased risk of musculoskeletal disorders and injuries.Aim:To investigate the upper extremity strength in generic push–pull modes while using hand tools and forecasting the limits of the workers while frequent or continuous operation.Settings and Design:The study was conducted among men workers in Ahmedabad city, India, and the design was cross-sectional study.Materials and Methods:In all, 100 men were recruited (Group 1: 18–39 years and Group 2: 40–60 years). Upper extremity muscular strength (isometric mode) testing of the preferred hand during push–pull type of manual hand-tool operations was carried out for 60 s. Forecasting of strength to generate predictions for future events (120 s) based on known past events (measured 60 s) was carried out using Holt–Winters time-series model.Statistical Analysis:Descriptive statistics was used for analysis. For prediction model evaluation, WEKA 3.8.2 was used.Results:Anthropometric parameters of both groups were similar, having no effect on generated strength. Largely, pull strength was recorded to be higher than push strength, wherein Group 2 men generated slightly higher strength. Seated strength was also higher than standing exertion. Forecasting reveals steady strength values for Group 1 men, whereas steep decline among Group 2 men with increasing duration of trial.Conclusion:The strength data generated would aid in work schedule design. Strength forecasting model would assist in developing engineering guidelines in the design of tools at workplace.

Cortical Effects on Ipsilateral Hindlimb Muscles Revealed with Stimulus-Triggered Averaging of EMG Activity.

While a large body of evidence supports the view that ipsilateral motor cortex may make an important contribution to normal movements and to recovery of function following cortical injury (Chollet et al. 1991; Fisher 1992; Caramia et al. 2000; Feydy et al. 2002), relatively little is known about the properties of output from motor cortex to ipsilateral muscles. Our aim in this study was to characterize the organization of output effects on hindlimb muscles from ipsilateral motor cortex using stimulus-triggered averaging of EMG activity. Stimulus-triggered averages of EMG activity were computed from microstimuli applied at 60-120 μA to sites in both contralateral and ipsilateral M1 of macaque monkeys during the performance of a hindlimb push-pull task. Although the poststimulus effects (PStEs) from ipsilateral M1 were fewer in number and substantially weaker, clear and consistent effects were obtained at an intensity of 120 μA. The mean onset latency of ipsilateral poststimulus facilitation was longer than contralateral effects by an average of 0.7 ms. However, the shortest latency effects in ipsilateral muscles were as short as the shortest latency effects in the corresponding contralateral muscles suggesting a minimal synaptic linkage that is equally direct in both cases.

Predictive model of the human muscle fatigue: application to repetitive push-pull tasks with light external load

Repetitive tasks in industrial works may contribute to health problems among operators, such as musculo–skeletal disorders, in part due to insufficient control of muscle fatigue. In this paper, a predictive model of fatigue is proposed for repetitive push/pull operations. Assumptions generally accepted in the literature are first explicitly set in this framework. Then, an earlier static fatigue model is recalled and extended to quasi–static situations. Specifically, the maximal torque that can be generated at a joint is not considered as constant, but instead varies over time accordingly to the operator's changing posture. The fatigue model is implemented with this new consideration and evaluated in a simulation of push/pull operation.

Properties of primary motor cortex output to hindlimb muscles in the macaque monkey.

The cortical control of forelimb motor function has been studied extensively, especially in the primate. In contrast, cortical control of the hindlimb has been relatively neglected. This study assessed the output properties of the primary motor cortex (M1) hindlimb representation in terms of the sign, latency, magnitude, and distribution of effects in stimulus-triggered averages (StTAs) of electromyography (EMG) activity recorded from 19 muscles, including hip, knee, ankle, digit, and intrinsic foot muscles, during a push-pull task compared with data reported previously on the forelimb. StTAs (15, 30, and 60 μA at 15 Hz) of EMG activity were computed at 317 putative layer V sites in two rhesus macaques. Poststimulus facilitation (PStF) was distributed equally between distal and proximal muscles, whereas poststimulus suppression (PStS) was more common in distal muscles than proximal muscles (51/49%, respectively, for PStF; 72/28%, respectively, for PStS) at 30 μA. Mean PStF and PStS onset latency generally increased the more distal the joint of a muscle's action. Most significantly, the average magnitude of hindlimb poststimulus effects was considerably weaker than the average magnitude of effects from forelimb M1. In addition, forelimb PStF magnitude increased consistently from proximal to distal joints, whereas hindlimb PStF magnitude was similar at all joints except the intrinsic foot muscles, which had a magnitude of approximately double that of all of the other muscles. The results suggest a greater monosynaptic input to forelimb compared with hindlimb motoneurons, as well as a more direct synaptic linkage for the intrinsic foot muscles compared with the other hindlimb muscles.

Cortical output to fast and slow muscles of the ankle in the rhesus macaque

The cortical control of fast and slow muscles of the ankle has been the subject of numerous reports yielding conflicting results. Although it is generally agreed that cortical stimulation yields short latency facilitation of fast muscles, the effects on the slow muscle, soleus, remain controversial. Some studies have shown predominant facilitation of soleus from the cortex while others have provided evidence of differential control in which soleus is predominantly inhibited from the cortex. The objective of this study was to investigate the cortical control of fast and slow muscles of the ankle using stimulus triggered averaging (StTA) of EMG activity, which is a sensitive method of detecting output effects on muscle activity. This method also has relatively high spatial resolution and can be applied in awake, behaving subjects. Two rhesus macaques were trained to perform a hindlimb push-pull task. Stimulus triggered averages (StTAs) of EMG activity (15, 30, and 60 μA at 15 Hz) were computed for four muscles of the ankle [tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus] as the monkeys performed the task. Poststimulus facilitation (PStF) was observed in both the fast muscles (TA, MG, and LG) as well as the slow muscle (soleus) and was as common and as strong in soleus as in the fast muscles. However, while poststimulus suppression (PStS) was observed in all muscles, it was more common in the slow muscle compared to the fast muscles and was as common as facilitation at low stimulus intensities. Overall, our results demonstrate that cortical facilitation of soleus has an organization that is very similar to that of the fast ankle muscles. However, cortical inhibition is organized differently allowing for more prominent suppression of soleus motoneurons.

The Baltimore Therapeutic Equipment work simulator: biomechanical and physiological norms for three attachments in healthy men.

The Baltimore Therapeutic Equipment (BTE) work simulator is routinely used by occupational therapists in functional capacity evaluation. Currently, there is a lack of normative data for various attachments on this instrument. The purposes of this study were to (a) establish norms for the biomechanical and physiological responses during three tasks on the BTE work simulator, namely, wheel-turn, push-pull, and overhead-reach; (b) compare these responses during the three tasks, and (c) examine the interrelationships of these responses during the tasks. Twenty healthy men completed five testing sessions: (a) task familiarization on the BTE work simulator to identify the work intensity, which was perceived as hard on the Borg scale; (b) an incremental arm ergometer exercise test to determine their peak oxygen uptake (pVO2) and peak heart rate (pHR); and (c) one of the three tasks on the BTE work simulator for 4 min in each of the next three sessions. Analysis of variance indicated that torque, work, and power during the overhead-reach were significantly higher (p = .000) compared with the wheel-turn and push-pull tasks. However, no significant differences (p > .05) were observed among the tasks for the VO2 and HR, which were approximately 50% and 70% of pVO2 and pHR respectively. Although there was a significant relationship (p < .05) among tasks for the torque, work, and power, the common variance ranged only between 38% and 67%. The relative pVO2 was significantly related to work (p = .028) and power (p = .027) only during the push-pull task but not the wheel-turn and overhead-reach tasks. These results suggest that occupational therapists should include as many tasks as possible when designing functional capacity evaluation test batteries, and that there is no consistent relationship between cardiorespiratory fitness and performance of various tasks on the BTE work simulator.

Evaluation of Localized Muscle Fatigue Using Power Spectral Density Analysis of the Electromyogram

Surface electromyograms (EMGs) taken from three upper torso muscles during a push-pull task were analyzed by a power spectral density technique to determine the operational feasibility of the technique for identifying changes in the EMGs resulting from muscular fatigue. The EMGs were taken from four subjects under two conditions (1) in shirtsleeves and (2) in a pressurized space suit. This study confirmed that frequency analysis of dynamic muscle activity is capable of providing reliable data for many industrial applications where fatigue may be of practical interest. The results showed significant effects of the pressurized space suit on the pattern of shirtsleeve fatigue responses of the muscles. The data also revealed (1) reliable differences between muscles in fatigue-induced responses to various locations in the reach envelope at which the subjects were required to perform the push-pull exercise and (2) the differential sensitivity of muscles to the various reach positions in terms of fatigue-related shifts in EMG power.

Design of controls using force as a criterion.

A force platform was used to study the effect of varying the height and handle orientation of a push-pull task. Each of the ten subjects performed the task at knee, hip, waist, chest, and eye heights and at each of the heights the handle was oriented in five different positions. Even though the force required for the task itself did not vary, changing the height of the handle forced each subject to exert a force to maintain his own body position. This force exerted by the subject was minimized when the handle was at chest height. The only previous studies on optimum work heights have concerned work surface location. Since their usual recommendations are to place a work surface below rather than above the elbow, it seems additional experimentation is desirable.