Bicycle messengers: energy expenditure and exposure to air pollution

The purpose of the study was to determine the level of energy expenditure and exposure to air pollution for bicycle messengers. Relationships between heart rate (HR) and oxygen uptake, and between HR and pulmonary ventilation (VE) for each participant were established in laboratory tests. Air pollution and HR were measured during one working day. The total oxygen uptake was then described as the total energy expenditure in Joule (J) and in multiples of the energy expenditure at rest (MET). The mean energy expenditure during a working day (8 h) was 12 MJ, (4.8 MET). The level of air pollution exposure when cycling seemed to be comparable with the levels of exposure when sitting inside a vehicle. The VE during cycling was four times higher than resting value. Increased VE led to increased exposure to air pollution.     

Bicycle messengers: energy expenditure and exposure to air pollution

The purpose of the study was to determine the level of energy expenditure and exposure to air pollution for bicycle messengers. Relationships between heart rate (HR) and oxygen uptake, and between HR and pulmonary ventilation (VE) for each participant were established in laboratory tests. Air pollution and HR were measured during one working day. The total oxygen uptake was then described as the total energy expenditure in Joule (J) and in multiples of the energy expenditure at rest (MET). The mean energy expenditure during a working day (8 h) was 12 MJ, (4.8 MET). The level of air pollution exposure when cycling seemed to be comparable with the levels of exposure when sitting inside a vehicle. The VE during cycling was four times higher than resting value. Increased VE led to increased exposure to air pollution.     

Loon Copter: Implementation of a hybrid unmanned aquatic–aerial quadcopter with active buoyancy control

Aquatic–aerial unmanned vehicles recently became the focus of many researchers due to their various possible applications. Achieving a fully operational vehicle that is capable of aerial, water‐surface, and underwater operations is a significant challenge considering the vehicle's air–water–air transition, propulsion system, and stability underwater. We present in this paper an unconventional unmanned hybrid aquatic–aerial quadcopter with active buoyancy control that is capable of aerial flight and water‐surface operation, as well as subaquatic diving. We report on the first successful prototype of the vehicle, named the Loon Copter, to provide initial evaluation results of its performance in both mediums. The Loon Copter uses a single set of motors and propellers for both air and underwater maneuvering. It utilizes a ballast system to control vehicle buoyancy and depth underwater, as well as to perform seamless air‐to‐water and water‐to‐air transitions. A closed loop control algorithm is utilized for the vehicle's aerial and water‐surface stability and maneuver, whereas an open loop control algorithm is used for underwater maneuver. The experimental results show a fully operational prototype with six degrees of freedom underwater, stable flight, operation capabilities on water surface, and agile maneuvering underwater.     

Physiological workload reactions to increasing levels of task difficulty

The sensitivity of physiological measures to mental workload was investigated in a flight simulator. Twelve pilots had to fly through a tunnel with varying levels of difficulty. Additionally, they had to perform a memory task with four levels of difficulty. The easiest memory task was combined with the easiest tunnel task and the most difficult memory task with the most difficult tunnel task. Between the tunnel tasks, subjects had to fly a pursuit task in which a target jet had to be followed. Rest periods before and after the experiment were used as a baseline for the physiological measures. Mental workload was measured with heart period, continuous blood pressure, respiration and eye blinks. Several respiratory parameters, heart rate variability, blood pressure variability and the gain between systolic blood pressure and heart period (modulus) were scored. All measures showed differences between rest and flight, and between the pursuit and the tunnel task. Only heart period was sensitive to difficulty levels in the tunnel task. Heart rate variability increased when respiratory activity around 0.10 Hz increased, which occurred often. The modulus was hardly influenced by respiration and therefore appears to be a better measure than heart rate variability. Among the respiratory parameters, the duration of a respiratory cycle was the most sensitive to changes in workload. The time in between two successive eye blinks (blink interval) increased and the blink duration decreased as more visual information had to be processed. Increasing the difficulty of the memory task led to a decrement in blink interval, probably caused by subvocal activity during rehearsal of target letters. The data show that physiological measures are sensitive to mental effort, whereas rating scales are sensitive to both mental effort and task difficulty.     

Workload measurement using physiological and activity measures for validation test: A case study for the main control room of a nuclear power plant

In design of safety-critical and social-technical systems such as a nuclear power plant, practitioners are required to conduct a performance-based Integrated System Validation (ISV) test to verify that the system design could support the safe operation of the plant. Measurement of workload should be included. However, subjective workload measurements could not provide detailed information and continuous monitoring of the changing workload. This study compared physiological (heart rate difference, heart rate variability, respiration rate and breathing wave amplitude) and activity (number of walking steps, peak acceleration, activity level, and inclination) measures with workload defined as intensity of task demand and estimated with a task complexity measure in an ISV test. The test was conducted on a full-scale simulator using a beyond design-basis accident scenario. The results show that heart rate difference and respiration rate are positively correlated with the estimated workload, while heart rate variability and breathing wave amplitude are negatively correlated with the estimated workload. For operations using traditional panels, high workload is accompanied by larger number of walking steps, higher activity level, and smaller angles of inclination. It is suggested that continuous monitoring of cardiovascular, respiration, and activity measures can detect workload change during the ISV test. Relevance to industry: This study provides recommendations for continuous monitoring of workload during an ISV test of a nuclear power plant. The identified physiological and activity measures can be applied in detecting workload change. The findings are supportive in meeting regulatory requirements and improving system design in the nuclear domain.     

OPTIMAL FORM AND DIMENSIONS OF HAND-GRIPS ON CERTAIN CONCRETE BUILDING BLOCKS

The optimal form and dimensions of hand-grips for handling certain types of concrete building blocks were found by theoretical considerations and laboratory experiments. Such grips wore found to reduce the physiological workload considerably. The maximal lifting power proved to be a far bettor criterion for the evaluation of minor changes in dimensions of handgrips than energy expenditure or heart rate during work.     

Comparative analysis of the workload in seated and standing horizontal submaximal lifting tasks

The objective of the present laboratory study was to analyse physiological responses of horizontal lifting tasks when they were performed in sitting and standing positions. Heart rate and blood pressure were used as indices of circulatory strain. Lifting tasks were performed under four lifting positions: sitting-forward lift, sitting-twist lift, standing-forward lift, and standing-twist lift. The weights of the loads were 3, 5 and 7 kg and the frequencies of handling were 1, 4 and 6 lifts/min. This study supports the idea that heart rate is a sensitive measure for evaluating the effects of seated horizontal lifting tasks. The lifting positions and workload (frequency × load × distance) are important parameters in the design of these types of tasks. It appears that within the experimental values examined in this study, a seated position could be recommended while performing horizontal lifting tasks at workloads ≤4·6 kg.m.min ^?1;. The results are supported by smaller physiological responses.     

Maximum frequency acceptable to female workers for one-handed lifts in the horizontal plane

Abstract

A laboratory study was conducted to determine the maximum frequencies acceptable to female workers for one-handed lifts in the horizontal plane. A psychophysical method was used to determine maximum acceptable frequency for an 8-hour workday. Ten female college students were required to lift continuously three different loads to two different reach distances (38 and 63 cm) on a 91 cm high work table. The lifting task was paced by a repeating timer which the subject controlled according to her subjective feelings of fatigue. Heart rate and RPE were measured during the last 5min of the experiment to determine the physiological level of functioning and perceived exertion. Psychophysically determined maximum acceptable frequencies were compared with the standards based on methods-time measurement (MTM) analysis.

Statistical analysis showed that both the weight of the load and reach distance had a significant effect on maximum frequency acceptable to the subjects. No single value for percentage of maximum frequency can be used to establish permissible one-handed lift limits in women; rather, this value depends upon the weight of the object and distance of lift. The average maximum acceptable frequency was 51% of the maximum frequency that the subjects could maintain for a period of 4min. The subjects selected workloads which resulted in a mean heart rate of 101 beats/min. The subjects rated the perceived exertion ranging from ‘fairly light’ to ‘somewhat hard’. Performance based on MTM analysis ranged from 11% below to 32% above the maximum workload acceptable to the subjects. The non-significant heart rate differences found among the six load-distance combinations lend strong support for the use of psychophysical methodology in future studies of fatigue criteria. The study also supports the previous findings that separate physiological fatigue criteria are needed for tasks involving arm work and whole body exertion.     

Physical Workload in Different Body Postures,While Working Near to,or Below Ground Level

The physical load of different working postures during a light job at low working level was compared while varying the frequency of forward movement and working level. The postures compared were bending, kneeling, squatting and sitting on a low stool. Energy expenditure, heart rate and the increase in heart rate over a five minutos' period were used as parameters. The following conclusions can be drawn. Bending and kneeling require less energy and arc less strenuous, when one hand (arm) is used as a support to balance the trunk. At high forward movement frequencies (more than 4 metres per minute or 5 movements per minute) the bending posture without arm support is loss strenuous than squatting and sitting on a one-legged stool. At low movements frequencies the squatting posture is preferable. Heart rate and energy consumption were slightly higher than that when sitting, but performance and also the gradient of the heart rate were slightly more favourable. The working height, varied from ? 14 cm to + 16 cm in comparison with the floor level, influenced the workload less. A remarkable increase in the work load was observed in the bending position only when the working level was lower than the level of the feet. If work has to be carried out in the ground itself, then squatting appears to be the most favourable position.     

UUV水下回收中的视觉和短基线定位融合

为了使UUV在水下坞舱回收过程中利用视觉和短基线(short baseline-SBL)进行导引定位,提出了一种视觉和短基线的自适应融合定位方法,以提高导引定位的精度.介绍了短基线定位和视觉定位2种定位系统及其工作原理,以及定位数据的野值剔除和去噪方法.野值剔除采用了一种基于数据变化率的自适应在线野值剔除方法,数据去噪采用了软阈值小波滤波方法.针对传统卡尔曼滤波进行数据融合时先验知识不足的缺点,提出了一种基于模糊逻辑的在线自适应卡尔曼滤波融合方法.通过获取的实时测量数据,实时调整噪声的协方差矩阵来融合2种定位数据.水下回收水池试验结果表明,定位传感器的绝大部分野值被剔除且去噪效果明显,视觉和短基线融合后的定位精度有很大提高,证明了所提方法的有效性.     

Book Review

Six unilateral above-knee amputees using prostheses with quadrilateral sockets of the ischial-bearing typo, who were otherwise able-bodied persons, were evaluated economically by subjecting them to the physical exercise of walking on level ground with graded loads by shoulder pack or rucksack method

During tests, the energy expenditure, oxygen consumption, pulmonary ventilation and peak heart rate were measured for each subject. Performances of the teat group subjects were compared with those of a control group comprising six normal, healthy, adult males of sedentary habits

Results showed a consistently high rise in all the physiological parameters for the test group even when walking without loads and with graded loads as compared to the corresponding values from control subjects. In other words the tasks undertaken by the test group subjects appeared to be heavy according to the existing norms of heaviness of work. Thus the tasks which may be ‘ light ‘ for normal individuals may become ‘ heavy ’ or ‘ very heavy ’ for the above-knee amputees and encroach greatly on their physiological reserves

This study has shown that evaluative tests combining both static and dynamic muscular work in addition to the usual leg work involved in a routine lower extremity activity, render diminutive effects to personal factors contributing variability in the performance of above-knee amputees fitted with prostheses. From this point of view the present study and the mode of tasting have proved to be an improvement over the methods employed by Ganguli et al. (1974), thus setting up norms for above-knee rehabilitee performance.     

Workload demand in police officers during mountain bike patrols

To the authors' knowledge this is the first paper that has used the training impulse (TRIMP) ‘methodology’ to calculate workload demand. It is believed that this is a promising method to calculate workload in a range of professions in order to understand the relationship between work demands and aerobic fitness. The aim of this study was to assess workload demand in police officers from the Utrecht police department in the Netherlands, during patrol by mountain bike. Maximum oxygen intake, maximum heart rate (HR_max), ventilatory threshold (VT)1 and VT2 were determined with a maximal exercise test on a bicycle ergometer. Heart rates were registered throughout three shifts in 20 subjects using a heart rate monitor. Exercise intensity was divided into three phases: phase I (between 40% of HR_max and VT1); phase II (between VT and the respiratory compensation point (RCP)); and phase III (>RCP). The total TRIMP score was obtained by summating the results of the three phases. Average daily workload demands of 355 TRIMPs per day and 1777 TRIMPs per week were measured. Workload demand approached and in some cases exceeded the upper limit of 2000 TRIMPs per week threshold level for physiological stress demands in professional male cyclists.     

Physiological response of beach lifeguards in a rescue simulation with surf

The objective of this study was to examine the physiological response of 14 lifeguards in a swimming pool simulation with 1.7 m waves and to study the efficiency of the torpedo buoy. The rescue time was determined with and without material, as were lactate levels, heart rate and VO_2max. The results obtained showed a VO_{2 max} rate of 3.4 ± 0.8 l/min without equipment and 3.3 ± 0.8 l/min with equipment. Moreover, the time taken to swim towards the victim without equipment decreased by 7.7 s, while towing time was reduced by 10.8 s if said equipment was used. These results show that aquatic rescue makes considerable physiological demands on the swimmer and they also provide important data on the type of training and aptitude levels required by individuals wishing to join these rescue groups. The equipment currently used has a negative affect on the swim.

Statement of Relevance: The study shows that beach rescues make very high physiological demands on rescuers, thus underlining the need to perform entry tests for these highly demanding rescue teams. The auxiliary equipment is a help in the return time of rescue. However, it causes delays in the approach to the victim.     

Design and performance evaluation of a biomimetic microrobot for the father–son underwater intervention robotic system

Underwater intervention is a favorite and difficult task for AUVs. To realize the underwater manipulation for the small size spherical underwater robot SUR-II, a father–son underwater intervention robotic system (FUIRS) is proposed in our group. The FUIRS employs a novel biomimetic microrobot to realize an underwater manipulation task. This paper describes the biomimetic microrobot which is inspired by an octopus. The son robot can realize basic underwater motion, i.e. grasping motion, object detection and swimming motion. To enhance the payload, a novel buoyancy force adjustment method was proposed which can provides 11.8 mN additional buoyancy force to overcome the weight of the object in water. Finally, three underwater manipulation experiments are carried out to verify the performance of the son robot. One is carried by swimming motion and buoyancy adjustment; the other two are only carried by buoyancy adjustment. And the experimental results show that the son robot can realize the underwater manipulation of different shape and size objects successfully. The swimming motion can reduce the time cost of underwater manipulation remarkably.     

Physical,mental, emotional,and subjective workload components in train drivers

This study, using 12 train drivers on a high speed track and 11 drivers on a mountain track, tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work. With the simultaneous recording and on-line analysis of heart rate and physical activity, the emotional component in terms of the so-called additional heart rate was separated from the physical component. Mental workload was calculated by the heart rate variability and by shifts in the T-wave amplitude of the ECG. Speed of the train, mode of driving, and stress of the situation were rated by two observers who accompanied the drivers in the cabin. During speeds up to l00km/h as compared to standstills no heart rate changes occurred, but with speeds from l00km/h up to 200 km/h heart rate decreased indicating a monotony effect. However, heart rate variability, and T-wave amplitude indicated higher mental load during driving in most speed categories. Starting the train and coming to a halt showed greater emotional workload as compared to moving. Observer ratings of stress and subjective ratings of stress by the drivers revealed several discrepancies. Discrepancies were also seen between workload as indicated by the physiological parameters, and corresponding stress ratings by the observers or by the drivers.     

An experimental evaluation of instantaneous self-assessment as a measure of workload

Instantaneous self-assessment (ISA) is a technique that has been developed as a measure of workload to provide immediate subjective ratings of work demands during the performance of primary work tasks such as air traffic control. This paper reports a study that compared the results of ISA with those gathered from other established workload evaluation techniques; subjective ratings collected at the end of the task, mean heart rate and heart rate variability, and error in the primary task of tracking. ISA ratings were found to be correlated significantly with the post-task ratings of workload, heart rate variability, and task performance. Generally each of the techniques was sensitive to variations in task difficulty. However, performance on the primary tracking task was found to be poorer during periods when ISA responses were required, regardless of whether they were spoken or manual responses. This finding suggests that the usefulness of the technique is limited in comparison to less intrusive measures of workload.     

Heart rate strain in cable hauler choker setters in New Zealand logging operations.

This study examined the physical strain experienced by cable hauler choker setters, and the applicability of heart rate indices for measuring physical strain in commercial forest harvesting operations in New Zealand. The heart rate of four choker setters were recorded continuously throughout the working day and applied to heart rate indices. Based on the relative heart rate at work (%HRR), ratio of working heart rate to resting heart rate and 50% level indices, the mean working heart rate (HRw) of 106 bt. min(-1) +/- 6.9 (mean +/- SD) placed choker setting in the moderate workload category. The specific tasks of line shifts (120.3 +/- 4.8 bt. min(-1)), hooking up drags (118.8 +/- 6.6 bt. min(-1)) and uphill travel (126.1 +/- 12.9 bt. min(-1)), imposed the most severe workloads on the choker setters. This research also demonstrated that heart rate indices could be used as an effective means of determining the physiological strain of subjects working in New Zealand's commercial forest harvesting operations.     

A rapid appraisal of occupational workload from a modified scale of perceived exertion

A simple and rapid method of determining occupational workload among Indian women performing manual activities was developed based on the strong relationship between physiological responses and subjective feeling of exertion. A modified five point scale of perceived exertion, sequentially numbered 1 to 5, was created to simplify the complicated and time-consuming procedures using conventional methods of measuring energy expenditure, or even heart rate responses, during work of very short duration, especially in field situations. The scale denotes physiological workload: 1: very light; 2: light; 3: moderately heavy; 4: heavy; and 5: very heavy. A job-classification table based on energy expenditure and heart rate responses is also proposed, and different household activities such as grinding masalas, dish washing, sweeping, mopping, ironing, storing water, etc. have been graded accordingly.     

Effect of measurement duration on accuracy of pulse-counting

In this study, the relation between the measurement duration and accuracy of pulse-counting was quantitatively examined with special reference to low-frequency fluctuations in heart rate variability. The interbeat intervals of 70 healthy male subjects were measured in standing, sitting and supine positions. Pulse rates for various durations were calculated by objective-scoring simulation based on the heartbeat recordings of the subjects. The duration of pulse-counting continuously varied from 6 to 60 s in the simulation. Simulated pulse rates were compared with the rate calculated from the 60 s that includes the given duration, and the absolute difference between the two rates was defined as the error. Average errors of pulse-counting for 15 s were 1.89, 1.89 and 1.80 bpm for standing, sitting and supine positions, respectively. No difference in error was observed between standing and sitting positions; however, smaller errors were observed in the supine position.     

Monitoring of mental workload levels during an everyday life office-work scenario

Personal and ubiquitous healthcare applications offer new opportunities to prevent long-term health damage due to increased mental workload by continuously monitoring physiological signs related to prolonged high workload and providing just-in-time feedback. In order to achieve a quantification of mental load, different load levels that occur during a workday have to be discriminated. In this work, we present how mental workload levels in everyday life scenarios can be discriminated with data from a mobile ECG logger by incorporating individual calibration measures. We present an experiment design to induce three different levels of mental workload in calibration sessions and to monitor mental workload levels in everyday life scenarios of seven healthy male subjects. Besides the recording of ECG data, we collect subjective ratings of the perceived workload with the NASA Task Load Index (TLX), whereas objective measures are assessed by collecting salivary cortisol. According to the subjective ratings, we show that all participants perceived the induced load levels as intended from the experiment design. The heart rate variability (HRV) features under investigation can be classified into two distinct groups. Features in the first group, representing markers associated with parasympathetic nervous system activity, show a decrease in their values with increased workload. Features in the second group, representing markers associated with sympathetic nervous system activity or predominance, show an increase in their values with increased workload. We employ multiple regression analysis to model the relationship between relevant HRV features and the subjective ratings of NASA-TLX in order to predict the mental workload levels during office-work. The resulting predictions were correct for six out of the seven subjects. In addition, we compare the performance of three classification methods to identify the mental workload level during office-work. The best results were obtained with linear discriminant analysis (LDA) that yielded a correct classification for six out of the seven subjects. The k-nearest neighbor algorithm (k-NN) and the support vector machine (SVM) resulted in a correct classification of the mental workload level during office-work for five out of the seven subjects.