Pernille Nielsen | University College Capital (original) (raw)

Papers by Pernille Nielsen

Clinical Biomechanics, 2000

Objective. To develop and validate a method, based on quantitative ultrasound image analysis, to ... more Objective. To develop and validate a method, based on quantitative ultrasound image analysis, to objectively analyse and characterize the ultrasound images of m. supraspinatus. Design. Quantitative ultrasonography was performed on the supraspinatus muscle of 14 healthy subjects. Methods. A computerized analysis using ®rst-order grey-scale statistics to evaluate the muscle tissue composition was developed and validated. Results. Data from one scanning site were not representative for the whole muscle due to muscle inhomogenity. Using ®rst-order grey-scale statistics the scanning direction was of no importance. By using a scanning session consisting of three dierent scanning sites along the muscle in two directions, longitudinally and transversely, to characterize the tissue composition of the muscle, a high day-today reproducibility was obtained. Conclusion. The described scanning session is a relatively sensitive and reproducible method for studying the muscle tissue composition. Relevance Quantitative ultrasonography seems to be a potential clinical and occupational examination method to detect tissue composition of myalgic muscles compared to healthy muscles.

Journal of human ergology, 2010

Surface electromyograms(EMG) during test contractions (TCs) were studied to assess the muscle str... more Surface electromyograms(EMG) during test contractions (TCs) were studied to assess the muscle strain in simulated mushroom picking. Additionally, the duration of the TC for the effective assessment was investigated. Nine female subjects performed standardized shoulder abduction and a stooped posture for one minute as TCs. Each experiment consisted of a 60-min rest, three work periods (W1-W3), a 30-min rest, and two work periods (W4 and W5) separated by a 30-min rest period. The duration of each work period was about 20 min. A total of 18 TCs was performed between the work periods and every 10 minutes in the rest periods. EMGs were recorded from the trapezius, infraspinatus, deltoid, and erector spinae muscles. The amplitude of EMG (AEMG) and mean power frequency (MPF) of EMG were calculated. Each TC was divided equally into three parts. Ratings of perceived exertion (RPE) in the neck, shoulder and low-back were reported during TCs. The work increased RPE of all the parts. AEMG and R...

Applied Ergonomics, 1998

The aim of the study was to investigate the muscular load on the lower back and shoulders and the... more The aim of the study was to investigate the muscular load on the lower back and shoulders and the circulatory load on employees at a post center during repetitive lifting of mail transport boxes. A mock-up was designed in the laboratory, a total of nine combinations of lifting height and frequency were studied. Surface EMG was recorded bisymmetrically from m. erector spinae (L3-level) and m. trapezius. The circulatory load was evaluated by measuring the heart rate. The results show a trade off between the low back and shoulders. The maximum load on the low back occurred at the low lifting height (36.3 and 54.4 cm) whereas the maximum load on the shoulders occurred at the high lifting height (144.9 and 163.0 cm).

Medicine Amp Science in Sports Amp Exercise, Apr 30, 2006

Wednesday Afternoon Poster presentations Posters displayed from 1: 00-6: 00 pm. One-hour author p... more Wednesday Afternoon Poster presentations Posters displayed from 1: 00-6: 00 pm. One-hour author presentation times are staggered from 2: 00-3: 00 pm., 3: 00-4: 00 pm., and 4: 00-5: 00 pm.: B-22 Free Communication/Poster-Circulation: Microvascular/oxygenation: ...

BMC musculoskeletal disorders, Jan 18, 2006

The echogenicity patterns of ultrasound scans contain information of tissue composition in muscle... more The echogenicity patterns of ultrasound scans contain information of tissue composition in muscles. The aim was: (1) to develop a quantitative ultrasound image analysis to characterize tissue composition in terms of intensity and structure of the ultrasound images, and (2) to use the method for characterization of ultrasound images of the supraspinatus muscle, and the vastus lateralis muscle. Computerized texture analyses employing first-order and higher-order grey-scale statistics were developed to objectively characterize ultrasound images of m. supraspinatus and m. vastus lateralis from 9 healthy participants. The mean grey-scale intensity was higher in the vastus lateralis muscle (p < 0.05) than in the supraspinatus muscle (average value of middle measuring site 51.4 compared to 35.0). Furthermore, the number of spatially connected and homogeneous regions (blobs) was higher in the vastus lateralis (p < 0.05) than in the supraspinatus (average for m. vastus lateralis: 0.092...

Andersen LL, Andersen CH, Zebis MK, Nielsen PK, Søgaard K, Sjøgaard G. Effect of physical trainin... more Andersen LL, Andersen CH, Zebis MK, Nielsen PK, Søgaard K, Sjøgaard G. Effect of physical training on function of chronically painful muscles: a randomized controlled trial. Pain and tenderness of the upper trapezius muscle is frequent in several occupational groups. The objective of this study is to investigate the effect of three contrasting interventions on muscle function and pain in women with trapezius myalgia. A group of employed women (n ϭ 42) with a clinical diagnosis of trapezius myalgia participated in a 10-wk randomized controlled intervention: specific strength training of the neck/shoulder muscles, general fitness training performed as leg bicycling, or a reference intervention without physical activity. Torque and electromyography (EMG) were recorded during maximal shoulder abductions in an isokinetic dynamometer at Ϫ60, 60, 0, and 180°/s. Furthermore, a submaximal reference contraction with only the load of the arms was performed. Significant changes were observed only in the specific strength training group. Pain decreased by 42-49% (P Ͻ 0.01-0.05). Whereas the EMG activity of the unaffected deltoid remained unchanged during the maximal contractions, an increase in EMG amplitude (42-86%; P Ͻ 0.001-0.05) and median power frequency (19%; P Ͻ 0.001) were observed for the painful trapezius muscle. Correspondingly, torque increased by 18 -53% (P Ͻ 0.001-0.05). EMG during the reference contraction decreased significantly for both the trapezius and deltoid muscles (P Ͻ 0.01). In conclusion, specific strength training relieves pain and increases maximal activity specifically of the painful trapezius muscle, leading to increased shoulder abduction strength in women with trapezius myalgia. Furthermore, decreased relative workload may indirectly augment pain reduction.

Spine, 1999

Brief (30-second) isometric trunk extensions at 5%, 20%, 40%, 60%, and 80% of maximal voluntary c... more Brief (30-second) isometric trunk extensions at 5%, 20%, 40%, 60%, and 80% of maximal voluntary contraction (MVC) and 3 minutes of prolonged trunk extension (20% MVC) in erect position were studied in nine healthy male subjects. To investigate the intercorrelation between intramuscular pressure and tissue oxygenation of the paravertebral muscles during submaximal isometric contractions and further, to evaluate paravertebral electromyogram and intramuscular pressure as indicators of force development. Local physiologic responses to muscle contraction are incompletely understood. Relative oxygenation was monitored with noninvasive near-infrared spectroscopy, intramuscular pressure was measured with a transducer-tipped catheter, and surface electromyogram was monitored at three recording sites. The root mean square amplitudes of the paravertebral electromyogram (L4, left and right; T12, right) and intramuscular pressure measured in the lumbar multifidus muscle at L4 increased with greater force development in a curvilinear manner. A significant decrease in the oxygenation of the lumbar paravertebral muscle in response to muscle contraction was found at an initial contraction level of 20% MVC. This corresponded to a paravertebral intramuscular pressure of 30-40 mm Hg. However, during prolonged trunk extension, no further decrease in tissue oxygenation was found compared with the tissue oxygenation level at the end of the brief contractions, indicating that homeostatic adjustments (mean blood pressure and heart rate) over time were sufficient to maintain paravertebral muscle oxygen levels. At a threshold intramuscular pressure of 30-40 mm Hg during muscle contraction, oxygenation in the paravertebral muscles is significantly reduced. The effect of further increase in intramuscular pressure on tissue oxygenation over time may be compensated for by an increase in blood pressure and heart rate. Surface electromyogram amplitudes and intramuscular pressure can be used as indicators of paravertebral muscle force.

Muscle & Nerve, 2010

The objective of this study was to investigate morphological and physiological characteristics of... more The objective of this study was to investigate morphological and physiological characteristics of painful muscles in women with (MYA, n ¼ 42) and without (CON, n ¼ 20) trapezius myalgia, and assess changes in response to a 10-week, randomized, controlled trial. MYA accomplished: (1) specific strength training (SST); (2) general fitness training (GFT); or (3) reference intervention (REF). Differences in muscle morphology could not be detected by ultrasound imaging. Significantly lower pressure pain threshold (PPT) and shoulder torque were observed for MYA, indicating pain-related lack of full activation. After 10 weeks, increased shoulder torque and PPT of the painful trapezius were observed in SST solely. The PPT of a pain-free reference muscle was increased in response to both SST and GFT, indicating a general effect of physical activity on pain perception. This study shows clinically relevant improvement in pain sensitivity and muscle strength capacity in response to SST.

Medicine & Science in Sports & Exercise, 2006

Journal of Biomechanics, 2007

Journal of Biomechanics, 2008

The present study investigated the effect of chronic neck muscle pain (defined as trapezius myalg... more The present study investigated the effect of chronic neck muscle pain (defined as trapezius myalgia) on neck/shoulder muscle function during concentric, eccentric and static contraction. Forty-two female office workers with trapezius myalgia (MYA) and 20 healthy matched controls (CON) participated. Isokinetic (À60, 60 and 1801 s À1 ) and static maximal voluntary shoulder abductions were performed in a Biodex dynamometer, and electromyography (EMG) obtained in the trapezius and deltoideus muscles. Muscle thickness in the trapezius was measured with ultrasound. Pain and perceived exertion were registered before and after the dynamometer test.

Journal of Applied Physiology, 2008

Purpose: Pain and tenderness of the upper trapezius muscle is frequent in several occupational gr... more Purpose: Pain and tenderness of the upper trapezius muscle is frequent in several occupational groups. The objective of this study is to investigate the effect of three contrasting interventions on muscle function and pain in women with trapezius myalgia.

International Archives of Occupational and Environmental Health, 2009

To investigate the effects of cognitively demanding work tasks and office noise on heart rate var... more To investigate the effects of cognitively demanding work tasks and office noise on heart rate variability (HRV), cardiovascular responses and electromyography (EMG) activity in the trapezius muscles. Ten female volunteers were exposed to simulated open-plan office noise for 35 min (Leq 65 dBA), while engaged in cognitively demanding tasks. Task performance, self-rated stress and energy, affective state, perceived exertion in the shoulders and in the head, EMG in the left and right trapezius muscle, blood pressure, heart period length, HRV, and salivary cortisol were measured. Cognitively demanding work tasks were associated with changes in HRV, systolic blood pressure and EMG that reflects increased sympathetic activity in the autonomic nervous system. No effect of noise was observed, except for a higher rating of perceived exertion in the head and, contrary to expectations, a 4% lower diastolic blood pressure in the noise conditions. Psychophysiological measures reflected the mental load imposed by cognitive work tasks. Short-term exposure to office noise resulted in increased ratings of perceived exertion in the head, but not in physiological stress reactions.

European Journal of Applied Physiology, 2012

The aim of this randomized controlled trial was to assess changes in myalgic trapezius activation... more The aim of this randomized controlled trial was to assess changes in myalgic trapezius activation, muscle oxygenation, and pain intensity during repetitive and stressful work tasks in response to 10 weeks of training. In total, 39 women with a clinical diagnosis of trapezius myalgia were randomly assigned to: (1) general Wtness training performed as leg-bicycling (GFT); (2) speciWc strength training of the neck/shoulder muscles (SST) or (3) reference intervention without physical exercise. Electromyographic activity (EMG), tissue oxygenation (near infrared spectroscopy), and pain intensity were measured in trapezius during pegboard and stress tasks before and after the intervention period. During the pegboard task, GFT improved trapezius oxygenation from a relative decrease of ¡0.83 § 1.48 M to an increase of 0.05 § 1.32 M, and decreased pain development by 43%, but did not aVect resting levels of pain. SST lowered the relative EMG amplitude by 36%, and decreased pain during resting and working conditions by 52 and 38%, respectively, without aVecting trapezius oxygenation. In conclusion, GFT performed as leg-bicycling decreased pain development during repetitive work tasks, possibly due to improved oxygenation of the painful muscles. SST lowered the overall level of pain both during rest and work, possibly due to a lowered relative exposure as evidenced by a lowered relative EMG. The results demonstrate diVerential adaptive mechanisms of contrasting physical exercise interventions on chronic muscle pain at rest and during repetitive work tasks.

European Journal of Applied Physiology, 2010

Work-related neck/shoulder muscle pain has been associated with increased anaerobic muscle metabo... more Work-related neck/shoulder muscle pain has been associated with increased anaerobic muscle metabolism. Thus, interventions to enhance oxygenation of painful muscles seem relevant. While cycling with relaxed shoulders has been shown to result in acute neck/shoulder muscle pain reduction, the effect on tissue oxygenation remains unknown. The aim of the present study was to investigate tissue oxygenation of the passive trapezius muscle during and after cycling in female workers with (MYA) and without (CON) trapezius myalgia. Eligible participants (n = 17 MYA, n = 8 CON) performed 20 min sub-maximal cycling in an upright position with relaxed shoulders. Near-infrared spectroscopy was used to measure trapezius muscle oxygenation during and 2 min after the cycling period. For both MYA and CON, oxygenation of the passive trapezius increased in a linear fashion over time, to values approximately 5 microM above baseline at the end of the cycling period, with no significant group difference (CON 5.2, MYA 4.9 microM). Two min after termination of exercise, oxygenation was increased further in both groups, but significantly more in CON (8.8 microM) than in MYA (7.0 microM) (P = 0.05). In conclusion, cycling increases oxygenation of resting neck/shoulder muscles in women with and without trapezius myalgia, indicating acute positive effects of either neural or humoral factors on vascular beds of distant relaxed muscles. Although this beneficial response was observed in both groups, the post-exercise response was lower in women with trapezius myalgia.

European Journal of Applied Physiology, 2008

The purpose of this study was to investigate how the ocular surface area (OSA) and the eye blink ... more The purpose of this study was to investigate how the ocular surface area (OSA) and the eye blink frequency (BF) are aVected by a high versus a low-monitor position during visual display unit (VDU) work with varying cognitive demands. In a balanced randomized (2 £ 2) design ten healthy subjects (Wve males, Wve females) completed two diVerent tasks on the VDU in a simulated oYce environment (23°C and 30-35% relative humidity); an active task with demands on vision and hand-eye coordination, and a passive task. Two monitor positions were used: high (the monitors' upper edge at the same height as the subjects' eyes) and low (lowered by 25° and perpendicular to gaze angle). Each task lasted 10 min. An OSA-proxy was measured from video recordings, and BF was sampled by electrooculography. The eVect of lowering the gaze angle by 25° decreased the OSA-proxy signiWcantly (P < 0.01) during the active task, indicating that a low position of the monitor may be preferable even though the BF also decreased. Overall, the OSA-proxy was 6% higher during the active task compared to the passive while BF during the active task was 69% lower than during the passive task. The low BF during the active task was succeded by a burst with high BF after cessation of the active task, indicating a compensatory blinking process. This stresses that interchange of work tasks with diVerent cognitive load is as important as the monitor position in the prevention of visual and musculoskeletal disorders.