The Influence Of Mental Workload On Surface EMG And Muscle Oxygenation Induced By The Static Wrist Weight-bearing Exercise Of The Upper Limb Muscle

Research ObjectivesThere are lots of investigations indicated that the existence of mental workload accelerates the development of the occupational musculoskeletal disease. In order to overcome subjectivity of participants’evaluation in the investigating research, researchers adopt experimentation to explore muscle activity in two kinds of experimental conditions, which are the isolated existence of physical load and the coexistence of mental workload and physical load respectively, but there are large differences in research results. Based on the inconsistency of previous research results, this research makes a comparison on the variation of related muscle surface electromyography (EMG) and muscle oxygenation, which compares against an experimental group with the coexistence of mental workload and static movement and a control group with static movement. The purpose of the research is to demonstrate whether the existence of mental workload can affect surface EMG in the static muscular movement and muscle oxygenation in the particular muscle.Research MethodsThis research adopts laboratory experiment to test twelve healthy girls. Twelve healthy girls at the static wrist weight-bearing exercise while visual display terminal(VDT) operations, which divides experimental subjects into two groups: VDT work as a mental arithmetic task for the experimental group, VDT work for the reported number of tasks to the control group. Moreover, this research selects 30%, 50%, and 70% maximum voluntary contraction (MVC) as weight-bearing wrist three different levels of physical loads and adopts the surface EMG analytical technique and the real-time wireless blood oxygenation monitoring technique to monitor muscle activity synchronously. Furthermore, this research selects averaged electromyogram (AEMG) and mean power frequency (MPF) based on surface EMG index and muscle oxygen saturation according to muscle oxygen signal index.Research ResultsWhen the physical load is 50% MVC, the MPF of triceps brachii muscle in the experimental group with the coexistence of mental workload and physical load is 66.9261. In the control group, the MPF is 64.1451, so the MPF index of triceps brachii muscle in the experimental group significantly higher than the control group (t=-3.215, p-0.008). Similarly, when the physical load is 50% MVC, the MPF of brachioradialis in the experimental group is 59.5937 while the control group is 58.9411, so the MPF index of brachioradialis in the experimental group obviously higher than in the control group (t=-2.419, p=0.034). Meanwhile, when the physical load is 50% MVC, the muscle oxygen saturation of triceps brachii muscle in the experimental group is 59.6832, but the control group is 56.1110, so the muscle oxygen saturation of triceps brachii muscle in the experimental group significantly higher than the control group (t=-2.502, p=0.029). In addition, when the physical load is 30% MVC, the AEMG of brachioradialis in the experimental group is 66.5094, yet the AEMG is 57.9270 in the control group, so the MPF index of brachioradialis in the experimental group obviously higher than those in the control group (t=3.037, p=0.011).Research ConclusionsThe research result shows that the mental workload can influence surface EMG and muscle oxygenation induced by the static wrist weight-bearing exercise. To be specific, the existence of mental workload leads to the increases of MPF in the static wrist weight-bearing exercise of the upper limb muscle, AEMG, and muscle oxygen saturation in the real-time wireless blood oxygenation monitoring system. Also, this variation exists differences in the different levels of physical load and different kinds of muscles.