The effects of extended work under sleep deprivation conditions on team-based performance

Teamwork is becoming increasingly common in today's workplaces; however, little research has examined how well teams perform under sleep deprivation conditions. The purpose of the current study was to examine the effect of extended work under sleep deprivation conditions on team performance. A total of 24 participants were sleep deprived for 30 h and completed 16 h of sustained operations during the last portion of the sleep deprivation period. The participants completed the Wombat, a complex task including vigilance and cognitive components, with a partner in four 24-min testing sessions during the sustained operations period. The results indicated that team performance increased during the work period while, within each testing session, team performance on vigilance tasks remained stable and overall performance decreased. The current results suggest that performance on two-person teams results in improved performance but does not fully counteract the decreases in performance within each work period. Performance in two-person teams increased across an extended work shift under sleep deprivation conditions. However, vigilance performance remained stable while overall performance decreased when examining performance in 8-min segments. These results suggest that averaging team-based performance over a longer testing period may mask the negative effects of sleep deprivation.

Statement of Relevance: Performance in two-person teams increased across an extended work shift under sleep deprivation conditions. However, vigilance performance remained stable while overall performance decreased when examining performance in 8-min segments. These results suggest that averaging team-based performance over a longer testing period may mask the negative effects of sleep deprivation.     

The use of prophylactic naps and caffeine to maintain performance during a continuous operation

After a normal baseline night of sleep and a morning of baseline test performance, 24 young adult male subjects returned to bed from 16:00-20:00 prior to a 24?h period of sleep loss. Twelve subjects received caffeine 200?mg at 01:30 and 07:30. Performance tests (correctly completed addition problems, vigilance sensitivity, and logical reasoning correct responses) all indicated maintenance of baseline performance levels in the caffeine group after administration of caffeine while performance declined in the placebo group. Similar results were found for the Multiple Sleep Latency Test and Oral Temperature, which both remained near baseline levels throughout the observation period in subjects receiving caffeine. The results indicated that the combination of a prophylactic nap and caffeine was more effective in maintaining nocturnal alertness and performance than was the nap alone. Of more interest was the fact that the group which was given the combination of nap and caffeine was able to maintain alertness and performance at very close to baseline levels throughout a 24?h period without sleep.     

Muscular strength profiles and anthropometry in random samples of men aged 31–35, 51–55 and 71–75 years

Maximal isometric muscular strength and anthropometric characteristics were studied among three random samples each containing about 180 Finnish men belonging to three generation cohorts, and having a mean age of 32·9 ± 1·4, 53·1 ± 1·5 and 72·7± 1·4 years. Strength was measured on special dynamometers for grip, trunk and knee extension and trunk and elbow flexion. The anthropometric characteristics included body height, weight, body-mass index, skeletal weight, fat weight and a weight factor.

The youngest cohort had the highest and the oldest cohort the lowest values for strength as well as body height and fat-free body weight, while the middle-aged group had the highest and the youngest group the lowest values for body weight, fat weight, body-mass index and for the weight factor.

In correlation analysis grip strength was found to have the highest correlation with chronological age and to be least affected by the body anthropometric variables among the strength variables studied. On a percentage scale the decline of strength from the youngest to the oldest cohort was in the order: knee extension (47%), hand grip (42%), trunk extension (42%), trunk flexion (35%) and elbow flexion (35%). The body-mass index was found to be an important variable to be controlled in studying differences between age groups in muscle strength.     

Upper to lower body muscular strength and endurance ratios for women and men

Abstract

This study examined possible gender differences for relative upper (elbow) to lower (knee) body strength and endurance, as well as relative flexion to extension strength and endurance. Seven women and nine men who were matched for both upper and lower body aerobic power were tested on an isokinetic strength instrument. Absolute isokinetic strength was lower (P<0-01) for the women than the men for all measurements. When strength was expressed per lean body weight, the women were weaker (P<005) only for elbow flexion strength. The women had a lower (P<005) upper to lower body strength ratio for flexion, but not for extension. There were also no differences (P>005) in isokinetic endurance fatigue decrements, or upper to lower body endurance ratios between genders. These data indicated that there were differences in absolute strength between the genders, but strength per lean body weight, as well as upper to lower body ratios for strength and endurance were similar for both genders. It was recommended that aerobic fitness and level of training be taken into account when strength and endurance were compared between the genders.     

Gender influences on performance,mood and recovery sleep in fatigued aviators

Female aviators now are able to serve in combat roles, but few studies have addressed potential differences between the ability of males and females to withstand combat stressors. This study examined responses of men and women to one operational stressor, sleep deprivation. Pilots were tested on flight performance and mood during 40-h periods of sustained wakefulness. Baseline and recovery sleep also were examined. Gender produced no operationally significant effects on flight performance or recovery sleep. Although mood tests showed that women felt less tense and more energetic than men, there were no interactions between sleep deprivation and gender on either flight performance or psychological mood.     

Sleep patterns,shiftwork, and individual differences: a comparison of onshore and offshore control-room operators

Abstract

The sleep patterns of offshore control-room operators were compared with those of personnel carrying out similar work onshore, taking into account individual differences in age, number of years of shiftwork, and neuroticism. The dependent variables were self-reported sleep quality and duration for day-shift (D-S) and night-shift (N-S) work, and during leave periods (L-P) Offshore workers reported longer N-S sleep duration, and lower D-S sleep quality than those onshore, but the two groups did not differ in L-P measures. The effects of environmental differences (onshore versus offshore) on sleep patterns were more marked than those of the two different shift systems (weekly rotation and fast rotation) in operation onshore. Age was negatively related to both duration and quality of sleep; over and above age, number of years of shiftwork was negatively related to sleep duration. Neuroticism was also negatively related to sleep duration and, more strongly, to sleep quality. These findings are discussed in relation to the literature on shiftwork and sleep in general, and the characteristics of the offshore environment in particular     

Sleep and errors in a group of Australian hospital nurses at work and during the commute

There is a paucity of information regarding Australian nurses' sleep and fatigue levels, and whether they result in impairment. Forty-one Australian hospital nurses completed daily logbooks for one month recording work hours, sleep, sleepiness, stress, errors, near errors and observed errors (made by others). Nurses reported exhaustion, stress and struggling to remain (STR) awake at work during one in three shifts. Sleep was significantly reduced on workdays in general, and workdays when an error was reported relative to days off. The primary predictor of error was STR, followed by stress. The primary predictor of extreme drowsiness during the commute was also STR awake, followed by exhaustion, and consecutive shifts. In turn, STR awake was predicted by exhaustion, prior sleep and shift length. Findings highlight the need for further attention to these issues to optimise the safety of nurses and patients in our hospitals, and the community at large on our roads.     

Standard and alternative methods of stretcher carriage: performance,human factors,and cardiorespiratory responses

Transporting a casualty on a stretcher is a common task for medical and military personnel. Stretchers are usually carried by hand, but distributing the load to other parts of the body may have advantages. To examine alternative carriage methods, 11 soldiers walked on a treadmill at 4.8 km/h while performing two person carries of a stretcher containing an 80-kg manikin. In separate trials, soldiers carried the stretcher using: (1) hand carriage, (2) shoulder straps, (3) a specially designed harness that allowed load shifting between the hips and shoulders (hip-shoulder system), and (4) a clip that fitted on the belt of standard military load carrying equipment (LCE) and placed the stretcher mass mainly on the hips. With each system, subjects walked until volitional fatigue or 30 min. While walking, expired gases and heart rates were obtained and subjects rated their perceived exertion (Borg Scale). At the conclusion of all four trials, subjects rated each system on a number of subjective measures. Results showed that average (±SD) carriage times were 2.7±1.4, 14.5±8.3, 25.4±8.1, and 21.7±9.9 min with the hand, shoulder, hip-shoulder and LCE systems respectively (p<0.01). Hand carriage resulted in considerably more cardiorespiratory stress (higher heart rate and minute ventilation, p<0.05) than the other three systems, but there were few consistent differences among the other three systems. Perceived exertion in the upper body was less with the hip-shoulder and LCE systems than with the other two systems (p<0.05). Subjects preferred the hip-shoulder and LCE systems overall and for specific subjective characteristics such as comfort, ease of use and stability (p<0.01). These data indicate that moving the stretcher load from the hands and placing that load on the shoulders and/or hips results in improved performance, reduced cardiorespiratory stress and favourable subjective evaluations. Further developmental work should focus on the hipshoulder and LCE systems.     

Adapting exercise selection to performance,effort and self-esteem

ABSTRACT

Adapting to learner characteristics is essential when selecting exercises for learners in an intelligent tutoring system. This paper investigates how humans adapt next exercise selection (in particular difficulty level) to learner personality, invested mental effort, and performance to inspire an adaptive exercise selection algorithm. First, the paper describes the investigations to produce validated materials for the main studies, namely the creation and validation of self-esteem personality stories, mental effort statements, and mathematical exercises with varying levels of difficulty. Next, through empirical studies, we investigate the impact on exercise selection of learner's self-esteem (low versus high self-esteem) and effort (minimal, little, moderate, much, and all possible effort). Three studies investigate this for learners who had different performances on a previous exercise: just passing, just failing, and performed well. Participants considered a fictional learner with a certain performance, self-esteem and effort, and selected the difficulty level of the next mathematical exercise. We found that self-esteem, mental effort, and performance all impacted the difficulty level of the exercises selected for learners. Finally, using the results from the studies, we propose an algorithm that selects exercises with varying difficulty levels adapted to learner characteristics.     

Sleep in a live-in mining operation: The influence of start times and restricted non-work activities

The amount of sleep obtained between shifts is influenced by numerous factors including the length of work and rest periods, the timing of the rest period relative to the endogenous circadian cycle and personal choices about the use of non-work time. The current study utilised a real-world live-in mining environment to examine the amount of sleep obtained when access to normal domestic, family and social activities was restricted. Participants were 29 mining operators (26 male, average age 37.4 ± 6.8 years) who recorded sleep, work and fatigue information and wore an activity monitor for a cycle of seven day shifts and seven night shifts (both 12 h) followed by either seven or fourteen days off. During the two weeks of work participants lived on-site. Total sleep time was significantly less (p < 0.01) while on-site on both day (6.1 ± 1.0 h) and night shifts (5.7 ± 1.5 h) than days off (7.4 ± 1.4 h). Further, night shift sleep was significantly shorter than day-shift sleep (p < 0.01). Assessment of subjective fatigue ratings showed that the sleep associated with both days off and night shifts had a greater recovery value than sleep associated with day shifts (p < 0.01). While on-site, participants obtained only 6 h of sleep indicating that the absence of competing domestic, family and social activities did not convert to more sleep. Factors including shift start times and circadian influences appear to have been more important.     

Sleep and circadian rhythms in mining operators: limited evidence of adaptation to night shifts

Cumulative sleep deprivation is often associated with work patterns involving night shift or early morning shifts. Adaptation of the circadian system to the shift pattern is reported to promote improved duration and quality of sleep and a concurrent improvement in performance. The current study followed twenty-nine operators at a live-in mining operation working to a seven-day, seven-night shift pattern who collected saliva samples for melatonin measurement, recorded sleep using activity monitors and diaries, and underwent performance testing (psychomotor vigilance task) for one complete roster cycle. The time of onset of melatonin secretion changed significantly (P=0.022) across the week of both Day and Night shifts (2104 h ± 16 min versus 2130 h ± 16 min, respectively), but the small magnitude of the change indicates a lack of true circadian rhythm adaptation to the lifestyle. Total sleep time was longer following the seventh Day shift (associated with a period of 24 h off prior to the commencement of Night shifts). There were no other changes in total sleep time. Further, there were no improvements in sleep onset latency or sleep efficiency on Day or Night shifts. However, reaction times recorded at the end of the shifts slowed across the seven Day and seven Night shifts indicative of impairments in psychomotor performance (F(6,168)=6.087, P<0.001). The results suggest that previous reports of adaptation to consecutive night shifts cannot necessarily be applied to onshore or Australian environments. Adaptation is dependent on factors such as light exposure, environmental conditions, shift parameters such as wake-up, work start and work end times and individual characteristics.     

Entropy analysis of muscular near-infrared spectroscopy (NIRS) signals during exercise programme of type 2 diabetic patients: Quantitative assessment of muscle metabolic pattern

Diabetes mellitus (DM) is a metabolic disorder that is widely rampant throughout the world population these days. The uncontrolled DM may lead to complications of eye, heart, kidney and nerves. The most common type of diabetes is the type 2 diabetes or insulin-resistant DM.     

Effects of a vertical keyboard design on typing performance, user comfort and muscle tension

To circumvent the awkward pronated hand position inherent to conventional horizontal keyboards, a vertical, split keyboard was designed with flexible cushions supporting the wrists, allowing relaxed hand and arm postures. During eight twice-weekly 30-min training sessions, the performance and subjective comfort of nine experienced typists were tested. Typing speed and error percentage, and surface electromyographic activity of six forearm muscles and two postural muscles were recorded in separate sessions at the end of each week. Typing speed rapidly recovered to the preset rate of 300 keystrokes/min and error percentages were similar for the two keyboards. The vertical keyboard caused lower muscular activity in especially finger extensor muscles, did not increase postural muscle activity, and self-reported comfort was higher. Thus, the vertical keyboard was easily mastered, was experienced as comfortable, and caused less stress on muscles sensitive to repetitive strain injuries.     

The effects of lumbar massage on muscle fatigue,muscle oxygenation,low back discomfort,and driver performance during prolonged driving

This paper reviews results of comparisons between novice and expert operators in the supervision of dynamic environments. Firstly, the characteristics of expertise and its operational definitions are discussed. Secondly, the main dimensions of the complexity of these environments are described and the difficulties operators have in coping with complexity are examined. Research work carried out in field studies is then overviewed in order to assess the role of expertise in the three components of process control: monitoring, diagnosis and decision-making and executive control. The discussion stresses the convergent results of various studies. In spite of the diversity of task domains and of novice-expert definitions, results converge on three points: experts are better at producing inference, in anticipating, and have a more functional view of the process. Divergent results on directionality of reasoning, depth of knowledge in relation to performance and synchronization of actions are also discussed. Finally, further research trends are outlined.     

The sleep and performance of train drivers during an extended freight-haul operation

The sleep and performance of train drivers was monitored across a 106-h rail operation between the Australian cities of Adelaide and Perth. The drivers worked alternating 8-h shift rotations across the operation and rested in specially equipped, crew-van carriages during non-work periods. The crew-van rest opportunities were associated with shorter bedtime spans, less total sleep time, and poorer sleep efficiency than sleeps initiated at home. The duration of crew-van sleeps was primarily dependent on the time of day at which the rest opportunities occurred. Overall, drivers incurred a significant cumulative sleep loss across the duration of the operation. Despite the deficit, drivers were able to sustain vigilance performance across the operation.     

A methodology for muscular isometric endurance and fatigue research

The objective of this study was to develop a reliable statistical method of finding a cut-off point between the endurance section and the fatigue section from a single endurance-fatigue curve of force versus time for extended times. Two age groups (20–29, 50–59 years old) with 10 subjects in each group participated in this study. Two muscle groups (biceps and quadriceps) were tested at five levels of % MVC (20, 40, 60, 80 and 100 % MVC). Subjects were instructed to exert a force and reach a designated % MVC level and maintain that level for as long as possible until asked by the experimenter to stop. Each condition was tested for five minutes. The method developed used the sum of squares technique to find the optimal cut-off point on the curve thus, determining the endurance time. The methodology proved to be useful and reliable. The steps involved along with an example are discussed.     

Sleepiness,alertness and performance during a laboratory simulation of an acute shift of the wake-sleep cycle

Monitoring the presence of sleepiness on the job and its effects on performance is of primary importance for improving schedule systems of shiftworkers. Shiftworkers, often involved in night-time operations and irregular work schedules, frequently complain of nocturnal sleepiness especially in conditions of abrupt shift of the wakesleep cycle. In this study, the authors evaluated the effects of a laboratory simulation of acute night-shift changes on sleepiness, vigilance and performance, using Maintenance of Wakefulness Test,Multiple Sleep Latency Test and three pencil and paper tests: Digit Symbol Substitition Test, ‘Deux Barrages’ Test and a 3-Letter Cancellation Task. All of the tests were administered four times at 2-hourly intervals during the night after daytime sleep. Results showed that the ability to maintain wakefulness and to perform simple visuo-attentive tasks is substantially spared during the night. On the other hand, sleep tendency and performance on a more complex and monotonous task (Letter Cancellation Task) reveal, respectively, increasing sleepiness and degrading performance.     

Intelligence,Work Performance,and Inspection Time

The additivity of strengths for teams of two and three untrained female subjects in eam-work was evaluated in static (isometric) and dynamic (isokinetic) terms. Eight healthy college students were tested under laboratory conditions. Four standard values were used to evaluate isometric strengths: arm, leg, stooped back, and composite measures. The isokinetic strength was tested by means of dynamic lift strength and dynamic back extension. Following individual measurement of the subjects, they were tested in two-member and three-member teams. Two-female teams w«re evaluated in terms of 28 combinations for each of the six measures; the three-female teams were tested in 56 combinations among the subjects. With the exception of isometric arm strength, the actual team strengths were significantly lower then the corresponding sums of the team-members' individual strengths. On average, the isometric back, leg and composite strengths were approximately 83·3% for the two-female teams, and 83·9% for the three-female teams. The isokinetic strengths for two-female and three-female teams accounted for about 68·0% and 68·4% of the sums, respectively. These results indicate that lifting strength of females in team-work is generally not additive and depends upon the muscle group in use, and suggests that lifting capacity in team-work will be reduced as the number of team members increases.