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Mean Power Frequency (mean + power_frequency)
Selected AbstractsInfluence of playing wind instruments on activity of masticatory musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2007A. GOTOUDA Summary, The aim of this study was to elucidate the influence of change in sound tone of playing wind instruments on activity of jaw-closing muscles and the effect of sustained playing for a long time on fatigue of jaw-closing muscles. Electromyograms (EMG) of 19 brass instrument players and 14 woodwind instrument players were measured while playing instruments in tuning tone and high tone and under other conditions. Nine brass instrument players and nine woodwind instrument players played instruments for 90 min. Before and after the exercise, power spectral analyses of EMG from masseter muscles at 50% of maximum voluntary clenching level were performed and mean power frequency (MPF) were calculated. Root mean square (RMS) of EMG in masseter and temporal muscles while playing were slightly larger than those at rest but extremely small in comparison with those during maximum clenching. Root mean square in orbicularis oris and digastric muscles were relatively large when playing instruments. In the brass instrument group, RMS in high tone was significantly higher than that in tuning tone in all muscles examined. In the woodwind instrument group, RMS in high tone was not significantly higher than that in tuning tone in those muscles. Mean power frequency was not decreased after sustained playing in both instrument groups. These findings indicate that contractive load to jaw-closing muscles when playing a wind instrument in both medium and high tone is very small and playing an instrument for a long time does not obviously induce fatigue of jaw-closing muscles. [source] Relationship between muscle oxygenation and electromyography activity during sustained isometric contractionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2008Eiji Yamada Summary The purpose of this study was to clarify the relationship between electromyography (EMG) spectrum changes and muscle oxygenation measured by near-infrared time-resolved spectroscopy (TRS). Each subject performed sustained isometric knee extension at 50% of the maximal voluntary contraction load for 1 min. Surface EMG and TRS were simultaneously recorded from the right vastus lateralis muscle. Mean power frequency (MPF) of the power spectrum was calculated every 5 s during isometric contraction using fast Fourier transform, and decrease in the slope of MPF for 1 min was calculated using the least squares method. The maximal changes in oxygenated haemoglobin and myoglobin (Oxy Hb/Mb) and in deoxygenated haemoglobin and myoglobin (Deoxy Hb/Mb) from pre-contraction values of 1 min were calculated. There were significant relationships between the decrease in the slope of MPF and the maximal changes in Oxy Hb/Mb and Deoxy Hb/Mb (P < 0·05). These findings suggested that changes in Oxy Hb/Mb and Deoxy Hb/Mb indicate muscle fatigue assessed by EMG. [source] Task-related electromyographic spectral changes in the human masseter and temporalis musclesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2002Mauro Farella The masticatory muscles differ in their fiber type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study, surface EMG activity was picked up from the masseter and from the anterior and posterior temporalis muscles of nine adult subjects. At a bite force level as low as 25 N, the mean power frequency (MPF) values of the posterior temporalis were significantly lower than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude, whereas the MPF values of the anterior and posterior temporalis did not change significantly. The MPF values were significantly influenced by the direction of bite force. The observed changes of MPF are possibly related to the recruitment of different fiber types, and support the concept that the masticatory muscles behave heterogeneously. [source] Influence of playing wind instruments on activity of masticatory musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2007A. GOTOUDA Summary, The aim of this study was to elucidate the influence of change in sound tone of playing wind instruments on activity of jaw-closing muscles and the effect of sustained playing for a long time on fatigue of jaw-closing muscles. Electromyograms (EMG) of 19 brass instrument players and 14 woodwind instrument players were measured while playing instruments in tuning tone and high tone and under other conditions. Nine brass instrument players and nine woodwind instrument players played instruments for 90 min. Before and after the exercise, power spectral analyses of EMG from masseter muscles at 50% of maximum voluntary clenching level were performed and mean power frequency (MPF) were calculated. Root mean square (RMS) of EMG in masseter and temporal muscles while playing were slightly larger than those at rest but extremely small in comparison with those during maximum clenching. Root mean square in orbicularis oris and digastric muscles were relatively large when playing instruments. In the brass instrument group, RMS in high tone was significantly higher than that in tuning tone in all muscles examined. In the woodwind instrument group, RMS in high tone was not significantly higher than that in tuning tone in those muscles. Mean power frequency was not decreased after sustained playing in both instrument groups. These findings indicate that contractive load to jaw-closing muscles when playing a wind instrument in both medium and high tone is very small and playing an instrument for a long time does not obviously induce fatigue of jaw-closing muscles. [source] Task-related electromyographic spectral changes in the human jaw musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2002M. FARELLA The masticatory muscles differ in their fibre type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study surface EMG activity was picked up from the masseter, and anterior and posterior temporalis muscles of nine adult subjects. Direction and magnitude of bite force were recorded using a three-component force transducer. Bite forces were exerted in five different directions: vertical, forward, backward, to the right and to the left of the subject. Non-vertical forces were kept at an angle of 15° from the vertical. Force levels of 25, 50, 100 and 200 N were exerted in each of the investigated directions. Data collected were analysed by means of a regression model for repeated measurements. It appeared that the mean power frequency (MPF) values of the posterior temporalis were significantly lower (P < 0·01) than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude (P < 0·001) whereas the MPF values of the anterior and posterior temporalis did not change significantly (P > 0·05). The MPF values were significantly influenced by the direction of bite force (P < 0·01). The observed changes of MPF are possibly related to the recruitment of different fibre types and support the concept that the masticatory muscles behave heterogeneously. [source] Differences in the fatigue of masticatory and neck muscles between male and femaleJOURNAL OF ORAL REHABILITATION, Issue 6 2002H. M. Ueda The purpose of this study was to investigate the nature of fatigue and recovery of masticatory and neck muscles and the differences between sexes in normal subjects during experimentally induced loading. Subjects consisted of eight males (mean age: 27·6 years) and eight females (mean age: 24·2 years) selected from the volunteers in the Faculty of Dentistry, Hiroshima University. The inclusion criteria for the subjects were as follows: (1) good general health, (2) normal horizontal and vertical skeletal relationships, (3) no severe malocclusions and (4) no complaints of temporomandibular disorders. Each subject was requested to bite an occlusal-force meter with 98, 196 and 294 N forces on the first molar region per side for 45 s. Activities of the masseter and sternocleidomastoid (SCM) muscles were recorded during these performances. Fatigue and recovery ratios were calculated with mean power frequency of power spectrum using a fast Fourier transform algorithm. Significant differences in the fatigue ratios between both sexes were found for the masseter muscle with 98, 196 and 294 N bite forces. Meanwhile, the SCM presented a significant difference between both sexes only at 98 N biting. Significant differences in the recovery ratios between both sexes were more prominent in the masseter muscle than in the SCM. These results suggest that the differences in muscle endurance between sexes may have some association with higher susceptibility of craniomandibular disorders in females than in males. [source] A freezing-like posture to pictures of mutilationPSYCHOPHYSIOLOGY, Issue 3 2005Tatiana M. Azevedo Abstract Postural sway and heart rate were recorded in young men viewing emotionally engaging pictures. It was hypothesized that they would show a human analog of "freezing" behavior (i.e., immobility and heart rate deceleration) when confronted with a sustained block of unpleasant (mutilation) images, relative to their response to pleasant/arousing (sport action) or neutral (objects) pictures. Volunteers stood on a stabilometric platform during picture viewing. Significantly reduced body sway was recorded during the unpleasant pictures, along with increased mean power frequency (indexing muscle stiffness). Heart rate during unpleasant pictures also showed the expected greater deceleration. This pattern resembles the "freezing" and "fear bradycardia" seen in many species when confronted with threatening stimuli, mediated by neural circuits that promote defensive survival. [source] | ||||||||||