The measurement of meaning

The aim of this study was to analyze electromyography (EMG) responses of vastus lateralis muscle to different whole-body vibration frequencies. For this purpose, 16 professional women volleyball players (age, 23.9 6 3.6 years; height, 182.5 6 11.1 cm; weight, 78.4 6 5.6 kg) voluntarily participated in the study. Vibration treatment was administered while standing on a vibrating platform with knees bent at 1008 (Nemes Bosco-system, Rome, Italy). EMG root mean square (rms) and was recorded for 60 seconds while standing on the vibrating plate in the following conditions: no vibrations and 30-, 40-, and 50-Hz vibration frequencies in random order. The position was kept for 60 seconds in each treatment condition. EMGrms was collected from the vastus lateralis muscle of the dominant leg. Statistical analysis showed that, in all vibration conditions, average EMGrms activity of vastus lateralis was higher than in the no-vibration condition. The highest EMGrms was found at 30 Hz, suggesting this frequency as the one eliciting the highest reflex response in vastus lateralis muscle during whole-body vibrations in half-squat position. An extension of these studies to a larger population appears worthwhile to further elucidate the responsiveness of the neuromuscular system to whole-body vibrations administered through vibrating platforms and to be able to develop individual treatment protocols.

/pdf/electromyography-activity-of-vastus-lateralis-muscle-during-3415pwbxdz.pdf

Electromyography activity of vastus lateralis muscle during whole-body vibrations of different frequencies

Summary This randomized cross-over study was designed to investigate the effects of a 4-min vibration bout on muscle performance and body balance in young, healthy subjects. Sixteen volunteers (eight men, eight women, age 24‐33 years) underwent both the 4-min vibration- and sham-interventions in a randomized order on different days. Six performance tests (stability platform, grip strength, isometric extension strength of lower extremities, tandem-walk, vertical jump and shuttle run) were performed 10 min before (baseline), and 2 and 60 min after the intervention. The effect of vibration on the surface electromyography (EMG) of soleus, gastrocnemius and vastus lateralis muscles was also investigated. The vibration-loading, based on a tilting platform, induced a transient (significant at the 2-min test) 2AE5% net benefit in the jump height (Pa 0AE019), 3AE2% benefit in the isometric extension strength of lower extremities (Pa 0AE020) and 15AE7% improvement in the body balance (Pa 0AE049). In the other 2-min or in the 60-min tests, there were no statistically significant differences between the vibration- and sham-interventions. Decreased mean power frequency in EMG of all muscles during the vibration indicated evolving muscle fatigue, while the root mean square voltage of EMG signal increased in calf muscles. We have shown in this study that a single bout of whole body vibration transiently improves muscle performance of lower extremities and body balance in young healthy adults.

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Effect of a vibration exposure on muscular performance and body balance. Randomized cross-over study

Roelants, M,, S,M,P, Verschueren, C, Delecluse, O, Levin, and V. Stijnen, Whole-body-vibration—induced increase in leg muscle activity during different squat exercises, J. Strength Cond. Res. 20(l):124-129. 2006,—This study analyzed leg mus- cle activity during whole-body vibration (WBV) training. Sub- jects performed standard unloaded isometric exercises on a vi- brating platform (Power Plate): high squat (HS), low squat (LS), and 1-legged squat (OL), Muscle activity of the rectus femoris, vastus lateralis, vastus medialis, and gastrocnemius was record- ed in 15 men (age 21,2 ± 0,8 years) through use of surface elec- tromyography (EMG), The exercises were performed in 2 con- ditions: with WBV and without (control (CO)) a vibratory stim- ulus of 35 Hz, Muscle activation during WBV was compared with CO and with muscle activation during isolated maximal volun- tary contractions (MVCs), Whole-body vibration resulted in a significantly higher (p < 0,05) EMG root-mean-square compared with CO in all muscle groups and all exercises (between -1-39,9 ± 17,5% and +360,6 ± 57,5%), The increase in muscle activity caused by WBV was significantly higher (p < 0,05) in OL com- pared with HS and LS, In conclusion, WBV resulted in an in- creased activation of the leg muscles. During WBV, leg muscle activity varied between 12,6 and 82,4% of MVC values.

http://www.luzimarteixeira.com.br/wp-content/uploads/2015/07/WHOLE-BODY-VIBRATION.pdf

Whole-body-vibration--induced increase in leg muscle activity during different squat exercises

The aim of this review was to examine the physiological effects of vibration exercise (VbX), including the cardiovascular indices and to elucidate its potential use for those with compromised health. VbX has long been acknowledged as a potential modality in sport, exercise, and health sectors. Muscle force and power have been shown to increase after VbX for athletes, the aged and those with diseases, where neural factors are thought to be the main contributor. Further, similarities to the tonic vibration reflex have been used to propose that the muscle spindle plays a role in activating the muscle which could benefit those with compromised health. There is strong evidence that acute VbX can enhance upper and lower-body muscle power, and there is some indication that longer-term VbX can augment muscle power of upper and lower body extremities, although this is less convincing. It is not conclusive whether VbX increases force attributes. This has been fraught by the type and parameters used for various muscle contractions, and the different sample populations that have varied in chronological age, experience and training status. VbX provides an insufficient stimulus to enhance cardiovascular indices, where VbX cannot increase heart rate to the same extent as conventional aerobic exercise. But when conventional aerobic exercise is not possible, for example, in aged, cardiovascular compromised persons, VbX could be implemented at an early stage because it could provide a safe induction of a slight elevation of cardiovascular function indices while providing neural and myogenic benefits. In conclusion, VbX is a safe modality to increase physiological responses of reflex and muscle activity, and muscle function, for athletes, the aged and compromised health. However, further research should focus on the optimum dose relationship of frequency, amplitude and duration for the various populations.

/pdf/the-potential-neural-mechanisms-of-acute-indirect-vibration-3lp4j3orhx.pdf

The potential neural mechanisms of acute indirect vibration.

The influence of vibration frequency (40, 80, 100, 120, 150, or 200 Hz) at selected displacement amplitudes (0.2, 0.3 mm) on tonic vibration reflex (TVR) characteristics was investigated. The degree of synchronization of motor unit activity with vibratory stimuli in ten humans was determined using the electromyographic (EMG) activity of the finger and wrist flexor muscles when vibration was applied to the distal tendons of the hand flexor muscles. The EMG spectral analysis indicates that harmonic and subharmonic motor unit synchronization mechanisms contribute to the modulation of the amplitude of the TVR as the vibration frequency increases. Harmonic synchronization decreases while subharmonic synchronization increases as vibration frequency increases. It is suggested that the synchronization process influences muscle fatigue, since it forces the driving of motor units, leading to a decrease in contraction efficiency. This phenomenon most probably results from an impairment of excitation-contraction coupling. High-frequency vibration (>150 Hz) tends to induce less motor unit synchronization in a frequency range beyond the known mechanical resonance of biological tissues. The findings of this study may be applied to the design of hand-held power tools, since their vibration triggers the TVR in active muscles.

/pdf/analysis-of-the-tonic-vibration-reflex-influence-of-2vdqnexyot.pdf

Analysis of the tonic vibration reflex: influence of vibration variables on motor unit synchronization and fatigue

Generative CAPP through projective feature recognition

This study shows a way to develop web design guidelines through the quality function deployment (QFD) approach. The voice of the customer (VOC) and design elements were collected from a group of users and web design experts. Design elements that have an impact on the search performance and subjective sensibility of the users were identified. Desirable levels of several design elements were then investigated by experiments. To quantify the effects of the design elements on the search performance and subjective sensibility of the users, simulators were designed and used in experiments. Performance tests showed that the location of the table of contents and the method of menu display have significant influence on the search time. Sensibility assessment tests showed that brighter background makes the users feel more comfortable. Yellow header and scanning column makes users feel the page has simplicity and sensibility, while blue or green make the users feel balanced. The text style does not have an impact on...

Enhancement of web design quality through the QFD approach

Work-related musculoskeletal disorders (WMSDs) refer to a collection of painful disorders of muscles, nerves, tendons, ligaments, joints, cartilage, or spinal discs that are caused or made worse by work conditions. The physical risk factors of WMSDs include: repetitive, forceful, or prolonged exertions; frequent or heavy lifting; pushing, pulling, or carrying of heavy objects; prolonged awkward postures; and vibration. Jobs or working conditions that combine risk factors may increase the risk of WMSDs. Although the physical risk factors are important ones, there are also plausible factors that may provoke a disorder or indirectly influence other risk factors, such as organizational and psychosocial factors. Individual factors may also influence the degree of risk from specific exposures. In many industrialized countries, WMSDs have become a major problem of occupational health, and are the leading causes of lost-time. In Korea, the number of WMSDs compensations has drastically increased from 128 in 1995 to 4,112 in 2004, the latter number representing 44.8% of total occupational disease compensations. In Korea, the societal attention to WMSDs has grown much since the national economic crisis of 1998. At the end of 1997, the Korean economy fell into a crisis triggered by a shortage of foreign exchange, and Korea had to receive IMF’s (International Monetary Fund) relief aid in 1998. After that, Korea has been struggling not only to reform its monetary system, but also to promote drastic reforms in its economic structure with the aim of improving the productivity of Korean industry. However, it is widely perceived in Korea that the economic crisis caused changes in the work environment due to downsizing of work forces and increased work load. The objective of this survey was to study how Korean workers’ perceived the changes in their work environment during the post-IMF period of 2001–2003, and to investigate if there is any relation between the perception of changed working conditions and the occurrence of WMSDs. Workers at a major automotive company in Korea were studied for this purpose.

http://joh.sanei.or.jp/pdf/E49/E49_2_10.pdf

Workers' perception of the changes of work environment and its relation to the occurrence of work-related musculoskeletal disorders.

The objective of this paper is to report how workers' actively participate in a participatory ergonomics (PE) program, and how this program resulted in improved working conditions and decreased occurrence of work-related musculoskeletal disorders (WMSDs). A major tire manufacturing company in Korea was studied. Most of the activities in the PE program were designed and actually practiced by the workers and their union. The results revealed some positive effects of applying a PE program to the employees. It was shown that incidence of the WMSDs as well as the lost work days and the economic cost incurred by the WMSDs decreased with the PE program.

/pdf/case-on-a-union-driven-participatory-ergonomics-program-to-2hh4jtb4wo.pdf

Hee-Sok Park

Papers

Analysis of the tonic vibration reflex: influence of vibration variables on motor unit synchronization and fatigue

Generative CAPP through projective feature recognition

Enhancement of web design quality through the QFD approach

Workers' perception of the changes of work environment and its relation to the occurrence of work-related musculoskeletal disorders.

Case on a union-driven participatory ergonomics program to control work-related musculoskeletal disorders in Korea