Biomedical subjects

G-A Hansson

Publications and source records attributed to G-A Hansson.

3 recordsLinked to original sources

PubMed2003

The impact of working technique on physical loads - an exposure profile among newspaper editors.

The aim of this study was to investigate the possible associations between working technique, sex, symptoms and level of physical load in VDU-work. A study group of 32 employees in the editing department of a daily newspaper answered a questionnaire, about physical working conditions and symptoms from the neck and the upper extremities. Muscular load, wrist positions and computer mouse forces were measured. Working technique was assessed from an observation protocol for computer work. In addition ratings of perceived exertion and overall comfort were collected. The results showed that subjects classified as having a good working technique worked with less muscular load in the forearm (extensor carpi ulnaris p=0.03) and in the trapezius muscle on the mouse operating side (p=0.02) compared to subjects classified as having a poor working technique. Moreover there were no differences in gap frequency (number of episodes when muscle activity is below 2.5% of a reference contraction) or muscular rest (total duration of gaps) between the two working technique groups. Women in this study used more force (mean force p=0.006, peak force p=0.02) expressed as % MVC than the men when operating the computer mouse. No major differences were shown in muscular load, wrist postures, perceived exertion or perceived comfort between men and women or between cases and symptom free subjects. In conclusion a good working technique was associated with reduced muscular load in the forearm muscles and in the trapezius muscle on the mouse operating side. Moreover women used more force (mean force and peak force) than men when operating the click button (left button) of the computer mouse.

Adult↗

PubMed2003

Influence of the subcutaneous fat layer, as measured by ultrasound, skinfold calipers and BMI, on the EMG amplitude.

Surface electromyography (sEMG) is an important tool to estimate muscular activity at work. There is, however, a great inter-individual variation, even in carefully standardized work tasks. The sEMG signal is attenuated in the subcutaneous tissues, differently for each subject, which requires normalization. This is commonly made in relation to a reference contraction, which by itself, however, introduces a variance. A normalization method that is independent of individual motivation, motor control and pain inhibition would be desirable. The aim of the study was to explore the influence of the subcutaneous tissue thickness on sEMG amplitude. Ultrasound measurements of the muscle to skin surface distance were made bilaterally over the trapezius muscle in 12 females. Skinfold caliper measurements from these sites, as well as from four other sites, were made, body mass index (BMI) was recorded, and sEMG was recorded at maximal and submaximal contractions. The muscle-electrode distance, as measured by ultrasound, explained 33% and 31% (on the dominant and non-dominant sides respectively) of the variance of the sEMG activity at a standardized submaximal contraction (average between the sides, 46%); for maximal contractions the explained variance was 21%. Trapezius skinfold measurements showed poor correlations with sEMG. Instead, the mean of skinfold measurements from other sites explained as much as 68% (submaximal contraction). The corresponding figure for BMI was 67%. In conclusion, skinfold thickness explains a major part of the inter-individual variance in sEMG amplitude, and normalization to this measure is a possibility worth further evaluation.

Adipose Tissue↗

PubMed2003

Modular data logger system for physical workload measurements.

Direct technical measurements of physical workload have advantages in studies of work-related musculoskeletal disorders. A data logger has been developed, based on 20 and 40 Mbyte PCMCIA (Personal Computer Memory Card International Association) flash memory cards, for electromyography (EMG), inclinometry and goniometry. They are provided with an input for marking of events that can be used for synchronization with other loggers and with video recordings. To make the data easier to access by the preceeding analysis software, application software has also been developed that reorganizes the data. The loggers are easy to operate and enable whole-day ambulatory field recordings without any need for reduction or compression of the data.

Electronic Data Processing↗