Biomedical subjects

Marco J M Hoozemans

Publications and source records attributed to Marco J M Hoozemans.

9 recordsLinked to original sources

PubMed2006

The effect of joystick handle size and gain at two levels of required precision on performance and physical load on crane operators.

The study was designed to determine the effect of joystick handle size and (display-control) gain at two levels of required task precision on performance and physical load on crane operators. Eight experienced crane operators performed a simulated crane operation task on a computer by use of a joystick with either a short or a large handle. The task was performed at three gain levels and at two levels of required precision. Task performance, wrist and forearm postures, upper extremity muscle activity, perceived exertion and perceived comfort were measured.Task performance improved when using the joystick with the short handle and when working at a higher gain, while physical load decreased or remained the same. An increased level of required task precision was associated with a lower performance, but physical load was not affected. External validity of the simulated crane task seemed sufficient enough to extrapolate the results to practice.A joystick with a short handle is recommended, as this leads to an increased performance whilst the operator's physical load decreases or remains the same. Further optimization of performance and physical load can be achieved by optimizing gain settings of the joystick in relation to the task and type of joystick used.

Adult↗

PubMed2005

Workload of window cleaners using ladders differing in rung separation.

The objective of the present study was to compare energetic workload, perceived exertion, perceived discomfort, safety, and mechanical load at lower limb joints among window cleaners during usage of extension ladders with 30 and 35 cm rung separation. Eleven healthy male professional window cleaners of short and tall stature participated in this study. No significant differences between 30 and 35 cm rung separation were observed for the energetic workload. Results concerning the perceived exertion, discomfort, and safety indicate that 35 cm rung separation is preferred. Based on the mechanical load at the hip, knee, and ankle during ascending and descending the ladder, 30 cm rung separation is preferable to 35 cm rung separation. It is advised to climb ladders with the knees inside the side rails of the ladder, but this seems only possible with 35 cm rung separation. Findings of the presents study suggest that overall, a 35 cm rung separation is marginally favourable while using extension ladders.

Adult↗

PubMed2004

Prediction of handgrip forces using surface EMG of forearm muscles.

Evaluation of handgrip forces constitutes an essential component of ergonomic evaluation (e.g. of hand tools), but is difficult to perform at the workplace. The present study describes a series of experiments on 8 healthy male subjects to determine the validity of linear regression models using the surface electromyography (EMG) of up to 6 forearm muscles to predict handgrip forces. For isometric gripping tasks, normalized EMG to grip force calibrations using a series of dynamic force bursts up to 300 N resulted in a valid prediction of grip forces based on the EMG of 6 forearm muscles. Absolute differences between observed and predicted grip force were small (between 27 and 41 N) which shows that the proposed method might be used for the ergonomic evaluation of the use of hand tools. The EMG - handgrip force model appeared to be minimally affected by grip width, i.e. a model for 67 mm grip width was able to validly predict grip forces for 59 and 75 mm grip widths. Furthermore, it was shown that of the 6 forearm muscles studied at least 3 have to be assessed to arrive at a sufficient level of validity, while it seems to be irrelevant which 3 of those 6 forearm muscles are assessed.

Adult↗

PubMed2004

Mechanical loading of the low back and shoulders during pushing and pulling activities.

The objective of this study was to quantify the mechanical load on the low back and shoulders during pushing and pulling in combination with three task constraints: the use of one or two hands, three cart weights, and two handle heights. The second objective was to explore the relation between the initial and sustained exerted forces and the mechanical load on the low back and shoulders. Detailed biomechanical models of the low back and shoulder joint were used to estimate mechanical loading. Using generalized estimating equations (GEE) the effects were quantified for exerted push/pull forces, net moments at the low back and shoulders, compressive and shear forces at the low back, and compressive forces at the glenohumeral joint. The results of this study appeared to be useful to estimate ergonomics consequences of interventions in the working constraints during pushing and pulling. Cart weight as well as handle height had a considerable effect on the mechanical load and it is recommended to maintain low cart weights and to push or pull at shoulder height. Initial and sustained exerted forces were not highly correlated with the mechanical load at the low back and shoulders within the studied range of the exerted forces.

Adult↗

PubMed2004

Effectiveness of a multidisciplinary occupational training program for chronic low back pain: a prospective cohort study.

OBJECTIVE: To evaluate the effectiveness of a 12-wk multidisciplinary occupational training program for patients with chronic low back pain and to identify prognostic factors for treatment success. DESIGN: A total of 51 participants were evaluated at baseline, at discharge, and at 1 yr after conclusion of the program. The evaluation included a physical examination and assessment of functional disability, psychological factors, and coping styles. The main target of the program is full work resumption. The central outcome measures therefore are three variables on return to work. RESULTS: Analysis of variance for repeated measures revealed significant beneficial changes during the program for all measures except for several coping-style variables. The acquired level of maximum oxygen uptake, trunk flexibility, functional disability, and catastrophizing were maintained at 1-yr follow-up. At 1-yr follow-up, >60% of the participants had fully returned to work, which is an increase of >40% compared with baseline. Regression analyses showed that sex, age, the baseline values of reinterpretation of pain sensations, and functional disability and changes in trunk flexibility scores during the program are important prognostic factors for complete return to work. CONCLUSIONS: Based on the current findings, the program seems to be efficacious in the short term. Future attention must be directed toward maintaining these results, although work resumption rates improved considerably 1 yr after conclusion of the program.

Abdominal Muscles↗

PubMed2003

Effect of a redesigned two-wheeled container for refuse collecting on mechanical loading of low back and shoulders.

The objective of this study was to compare the mechanical and perceived workload when working with a redesigned two-wheeled container and working with a standard two-wheeled container for refuse collecting. The three changes in the design of the container were a displacement of the position of the centre of mass in the direction of the axis of the wheels, a slight increase in the height of the handle and a slight increase in the horizontal distance between the handle and the wheel-axis, and an increase in the diameter of the wheels. The volume of the container remained 0.240 m3. Nine refuse collectors performed some of their most frequent daily activities with both types of containers in the laboratory. Kinematics and exerted hand forces were assessed as input for detailed 3D biomechanical models of the low back and shoulder to estimate net moments at the low back and shoulders, compressive forces at the low back and contact forces at the glenohumeral joint. Also, the refuse collectors rated the ease of handling the two-wheeled containers on a five point scale. The use of the redesigned container resulted in a decrease of the exerted hand forces of 27%, decreases in the net moments at the low back and shoulders of 8% and 20%, respectively, and a decrease of 32% of the contact force at the glenohumeral joint when compared to the standard container. However, pulling an empty redesigned container on to the pavement resulted in an increase of the shoulder moment of more than 100%. No differences between container types were found for the compressive forces at the low back. Pushing and pulling with the redesigned container was rated as easier than pushing and pulling with the standard container. No differences in subjective ratings were found for the tasks of turning the container or pulling an empty container onto the pavement. It is concluded that, provided that empty containers are placed back onto the pavement as infrequently as possible, the introduction of the redesigned container could result in a reduction of the low back and shoulder load for refuse collectors.

Adult↗

PubMed2002

Evaluation of ergonomic adjustments of catering carts to reduce external pushing forces.

An existing standard catering cart was compared with two prototypes for pushbar and castor design. The first objective of this study was to find out which cart was accompanied with the lowest manually exerted external forces in pushing in a straight way and in pushing a 90 turn. The second objective was to explore effects of the pushbar and castor design of the carts. In the initial and ending phase, the prototypes were accompanied with higher exerted forces compared with the standard catering cart. In pushing straight. the reversed start position of the bigger castors of the prototypes hampered a fluent acceleration and caused higher initial forces. In decelerating, the lower rolling friction of the bigger castors required higher forces to stop the prototypes compared to the standard cart. During the sustained phase, the prototype carts were more favourable. Effects of pushbar and castor design were studied during a turn. The vertical pushbars of the prototypes resulted in lower time-integrated pushing forces. Providing an axis of rotation for turning activities by means of a fixed wheel was proven to be advantageous.

Adult↗

PubMed2002

Precision of estimates of mean and peak spinal loads in lifting.

A bootstrap procedure was used to determine the statistical precision of estimates of mean and peak spinal loads during lifting as function of the numbers of subjects and measurements per subject included in a biomechanical study. Data were derived from an experiment in which 10 subjects performed 360 lifting trials each. The maximum values per lift of the lumbar flexion angle, L5S1 sagittal plane moment, and L5S1 compression force were determined. From the data set thus compiled, 3000 samples were randomly drawn for each combination of number of subjects and number of measurements considered. The coefficients of variation of mean and peak (defined as mean plus 2 standard deviations) spinal loads across these samples were calculated. The coefficients of variation of the means of the three parameters of spinal load decreased as a linear function of the number of subjects to a power of about -0.48 and number of measurements to a power of about -0.06, while the corresponding powers for peak loads were about -0.44 and -0.11.

Analysis of Variance↗

PubMed2002

Low-back and shoulder complaints among workers with pushing and pulling tasks.

OBJECTIVES: Low-back and shoulder complaints were examined in relation to self-reported and objectively assessed exposure to work-related pushing and pulling. METHODS: Workers from several companies (eg, nursing homes and flower auctions) with pushing and pulling tasks and, as reference, workers without physically demanding tasks were invited to participate. Altogether 829 workers initially received a questionnaire, of whom 459 responded both initially and after 1 year of follow-up. Initially, self-reported exposure to pushing and pulling was assessed by questionnaire. Furthermore, a representative sample of 131 workers was observed at work using TRAC (task recording and analysis on computer) to assess exposure to pushing and pulling objectively. For exposure to pushing and pulling, the workers were classified into a reference group and medium and high exposure groups. Initially and in the follow-up, the 12-month prevalence of low-back and shoulder complaints was assessed. Complaints reported in the follow-up were separately used as dependent variables to calculate prevalence rate ratios (PR) in a Cox's proportional hazard regression analysis. RESULTS: The adjusted PR values were not significant for low-back complaints. For shoulder complaints, both the medium and high exposure groups showed significant adjusted PR values for self-reported exposure and observed duration of pushing and pulling when compared with the reference group (PR range 2.18-4.86). For the observed frequency of pushing and pulling, only the medium exposure group showed a significant PR, of 3.95. CONCLUSIONS: The findings suggest a rather strong relationship between pushing and pulling and shoulder complaints. The evidence for a relationship between pushing and pulling and low-back complaints is limited.

Adult↗