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PubMed2000

Cognitive impairment and the brain dopaminergic system in Parkinson disease: [18F]fluorodopa positron emission tomographic study.

OBJECTIVE: To investigate the role of the brain dopaminergic system in cognitive impairment in patients with Parkinson disease (PD). DESIGN: We studied 28 patients with PD and 16 age-matched healthy control subjects using [18F] fluorodopa (fluorodopa F 18) positron emission tomography. Patients with PD showed a variable degree of cognitive impairment, which was assessed using the Mini-Mental State Examination and detailed neuropsychologic assessment, including tests sensitive for frontal lobe function. RESULTS: [18F] Fluorodopa uptake was reduced in the putamen (to 36% of the control mean; P<.001), the caudate nucleus (to 61% of the control mean; P<.001), and the frontal cortex (to 45% of the control mean; P<.001) in patients with PD compared with controls. There was no significant association between the degree of overall cognitive impairment of patients and [18F] fluorodopa uptake values. The influx constant (Ki(occ)) in the caudate nucleus had a negative association with performance in the attention-demanding Stroop interference task, especially with the interference time. The Ki(occ) in the frontal cortex had a positive correlation with performance in the digit span (backwards), verbal fluency, and verbal immediate recall tests. Thus, the better the patient performed in tasks demanding immediate and working memory and executive strategies, the better the [18F] fluorodopa uptake in the frontal cortex. In the putamen, no significant correlation was seen between the Ki(occ) value and any of the cognitive tests. The severity of the motor symptoms of PD and [18F]fluorodopa uptake showed a negative correlation in the putamen (r = -0.38; P = .04), and in the caudate nucleus a similar trend was seen (r = -0.36; P = .06). CONCLUSIONS: Reduced [18F]fluorodopa uptake in PD in the caudate nucleus (and frontal cortex) is related to impairment in neuropsychologic tests measuring verbal fluency, working memory, and attentional functioning reflecting frontal lobe function. This indicates that dysfunction of the dopamine system has an impact on the cognitive impairment of patients with PD. However, our results do not exclude the possibility of more generalized cognitive impairment in PD, the pathophysiology of which is probably different and more generalized.

Aged↗
PubMed2002

Postural sway measurements: a potential safety monitoring technique for workers wearing personal protective equipment.

This study investigated the use of postural sway measurements as a potential safety monitoring technique. Sixteen healthy male volunteers (age: 41.8+/-9.3 years) participated in this study. The level of neurophysiological strain and the ability to maintain upright balance for workers wearing personal protective equipment (PPE) were investigated. Three levels of PPE, the United States Environmental Protection Agency (USEPA)-defined levels A, B, and C, were worn in random order while performing two randomly ordered tasks, resting and a workload. After the workload task, the perceived exertion and discomfort were recorded. Postural sway, measured using a microprocessor-based force platform system, was assessed after each task. The variables of sway area and sway length were calculated from stabilograms. These measurements were taken for three sway tests: 1) Eyes open (EO), 2) Eyes closed on a four-inch foam (FC), and 3) a dynamic test with the subject reaching for a weight placed in front, lifting it to his or her chest, and lowering back to the shelf four times (RE). The heart rate was significantly higher for the workload task (p < 0.05), and the levels A and B PPE demonstrated significantly higher perceived exertion results than level C PPE (p < 0.05). The heart rate and perceived exertion were not significantly correlated with the sway measurements. Level A produced significant self-reported discomfort results for the upper back, lower back, and thighs. The sway variables showed significant differences with the PPE levels and the task. The workload task produced significantly higher sway length than the resting task (p < 0.05) for all test conditions. The PPE level B produced significantly higher sway length than PPE level A (p < 0.05) in the FC test condition. These results indicate that postural stability is altered with PPE use and with fatigued postural muscles. In summary, postural sway measurements may be used as a potential safety monitoring technique.

Adult↗
PubMed2002

[Relationship between chronic fatigue and subjective symptoms of fatigue with performance status (P.S.) and subjective fatigue scale for young adults (SFS-Y)].

OBJECTIVE: Today, fatigue complaints in adolescence are regarded as an issue for young adults as they may progress to the chronic fatigue syndrome. The purpose of this study was to examine the relationships between chronic fatigue based on self-reported performance states (P.S.) and subjective symptoms of fatigue assessed with a fatigue scale for young adults (SFS-Y). METHOD: The SFS-Y consisted of 24 item questions represonting 6 sub-scales, for difficulty in concentrated thinking, languor, reduced activation, reduced motivation, drowsiness and feeling of physical disintegration. The SFS-Y and for assessing fatigue symptoms and P.S. for chronic fatigue were administered to 548 male and female students aged 15-18 yr and to 608 male students aged 16-18 yr, respectively. Discriminant analysis and a logistic analysis model were employed to define the relevance of subjective symptoms of fatigue to chronic fatigue. RESULTS: It was determined that the SFS-Y can discliminate P.S. with high probability (74.0-81.4%), with accuracy beyond a fixed level. In particular, the correlation with "difficulty in concentrated thinking" was high. CONCLUSION: It was judged that the SFS-Y is effective as an index for discrimination of chronic fatigue in young adults with a particularly high relationship between "difficulty in centrated thinking" and chronic fatigue.

Adolescent↗
PubMed2005

Myosin heavy chain isoform expression and in vivo isometric performance: a regression model.

This investigation estimated the amount of variance in voluntary in vivo muscle performance that can be explained by relative myosin heavy chain (MHC) isoform expression. The role of the relative expression of these proteins in relation to in vitro force and velocity performance is well understood, but the in vivo model is less clear. Twenty-two men and women (mean +/- SD age, 27 +/- 6 years) performed isometric knee extensor actions in which peak force and rate of force development (RFD) were measured. The results of regression analysis showed that the inclusion of MHC IIb explained a significant (19.9%, p < 0.05) amount of variance in relative peak force (adjusted for muscle mass) and 14.1% of the variance in the first half of the rise phase of the force-time curve (RFD(0-50%)) (p < 0.1). The addition of MHC I into this model explained a significant (p < 0.05) amount of variance above that accounted for by MHC IIb in RFD (45.4%), RFD(0-50%) (50.8%), and RFD(50-100%) (second half of the rise phase of the force-time curve) (37.4%). Since the percentage of MHC IIb is reduced rather quickly with training, these data suggest that peak force may also be affected quickly by training. The percentage of MHC I has a longer course for change with training; therefore, it may be inferred that the greatest changes in RFD variables will likely occur during a longer course.

Adult↗
PubMed2002

Relationship between football playing ability and selected performance measures.

The relationships between football playing ability (FPA) and selected anthropometric and performance measures were determined among NCAA Division I-A football players (N = 40). Football playing ability (determined by the average of coaches' rankings) was significantly correlated with vertical jump (VJ) in all groups (offense, defense, and position groups of wide receiver-defensive back, offensive linemen-defensive linemen, and running back-tight end-linebacker). Eleven of 50 correlations (groups by variables), or 22%, were important for FPA. Five of the 11 relationships were related to VJ. Forward stepwise regression equations for each group explained over half of the criterion variable, FPA, as indicated by the R(2) values for each model. Vertical jump was the prime predictor variable in the equations for all groups. The findings of this study are discussed in relation to the specificity hypothesis. Strength and conditioning programs that facilitate the capacity for football players to develop forceful and rapid concentric action through plantar flexion of the ankle, as well as extension of the knee and hip, may be highly profitable.

Adult↗
PubMed2002

Reconstructing human contributions to accidents: the new view on error and performance.

PROBLEM: How can human contributions to accidents be reconstructed? Investigators can easily take the position a of retrospective outsider, looking back on a sequence of events that seems to lead to an inevitable outcome, and pointing out where people went wrong. This does not explain much, however, and may not help prevent recurrence. METHOD AND RESULTS: This paper examines how investigators can reconstruct the role that people contribute to accidents in light of what has recently become known as the new view of human error. The commitment of the new view is to move controversial human assessments and actions back into the flow of events of which they were part and which helped bring them forth, to see why assessments and actions made sense to people at the time. The second half of the paper addresses one way in which investigators can begin to reconstruct people's unfolding mindsets. IMPACT ON INDUSTRY: In an era where a large portion of accidents are attributed to human error, it is critical to understand why people did what they did, rather than judging them for not doing what we now know they should have done. This paper helps investigators avoid the traps of hindsight by presenting a method with which investigators can begin to see how people's actions and assessments actually made sense at the time.

Accident Prevention↗
PubMed2003

Influence of the base-line determination on work efficiency during submaximal cycling.

AIM: The purpose of this study was to compare work efficiency values (WE = work accomplished/energy expenditure above exercising with 0 load) among different unloaded base-line correction techniques for different power outputs. METHODS: Twelve healthy men performed 6 5-min steady-state exercises of 0 (unloaded), 40, 80, 120, 160 and 200 W at a pedalling rate of 90 rpm on a cycle ergometer. Three different unloaded base-line corrections were used for WE calculation: an actual measurement of VO(2) corresponding to the unloaded pedalling exercise, the y-intercept value of the linear regression between VO(2) and power output and the y-intercept value of the curvilinear VO(2)-power regression. RESULTS: The present study demonstrated that WE was significantly higher when determined using the actual measurement of the unloaded VO(2) than y-intercept values of the linear (p<0.001) and curvilinear (p<0.05) VO(2)-power regressions. WE based on theoretical determinations (linear vs curvilinear regressions) were not significantly different. The power output significantly affected all WE index, with higher WE being measured when the power output was low and lower WE when power output was high. CONCLUSION: The high WE values determined using the actual VO(2) measurement could be explained by (i) the additional energy expended to stabilise the body in addition to the energy expenditure of moving the lower limbs without power production and by (ii) the difficulty to experimentally reproduce the unloaded condition. The large range of WE values measured in the present study is due to differences in the procedures used to determine the unloaded VO(2) (and thus differences in unloaded VO(2) values) as well as differences in the cycling intensities.

Adult↗
PubMed2002

Effects of regular training at the same time of day on diurnal fluctuations in muscular performance.

The aim of this study was to determine whether there is an effect of time of day on the adaptation to strength training at maximal effort. Fourteen participants took part in this experiment. Their peak anaerobic power (Wingate anaerobic test) and peak knee extension torque at six angular velocities (1.05, 2.10, 3.14, 4.19, 5.24 and 6.29 rad x s(-1)) were recorded in the morning (between 07:00 and 08:00 h) and in the evening (between 17:00 and 18:00 h) just before and 2 weeks after a 6 week course of regular training. Seven of them trained only in the morning and seven only in the evening. Multivariate analysis of variance revealed a significant group x pre-/post-training x time of day interaction effect for peak torque and peak anaerobic power. Before training, in both groups, peak torque and peak anaerobic power were significantly higher in the evening than in the morning. After training, there was no significant difference in peak torque and peak anaerobic power between the morning and the evening for the morning training group. In contrast, in the evening training group, peak torque and peak anaerobic power were higher in the evening than in the morning. As a result of training, both peak torque and peak anaerobic power increased from their initial values as expected. The morning training group improved their peak anaerobic power significantly in the morning and in the evening, the absolute increase being larger in the morning than in the evening. The evening training group did not improve their peak anaerobic power in the morning, whereas it improved significantly in the evening. Although peak torque was significantly improved by training in the morning and evening in both groups, the absolute increase was greater in the morning than in the evening in the morning training group, whereas the opposite was the case for the evening training group. These results suggest that training twice a week at a specific hour increases the peak torque and the peak anaerobic power specifically at this hour and demonstrates that there is a temporal specificity to strength training.

Adaptation, Physiological↗
PubMed1993

Single-character processing in a case of pure alexia.

The processing of single characters in a pure alexic patient was studied in an attempt to identify the impairment responsible for his reading disorder. Observations from Experiments 1 to 4 suggested a deficit of identification of alphanumeric stimuli without any impairment affecting the elaboration of a structural description of visual stimulation. Experiment 5 indicated that the identification disorder results from a defect in the selective processes--activation and/or inhibition--that must come into play for achieving an appropriate match between a structural description of the stimulation and representations of the identities of known stimuli. The possible implications of this deficit in single-character identification for word reading are discussed.

Adult↗
PubMed1990

Normal variation of P300 in children: age, memory span, and head size.

The P300 (P3) event-related brain potential was elicited in a group of 50 children and young adults (4-20 years). A simple auditory task was employed in which subjects indicated with a finger movement when a randomly occurring target tone (high pitch) was presented in a series of standard (low pitch) tones. The probability of the target tone was varied across conditions at 10%, 30%, or 50% to assess possible developmental changes in P300 amplitude. Memory capacity was assessed with forward and reverse digit spans. Circumference of the head also was measured. P300 latency decreased with age, and P300 amplitude tended to become larger with age. Polynomial regression analyses revealed significant quadratic trends in these relationships, with changes leveling off for older subjects. Digit span and head circumference also were related curvilinearly to P300 values. Multiple regression analysis indicated that changes in age and memory span both predicted significant changes in P300 latency and amplitude. Target stimulus probability generally affected all subjects in a similar fashion, although the strength of the correlational relationships tended to decline with increases in probability. Developmental changes for the N1, P2, and N2 components from the standard stimuli also were obtained. The results are discussed in terms of previous P3 findings for children and their implications for future studies.

Acoustic Stimulation↗
PubMed2005

A systems analysis of the Ladbroke Grove rail crash.

On 5 October 1999, near London Paddington Station, two trains collided on a main line near Ladbroke Grove. The immediate "human error" that preceded this crash was a Signal Passed At Danger (SPAD). Thirty-one people lost their lives and many more were injured. The crash prompted an extensive multi-disciplinary investigation and hearing to identify the factors that contributed to the Signal Passed At Danger event. This included the involvement of psychologists to consider the human factors "responsible" for the crash and the broader system context, including the operational and organizational environment that may have contributed. This paper summarizes the key factors identified in relation to this crash within a system analysis framework. This framework considers multiple sources of influence upon the driver in relation to the committed Signal Passed At Danger. These influences include direct factors attributable to the driver and the immediate circumstances of the event, as well as indirect, or latent, factors within the operational procedures and the management of the organization. This systemic combination of factors, not an isolated case of human error, conspired to propagate the events that resulted in the Signal Passed At Danger event and subsequent crash. This particular case demonstrates that train crashes cannot be distilled to a single causal factor. Rather, such crashes result from a system failure in which unpredicted interactions between direct and indirect influences coincide at an inopportune instant.

Accident Prevention↗
PubMed2006

Cross-cultural differences in driving skills: a comparison of six countries.

The first aim of the present study was to investigate the applicability of the two-factor structure (perceptual-motor skills by 11 items, e.g., "fluent driving"; safety skills by 9 items, e.g., "conforming to the speed limits") of the Driver Skill Inventory (DSI) among British, Dutch, Finnish, Greek, Iranian, and Turkish drivers. It was also hypothesized that the combination of self reported high ratings of perceptual-motor skills and low ratings of safety skills creates a serious risk for dangerous driving and road accident involvement. The second aim of this study was, therefore, to investigate this asymmetric relationship between perceptual-motor and safety skills in traffic penalties and accident involvement. Two hundred and forty two drivers were chosen from each of the six countries, matched for age and sex. The results of exploratory factor analyses together with target rotation showed that the two-factor structure of DSI found in "safe" Northern and Western European countries were highly congruent. However, the safety skills factor of DSI in Greece, Iran, and Turkey was relatively incongruent in spite of high factor similarity found in perceptual-motor skills. The asymmetric relationship between perceptual-motor and safety skills on traffic penalties was found in Finland and Turkey. A negative relationship between safety skills and the number of accidents was found both in Greece and Iran while a positive relationship between perceptual-motor skills and the number of accidents was found only in Iran.

Accidents, Traffic↗
PubMed2005

Human error risk management methodology for safety audit of a large railway organisation.

This paper considers the application of the human error risk management for engineering systems (HERMES) methodology for safety assessment studies. The application concerns the recurrent safety audits (RSA) of a large organisation in the domain of railway transportation systems. The objective of the study was the identification of the most relevant areas of intervention for improving safety and reliability of the service. The methodology has been applied to the whole organisation and its working processes. Specific attention was paid to train drivers. A number of critical indicators of safety and recurrent safety audit matrices were identified, which enabled the assessment of the safety level of the organisation and the generation of safety recommendations. The application of HERMES to this case study shows that the methodology is applicable in practice and can give valuable and significant results.

Efficiency, Organizational↗
PubMed2005

Timeliness and task specification in designing for human factors in railway operations.

Human error is often related to flaws in system design which might have been avoided had greater attention been paid to human factors knowledge and methods as the system was developed. The paper considers the role of human factors in system design and argues that adopting an operational perspective in identifying human factors issues ensures that subsequent human factors advice is focused upon real needs and is consistent with how managers and engineers choose to manage their systems. It also considers the issue of timeliness of human factors input. Failure to consider human factors issues at a time when other design decisions are being taken often means that it is less straightforward to accommodate changes. Thus, managers and engineers may resist dealing effectively with potential human factors problems for reasons of cost and delay in meeting project milestones.

Ergonomics↗
PubMed2006

Principal component analysis of lifting waveforms.

BACKGROUND: One limiting factor in lifting research design has been the inability to effectively analyze waveform data, especially when differences in body mass, height, and load magnitude influence the derived kinetic variables. The purpose of this study was to demonstrate the sensitivity of principal component analysis to quantify clinically relevant differences in kinetic lifting waveforms over three load magnitudes and between two separate populations. METHODS: Principal component analysis was applied to five kinetic lifting waveforms. The derived principal component scores were used as the dependent measures in a two-way (clinical status x load magnitude) MANOVA. FINDINGS: Significant low back pain group differences (P<0.05) were found for three of the principal component scores on extension moment generation in the sacral and thoracic regions and for trunk compression. Significant differences were found for each variable with respect to the magnitude across the entire lift time between the three load conditions, as well as four significant differences related to inferred mechanical changes that resulted from lifting increasingly heavier loads. INTERPRETATION: Principal component analysis of kinetic lifting waveforms was shown to be insensitive to a confounding factor of different load magnitudes when attempting to identify previously determined clinically relevant differences in the waveform trajectories. The analysis was able to partition the variability attributed to the direct influence of different external load magnitudes, versus those differences in spinal loading that arose from the variations in the lifting mechanics of increasing loads. The technique could be beneficial for other kinetic analyses where confounding magnitude modifiers like body size are present.

Adult↗
PubMed2006

Task-specific recruitment of motor units for vibration damping.

Vibrations occur within the soft tissues of the lower extremities due to the heel-strike impact during walking. Increases in muscle activity in the lower extremities result in increased damping to reduce this vibration. The myoelectric intensity spectra were compared using principal component analysis from the tibialis anterior and lateral gastrocnemius of 40 subjects walking with different shoe conditions. The soft insert condition resulted in a significant, simultaneous increase in muscle activity with a shift to higher myoelectric frequencies in the period 0-60 ms after heel-strike which is the period when the greater vibration damping occurred. These increases in myoelectric frequency match the spectral patterns which indicate increases in recruitment of faster motor units. It is concluded that fast motor units are recruited during the task of damping the soft-tissue resonance that occurs following heel-strike.

Computer Simulation↗