The Response of Denervated Muscle to Long-Term Electrical Stimulation.

Adapted from: Lømo T, Westgaard RH, Hennig R, Gundersen K. The response of denervated muscle to long-term electrical stimulation, In: Carraro U, Angelini C, eds. Proceedings of the First Abano Terme Meeting on Rehabilitation, 1985 August 28-30, Abano Terme, Padova, Italy, An International Symposium, Satellite Meeting of the XIII World Congress of Neurology, Hamburg 1985. Cleup Padova 1985. pp 81-90.

Heart rate variability in fibromyalgia patients and healthy controls during non-REM and REM sleep: a case-control study.

OBJECTIVES: To investigate heart rate variability (HRV) in fibromyalgia (FM) patients and healthy controls (HCs) during different sleep stages, and to examine the association of HRV with pain and sleep quality. METHOD: Polysomnography was recorded from 23 female FM patients and 22 age- and sex-matched HCs. HRV was recorded from bedtime until awakening including the standard deviation of normal-to-normal intervals (SDNN), the root mean square successive difference (RMSSD), and the low (LF; 0.04-0.15 Hz) and high (HF; 0.15-0.4 Hz) frequency power. Subjective scores of neck/shoulder pain and sleep quality were obtained at bedtime and awakening. RESULTS: Both patients and HCs showed high incidence of arousals per hour (FM: 16 ± 9.7; HCs: 17 ± 11). RMSSD was lower in patients than HCs during non-rapid eye movement (non-REM) stage 2 (N2) sleep (mean ± SD; 30 ± 12 ms vs. 42 ± 13 ms, p < 0.002) and during REM sleep (23 ± 11 ms vs. 37 ± 16 ms, p < 0.003). HRV did not differ between groups during N3 sleep (p > 0.19 for all comparisons). In patients, SDNN, RMSSD, and HF power showed modest positive correlations with sleep quality (HF power during N3 sleep showed the highest correlation; Spearman's ρ = 0.54) and modest negative correlations with neck/shoulder pain (RMSSD during N3 sleep showed the highest correlation with pain at bedtime; Spearman's ρ = -0.51). CONCLUSIONS: RMSSD, indicative of parasympathetic predominance, is attenuated in FM patients compared to HCs during N2 sleep and REM sleep. This difference was not present for the HF component. HRV during sleep in FM patients is moderately and positively associated with sleep quality and moderately and negatively associated with neck/shoulder pain.

Occupational musculoskeletal and mental health: Significance of rationalization and opportunities to create sustainable production systems - A systematic review.

This literature review aims to identify occupational musculoskeletal and mental health effects of production system rationalization as well as organizational-level measures that may improve health outcome ("modifiers" in this review). A short review of the effect of ergonomic interventions is included as background and rationalization is discussed as a theoretical concept. Indicator variables for occupational musculoskeletal and mental health and related risk factors are presented. Variables with a generalized format were allowed in the literature searches (e.g., job satisfaction and absenteeism were accepted as risk factor and health indicator, respectively), suitable for the research fields of work sociology, organization science, human resource management (HRM) and economics research. One hundred and sixty-two studies of rationalization effects on health and risk factors and 72 organization-level modifier results were accepted into the final database. Entries were sorted by rationalization strategy and work life sector, and trends in outcome (positive, mixed, no effect, or negative effect on health and risk factors) were determined. Rationalizations have a dominant negative effect on health and risk factors (57% negative, 19% positive); the most negative effects were found for downsizing and restructuring rationalizations in general (71 studies negative, 13 positive) and for the health care sector in particular (36 studies negative, 2 positive). The rationalization strategy High Performance Work System (HPWS) was associated with the highest fraction positive outcome studies (6 of 10 studies). Other rationalization strategies (lean practices, parallel vs. serial production and mechanization level) reported intermediate results, in part dependent on work life sector, but also on the year when studies were carried out. Worker participation, resonant management style, information, support, group autonomy and procedural justice were modifiers with favourable influence on outcome. It is concluded that production system rationalization represents a pervasive work life intervention without a primary occupational health focus. It has considerable and mostly negative influence on worker health, but this can be reduced by attention to modifiers. The results create a basis for new priorities in ergonomic intervention research.

A unilateral sympathetic blockade does not affect stress-related pain and muscle activity in patients with chronic musculoskeletal pain.

OBJECTIVE: Chronic musculoskeletal pain is often exacerbated by mental and social stress. The association between stress and musculoskeletal pain is potentially mediated by peripheral sympathetic nerves, either directly or indirectly through muscle activity. In the present study we wanted to determine whether sympathetic blockade could affect either the pain or the muscular activity experienced during mental stress in patients with chronic musculoskeletal pain. METHODS: We performed a unilateral anaesthetic blockade of the lower cervical sympathetic ganglion (ganglion stellatum) in 18 patients with chronic musculoskeletal pain (10 with fibromyalgia and eight with chronic shoulder/neck pain). After the blockade the patients performed a 60-minute stressful task with low-grade mental stress that has induced pain and muscle activity in earlier experiments. Surface electromyography (SEMG) of the forehead, temples, neck, and shoulders, and heart rate and blood pressure were recorded together with ratings of pain. RESULTS: We did not find any side or sidextime effect for pain or muscular activity in any of the four muscle groups (p>0.12). CONCLUSION: We investigated the potential involvement of peripheral sympathetic nerves in stress-related musculoskeletal pain. A peripheral sympathetic block did not affect pain and muscle responses to a stressful task. Other explanatory models should be implemented and tested experimentally to further investigate the clinical impression that mental stress exacerbates pain in patients with chronic musculoskeletal pain.

Stress-induced pain and muscle activity in patients with migraine and tension-type headache.

We recorded deep pain and surface electromyographic (EMG) responses to stress in 22 migraineurs during headache-free periods, 18 patients with tension-type headache (TTH), and 44 healthy controls. Sixty minutes of cognitive stress was followed by 30 min relaxation. EMG and pain (visual analogue scale) in the trapezius, neck (splenius), temporalis and frontalis areas were recorded. TTH patients had higher pain responses in temporalis and frontalis (with similar trends for trapezius and splenius) and more potentiation of pain during the test than controls. Migraine patients developed more pain in the splenius and temporalis than controls. Muscle pain responses were more regional (more pain in the neck and trapezius compared with the temporalis and frontalis) in migraine than in TTH patients. TTH patients had delayed pain recovery in all muscle regions compared with controls, while migraine patients had delayed pain recovery in a more restricted area (trapezius and temporalis). EMG responses were not different from controls in headache patients, and EMG responses did not correlate with pain responses. TTH patients had delayed EMG recovery in the trapezius compared with controls and migraine patients. These results support the concept that (probably central) sensitization of pain pathways and the motor system is important in TTH. Less pronounced and more regional (either peripheral or central) trigeminocervical sensitization seems to be important in migraine. Surface-detectable muscular activation does not seem to be causal for pain during cognitive stress either in migraine or in TTH.

Pain induced by low-grade stress in patients with fibromyalgia and chronic shoulder/neck pain, relation to surface electromyography.

The mechanisms of pain causation in fibromyalgia (FMS) and chronic shoulder/neck pain (SNP) are still debated. We wanted to compare muscle activity and pain development during and after low-grade mental stress in FMS and SNP patients. Twenty-three women with FMS, 29 women with chronic SNP and 35 healthy women performed a stressful task lasting 60 min followed by a 30 min recovery period. We recorded surface electromyography over the trapezius, neck, temporalis and frontalis muscles. Subjects reported their pain at the corresponding locations together with the development of fatigue and perceived tension. Significant differences between FMS and SNP groups were not observed either for muscular or subjective responses. SNP patients and controls responded with more pain in the trapezius and neck regions than in the forehead, in contrast to FMS patients who had a more generalized pain response. Development of pain, tension and fatigue was not related to muscle activity for any group. We conclude that FMS and SNP patients have similar pain and electromyographic responses. The results suggest that similar pathophysiological mechanisms are involved although the responses are more generalised in FMS than in SNP patients. Muscular activity did not explain the pain which developed during the stressful task for either group. Pain lasted longer during recovery in both FMS and SNP patients compared to healthy controls, possibly a result of disease-related sensitisation in pain pathways.

The influence of contraction amplitude and firing history on spike-triggered averaged trapezius motor unit potentials.

The spike-triggered averaged (STA) technique was used to examine trapezius motor unit potentials and their dependence on contraction amplitude and firing history. Individual motor unit firings were identified by a fine-wire intramuscular electrode, while STA-derived potentials were extracted from the simultaneously recorded surface electromyographic (SEMG) signal. Amplitude-controlled contractions and contractions with typing tasks and mental stress were carried out. STA potentials were mostly derived from 20 s intervals of firing. Motor unit synchrony was estimated by peristimulus time histograms (PSTHs). An association between SEMG amplitude and STA-derived motor unit potentials was found: motor unit area showed a four-fold increase when SEMG amplitude increased from 1.5 to 10.5% of the root mean square-detected SEMG signal at maximal voluntary contraction (%EMG(max)). Low- and higher threshold motor unit potentials, all with recruitment thresholds <10% EMG(max), had similar area at the same contraction amplitude. A significant increase in the STA-derived potentials was observed after 3 min of constant-amplitude contractions; however, this difference was reduced after 10 min and no longer present after 30 min of contraction. Motor unit synchrony accounted for, on average, 2.8% additional firings within 2 ms of the triggering motor unit. We conclude that the increase in STA-derived potentials with contraction amplitude is, to a major extent, due to motor unit synchrony, limiting the applicability of this method in postural muscles presenting wide motor unit potentials. The similar area of motor units at same SEMG amplitude may indicate that trapezius motor units recruited below 10% EMG(max) are of similar size and thus not organized according to the Henneman size principle.

The association between upper trapezius activity and thorax movement in classical singing.

This study aimed to examine in classical singing the phasing of the activity in upper trapezius (TR) to upper and lower thorax movement and to the phasing of activity in the intercostals (INT) and in the lateral abdominal (OBL) muscles. Electromyographic (EMG) activity was recorded from the TR, INT, and OBL muscles on the right side. Thorax movement (TX) was traced with two strain gauge sensors placed around the upper and lower thorax. Four professional opera singers (soprano, mezzo, tenor, and baritone) and four advanced student classical singers (three sopranos and one mezzo) participated. Three of the professional singers were 33 years, and one was 40 years. The students were between 23 and 30 years. Different arias, freely chosen by the singers from their professional repertoire, served as the singing task for the opera singers. All students sang "Summertime" from Porgy and Bess. All subjects performed their task three times with variation in vocal loudness (normal, forte, piano). Thereafter, for all subjects, a biofeedback (BF) procedure was performed on TR to lower TR activity and a repeat performance of the singing tasks was carried out. EMG activity from the three recording sites and upper and lower TX circumference were compared before and after BF. A phasing of upper TR activity to INT and OBL activity was discovered, all muscles supporting the expiration phase. During phonation, the upper TR contributes in the compression of upper TX, thus serving as an accessory muscle of expiration. Group results from both opera singers and student singers showed that EMG activity was significantly lowered after BF. The lowered TR activity resulted in an expanded upper TX circumference and less TX respiratory movement after BF.

Muscle activity in professional classical singing: a study on muscles in the shoulder, neck and trunk.

This study aimed to examine whether changes in the activity of shoulder and neck muscles have consequences for the activation of primary breathing muscles. It further aimed to compare muscle loading levels of professional and student singers. Four professional opera singers participated in the study. Previous unpublished recordings of 4 to 16 student singers and one opera singer were included to allow comparison of EMG loading levels between student and professional singers. Electromyographic (EMG) recordings of trapezius (TR), sternocleidomastoideus (STM), intercostals (INT), rectus abdominis (RC) and the lateral abdominal muscles (OBL) were performed. EMG biofeedback (BF) was performed on TR and STM to lower the activity in these two muscles and the potential change in EMG activity of INT, RC and OBL were examined. Three singing tasks were performed: aria, sustained tones and extreme tones. Each task was performed three times with variation in volume or pitch. Following the first performance of the singing tasks, the BF session was carried out and muscle activity recorded in a repeat performance of the same tasks. The EMG activity levels of all muscles were compared before and after BF. We found no significant effect of reduced TR/STM activity on the activation of INT, RC and OBL. Professional opera singers activated the TR, INT, RC and OBL muscles to higher levels than the student singers did. Another finding was large inter-subject variation in muscle usage, showing an idiosyncratic composition of the muscle contribution to subglottal pressure.

Firing patterns of low-threshold trapezius motor units in feedback-controlled contractions and vocational motor activities.

The study aimed to examine firing patterns of low-threshold trapezius motor units, with attention given to motor unit recruitment threshold. Different motor tasks were explored: shoulder elevation, arm movement in typing, and the motor response to mental stress. Contraction amplitudes in the range from 1 to 10% of the surface electromyographic (SEMG) signal at maximal voluntary contraction (1-10% EMGmax) were studied, representing the range of trapezius muscle activity commonly observed in daily living. Single motor unit activity was recorded by a quadrifilar fine-wire electrode. A surface electrode simultaneously recorded the SEMG signal. Low-threshold motor units showed a small increase in mean firing rate, from 10.5 to 12.5 pulses per second ( p<0.01), in constant-amplitude contractions when SEMG amplitude increased from <2% to >4% EMGmax. After the first few minutes, firing rates were similar for all motor units in a contraction, despite different recruitment thresholds. Firing rates of motor units with threshold <2% EMGmax were the same in constant-amplitude contractions, contractions with vocational arm movement, and contractions with imposed stress for SEMG amplitude at the same level. High-frequency firing patterns were observed in dynamic contractions, limited to bursts of up to a second duration. We conclude that low-threshold trapezius motor units have similar, stable firing rates in sustained contractions, independent of task and recruitment threshold, but with a small increase for increasing contraction amplitude.

Motor unit recruitment and derecruitment induced by brief increase in contraction amplitude of the human trapezius muscle.

The activity pattern of low-threshold human trapezius motor units was examined in response to brief, voluntary increases in contraction amplitude ('EMG pulse') superimposed on a constant contraction at 4-7 % of the surface electromyographic (EMG) response at maximal voluntary contraction (4-7 % EMGmax). EMG pulses at 15-20 % EMGmax were superimposed every minute on contractions of 5, 10, or 30 min duration. A quadrifilar fine-wire electrode recorded single motor unit activity and a surface electrode recorded simultaneously the surface EMG signal. Low-threshold motor units recruited at the start of the contraction were observed to stop firing while motor units of higher recruitment threshold stayed active. Derecruitment of a motor unit coincided with the end of an EMG pulse. The lowest-threshold motor units showed only brief silent periods. Some motor units with recruitment threshold up to 5 % EMGmax higher than the constant contraction level were recruited during an EMG pulse and kept firing throughout the contraction. Following an EMG pulse, there was a marked reduction in motor unit firing rates upon return of the surface EMG signal to the constant contraction level, outlasting the EMG pulse by 4 s on average. The reduction in firing rates may serve as a trigger to induce derecruitment. We speculate that the silent periods following derecruitment may be due to deactivation of non-inactivating inward current ('plateau potentials'). The firing behaviour of trapezius motor units in these experiments may thus illustrate a mechanism and a control strategy to reduce fatigue of motor units with sustained activity patterns.

Low-frequency oscillations (<0.3 Hz) in the electromyographic (EMG) activity of the human trapezius muscle during sleep.

The surface electromyographic (EMG) signal from right and left trapezius muscles and the heart rate were recorded over 24 h in 27 healthy female subjects. The root-mean-square (RMS) value of the surface EMG signals and the heartbeat interval time series were calculated with a time resolution of 0.2 s. The EMG activity during sleep showed long periods with stable mean amplitude, modulated by rhythmic components in the frequency range 0.05-0.2 Hz. The ratio between the amplitude of the oscillatory components and the mean amplitude of the EMG signal was approximately constant over the range within which the phenomenon was observed, corresponding to a peak-to-peak oscillatory amplitude of approximately 10% of the mean amplitude. The duration of the periods with stable mean amplitude ranged from a few minutes to approximately 1 h, usually interrupted by a sudden change in the activity level or by cessation of the muscle activity. Right and left trapezius muscles presented the same pattern of FM. In supplementary experiments, rhythmic muscle activity pattern was also demonstrated in the upper extremity muscles of deltoid, biceps, and forearm flexor muscles. There was no apparent association between the rhythmic components in the muscle activity pattern and the heart rate variability. To our knowledge, this is the first time that the above-described pattern of EMG activity during sleep is documented. On reanalysis of earlier recorded trapezius motor unit firing pattern in experiments on awake subjects in a situation with mental stress, low-FM of firing with similar frequency content was detected. Possible sources of rhythmic excitation of trapezius motoneurons include slow-wave cortical oscillations represented in descending cortico-spinal pathways, and/or activation by monoaminergic pathways originating in the brain stem reticular formation. The analysis of muscle activity patterns may provide an important new tool to study neural mechanisms in human sleep.

Muscle activity in the classical singer's shoulder and neck region.

The objective of this study is to characterize the level of use of the trapezius (TR) and the sternocleidomastoideus (STM) muscles by singing students. We further try to lower the activity in both muscles by use of biofeedback (BF) from electromyographic recordings (EMG). We finally examine whether the experiences from the BF session can be transferred into regular singing by maintaining a mental focus on the experiences made in the BF session. Two groups, each consisting of eight conservatory singing students, all in their first or second year of study, volunteered as subjects. Two singing procedures were used, a song and a sustained tone of maximum possible duration. EMG activity was recorded bilaterally from the TR and STM by use of an ambulatory monitoring system. EMG BF appeared to lower muscle activity in the two muscles, thus the experiences made in the BF session could be transferred into regular singing. We conclude that singers, although having an enhanced awareness of posture, still may have overuse of especially the TR muscle, but probably also the STM muscle.

Motor control of low-threshold motor units in the human trapezius muscle.

The firing pattern of low-threshold motor units was examined in the human trapezius and first dorsal interosseous (FDI) muscles during slowly augmenting, low-amplitude contractions that were intended to mimic contractile activity in postural muscles. The motor unit activity was detected with a special needle electrode and was analyzed with the assistance of computer algorithms. The surface electromyographic (EMG) signal was recorded. Its root-mean-square (RMS) value was calculated and presented to the subject who used it to regulate the muscle force level. In the trapezius, there was minimal, if any, firing rate modulation of early recruited motor units during slow contractions (< or =1% EMG(max)/s), and later recruited motor units consistently presented higher peak firing rates. As the force rate of the contraction increased (3% EMG(max)/s), the firing rates of the motor units in the trapezius approached an orderly hierarchical pattern with the earliest recruited motor units having the greatest firing rate. In contrast, and as reported previously, the firing rates of all motor units in the FDI always presented the previously reported hierarchical "onion-skin" pattern. We conclude that the low-threshold motor units in the postural trapezius muscle, that is the motor units that are most often called on to activate the muscle in postural activities, have different control features in slow and fast contractions. More detailed analysis revealed that, in the low force-rate contractions of the trapezius, recruitment of new motor units inhibited the firing rate of active motor units, providing an explanation for the depressed firing rate of the low-threshold motor units. We speculate that Renshaw cell inhibition contributes to the observed deviation of the low-threshold motor units from the hierarchical onion-skin pattern.

Shoulder and neck complaints in customer relations: individual risk factors and perceived exposures at work.

Perceived psychosocial and biomechanical exposures, individual factors and pain in the shoulder and neck were recorded in two groups of female service workers (healthcare and shopping centre workers). The jobs investigated were characterized by 'much' direct human relations, 'little' sitting and 'much' standing, and were light work by physiological or biomechanical criteria but potentially psychosocially demanding. A screening survey (n = 400 females) was the basis for the selected sample (n = 66 females), which was the object of the main investigation of this study. Reliability of the questionnaires was tested in a separate group of female healthcare workers (n = 29). Heart rate recordings through the work day estimated workload. There was a high prevalence of shoulder and neck pain (> 50%) for both work groups. In the two populations it proved difficult to explain shoulder and neck pain by reported physical and psychosocial exposures or individual factors, except by the variable 'perceived general tension', which clearly differentiated workers with and without pain. The findings in this study indicated, first, that perceived general tension might be an independent risk factor for muscle pain and, second, that this might be related to personality factors. However, this putative relationship must be verified in a longitudinal study. As no variable describing exposures in the working environment was associated with shoulder and neck pain, the question is posed whether such complaints can be considered work-related. Alternatively, the variables used to describe mechanical and psychosocial exposures in this study may have low specificity in characterizing work-related risk factors for service workers with customer relations.

EMG activity and pain development in fibromyalgia patients exposed to mental stress of long duration.

OBJECTIVE: To examine the distribution of stress-induced upper-body pain in fibromyalgia patients, and the possible association of pain with electromyographic activity in muscles near the sites of pain development. METHODS: Fifteen fibromyalgia patients and 15 pain-free subjects were exposed to low-level mental strain over a one-hour period. EMG was recorded from frontalis, temporalis, trapezius, and splenius capitis. Pain in the corresponding locations was recorded before the test, every 10 minutes during the test, and the 30-minute posttest period. RESULTS: The fibromyalgia patients developed pain during the test in all the above body locations. Pain development in all locations associated with trapezius EMG activity, but not with EMG activity in underlying muscles for forehead, temples, and neck. CONCLUSION: Stress-induced pain in fibromyalgia patients is not generally caused by muscle activity. The trapezius EMG response may be part of a general stress response that cause pain independently of motor activity in muscles.

Trapezius muscle activity as a risk indicator for shoulder and neck pain in female service workers with low biomechanical exposure.

Electromyographic activity of the upper trapezius muscles was recorded over the workday for two groups of service workers, shopping centre (n = 22) and healthcare workers (n = 44), both with low observed biomechanical exposure. Static and median EMG activity level, number of EMG gaps and gap time were determined. The variability of these variables over the workday was examined by calculating the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) of 1-h consecutive recording periods. All variables except gap time showed acceptable reliability (ICC = 0.69-0.78), i.e. the largest fraction of variance in the data set was due to intersubject variance, despite relatively large hour-to-hour variation (CV = 0.21 0.62). The EMG activity level in the trapezius muscles was low (static activity level < 1% EMGmax), despite the high prevalence of shoulder and neck pain for both groups of workers. In addition to the work recordings, tests were performed to determine intersubject variation in muscle activity when adopting a standardized resting posture, and in a dynamic muscle activity pattern during paced arm movement. Neither the EMG variables from the work recordings nor the tests with EMG recording indicated higher trapezius EMG activity levels for workers with pain in the shoulders and neck in this study. The low EMG levels are interpreted to indicate a low risk of developing shoulder and neck complaints due to biomechanical exposure for both groups of workers. The possibility of pain-initiating mechanisms, associated with stress and not mediated through muscle activity, is considered in the discussion.

Work-related musculoskeletal complaints: some ergonomics challenges upon the start of a new century.

Three themes likely to be important within health-related ergonomics in the coming years are discussed. The first two themes concern methods for risk analysis of low-level biomechanical and psychosocial exposures. The third theme is approaches to successful implementation of ergonomics interventions. Evidence on the assessment of low-level biomechanical and psychosocial exposures by instrumented measurements is discussed. It is concluded that, despite recent advances in our understanding of exposure-effect associations under these exposure conditions, we must at present rely on more subjective methods, employed in a collaboration between expert and worker. This approach to risk analysis identifies in most cases critical exposures in a work situation. The focus should then be on the successful implementation of measures against those exposures, as identification alone does not solve problems. The aim of improved health for the workers further requires that the full complement of risk factors be considered, including work, leisure time and person-based risk factors. Finally, the need to put ergonomics intervention initiatives in an organisational context is emphasised, and examples of approaches used by Norwegian companies are presented.

Motor unit substitution in long-duration contractions of the human trapezius muscle.

We examined the activity pattern of low-threshold motor units in the human trapezius muscle during contractions of 10 min duration. Three procedures were applied in sequence: 1) static contraction controlled by maintaining a constant low level of the surface electromyogram (EMG)-detected root-mean-square signal, 2) a manipulation task with mental concentration, and 3) copying a text on a word processor. A quadrifilar fine-wire electrode was used to record single motor unit activity. Simultaneously, surface electrodes recorded the surface EMG signal. During these contractions, low-threshold motor units showed periods of inactivity and were substituted by motor units of higher recruitment threshold. This phenomenon was not observed during the first few minutes of the contraction. In several cases the substitution process coincided with a short period of inactivity in the surface EMG pattern. Substitution was observed in five of eight experiments. These observations may be explained by a time-variant recruitment threshold of motor units, sensitive to their activation history and temporal variation in the activity patterns. We speculate that the substitution phenomenon protects motor units in postural muscles from excessive fatigue when there is a demand for sustained low-level muscle activity.

Ergonomic criteria in large-scale engineering design--I. Management by documentation only? Formal organization vs. designers' perceptions.

In engineering design projects ergonomics criteria may be supplied to project members along with other design requirements. A formal organization for human factors (HF) is set up where responsibilities pertaining to HF are specified. It is then assumed that the project functions according to this, and that the ergonomics criteria are known among project members. We have investigated the management of human factors in two large-scale offshore development projects. Our study shows that neither organization of HF nor ergonomics criteria were well known among project members. To be effective, the criteria have to be supported by one or more HF specialists who engage themselves actively in design.