Tove Østensvik1, Kaj Bo Veiersted, Petter Nilsen. 1. Department of Forest Resources, Norwegian Forest and Landscape Institute, Høgskoleveien 8, 1432 As, Norway. tove.ostensvik@skogoglandskap.no
Abstract
AIM: The purpose of this paper was to describe and evaluate different aspects of muscle activity patterns associated with musculoskeletal discomfort/pain. METHOD: Surface electromyography (sEMG) of the right upper trapezius and the right extensor digitorum muscles was conducted continuously during one working day in 19 male forest machine operators driving harvesters, 20 driving forwarders and 20 researchers at the Forest Research Institute. Perceived discomfort/pain in the right side of the neck and the right forearm was rated morning, noon and afternoon with Borg's CR-10 scale. Static, median and peak levels of muscle activity were analyzed and the number and total duration of EMG gaps (muscular rest) were calculated. Sustained low-level muscle activity (SULMA) was defined as continuous muscle activity above 0.5% of the maximal EMG activity quantified into 10 periods of predetermined duration intervals from 1.6 to 5s up to above 20 min. The number of SULMA periods is presented within each interval and as cumulative periods above the already determined levels. The operators handled control levers seated in a fixed position while the researchers performed mainly PC work and other varied tasks. RESULTS: A positive correlation was found between discomfort/pain in the right upper trapezius muscle region in the afternoon and cumulative SULMA periods above 10 min duration, and a negative correlation to cumulative SULMA periods also including the short durations. No specified patterns were found for discomfort/pain in the right extensor digitorum or for the other EMG measurements. All EMG measurements distinguished to some extent between the occupational groups, especially between machine operators driving harvesters and researchers. CONCLUSIONS: Number of SULMA periods longer than 10 min per hour was positively correlated, and predominantly short periods were negatively correlated, to complaints in the neck region. This seems promising in order to find duration limits for sustained low-level muscle activity as a risk factor for musculoskeletal disorders.
AIM: The purpose of this paper was to describe and evaluate different aspects of muscle activity patterns associated with musculoskeletal discomfort/pain. METHOD: Surface electromyography (sEMG) of the right upper trapezius and the right extensor digitorum muscles was conducted continuously during one working day in 19 male forest machine operators driving harvesters, 20 driving forwarders and 20 researchers at the Forest Research Institute. Perceived discomfort/pain in the right side of the neck and the right forearm was rated morning, noon and afternoon with Borg's CR-10 scale. Static, median and peak levels of muscle activity were analyzed and the number and total duration of EMG gaps (muscular rest) were calculated. Sustained low-level muscle activity (SULMA) was defined as continuous muscle activity above 0.5% of the maximal EMG activity quantified into 10 periods of predetermined duration intervals from 1.6 to 5s up to above 20 min. The number of SULMA periods is presented within each interval and as cumulative periods above the already determined levels. The operators handled control levers seated in a fixed position while the researchers performed mainly PC work and other varied tasks. RESULTS: A positive correlation was found between discomfort/pain in the right upper trapezius muscle region in the afternoon and cumulative SULMA periods above 10 min duration, and a negative correlation to cumulative SULMA periods also including the short durations. No specified patterns were found for discomfort/pain in the right extensor digitorum or for the other EMG measurements. All EMG measurements distinguished to some extent between the occupational groups, especially between machine operators driving harvesters and researchers. CONCLUSIONS: Number of SULMA periods longer than 10 min per hour was positively correlated, and predominantly short periods were negatively correlated, to complaints in the neck region. This seems promising in order to find duration limits for sustained low-level muscle activity as a risk factor for musculoskeletal disorders.
Authors: Allan Toomingas; Mikael Forsman; Svend Erik Mathiassen; Marina Heiden; Tohr Nilsson Journal: BMC Public Health Date: 2012-03-02 Impact factor: 3.295
Authors: Ryan J Marker; Jaclyn E Balter; Micaela L Nofsinger; Dan Anton; Nathan B Fethke; Katrina S Maluf Journal: Ergonomics Date: 2016-02-28 Impact factor: 2.561
Authors: Lars-Kristian Lunde; Markus Koch; Stein Knardahl; Morten Wærsted; Svend Erik Mathiassen; Mikael Forsman; Andreas Holtermann; Kaj Bo Veiersted Journal: BMC Public Health Date: 2014-10-16 Impact factor: 3.295