Biomedical subjects

Yung-Hui Lee

Publications and source records attributed to Yung-Hui Lee.

9 recordsLinked to original sources

PubMed2006

In-vehicle workload assessment: effects of traffic situations and cellular telephone use.

PROBLEM: Assessment of drivers' on-road workload is an important traffic safety consideration. This study was conducted to examine the effects of cellular phone communication on driving performance, with particular emphasis on variations in task demand in different traffic situations. METHOD: Twelve participants were asked to drive on urban roads and motorways with or without concomitant mathematical-addition tests relayed via cellular phone. Measurements included task and driving performance, physiological responses, and compensatory behavior. RESULTS: Analysis of task performance revealed that mean response time was markedly increased (11.9%) for driving on urban roads compared to motorways. The mean driving speed only decreased 5.8% in the presence of phone tasks in comparison to normal driving without distractions. In addition, overall physiological workload increased through compensatory behavior in response to the phone tasks. CONCLUSIONS: Driving with phone use in different traffic environments induced measurable variations in driver workload. IMPACT ON INDUSTRY: When faced with heavy traffic, a greater safety margin is typically adopted, with more lowered driving speed and restricted phone use, and it can be assumed that there is a general trade-off between tasks to preserve driving safety.

Adult↗

PubMed2005

Influence of heel height and shoe insert on comfort perception and biomechanical performance of young female adults during walking.

BACKGROUND: The possible negative effects of high-heeled shoes on subjective comfort perception and objective biomechanical assessment have been noted. Although shoe inserts have been widely applied in footwear to increase comfort and to reduce the frequency of movement-related injury, no study has attempted to identify insert effectiveness in high heels. The purpose of this study was to determine the effects of heel height and shoe inserts on comfort and biomechanics as represented by plantar pressure and ground reaction force (GRF). METHODS: Twenty young female adults performed the test conditions formed by the cross-matching of shoe inserts (shoe without insert and shoe with total contact insert [TCI]) and heel height (a flat, a low heel [3.8 cm] and a high heel [7.6 cm]). Two-way analyses of variance for repeated measures design were used to test condition effects on comfort rating, plantar pressure, and GRF during gait. To determine the biomechanical variables that can predict comfort, a multiple linear regression with stepwise method was done. RESULTS: The results showed that discomfort increased with heel height. In high heels, the plantar pressure in the heel and midfoot shifted to the medial forefoot, and the vertical and anteroposterior GRF increased. Use of the TCI reduced the peak pressure in the medial forefoot. Interestingly, the effectiveness of the TCI was greater in the higher heels than in the lower heels and in flat heels. The peak pressure in the medial forefoot, impact force, and the first peak vertical GRF could explain 75.6% of the variance of comfort in high-heeled gait. CONCLUSIONS: These findings suggest that higher heels result in decreased comfort, which can be reflected by both the subjective rating scale and biomechanical variables. Use of a TCI altered the biomechanics and therefore improved the comfort in high-heeled shoes.

Adult↗

PubMed2003

An investigation of stability limits while holding a load.

The objective of this study was to investigate the effects of load height and foot placement on the functional base of support (FBOS) limits and the postures that participants used when they reached their FBOS limits. Twelve young male participants were tested while holding a 12-kg load at reach (above their heads), at shoulder and knuckle height, and unladen under both wide and narrow foot placements. The FBOS limits and the centre of pressure (COP) excursion length were calculated based on data from a force platform. Postural angles when participants reached their FBOS limits were calculated from records of a 2-D motion analysis system. The results showed that the load height had greater effect on the posterior FBOS limit. As the load height decreased, the COP excursion length decreased. Participants were prone to using a hip strategy to maintain postural balance when reaching their FBOS limits. Quantitative data of FBOS limits and postural control while participants hold a load at various heights when reaching their FBOS limits is of value for designing a safe materials handling workplace.

Adolescent↗

PubMed2003

Inflight workload assessment: comparison of subjective and physiological measurements.

INTRODUCTION: Assessment of pilot workload during flight is an important aviation safety consideration. The aim of this study was to assess inflight pilot workload using both physiological and multidimensional subjective-ratings measurements (heart rate and NASA Task Load Index, respectively), comparing relative sensitivity during the four phases of flight: take-off, cruise, approach, and landing. METHODS: Ten male pilots volunteered to participate in the trials, which took place in a Boeing 747-400 flight simulator. Electrocardiography was performed throughout the test using the portable Cardiovis ECG system. Mean heart rate (HR) and incremental heart rate (delta HR) were considered indices of physiological workload. RESULTS: Peak HR was observed during take-off (83.2 bpm) and landing (88.6 bpm); moreover, delta HR was also greatest (14.2 bpm and 18.8 bpm). The Task Load Index (TLX) scale revealed that mental and performance demands were essential components of workload during flight. In addition, temporal demand was an important component of workload during take-off and physical demand was significant during cruise. Analysis of correlation revealed that the delta HR is significantly related to TLX scores (r = 0.81, n = 40). CONCLUSIONS: Management of the individual sources of stress, which tend to become predominant during different flight phases, should be emphasized in periodic recurrent training. For example, a pilot must be trained to cope with the increased temporal stresses associated with take-off. In addition, the recommendations will be concerned with maintaining vigilance, task allocation between pilots, and inflight rest during long-haul cruise.

Adult↗

PubMed2002

Factors in breathing maneuvers that affect trunk electromyogram during manual lifting.

STUDY DESIGN: A fully randomized experiment was conducted in a laboratory with a breath-by-breath monitor to control accurately the two factors of breathing maneuvers: breathholding duration and air volume within the thoracic cavity. OBJECTIVES: To resolve the controversy in previous reports about the effect of breathholding on the trunk electromyogram, and to verify the hypothesis that not only the factor of glottis closure, but also that of the air volume inside the thoracic cavity affects the trunk muscular activities during lifting. SUMMARY OF BACKGROUND DATA: Breathing was shown to affect spinal loading. However, there still is a debate about the effect of breathholding on trunk muscular activation during activities. It is possible that variations in air volume influence this effect. METHODS: Seven healthy, volunteer men participated in lifting tasks, in which lifting moment was standardized. Three breathing maneuvers were used: sustained breathholding with tidal volume of air, sustained breathholding with functional residual volume, and intended breath-nonholding involving inspiration within tidal capacity. Data on the surface electromyographic activation of the external oblique muscle, rectus abdominis, erector spinae, latissimus dorsi, air volume inside the cavity, and the duration of the one breath held in the last lift were collected and analyzed. RESULTS: Of the four muscles investigated, the breathing maneuvers affected only the external oblique muscle. The effect of sustained breathhold during lifting was the significantly increased activation of this muscle (P < 0.05). The effect of decreased air volume held was further increased activation. Intention to inspire normally during lifting decreased external oblique activation, but increased compensatory diaphragmatic effort, measured as inspiratory flow acceleration. CONCLUSIONS: Both the factors of the breathheld state and sustained air volume were verified to affect the external oblique activation during lifting. The current study emphasizes that both factors should be controlled in studies analyzing trunk electromyogram during activities. Otherwise, these breathing variations will be a confounding factor on electromyogram results.

Abdominal Muscles↗

PubMed2002

Human muscular and postural responses in unstable load lifting.

STUDY DESIGN: Most studies of manual material handling have focused on stable (fixed) loads. The muscular response during unstable load handling deserves more investigative attention. OBJECTIVES: To investigate muscular and postural responses during unstable load lifting, and to quantify the threat posed by such loads in the workplace. SUMMARY OF BACKGROUND DATA: Accurate assessment of load weight is important for lifters. Unfortunately, this information is not always available to individuals handling containers of liquids or shifting loads, or those encountering impact loading or a sudden unexpected load. METHODS: In this study, 12 subjects were subjected to time-variant loads, in which a box weighing 18 kg was used to generate a sudden 12 (kg. m)/second load impact internally during the lifting process. Responses were investigated as a function of different load-shift conditions (anterior-to-posterior and posterior-to-anterior rolling loads and stable load), two foot placements (wide and narrow stance), and two lifting techniques (stoop and squat). Normalized electromyography signals, joint angles, and total linear length for center of pressure (COP-length) were investigated. RESULTS: Lifting an unstable load significantly increases total lifting time, COP-length, and muscular contraction levels. When responding to impact momentum, subjects attempted to lift with greater elbow extension and shoulder and trunk flexion. A more flexed knee joint (approximately an additional 5 degrees ) was observed during preparation for load impact in the anterior-to-posterior rolling task, allowing the formation of a more stable platform to compensate for the load variation. The largest erector spinae contraction for unstable lifting was approximately 12% to 25% greater maximal voluntary contraction than for the stable analog. CONCLUSIONS: The normalized electromyography data demonstrate that the central nervous system detects and responds to the need to stabilize the joints closest to the location of load-shift perturbation.

Acceleration↗

PubMed2002

Effect of belt pressure and breath held on trunk electromyography.

STUDY DESIGN: This study examined the effect of a belt on ventilation and trunk muscle activities during repetitive lifting tasks with a control of breathing type and belt pressure. OBJECTIVES: To evaluate the effect of the lifting belt on the trunk muscle electromyography (EMG) and to parse out potential interaction between ventilatory changes and lifting belts. SUMMARY OF BACKGROUND DATA: Although both tensed thorax and compressed abdomen are considered to assist transferring the force from torso to pelvis in lifting, there has not been any consideration of the interaction between the two chambers in most published analyses. METHODS: Eleven male study participants participated in the study. They performed five minutes of paced repetitive squat lifts at frequencies of one or three lifts per minute, with loads of 10 or 25 kg. Belt pressure was set at 0 (no belt), 10, and 20 mm Hg. Study participants lifted with inspire-hold and expire-hold for a period of 5 minutes. Lift ventilation data and trunk muscle normalized electromyography (NEMG) (including rectus abdominis, external oblique, latissimus dorsi, and erector spinae) for the final lift were collected for analysis. RESULTS: The results indicate that the ventilation demand for lifting was not different with or without use of a belt. The prelifting erector spinae NEMG was 8-11% maximum voluntary contraction (MVC) lower and the latissimus dorsi NEMG was 15-21% MVC lower than that without belt. This is also the case in the lifting phase. The rectus abdominis NEMG was increased by 4% MVC and the external oblique NEMG was increased by 3-5% MVC while lifting with a belt. CONCLUSIONS: These data do not lead to a statistical effect of lifting belt pressure on ventilatory behavior. It appears that the use of a belt in lifting significantly decreased the back muscular activation yet increased the abdominal muscular activation. Thus, claims of benefits derived from the use of a belt in lifting remain controversial. The simultaneous controls of the air volume held and pressure of the belt during the moment-controlled lifting tasks allowed this presentation of belt effects on trunk muscle NEMG unique from that in most of the literature.

Abdomen↗

PubMed2002

Muscle response while holding an unstable load.

OBJECTIVE: Basic biomechanical measurement was applied to explore the physical risk associated with holding an unstable load. DESIGN: We investigated muscle response, before and after the initiation of the balance-recovery responses from perturbation when handling unstable loads. BACKGROUND: Most studies of muscle response and postural control during load handling focused on stable (fixed) loads. Investigation of muscle response while handling an unstable load deserves similar attention. METHODS: Twelve male subjects experienced time-variant loads (18 kg), with additional sudden 12 kgm/s impact momentum, under three different load-shift conditions (stable, posterior-to-anterior rolling, or anterior-to-posterior rolling load), and in three foot placements (straddle, wide, and narrow stance). Normalized electromyography (expressed as percentage of maximum voluntary contraction) for the brachioradialis, biceps, erector spinae, and hamstrings were measured. RESULTS: The maximal exertions for brachioradialis (91.0%) and biceps (42.5%) were observed approximately 0.1 s after posterior-to-anterior impact, with maximal measured contractions for erector spinae (57.2%) and hamstrings (59.9%) noted approximately 0.2 s after impact. CONCLUSIONS; The central nervous system detects and responds to the need to stabilize the joints close to the location of load-shift perturbation, with these responses determined according to the anatomical and functional limitation of each biomechanical link. RELEVANCE: Handling shifting loads, impact loading and sudden-unexpected loading may be more damaging to the musculoskeletal system than handling stable loads.

Adult↗

PubMed1998

Myo-electric behavior of the trunk muscles during static load holding in healthy subjects and low back pain patients.

OBJECTIVE: The purposes of this study were to examine coactivational activities of four trunk muscles in various static holding tasks, and to examine the differences of muscle activation patterns between normal subjects and low back pain (LBP) patients. DESIGN: We used an one-way analysis of variance (anova) with repeated measures to analyze the effect of the knee angles, trunk flexion angles, and loading conditions on the amount of EMG activity. BACKGROUND: Epidemiologic studies attribute a considerable proportion of the incidence of LBP to lifting-related injuries. The relationship between LBP and trunk muscles integrated electromyography (IEMG) is controversial. METHODS: Forty volunteer subjects with no experience of LBP and 47 LBP patients recruited from Chung-Gung Memory Hospital participated in this experiment. Surface IEMG signals of four right and left trunk muscles (rectus abdominis, external oblique, erector spinae, and latissimus dorsi) were obtained in static holding tasks. RESULTS: In knee flexion, LBP patients had significant IEMG pattern change than normal subjects. In trunk flexion and loading conditions, normal subjects had significant IEMG pattern change than LBP patients. CONCLUSIONS: Trunk muscle groups have different muscle coactivation patterns in functional posture of load holding. Using surface EMG can discriminate LBP patients from normal subjects.

Journal Article↗