title: Changes in interstitial noradrenaline, trapezius muscle activity and oxygen saturation during low-load work and recovery.
abstract: Both physical as well as mental demands result in an increased activity in the sympathetic nervous system (SNS) with changes in blood-pressure and heart-rate. Through local release of catecholamines, e.g. noradrenaline (NAd) SNS exerts various actions at the muscle level. The aims of this study were to investigate the effects of low-load repetitive work alone and in combination with mental demands on local muscle interstitial noradrenaline concentration [NAd](i), muscle activity and oxygenation, assessed with microdialysis, surface electromyography, and near-infrared spectroscopy, respectively. Healthy females (n = 15) were exposed to (1) 30 min repetitive work (RW) and (2) 30 min repetitive work with superimposed mental load (RWML) on two different occasions. Muscle [NAd](i) and muscle activity increased significantly in response to RW, but did not increase further during RWML. For RW, [NAd](i) was found to be inversely correlated to muscle activity. Oxygenation decreased significantly during work, independently of occasion. Our findings indicate that low-load work causes significantly increased trapezius muscle [NAd](i) in healthy females, and short periods of superimposed mental load do not add to this increase and further, that both muscle activity and oxygenation were unaffected by the superimposed mental load.
authors.affiliation: Centre for Musculoskeletal Research, University of Gävle, Box 7629, Umeå 907 12, Sweden. gerd.flodgren@hig.se
authors.forename: Gerd M
authors.initials: GM
authors.lastname: Flodgren
authors.forename: A G
authors.initials: AG
authors.lastname: Crenshaw
authors.forename: M
authors.initials: M
authors.lastname: Gref
authors.forename: M
authors.initials: M
authors.lastname: Fahlström
mesh_terms: D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology; D016526:Workload; D055815:Young Adult
chemical_list: D009638:Norepinephrine