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... Nugent et al., 2020). However, a variety of studies have explored forearm muscle recruitment patterns to investigate hand grip fatigue in relation to clutch design (Conrad and Marklin, 2014), prolonged riding (Marina et al., 2011), or repeated braking (Marina et al., 2013(Marina et al., , 2022. In emergency hard braking, we would expect postural bracing between hands at the handlebar grips and trunk through activation of shoulder extensors (anterior deltoid, AD). ...
... The method of data collection in the controlled environment reduced the influence of confounding variables and allowed for an accurate comparison of muscle activity after and without the use of an armrest. Furthermore, because of the controlled indoor setting in the laboratory, the impacts of weather and road conditions had no effect on muscle activity (Conrad and Marklin, 2014). ...
Introduction: Motorcycle is one of the main transports in Malaysia that has been used for decades either for daily life activities or for working. Motorcyclist is the most important element when issues that are related to motorcycle. Therefore, this study will be able to provide evidence to reduce level electromygraphy (muscle activity) with the intervention of armrest prototype which indirectly reduce riding discomfort during prolonged riding process.Method: In 2 different sessions (with and without armrest), 102 respondents were instructed to ride a motorcycle for 2 hours in a laboratory with riding simulator system. The video screen presented by projector a view as motorcyclist in road scenery with computer generated video simulating daytime riding condition. Besides that, Electromyography (EMG) signals were used to assess recorded muscle activity for the right and left arm with the surface of electrode attached. Results: Muscle activity of respondents showed that there are reductions of electromyography levels for both right and left arm’s muscles. There is a positive effect of exertion changes (%) on the flexor carpum radialis (right=24.54%, left=23.98%) and flexor carpum ulnaris (right=8.18%, left=10.62%) muscles of both arms with usage of prototype.
... The EMG signal was amplified using a BA1104m bio-instrumentation amplifier (Nihon Santeku Co., Ltd. Japan) before it was transmitted to the ML880 PowerLab 16/30 (ADInstruments, New Zealand) at a sampling rate of 1 kHz and recorded in LabChart v7.3.8 (ADInstruments, New Zealand) with a 10-350-Hz band-pass filter to eliminate noise signals (Kong and Lowe 2005a;Conrad and Marklin 2014). ...
The magnitude of hand- (HTV) and wrist- (WTV) transmitted vibration can negatively impact upper limb responses even during short-term exposure. This study aimed to establish the effects of various handle-grip designs on the harmful impacts of vibration, sustained grip exertion, and unnatural posture. The primary focus was to investigate how using a handle grip and how three shapes with two surface profiles affect HTV, WTV, and forearm muscle activities during exposure. The secondary goal was to evaluate the immediate effects on fundamental hand functions, perceived discomfort/comfort, and perceived vibration level after exposure. The final objective was to assess which of the handle designs had the least harmful effects. Fourteen young male adults were recruited and asked to consistently grip a vibrating handle structure for two-min while the primary parameters were recorded. Pre- and post-task measurements of secondary parameters were recorded on the six design conditions and one control condition (no handle grip). The study found that implementing a regular circular-smooth handle resulted in lower transmitted vibrations, leading to lower upper limb discomfort, higher grip comfort, and lower perceived vibration. Additionally, shape significantly affected HTV, resulting in grip strength reduction, while surface profile did not influence transmitted vibrations but significantly impacted ring and small finger sensitivity, finger and hand discomfort, and grip comfort. Finally, forearm muscle activities were unaffected, and no significant interaction effects were observed. Circular handles also had the least negative impacts, and elliptic handles had the most negative impacts on the upper extremity because of the level of hand-handle contact stress and hand grip effort. Meanwhile, the uneven distribution of vibration on the fingers and palm imposed by the rounded spikes on the patterned surface led to decreased finger sensitivity, higher discomfort, and lower grip comfort. Therefore, when machine operation involves moderate grip exertion, pronated forearm posture, and short-term handle vibration exposure, implementing a hard-solid handle with less hand-handle contact area, less grip effort, and even texture is recommended.
... (Mohd Hafzi et al., 2011;Khamis et al., 2013;Conrad and Marklin, 2014;Onawumi and Oyawale, 2016;Athirah Diyana et al., 2019). ...
Vibration transmitted to the upper limb is the primary source of occupational musculoskeletal disorder. Transmissibility is not just caused by vibration magnitude but is also directly influenced by the applied force and posture. This study investigated the effects of two forearm postures and grip force levels, when using dual‐handle guided equipment, on hand‐arm transmitted vibration and physiological responses. Sixteen young male adults were recruited. Pre‐task and post‐task assessments including grip strength and perceived discomfort were measured. The task was to hold a vibrating handlebar for 5 ‐min under four randomly sequenced conditions: N/PM/H—neutral/pronated forearm and mild/hard grip. Transmissibility and forearm muscle activities were recorded during each task. It was discovered that neutral posture led to higher wrist and elbow transmissibility, whereas hard grip resulted in higher elbow transmissibility, forearm muscle activities, grip strength reduction, and distal arm discomfort. Furthermore, the interaction between the effects of posture and force significantly influenced wrist extensor activity (NH > PH; NM = PM), proximal arm discomfort (NH < PH; NM = PM), and wrist transmissibility (PH > PM; NH = NM). Essentially, with constant vibration and exposure duration, the application of sustained hard grip had more negative physiological effects because of the greater physical workload toward the hands and forearms. Moreover, gripping hard during pronation led to higher discomfort that reached the proximal arm because a greater effort was required. Hence, a neutral forearm posture is recommended when the tasks require forceful movements and either posture is suggested when less powerful movements are involved.
Transportation/transshipment was essential to logistics, enhancing growing economy. Work related muscle fatigue was acknowledged as contribution to significant losses in occupational safety and health. The study was conducted to review applicable electromyography examining protocols and indicators. The searches were achieved over 3 relevant available electronics data bases as well as search engines with 733 articles found. Only 13 articles were included corresponding to the criteria. To assess muscle fatigue; examining protocols during real-time, before-after and simulation of operation tasks were found utilizing. Time domain (RMS, muscle activity, MVC) and frequency domain (MNF, MDF) functioned as EMG indicators. Real-time protocol seemed to provide most information needed. However, other remaining protocols were still fairly selectable if no choice.
