Training for Vigilance: Repeated Sessions with Knowledge of Results

Abstract

Two groups of subjects were run in a visual monitoring test, one with knowledge of results (KR) providing instant feedback of correct responses, commissive errors, and missed signals, and the other with no knowledge of results (NKR). The groups were run for five 48-minute sessions on consecutive days, with a follow-up transfer session five weeks later. Results showed significant differences in detection rates between the groups on all five training sessions, but not on the transfer session. Detection rates increased significantly during the five training sessions for both groups, and at approximately the same rate. Commissive errors were significantly different only in the first two training sessions, with the KR subjects showing more false alarms. Commissive errors did not increase or decrease over time within sessions, or over the five training sessions.     

Can experience modulate handler responses to boxes designed to decrease musculoskeletal load?*

Abstract

Biomechanical load during the handling of commercial (cardboard box with and without cut out) and non-commercial boxes (cardboard box with a retreat on the bottom edges), on experienced compared to inexperienced subjects was evaluated. Thirty-seven inexperienced and 21 experienced workers handled all boxes at shoulder and ground levels. Biomechanical load on upper limb was investigated through posture and electromyography (EMG) recordings. Comfort and effort were assessed immediately after each handling. In general, experienced workers had low range of motion. On the other hand, EMG was similar between both groups, except when non-commercial boxes were handled in non-favourable heights. Comfort was higher when a non-commercial box was handled versus a commercial one, regardless of the group. Both groups had a lower biomechanical load when handling the non-commercial boxes compared to the commercial ones. However, experienced workers did not have the same advantage as inexperienced subjects when handling those new boxes.

Practitioner Summary: Box designs favouring intuitive hand coupling and more efficient postures have potential to reduce the risk of upper-limb musculoskeletal disorders in inexperienced subjects. However, ergonomist has to deal with workers on different levels of experience. Results of this study can support the development of effective recommendations for the working context.     

EFFECTS OF NOISES OF HIGH AND LOW FREQUENCY ON BEHAVIOUR

Three groups of subjects worked for two sessions in noise at a five-choice serial reaction task. During one session the noise was restricted to frequencies above 2000 c.p.s., and during the other to frequencies below. The high frequency noise gave more errors in performance, although the difference was significant only at the highest intensity of 100 dB.

When reaction times were measured to the same noises, the first reaction of a series with the same type of stimulus was slower when the stimulus was low intensity and low frequency. With high frequency or high intensity stimuli this was not so.

It thus appears that sounds more likely to interfere with work also produce a faster reaction when themselves acting as signals, confirming a view already advanced about noise effects ; that the effect is due to competition between various stimuli to control response.     

The effect of feedback training on lumbosacral compression during simulated occupational lifting

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p?=?0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p?<?0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.     

The accuracy of the AATSR sea surface temperatures in the Caribbean

The Along-Track Scanning Radiometer (ATSR) series of instruments provides the means to obtain accurate measurements of sea surface temperature (SST), with a target total uncertainty of ± 0.3 K, 1σ. In this paper, we present validation results from 1 year of comparisons between 1 km resolution SSTs derived from the third instrument in the series, the Advanced ATSR (AATSR), and in situ measurements obtained during 2003 from the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) over the Caribbean.Our dataset consists of 99 cloud-free matchups, 25 of which are two-channel SST retrievals (daytime) and 74 three-channel SST retrievals (nighttime). Validation results for both dual- and nadir-view SSTs for these matchups are presented. We demonstrate that the dual-nadir SST measurement difference (D-N) can be used to classify matchups and attribute the likely cause of a particularly high D-N to outbreaks of Saharan dust. Under conditions of ‘normal’ D-N, the bias and standard deviation of the two- and three-channel dual-view retrievals is − 0.05 K and 0.26 K, and 0.02 K and 0.25 K, respectively. Dual-view SSTs obtained when the D-N is high over the Caribbean exhibit significant warm biases of 0.60 K and 0.32 K for two- and three-channel retrievals, respectively. Cool biases, with respect to the bias for ‘normal’ D-N, are observed in the nadir three-channel (N3) SSTs; for matchups with high D-N, the bias and standard deviation are − 0.16 K and 0.31 K, compared with 0.14 K and 0.24 K for ‘normal’ D-N. The distribution of the nadir two-channel retrievals is non-Gaussian and the apparent accuracy is comparatively poor, demonstrating clearly the advantages of using a sensor with dual-viewing capabilities to obtain a superior atmospheric correction, particularly when data from an additional short-wave infrared channel (e.g. at 3.7 μm) is not available.     

Low back stress, muscle usage, and the appearance of transient load movement during manual lifting

Neuromuscular involvement should be considered in biomechanical evaluations of a worker's job-related stresses as a potential aid to understanding and reducing the rising incidence of low back problems in industry. Because such interactions have seldom been investigated in multisegmental movements, the present study was undertaken to determine the effects of the involvement of the neuromuscular system during lifting by creating conditions in which subjects had prior knowledge (PK) of a load's magnitude as well as when they had no prior knowledge (NK). Two groups of subjects, experienced and inexperienced lifters (N=40), lifted loads varying from 6.8 to 13.6 kg under both the PK and NK conditions. Results indicated that two general patterns of load movement were used by the subjects: smooth and oscillatory (irregular transient), with higher peak L4/L5 forces and higher peak trunk movements found in the oscillatory pattern. Significant differences on all stress values were demonstrated by the inexperienced lifters. The inclusion of lift preparation and load knowledge considerations in training programmes and biomechanical models is recommended.     

A review of: “Visual Display Terminals and Workers' Health”, WHO Offset Publications 99, WHO,Geneva (1987), pp. vi + 206, Sw. F32, $19.20, ISBN 92 4 170099 8

Abstract

Military training aims to improve load carriage performance and reduce risk of injuries. Data describing the lumbar spine (LS) postural response to load carriage throughout training are limited. We hypothesised that training would reduce the LS postural response to load. The LS posture of 27 Marines was measured from upright MR images: with and without load (22.6 kg) at the beginning, middle, and end of School of Infantry (SOI) training. Disc degeneration was graded at L5–S1. No changes in posture and disc degeneration were found throughout training. During load carriage the LS became less lordotic and the sacrum more horizontal. Marines with disc degeneration had larger sacral postural perturbations in response to load. Our findings suggest that the postural response to load is defined more by the task needs than by the physical condition of the Marine.

Practitioner Summary: The effect of military training on lumbar spine posture is unknown. The lumbar posture of 27 Marines was measured from upright MR images, with and without load throughout infantry training. No changes in posture or IVD degeneration were found across training. Marines with degeneration at the L5–S1 level had larger sacral postural perturbations in response to load.     

The effects of toluene and alcohol on psychomotor performance

Abstract

Eight male subjects took part in four experimental sessions in an exposure chamber to assess the effects of toluene (80 p.p.m.) and alcohol (0.4 ml per kg body weight) individually and in combination on four measures of performance and also on mood. Alcohol caused a significant deterioration over the exposure session in performance on pursuit tracking and visual search tasks and also in mood. Toluene had no significant effect on any of the behavioural measures, but examination of mean scores for each treatment suggested a tendency for performance and mood to deteriorate more when alcohol and toluene were administered together than when alcohol was taken alone.     

On the utility of experiential cross-training for team decision making under time stress

This study investigated the effectiveness of experiential cross-training in a team context for team decision-making under time stress in a simulated naval surveillance task. It was hypothesized that teams whose members explicitly experience all team positions will perform better under time pressure due to a better shared Team Interaction Model (Cannon-Bowers et al. 1993). In addition, it was posited that experiential cross-training would reduce the negative effect of member reconfiguration that can occur in certain military situations. Three groups of teams participated in this study (cross-trained, reconfigured and control). The experiment involved three team training sessions, followed by three time-stressed exercise sessions. During training, one group of teams was cross-trained (CT) by asking each member to perform an entire session at each of the three team positions. Member reconfiguration (where each member was shifted to another's position) was unexpectedly introduced at the first of the exercise sessions for the CT group and for another group (reconfigured) that had not been cross-trained. A third (control) group was neither cross-trained nor reconfigured. During training, the performance of non-CT teams improved more quickly than that of CT teams. During the exercise, the CT group did not achieve the level of performance of the control teams. The immediate effect of team member reconfiguration was to degrade performance significantly for the non-CT teams, but not for the CT teams. The findings are discussed in terms of the multiple mental models' view of team performance (Cannon-Bowers et al. 1993) and the authors discuss the relative utility of crosstraining when overall training time is fixed.     

Validation and adjustment of the mathematical prediction model for human rectal temperature responses to outdoor environmental conditions

Abstract

Models to predict rectal temperature (T_re ) have been based on indoor laboratory studies. The present study was conducted to validate and adjust a previously suggested model for outdoor environmental conditions. Four groups of young male volunteers were exposed to three different climatic conditions (30°C, 65% rh; 31°C, 41% rh; 40°C, 20% rh). They were tested both in shaded and open field areas (radiation: 80 and 900 W-m^?2, respectively) at different work loads (100, 300 and 450 watt). Exercise consisted of two bouts of 10 minutes rest and 50 minutes walking on a treadmill, at a constant speed (1.4m ? s^?1) and different grades. The subjects were tested wearing cotton fatigues and protective garments. Their T_re and heart rate were monitored every 5 min and skin temperature every 15 min, oxygen uptake was measured towards the end of each bout of exercise; concomitantly, ambient temperature, relative humidity and solar load were monitored. We concluded that: (a) the corrected model to predict rectal temperature overestimates the actual measurements when applied outdoors; ( b) radiative and convective heat exchanges should be considered separately when using the model outdoors; ( c) radiative heat exchange should also be considered separately for short-wave radiation (solar radiation) and long-wave emission from the body to the atmosphere. Finally, an adjusted model to be used outdoors was suggested.     

Unimanual and Bimanual Control in a Compensatory Tracking Task∗

Abstract

This paper reports an experiment comparing the unimanual and bimanual control performance of human operators in a compensatory tracking task. Two variables of the control system dynamics, the target wave frequencies and the delayed visual feedback (DVF) of operator's hand control motion were also investigated. Target wave frequencies of 0.067 Hz, 0.167 Hz and 0.383 Hz, and DVF of 0.0, 0.2, 0.4, 0.8 and 1.5 s were used. The experiment was divided into one practice session run over four days and one experimental session of two days for each of the six subjects in the study. A computer system was designed to generate target wave patterns, to measure hand control motions, to regulate DVF conditions, and to record task data, all on a real-time basis. The results indicate that unimanual tracking was significantly superior to the bimanual tracking under DVF conditions and higher levels of wave frequency, but not under the zero DVF or low wave frequencies. Tracking performance in general degraded as a function of increased wave frequencies and of increased DVF. Motor learning was observed under three wave frequencies without DVF, but not when DVF conditions were introduced in a series of trials.     

ACTIVITY LEARNING AND THE OLDER WORKER

Previous experiments have shown the superiority, especially for older recruits, of training methods where procedures of learning were incorporated into tasks involving activity.

In the present paper, the so-called Activity Method is subjected to closer scrutiny in two laboratory experiments. In one experiment the subject was required to learn a concept of colour-picture relationship by placing numerous pictures onto a board, of different colours in such a way that the emergence of an overall concept depended on the activity itself. This form of active learning benefited all age groups, but especially older subjects.

In the second experiment, subjects were required to memorize the relationship between a series of villages and the counties to which they belonged using a method which obliged the subjects to sort them on to a board. The manual activity involved in sorting the associates while learning thorn impeded the older subjects.

It is postulated that Activity learning confers no benefit if it evokes a series of mechanical responses. On the other hand, where the activity engenders creative thinking, then it is a preferred method of learning.     

Physiological and biochemical responses during incremental uphill load carriage

The present study aimed to examine the effect of carrying different magnitudes of load on the changes and relationships of salivary Immunoglobulin A (IgA) and cortisol concentrations and the physiological parameters. Twelve Indian soldiers performed an intense uphill treadmill walking at two speeds viz. 2.5 km h⁻¹ and 4 km h⁻¹ without any load and carrying 10.7 kg, 17 kg and 21.4 kg loads for 36 min. Salivary IgA concentration relative to total protein decreased significantly after each exercise session and cortisol concentration increased concomitantly with physiological variables e.g. heart rate (HR), oxygen consumption (VO₂), minute ventilation (VE) and energy expenditure (EE). An inverse correlation (P < 0.05) was observed between IgA with HR for all the conditions except when the participants walked at 4 km h⁻¹ carrying 17 kg and 21.4 kg load. The degree and type of physiological and biochemical responses may help in designing combat training, operations and developing preventive strategies of military personnel involving intense exercise.Relevance to industry: Walking with load in incremental uphill terrain is highly stressful and fatiguing. Results of the present study will help in designing training schedules for maintaining the optimal fitness of an individual during uphill walking with loads in different speeds.     

The Role of Peripheral Vision in Static Balancing

Abstract

A study was made to determine the role of peripheral vision in static balancing. Three groups of subjects were tested under sighted and blindfold conditions, and also under a minimal cues condition.

One of these groups was trained in the use of peripheral vision and after five days achieved sighted competence under the minimal cues condition. A second group had no training, but practised for a similar period and showed no such improvement. The third group was tested with progressively decreasing amounts of peripheral vision, and the stage at which deterioration in performance occurred was noted. The results are discussed in relation to the use of peripheral vision, and in the relevance of this work to the training of the blind.     

Effects of sign characteristics and training methods on safety sign training effectiveness

This study investigated whether or not training methods affected the effectiveness of symbol training and if there were any relationships between sign symbol characteristics and training effectiveness. Altogether, 26 Mainland China industrial safety signs were used and 60 participants were randomly assigned into four equal-sized groups of control, paired-associate learning, recall training and recognition training. The result was that participants from all the training groups showed significantly greater improvement in comprehension performance than those in the control group, indicating that the training methods improved comprehension of the meaning of safety signs. Participants from the recall training group performed better in the post-training test than those from other training groups. It seems that the recall task elicited a deeper level of learning than the recognition task and that questioning and feedback had a positive effect on training effectiveness. The results also showed that sign characteristics had no significant influence on training effectiveness. It was concluded that recall training is more effective in enhancing comprehension of industrial safety signs than paired-associate learning or recognition training. The findings of this study provide a basis for useful guidelines for designing symbol-training programmes and for designing more user-friendly safety signs.

Statement of Relevance: The present study shows that recall training was more effective in improving comprehension of industrial safety signs than paired-associate learning or recognition training and cognitive sign features did not influence training effectiveness. They provide a basis for useful guidelines for designing symbol-training programmes and for designing more user-friendly safety signs.     

Localization performance of binaurally recorded sounds with and without training

One of the problems associated with listening to binaurally recorded sound events is localization confusions. The main objective of this investigation was to find out whether a short training session prior to listening to binaural recordings through headphones would facilitate correct spatial perception of the sound field. Focus was on the localization of the sound stimuli in median plane. Sound signals were recorded with an artificial head in three different conditions namely, anechoic, highly reverberant and moderately reverberant. Fourteen subjects participated in the listening tests. All subjects were required to localize all virtual sound stimuli under two different conditions. The first condition had a short training session binaurally recorded in the same environments as preceeding sound stimuli, and only sound stimuli recorded in the same environment were presented. The second condition did not have a training session, and sound stimuli recorded in different environments were presented. Results showed that a short training session prior to listening to binaurally recorded sounds through headphones was useful as it facilitated localization performance. The biggest effect was in reduced amount of sounds perceived inside the head. It was most pronounced for sound stimuli recorded in anechoic environment.     

Effects of handicraft sitting postures on lower trunk muscle fatigue

Fifteen male subjects were exposed to a primary tracking task and a variety of subsidiary tasks for a total of 15 hours. Tracking performance was assessed through the use of two error measures, amount of time off the target track, and number of times off target. Subsidiary performance tasks included: a vigilance task requiring subjects to respond to the deflection of the noodle of a small meter; two reaction time tasks requiring response to the onset of one or the other of two lights; mental multiplication, which required the solution of simple multiplication problems; and digit span, in which the subject was required to repeat as rapidly and as accurately as possible a sot of digits of either five, six or seven numbers in length. In addition, three physiological measures were obtained.

A significant decrement in trucking performance was obtained for both measures utilized. This decrement was not particularly abrupt in its occurrence but rather took place cumulatively over the entire course of the experiment. There was no clearly established performance decrement on the subsidiary tasks utilized in this investigation. A marked variability in performance over the course of the experimental session was characteristic of performance on these tasks. Performance on the vigilance task, and one of the reaction time tasks improved during the 15-hour test session.

The 17-Kotosteroid and 17-Hydroxyeortieoid values increased during the session but only in the case of the latter was the increase significant. The eosinophil count of subjects exposed to the test conditions decreased steadily throughout the experimental session. However, eosinophil measures obtained from control subjects increased during a similar time period.     

Examining endplate fatigue failure during cyclic compression loading with variable and consistent peak magnitudes using a force weighting adjustment approach: an in vitro study

Abstract

Repetitive movement is common in many occupational contexts. Therefore, cumulative load is a widely recognised risk factor for lowback injury. This study quantified the effect of force weighting factors on cumulative load estimates and injury prediction during cyclic loading. Forty-eight porcine cervical spine motion segments were assigned to experimental groups that differed by average peak compression magnitude (30%, 50% and 70% of predicted tolerance) and amplitude variation (consistent, variable). Cyclic loading was performed at a frequency of 0.5?Hz until fatigue failure occurred. Weighting factors were determined and applied instantaneously. Inclusion of weighting factors resulted in statistically similar cumulative load estimates at injury between variable and consistent loading (p?>?.071). Further, survivorship was generally greater when the peak compression magnitude was consistent compared to variable. These results emphasise the importance of weighting factors as an equalisation tool for the evaluation of cumulative low back loading exposures in occupational contexts.

Practitioner summary: Weighting factors can equalise the risk of injury based on compression magnitude. When weighted, the cumulative compression was similar between consistent and variable cyclic loading protocols, despite being significantly different when unweighted and having similar injury rates. Therefore, assessing representative occupational exposures without evaluating task performance variability may underestimate injury risk.

Abbreviations: FSU: functional spinal unit; UCT: ultimate compression tolerance     

Use of the average electromyogram in design evaluation Investigation of a whole-body task

The information content of the average electromyogram (AEMG) was investigated in a whole-body task, load carriage. Four subjects walked for approximately 2 hours at 5-6km/h with each of three different loads (20, 25 or 32 kg) in each of two placements on the back. EMG was sampled for 15 strides after 5, 37 and 97min walking. The myoelectric signal was telemetered from the tibialis anterior, vastus lateralis, biceps femoris, erector spinae and trapezius muscles, then processed digitally to yield the time average of the rectified electromyogram (AEMG).

Analyses of variance indicated a significant load magnitude by load placement by duration interaction on the trapezius muscle. The 20 kg load tended to elicit more EMG from trapezius than the other two over the entire duration of load carriage, but only for the high load placement. In the low placement all three loads elicited similar AEMG values from trapezius after 97min load carriage. Subjects responded quite differently to the independent variables, but all showed appreciable EMG changes in several of the experimental conditions. Individual differences, important in work task assessments, tended to be masked by examining group means alone.

The results indicate that AEMG measures do provide useful information in the investigation of whole-body tasks, but that their use is less straightforward in this capacity than in the investigation of more constrained or simplified tasks.     

Comparison of swimming with running as training stimuli

Abstract

The cardiovascular training effect was compared between swimming and running. Twenty-two healthy young adult women trained for 6 weeks either swimming or running with the same frequency,.duration and intensity (as judged by heart rate). Both groups showed significant improvement in cardiovascular fitness after training, assessed on a bicycle ergometer, with no significant difference between the two groups before or after training.