Biomedical subjects

Tzu-Hsien Lee

Publications and source records attributed to Tzu-Hsien Lee.

13 recordsLinked to original sources

PubMed2006

Maximum acceptable weight of manual load carriage for young Taiwanese males.

This study examined the maximum acceptable weight of carriage (MAWC) for young Taiwanese males experienced in manual load carriage tasks. The elements of the examined load carriage tasks included lifting a box from the floor to the waist height, turning around while holding the box, carrying the box at the waist height for a distance, lowering the box to the floor, turning around, and walking unloaded back to the original position. Subjects performed the load carriage tasks over different levels of carriage distance, frequency, box width (sagittal dimension), and handle according to a response surface design. The results showed that subjects' MAWC decreased with carriage distance, frequency and box width, while heart rate and rate of perceived exertion (RPE) increased with carriage distance, frequency and box width. The MAWC for box with handles was on average 1.5 kg more than that for box without handles, while the effects of handle on heart rate and RPE were very trivial.

Adult↗

PubMed2005

Maximum isoinertial lifting capabilities for different lifting ranges and container dimensions.

The aim of this study was to examine the effects of lifting range and container dimension on human maximum isoinertial lifting capability in the sagittal plane. Ten young and experienced lifters were tested for their maximum isoinertial lifting capabilities for 12 different lifting conditions (three lifting ranges x four container dimensions). The results showed that lifting range and container dimension significantly affected human maximum isoinertial lifting capability. The order for the highest to lowest lifting capability for the three lifting ranges was FK (from floor to knuckle height, 0-74 cm), FS (from floor to shoulder height, 0-141 cm) and KS (from knuckle height to shoulder height, 74-141 cm) regardless of the container dimension, and for the four container dimensions was 50 x 35 x 15 cm(3), 70 x 35 x 15 cm(3), 50 x 50 x 15 cm(3) and 70 x 50 x 15 cm(3) regardless of the lifting range. The mean(SD) maximum isoinertial lifting capability ranged from 29.3(3.3) kg for the combination of KS range and 70 x 50 x 15 cm(3) container to 53.2(5.7)kg for the combination of FK range and 50 x 35 x 15 cm(3) container. The results of this study can help our knowledge of human maximum isoinertial lifting capability and designing the upper limit of lifting weight.

Adult↗

PubMed2005

Lifting strengths in different horizontal distances of objects to be lifted.

This study recruited eleven healthy males and thirteen healthy females to examine their maximum two-handed isometric back lifting strength, upper-body lifting strength, arm lifting strength and shoulder lifting strength in three different horizontal distances of objects to be lifted (toes were anterior to, aligned with, and posterior to the exerted handle). The results showed that human lifting strength decreased significantly as the toe position shifted from anterior of the vertical plane of the exerted handle to posterior of the vertical plane of the exerted handle. The strength order relationship between back lifting strength and upper-body lifting strength was dependent on the horizontal distance of objects to be lifted. This study also observed that the effects of the horizontal distance of objects to be lifted on human lifting postural angles for the four assessed lifting types mainly occurred in the upper extremities. This study recommends that practitioners should not overlook the effects of the horizontal distance of objects to be lifted on lifting strength when evaluating workers' lifting strength for screening purposes.

Adult↗

PubMed2005

Ergonomic comparison of operating a built-in touch-pad pointing device and a trackball mouse on posture and muscle activity.

This study examined the effects of operating a built-in touch-pad pointing device and a trackball mouse on participants' completion times, hand positions during operation, postural angles, and muscle activities. 8 young men were asked to perform a cursor travel task on a notebook computer using both 60- and 80-cm high table conditions. Analysis showed that the trackball mouse significantly decreased completion times. Participants selected a hand position farther from the table edge and larger elbow angle for the trackball mouse than for the built-in touch-pad pointing device. Participants' neck, thoracic, and arm angles, or splenius capitis, trapezius, deltoid, and erector spinae muscle activities were not significantly affected by the devices, but table height significantly affected participants' completion times, hand positions, and postural angles.

Adolescent↗

PubMed2005

Psychophysically determined asymmetrical lifting capabilities for different frequencies and containers.

Ten young male participants were tested their psychophysically determined 4-h maximum acceptable weight of lifting (MAWL) of 90-degree asymmetric lifting for three lifting frequencies (1 lift/min, 2 lifts/min, 4 lifts/min) and three lifting containers (50 x 35 x 15 cm, 70 x 35 x 15 cm, 50 x 50 x 15 cm). The results showed that the MAWL decreased with increasing frequency and container width or length dimension, while the interaction effect of frequency and container on MAWL was not significant. The MAWL ranged from 13.7 kg to 18 kg for the nine (3 frequencies x 3 containers) lifting conditions. When averaged across the levels of the other independent variable, the MAWL decreased by 7.4% and 16.1% for 2 lifts/min and 4 lifts/min as compared with the MAWL of 1 lift/min, respectively, and decreased by 1.6% and 9.4% for 70 x 35 x 15 cm and 50 x 50 x 15 cm as compared with the MAWL of 50 x 35 x 15 cm, respectively. Additionally, the discrepancies between the MAWL data and the recommended weight limits derived from the revised NIOSH equation were discussed.

Adult↗

PubMed2004

Maximum isometric lifting strengths of men in teamwork.

This study reexamined the additivity of maximum isometric teamwork lifting strength using experienced and height-matched young male participants. The maximum isometric lifting strength was measured for four exertion heights (45, 75, 105, and 140 cm) and four lifting styles (one-, two, three-, and four-person exertions). The results showed that actual teamwork strength could be greater or lower than the sum of individual strengths. If it was greater, the difference between the two could be either significant or nonsignificant, but if it was lower, there was no significant difference between the two. Actual teamwork strength ranged from 90.0% to 134.8% of the sum of individual strengths, indicating that experienced and height-matched participants could overcome the problem of lack of coordination in isometric teamwork lifting. The results also showed that some teamwork members, especially weaker members, might be forced to exert strengths higher than their maximum individual voluntary strengths in teamwork lifting. To avoid such overexertion in teamwork, it is recommended that the weight of the handled load be controlled and lower than the sum of all members' strengths. Additionally, members with significantly different strength abilities should not be assigned to the same team. Actual or potential applications of this research include designing member assignments in teamwork lifting tasks.

Adult↗

PubMed2004

Human pulling strengths in different conditions of exertion.

This study tested 29 young Taiwanese men and 31 young Taiwanese women to examine the effects of pulling type (one-handed and two-handed) and height (48 cm, 84 cm, 120 cm, and 156 cm) on maximum horizontal isometric pulling strengths. Analysis showed differences in pulling strength between one-handed and two-handed efforts were surprisingly small for free pulling postures. The pulling strength decreased significantly with pulling height. The highest pulling strength was approximately two to three fold the lowest pulling strength across the four pulling heights. The women's pulling strength was approximately 59% to 67% of men's pulling strength. The test-retest correlations for pulling strength were satisfactory. The correlations between pulling strength and subjects' anthropometry were not sufficiently high to justify the prediction of strength. Most correlations between strengths in any two different pulling conditions were high and significant.

Adult↗

PubMed2004

Lifting strengths in different exertion heights conditioned on extended legs.

This study recruited seven height-matched healthy males to examine their maximum isometric lifting strengths across 13 exertion heights, ranging from 25 cm to 133 cm in increment of 9 cm. The results showed a nonlinear (increasing-decreasing-increasing) strength-height relationship for all subjects. The subjects' lifting strength was strongest (mean 1253.2 N) at the exertion height of 61 cm and weakest (mean 454.1 N) at the exertion height of 115 cm. Due to a large variability of strength ratio for the weakest individual strength to the strongest individual strength across the 13 exertion heights, ranging from 59.6% to 83.7%, practitioners should be cautious when assessing workers' lifting capacity based on strength testing.

Body Height↗

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

Minimal acceptable handling time intervals for lifting and lowering tasks.

A laboratory study was conducted to determine the minimal acceptable handling time interval (MAHTI) for 4 h of endurance manual materials handling tasks using a psychophysical approach. Nine experienced male subjects were recruited to perform manual materials handling tasks with three load weights (10, 15, and 20 kg) and six ranges (floor to knuckle, FK; knuckle to floor, KF; knuckle to shoulder, KS; shoulder to knuckle, SK; floor to shoulder, FS; shoulder to floor, SF). Subjects were asked to adjust the handling time interval to the minimum that they could perform without becoming strained, uncomfortable, tired, weakened, overheated, or out-of-breath for 4 h of the endurance handling period. The results showed that the heavier load produced a larger MAHTI, and the overall descending sequence of MAHTI values for the six ranges was FS, KS, SF, FK, KF, and SK. The MAHTI for each lifting task was significantly higher than that of its corresponding lowering task (p<0.05). All MAHTI data were further verified by tests run on an additional nine subjects; this showed that the psychophysically determined MAHTIs were appropriate with no apparent underestimation.

Adult↗

PubMed2003

Maximum acceptable weight of lift for asymmetric lifting.

10 undergraduate men were tested to determine the effects of lifting mode and frequency on psychophysically established maximum acceptable weight of lift for 4 hr. of work. The heart rate and rate of perceived exertion (RPE) of the individuals while lifting the maximum acceptable weight of lift were measured. When performing a 90 degrees asymmetric lifting, subjects lifted approximately 10% less weight than lifted in symmetric lifting. Nonsignificant differences in maximum acceptable weight of lift, heart rate, and RPE values were found between asymmetric lifting with trunk rotation and asymmetric lifting with leg rotation. The lifting frequency significantly affected the maximum acceptable weight of lift, heart rate, and RPE. Heart rate and RPE increased with lifting frequency. The maximum acceptable weight of lift at 2 lifts/min. and 4 lifts/min. were approximately 91.5% and 82.5% of that of 1 lift/ min., respectively.

Adult↗

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

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↗