Biomedical subjects

S Kihlberg

Publications and source records attributed to S Kihlberg.

8 recordsLinked to original sources

PubMed1997

Hand-arm symptoms related to impact and nonimpact hand-held power tools.

Hand and arm symptoms among workers using impact and non-impact hand-held power tools were investigated in a cross-sectional study and a 5-year follow-up study. The study population consisted of concrete workers (n = 103), truck assemblers (n = 234), electricians (n = 101), platers (n = 140) and lumberjacks (n = 102). Of the original 680 subjects, we followed up 312 after 5 years. A questionnaire concerning ongoing hand and arm symptoms, daily exposure to hand-held power tools, type of tool used, and individual factors was administered. More workers using low-frequency impact tools than workers using non-impact tools reported symptoms in the elbows and shoulders. Elbow symptoms were accentuated in the cross-sectional study, while shoulder symptoms were accentuated in the follow-up study. Wrist symptoms were reported by more of those working with high-frequency impact tools than of those using only non-impact tools when the analyses were controlled for age, years in the occupation and smoking habits. A possible explanation of the results found in this study is that low-frequency impact vibration is transmitted to the upper arm, and thus the elbow and shoulder are at risk, while high-frequency impact vibration is attenuated in the hand and wrist and may predominantly cause symptoms there.

Arm Injuries↗

PubMed1995

Acute effects of vibration from a chipping hammer and a grinder on the hand-arm system.

OBJECTIVES: The purpose of this study was to compare various effects on the hand-arm system of vibration exposure from a chipping hammer and a grinder with the same frequency weighted acceleration. Grip and push forces were measured and monitored during the exposure. The various effects were: muscle activity (measured with surface electrodes), discomfort ratings for different parts of the hand-arm system (made during and after exposure), and vibration perception threshold (for 10 minutes before and 10 minutes after the exposure). RESULTS: No increase in muscle activity due to exposure to vibration was found in the hand muscle studied. In the forearm, conversely, there was an increase in both muscle studied. For the upper arm the muscle activity only increased when exposed to impact vibration. Subjective ratings in the hand and shift in vibration perception threshold were effected more by the grinder than the hammer exposure. CONCLUSION: These results show that the reaction of the hand-arm system to vibration varies with frequency quantitatively as well as qualitatively. They do not support the notion that one single frequency weighted curve would be valid for the different health effects of hand-arm vibration (vascular, musculoskeletal, neurological, and psychophysiological).

Adult↗

PubMed1994

Reaction forces, tool handle displacements and discomfort ratings during work with shut-off nutrunners.

Reaction forces, hand-arm displacement and subjective ratings were studied during securing of threaded fasteners with nine right-angle nutrunners. The nutrunners had three different preset spindle torques and three different shut-off mechanisms. The tools were tested according to the international ISO method and with a method proposed by the authors in a previous study. Twelve male subjects participated in the study. A force platform measured the reaction forces between the subjects and the floor. Motions of the hand-arm system and shoulder were measured with an optoelectronic measuring system and a goniometer. Strong correlations between motions/ ground reaction forces and ratings were found. The ratings were also strongly correlated with the tool torque impulse, calculated according to ISO 6544, as well as with the time for which the torque exceeded 75% of the preset spindle torque multiplied by the preset spindle torque to produce a 'time-torque value'. The strongest correlation, though, was found with the time-torque value, but the difference was not large enough to propose a change of the ISO standard.

Journal Article↗

PubMed1994

Impaired nerve conduction in the carpal tunnel of platers and truck assemblers exposed to hand-arm vibration.

OBJECTIVES: The goal of this study was to assess the relative risks of sustaining impaired nerve conduction in the hands among vibration-exposed persons as opposed to nonvibration-exposed referents. METHODS: In a cross-sectional study design platers and truck assembly workers were contrasted to office workers. The 4-h frequency-weighted vibration was 4.6 m.s-2 and 1.0 m.s-2 for the platers and assemblers, respectively. The ergonomic factors were measured as forced grip time. The conduction velocity, distal latency time, and amplitude of the median nerve were measured for both hands. RESULTS: The sensory nerve conduction velocity was slower in the right hand than in the left. An increased risk of prolonged latency time was found for the platers and assemblers when contrasted to the office workers. The relative risks (rate ratios) of impaired nerve conduction for the carpal tunnel segment varied between 1.4 and 2.0 for the distal latency and between 0.9 and 1.7 for the nerve conduction velocity. The rate ratios were generally higher for the left-hand side than for the right-hand side. The risks were not proportional to either the weighted or unweighted vibration exposure. CONCLUSIONS: The contributions from vibration and ergonomic factors to impaired nerve conduction velocity were inseparable in this study. Ergonomic factors such as forceful gripping and extreme positions, apart from vibration exposure, may be strong determinants of impaired nerve conduction in the carpal tunnel area.

Adult↗

PubMed1993

Pneumatic tool torque reaction: reaction forces, displacement, muscle activity and discomfort in the hand-arm system.

Reaction forces, hand-arm displacement, muscle activity and discomfort ratings were studied during the securing of threaded fasteners with three angle nutrunners with different shut-off mechanisms, but with the same spindle torque (72-74 Nm). The three tools were tested according to the method specified in ISO 6544. One of the tools had an almost instantaneous shut-off. Another had a more slowly declining torque curve. For the third tool the maximum torque was maintained for a while before shut-off. Twelve male subjects participated in the study. A force platform measured the reaction force between the subject and the floor. The option of the hand-arm system and the shoulder was measured with an optoelectronic measuring system. The muscle activity (EMG) in six muscles in the arm and shoulder was measured with surface electrodes. Significant differences in the arm movements and ground reaction forces were found between the three tools. The smallest values were found with the fast shut-off tool while the delayed shut-off tool caused the largest values. The EMG measures gave inconsistent response patterns. Discomfort ratings were highly correlated with the time for which the tool torque exceeded 90% of peak preset torque, but the time for which the tool torque exceeded 90% of peak calculated by the method specified in ISO 6544. Nutrunners with a shut-off mechanism that causes a slowly decreasing torque or a torque that is maintained for a while before shut-off should be avoided. If no substitutes are available, then a torque reaction bar should be mounted on the tool.

Journal Article↗

PubMed1991

Outcome of the abduction external rotation test among manual and office workers.

Reactions during the Abduction External Rotation (AER) test were studied among 71 platers and 70 assemblers exposed to vibratory tools and manual work and 45 unexposed white collar workers. The frequency of positive neurological reactions was 31% among the platers, 6% among the assemblers, and 16% among the white collar workers. Platers reported the highest fatigue rates in the shoulder regions during the test. A positive association was noted between a pathological AER test and current problems in the neck/scapula or shoulder/upper arm regions, day- or night-time numbness in the hands, tension neck, and carpal tunnel syndrome. Age, length of daily vibration exposure, and vibration acceleration level were also positively associated with a positive AER test outcome. The results indicate that the outcome of the AER test is sensitive to neck and shoulder disorders but also, to some extent, to the carpal tunnel syndrome.

Adult↗

PubMed1987

Vibration in car repair work.

The main objective of the study was to find efficient hand tools which caused only minor vibration loading. Vibration measurements were carried out under standardised working conditions. The time during which car body repairers in seven companies were exposed to vibration was determined. Chisel hammers, impact wrenches, sanders and saws were the types of tools which generated the highest vibration accelerations. The average daily exposure at the different garages ranged from 22 to 70 min. The risk of vibration injury is currently rated as high. The difference between the highest and lowest levels of vibration was considerable in most tool categories. Therefore the choice of tool has a major impact on the magnitude of vibration exposure. The importance of choosing the right tools and working methods is discussed and a counselling service on vibration is proposed.

Journal Article↗

PubMed1983

A test rig for the measurement of vibration in hand-held power tools.

The purpose of the present project was to study the possibility of using a test rig for the measurement of vibration and noise from hand-held power tools. A test rig was designed to give the same effect on tool handle vibration as the human hand/arm system. Work was simulated by feeding the material to be processed against the tool, clamped into the rig, with the aid of a co-ordinate table. It was designed for use in studies of impact drills, chain saws, grinders and similar power tools. The report describes a proposal for testing the vibration properties of impact drills. Drilling with the test rig was compared with manual drilling. The difference in the acceleration level between the two methods was about 1 dB for ISO-weighted values in the critical direction. Both methods showed good reproducibility. The possibility of conducting noise level tests of a power tool in the rig was studied and the results are reported separately.

Journal Article↗