Subjective Discomfort Ratings Research Articles

Effects of Short-Term Hand Tractor Operation on Upper Limb Responses of Users

ABSTRACT Objectives Continuous exposure to hand-arm vibration integrated with poor posture and forceful movements are known causes of musculoskeletal disorders (MSD). In most related studies, force and vibration levels in experimental research is controlled. This study aims to determine how actual hand tractor field operation can affect the upper limb of users. It intends to characterize upper limb muscle activation applied during actual hand tractor usage. Lastly, it determines the immediate impacts on hand strength and perceived upper limb discomfort after the operation. Methods We recruited 15 farm operators with a mean working experience of 20.1 ± 12.2 years. They were asked to operate a hand tractor on paddy fields for at most 8 minutes. Handle vibration was measured using a tri-axial accelerometer. The total unweighted vibration acceleration was computed and used to represent the handle vibration magnitude. Muscle activation was measured using surface electromyography (sEMG). Six sEMG sensors were attached to the dominant and non-dominant side of the extensor carpi radialis (ECR), bicep, and deltoid. Pre- and post-task hand strength and subjective discomfort rating were also taken. Results The total unweighted handle vibration acceleration is 17.45 ± 7.53 m/s2. This exceeds the allowable safe value. Meanwhile, the percentage of maximum voluntary contraction (% MVC) of the muscles ranged from 6% to 14% with the ECR having a significantly higher activation (p < .05) than the bicep and deltoid. The post-task grip strength of the dominant hand was lower than its pre-task value (p < .01) while that of the non-dominant side did not vary significantly. There is a modest trend of higher hand discomfort of the non-dominant side on post-task than pre-task rating (p < .10). Although, overall, the perceived discomfort ranged from none to mild discomfort. Conclusion In conclusion, the study showed an indication that the effects of vibration on humans are evident even at mild muscle exertion, with the exertion predominantly concentrated on the distal arm area clearly affecting grip strength and hand discomfort. In such cases, future recommendations can revolve around the improvement of the hand tractor handle grip to impose grip comfort and ease.

Evaluation of the Effects of Passive Lower-Limb Exoskeletons on Muscle Activities According to Working Heights

Introduction: Research and development efforts regarding passive lower-limb exoskeletons are actively ongoing to reduce work-related musculoskeletal disorders (WMDSs) from improper and prolonged posture. The aims of this study were to evaluate the effects of passive lower-limb exoskeletons and working heights on muscle activity and subjective comfort ratings. Methods: In this study, 20 males performed a 10-min drilling task for three levels of working height (60, 85, and 110 cm), and three levels of intervention (WO: without exoskeleton, WCEX, and WCC) were used as independent variables. The EMG data of eight muscles and subjective discomfort ratings in each of the six body parts were analyzed in this study. Results: The results of this study confirm that the effect of wearing a lower-limb exoskeleton device may vary depending on the muscle type and working height. Overall, the positive effects of wearing were generally observed in the lower-limb muscles, whereas the muscle activity of the upper limbs showed an increasing trend when wearing the device at a height of 85 cm or more. Conclusions: Therefore, to obtain positive effects in both the upper- and lower-limb muscles, using the lower-limb exoskeletons at a working height of 85 cm or less is recommended.

Footwear Design and Biomechanics Evaluation for Clinical Nurses

Epidemiological investigations have shown a higher prevalence of work-related musculoskeletal disorders, (WRMDs) among nursing professionals. More than most other occupational groups. Most nursing activities require long periods of standing and walking. These job requirements can cause WRMDs problems in the lower limbs, and there are few footwear products available specifically for use by clinical nurses. Therefore, improving the current clinical nurse shoes and improving the wearing comfort of clinical nurse shoes are the necessary conditions to reduce the lower limb discomfort of clinical nurses. The purpose of this study is :(1) to test and obtain the foot morphology and walking gait characteristics of nurses in standing state by using human foot scanning and sports biomechanics technology, and to design comfortable clinical nursing footwear products suitable for nurses through shoe last optimization and application of environmentally friendly materials. (2) Sports biomechanical testing technology was used to test and compare the developed clinical care shoes with other shoes in the market, and the biomechanical characteristics of participants wearing different shoes were measured and compared to verify the design effect of clinical care shoes and improve it. This research method is divided into three stages. First, field observations and exercise biomechanics tests of the participants were performed, and data acquisition included plantar pressure characteristics, a three-dimensional foot model, foot surface temperature distribution, walking speed, and proportions of walking, standing, and sitting. Secondly, the clinical nursing shoes were designed based on the test results and the sample shoes were made. Finally, the function of professional nursing was evaluated through the exercise biomechanical testing technique. Measurements included lower limb joint range of motion (ROM), foot Pressure, ground reaction force (GRF), and subjective discomfort ratings for the lower body and feet. To summarize the findings of this study, comfortable clinical care shoes should emphasize arch support at the sole, use three-dimensional vertical insoles, and design heel height below 5 cm to significantly reduce plantar pressure distribution and ground impact, increase ankle flexibility, and recommend the use of pressure socks to reduce the risk of varicose veins in the lower extremities.

Efficacy of passive upper-limb exoskeletons in reducing musculoskeletal load associated with overhead tasks

Overhead work can pose substantial musculoskeletal stress in many industrial settings. This study aimed to evaluate the efficacy of passive upper-limb exoskeletons in reducing muscular activity and subjective discomfort ratings. In a repeated-measures laboratory experiment, 20 healthy male participants performed 10-min drilling tasks with and without two passive upper-limb exoskeletons (VEX and Airframe). During the tasks, muscle activity in eight muscles (upper limb - upper trapezius, middle deltoid, biceps brachii, triceps brachii; low back - erector spinae; lower limb - rectus femoris, biceps femoris, tibialis anterior) was collected using electromyography as a physical exertion measure. Subjective discomfort rating in six body parts was measured using the Borg's CR-10 scale. The results showed that muscle activity (especially in the upper-limb muscles) was significantly decreased by 29.3–58.1% with both exoskeletons compared to no exoskeleton condition. The subjective discomfort ratings showed limited differences between the conditions. These findings indicate that passive upper-limb exoskeletons may have potential as an effective intervention to reduce muscular loading and physical exertion during overhead work.

Prevalence and associated risk factors of musculoskeletal disorders (MSDs) and physiological stress among the female brick molders of West Bengal, India

Objective: Women play a significant role in the Indian economy and are regarded as the backbone of the brickfield industry where they face a variety of stressors that predispose them to increased risk of developing musculoskeletal disorders. The present study aimed to estimate the prevalence of upper limb musculoskeletal disorders and physiological stress compared to a control group. Methods: The Nordic Modified Questionnaire (NMQ) was completed by 85 women brick molders to assess feelings of discomfort (pain) in different parts of the body. Furthermore, the Rapid Upper Limb Assessment (RULA) posture analysis tool explored the risk of upper-limb musculoskeletal disorders (ULMSDs). Handgrip strength was also measured using a handgrip dynamometer, and cardiovascular stresses were assessed by measuring heart rate, blood pressure and lung function parameters. Results: The results of the study revealed that upper limb MSDs are a significant problem among women brick molders, primarily involving the hand (97.6%), shoulder (94.1%), wrist (72.9%) and fingers (56.5%). Subjective discomfort ratings among the brick molders indicated pain (96.5%), followed by tingling (90.6%), numbness (88.2%) and stiffness (61.2%) in their hands. The detailed analysis of the RULA score revealed that the upper arms, lower arms and wrists were high-risk areas for MSDs. Soon after completion of work, the participants experienced reductions in the hand-grip strength compared to the control group. Heart rate brick molders as higher in comparison to control group, just after the completion of work. However, there was no significant change in maximum Heart rate (HRmax) and Heart Rate Reserve (HRR) between the two groups, but significant associations were observed in net cardiac cost (NCC) and relative cardiac cost (RCC). Blood pressure measures were higher in the brick molders after work as well Conclusion: Women brick molders engaged continuously in highly repetitive hand-intensive jobs and suffered from discomfort in the upper extremities. The RULA posture analysis results indicated that the working posture of women brick molders were at high risk for MSDs, which requires changes immediately. Female brick molders also presented with reduced lung function values compared to the controls Findings of this study highlight the need for various ergonomic interventions that can be applied to improve the safety of the molders and workplace conditions of the brickfield during molding activities.

A comfort analysis of AR glasses on physical load during long-term wearing

The present study investigated the effect of the physical load of augmented reality (AR) glasses on subjective assessments for an extended duration of a video viewing task. Ninety-six subjects were recruited for this test and were divided by spectacle use, sex, age, and body mass index (BMI). Four glasses frame weights were assessed. To investigate their effectiveness, a novel prototype adopting three design interventions, (1) adjustable frame width, (2) ergonomic temples, and (3) fixed centre of gravity, was designed with regard to subjective discomfort ratings (nose, ear, and overall). Subjective discomfort in all regions was significantly increased with increasing physical load on the nose. In addition, non-spectacle users, women, older users, and participants in the middle BMI category reported higher discomfort than other groups. This finding could have important implications for the ergonomic design of AR glasses and could help to identify design considerations relevant to the emerging wearable display industry. Practitioner summary: This research aims to explore the influence of the physical load of augmented reality (AR) glasses. It found that discomfort was increased with added nose load. Non-spectacle users, women, older users, and participants in the middle BMI category were more sensitive to discomfort. The results have important implications for glasses-type wearables’ design.

Evaluation of subjective discomfort of the seated human body exposed to vertical vibration using dynamic body pressure

Pressure distribution has been regarded as a crucial parameter for static comfort evaluation of the seated human body. However, the association between the pressure distribution and subjective rating, exposed to vertical vibration, is still unclear. This study devotes to characterizing the vibration discomfort of the seated human body on a foam seat using dynamic body pressure distribution and investigating the associations between them. First, the dynamic body pressure of twelve subjects seated on a foam seat exposed to vertical random excitation was measured at frequencies from 0.5 to 20 Hz with six magnitudes (0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 m/s2 r.m.s.). Meanwhile, the subjective discomfort rating of the foam seat was evaluated with the relative magnitude estimation method. Then, the influence of vibration magnitude on subjective discomfort ratings and dynamic body pressure indicators was investigated. The results show that with the increase of vibration magnitude, the mean average dynamic pressure, the mean peak dynamic pressure, the mean dynamic contact area, and the normal dynamic force had no significant change. On the contrary, the subjective discomfort ratings, normal dynamic force change rate root-mean-square, and the indicators related to pressure change rate root-mean-square increased significantly. Finally, the relation between the subjective discomfort ratings and dynamic body pressure indicators was analyzed using Stevens’ power law. The linear regression fitting accuracy of the average dynamic pressure change rate root-mean-square, peak dynamic pressure change rate root-mean-square, area pressure change rate root-mean-square, and normal dynamic force change rate root-mean-square with discomfort ratings were above 95%. The four dynamic body pressure indicators are highly correlated with the subjective discomfort ratings, which can be used as objective indicators for vibration discomfort evaluation.

Sex differences in perceived discomfort during seated static posture holding

This study investigated how sex modifies postural discomfort perception during a sagittally-symmetric, seated static posture holding (SPH) task. Ten male and 10 female participants performed SPH and conducted subjective discomfort ratings in a total of 108 task conditions. A regression analysis found that the impacts of the body joint reactive moments on perceived discomfort were larger for the female group than the male whereas that of the shoulder joint angle was more pronounced for the male than the female. Also, some of the 108 task conditions were found to be more uncomfortable for the male group, while some others, for the female. The observed sex impacts are thought to be due to the sex differences in physical work capacities (muscular strength and joint flexibility). The results suggest that new posture analysis tools allowing sex-specific analyses are needed as they would improve the accuracy and precision of ergonomics posture analyses. Practitioner summary: This study empirically investigated how sex modifies postural discomfort perception during a seated posture holding (SPH) task. Sex was found to modify the impacts of joint reactive moments and the shoulder joint angle. The study results seem to reflect the sex differences in muscular strength and joint flexibility.

Relating individual motion sickness levels to subjective discomfort ratings

High levels of vehicle automation are expected to increase the risk of motion sickness, which is a major detriment to driving comfort. The exact relation between motion sickness and discomfort is a matter of debate, with recent studies suggesting a relief of discomfort at the onset of nausea. In this study, we investigate whether discomfort increases monotonously with motion sickness and how the relation can best be characterized in a semantic experiment (Experiment 1) and a motion sickness experiment (Experiment 2). In Experiment 1, 15 participants performed pairwise comparisons on the subjective discomfort associated with each item on the popular MIsery SCale (MISC) of motion sickness. In Experiment 2, 17 participants rated motion sickness using the MISC during exposures to four sustained motion stimuli, and provided (1) numerical magnitude estimates of the discomfort experienced for each level of the MISC, and (2) verbal magnitude estimates with seven qualifiers, ranging between feeling ‘excellent’ and ‘terrible’. The data of Experiment 1 show that the items of the MISC are ranked in order of appearance, with the exception of 5 (‘severe dizziness, warmth, headache, stomach awareness, and sweating’) and 6 (‘slight nausea’), which are ranked in opposite order. However, in Experiment 2, we find that discomfort associated with each level of the MISC, as it was used to express motion sickness during exposure to a sickening stimulus, increases monotonously; following a power law with an exponent of 1.206. While the results of Experiment 1 replicate the non-linearity found in recent studies, the results of Experiment 2 suggest that the non-linearity is due to the semantic nature of Experiment 1, and that there is a positive monotonous relation between MISC and discomfort in practice. These results support the suitability of MISC to assess motion sickness.

Circadian and homeostatic sleep-wake regulation of secretory immunoglobulin A (sIgA): Effects of environmental light and recovery sleep

Secretory Immunoglobulin A (sIgA) builds the first line of the human immune defense. It is not clear whether the power of this defence line is constant across the 24-h day, depends on sleep pressure levels and can be influenced by external lighting conditions. Thus, in 10 healthy young volunteers, we retrospectively analyzed saliva samples for sIgA levels under strictly controlled laboratory conditions across 40 ​h of extended wakefulness under two lighting conditions (dim light 8 lx and blue-enriched light 250 lx, 9000 ​K) to test for circadian and homeostatic sleep-wake influences. We compared the temporal profile of sIgA with the circadian time course of melatonin and cortisol along with subjective sleepiness levels, assessed in the same study by Gabel et al. (2017). The 40-h time course of sIgA exhibited a clear circadian modulation with peak values in the mornings coinciding with the individuals' habitual rise-time. In addition, sIgA levels progressively increased throughout the 40 ​h of extended wakefulness and were temporally correlated with subjective sleepiness but not with subjective ratings of tension and discomfort. In contrast to the circadian profile of melatonin and cortisol, sIgA levels were not significantly altered by the lighting conditions. Unexpectedly, sIgA levels in the morning after recovery sleep from 40 ​h of extended wakefulness rose considerably by more than an order of magnitude (10 times more) compared to morning levels after baseline sleep. We have evidence that diurnal sIgA levels in humans are regulated by the circadian timing system, and challenging the status of the sleep-wake homeostat (i.e. extended wakefulness) boosts human sIgA levels. Thus, besides a person's circadian phase position, the first line of human immune defense also strongly depends on the person's sleep-wake history and actual sleepiness levels. In sum, the fight against pathogenic microorganisms by a key immunological component (sIgA) is modulated by two fundamental processes implicated in human sleep-wake regulation.

Ergonomic evaluation and field validation of the insole padding system

AbstractInsoles are typically worn to increase comfort in performing daily activities. Many studies have investigated the effects of insoles with different properties. This study performed an ergonomic evaluation of three insole types, with a focus on assessing the effectiveness of an insole padding system (IPS). The objectives of this study were (1) to perform an ergonomic evaluation of three insoles and (2) to perform a field validation study to examine the effectiveness of IPS wearing among nurses. The study involved two phases. In the first phase, 15 healthy females participated in an experiment evaluating three insoles (general flat insole, ergo‐insole, and IPS). The outcome measurements were electromyography activity of four muscles, plantar pressure distribution in seven zones, and subjective discomfort rating. In the second phase, 100 nurses were recruited for the Nordic Musculoskeletal Questionnaire survey and 43 nurses participated in the field evaluation study. The results indicated that walking with the IPS was associated with lower plantar pressures in the midfoot and heel regions. Participants who wore ergo‐insole and IPS exhibited lower overall subjective discomfort ratings. Lower‐extremity discomfort was significantly improved after wearing the IPS for 2 weeks. The findings of this study suggest that walking with the IPS can result in less discomfort in the lower extremities than walking with the conventional insoles. IPS wearing is effective in improving lower‐extremity discomfort in persons who require prolonged standing and walking in daily life.

Development and evaluation of attachable anti-vibration handle

Blueberry production has skyrocketed in the past two decades due to an exponential increase in consumer demand around the world. Hand harvesters are used, avoiding damage to the fruit and increasing harvesting efficiency multifold when compared with that of hand-picking. The downside of these hand harvesters is their high Hand Arm Vibration (HAV), which is very dangerous for the worker and can cause hand-arm vibration syndrome (HAVS). The aim of this study is to propose a spring-based anti-vibration handle that can be attached to vibrating equipment (blueberry hand harvester). Four different parameters were measured for the developed spring-based handles: hand arm vibration, wrist posture, muscle activity, and subjective discomfort rating. Results have shown that the use of a spring-based handle can reduce HAV by 61.1%, which is within the exposure limit values (ELV) defined by the European Union.

A physiological and biomechanical investigation of three passive upper-extremity exoskeletons during simulated overhead work

The objective of this study was to evaluate three passive upper-extremity exoskeletons relative to a control condition. Twelve subjects performed an hour-long, simulated occupational task in a laboratory setting. Independent measures of exoskeleton, exertion height (overhead, head height), time, and their interactions were assessed. Dependent measures included changes in tissue oxygenation (ΔTSI) in the anterior deltoid and middle trapezius, peak resultant lumbar spine loading, and subjective discomfort in various body regions. A statistically significant reduction in ΔTSI between exoskeleton and control was only observed in one instance. Additionally, neither increases in spinal loading nor increases in subjective discomfort ratings were observed for any of the exoskeletons. Ultimately, the exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing to the subjects, denoted by low ΔTSI values across conditions. Results may vary for tasks requiring constant arm elevation or higher force demands. Practitioner summary This study quantified the benefits of upper-extremity exoskeletons using NIRS, complementary to prior studies using EMG. The exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing, and results may vary for an experimental task with greater demand on the shoulders. Abbreviations: WMSD: work-related musculoskeletal disorder; EMG: electromyography; NIRS: near-infrared spectroscopy; NIR: near-infrared; Hb: haemoglobin; Mb: myoglobin; TSI: tissue saturation index; ATT: adipose tissue thickness

Guidelines for Working Heights of the Lower-Limb Exoskeleton (CEX) Based on Ergonomic Evaluations.

The aim of this study was to evaluate the muscle activities and subjective discomfort according to the heights of tasks and the lower-limb exoskeleton CEX (Chairless EXoskeleton), which is a chair-type passive exoskeleton. Twenty healthy subjects (thirteen males and seven females) participated in this experiment. The independent variables were wearing of the exoskeleton (w/ CEX, w/o CEX), working height (6 levels: 40, 60, 80, 100, 120, and 140 cm), and muscle type (8 levels: upper trapezius (UT), erector spinae (ES), middle deltoid (MD), triceps brachii (TB), biceps brachii (BB), biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA)). The dependent variables were EMG activity (% MVC) and subjective discomfort rating. When wearing the CEX, the UT, ES, RF, and TA showed lower muscle activities at low working heights (40–80 cm) than not wearing the CEX, whereas those muscles showed higher muscle activities at high working heights (100–140 cm). Use of the CEX had a positive effect on subjective discomfort rating at lower working heights. Generally, lower discomfort was reported at working heights below 100 cm when using the CEX. At working heights of 100–140 cm, the muscle activity when wearing the CEX tended to be greater than when not wearing it. Thus, considering the results of this study, the use of the lower-limb exoskeleton (CEX) at a working height of 40–100 cm might reduce the muscle activity and discomfort of whole body and decrease the risk of related disorders.

Transfer of training—Virtual reality training with augmented multisensory cues improves user experience during training and task performance in the real world

Virtual reality (VR) can create safe, cost-effective, and engaging learning environments. It is commonly assumed that improvements in simulation fidelity lead to better learning outcomes. Some aspects of real environments, for example vestibular or haptic cues, are difficult to recreate in VR, but VR offers a wealth of opportunities to provide additional sensory cues in arbitrary modalities that provide task relevant information. The aim of this study was to investigate whether these cues improve user experience and learning outcomes, and, specifically, whether learning using augmented sensory cues translates into performance improvements in real environments. Participants were randomly allocated into three matched groups: Group 1 (control) was asked to perform a real tyre change only. The remaining two groups were trained in VR before performance was evaluated on the same, real tyre change task. Group 2 was trained using a conventional VR system, while Group 3 was trained in VR with augmented, task relevant, multisensory cues. Objective performance, time to completion and error number, subjective ratings of presence, perceived workload, and discomfort were recorded. The results show that both VR training paradigms improved performance for the real task. Providing additional, task-relevant cues during VR training resulted in higher objective performance during the real task. We propose a novel method to quantify the relative performance gains between training paradigms that estimates the relative gain in terms of training time. Systematic differences in subjective ratings that show comparable workload ratings, higher presence ratings and lower discomfort ratings, mirroring objective performance measures, were also observed. These findings further support the use of augmented multisensory cues in VR environments as an efficient method to enhance performance, user experience and, critically, the transfer of training from virtual to real environment scenarios.

Subjective Preferences and Discomfort Ratings of Backrest and Seat Pan Adjustments at Various Speeds

Power seats (i.e., electrically adjustable seats that can be designed to move in several ways) have become increasingly common in airplanes, vehicles, and offices. Many studies have investigated the effects of seat attitude parameters, for example, the inclined angles of a backrest, on discomfort during the adjustment process. However, few studies have considered discomfort under different speeds during the adjustment process. In this study, we investigated discomfort with three speeds (i.e., “fast”, “median”, and “slow” corresponding to three durations of 15, 20, and 25 s, respectively) and two adjustments of a power seat, i.e., incline angle adjustment of the backrest and fore-and-aft position adjustment of the seat pan. We also investigated the effects of different physiological parameters on subjects’ discomfort. Twenty-four subjects (12 males and 12 females) completed a questionnaire to indicate their adjustment condition preferences, to rate their overall discomfort during the adjustment processes on a category-ratio scale, and to rate their local body discomfort. The majority of subjects preferred the fast speed adjustment condition and the trend was that a lower backrest adjustment speed increased discomfort during the process. The dominant local discomfort was in the upper and lower back regions during the backrest adjustment, whereas there was no obvious dominant local discomfort during the seat pan adjustment. The physiological parameters also had significant correlations with discomfort in some adjustment movements, for example, the discomfort was negatively correlated with height during the backrest adjustment.

The nature effect in motion: visual exposure to environmental scenes impacts cognitive load and human gait kinematics.

Prolonged exposure to urban environments requires higher cognitive processing resources than exposure to nature environments, even if only visual cues are available. Here, we explored the moment-to-moment impact of environment type on visual cognitive processing load, measuring gait kinematics and reaction times. In Experiment 1, participants (n = 20) walked toward nature and urban images projected in front of them, one image per walk, and rated each image for visual discomfort. Gait speed and step length decreased for exposure to urban as compared with nature scenes in line with gait changes observed during verbal cognitive load tasks. We teased apart factors that might contribute to cognitive load: image statistics and visual discomfort. Gait changes correlated with subjective ratings of visual discomfort and their interaction with the environment but not with low-level image statistics. In Experiment 2, participants (n = 45) performed a classic shape discrimination task with the same environmental scenes serving as task-irrelevant distractors. Shape discrimination was slower when urban scenes were presented, suggesting that it is harder to disengage attention from urban than from nature scenes. This provides converging evidence that increased cognitive demands posed by exposure to urban scenes can be measured with gait kinematics and reaction times even for short exposure times.

Measuring Drivers’ Physiological Response to Different Vehicle Controllers in Highly Automated Driving (HAD): Opportunities for Establishing Real-Time Values of Driver Discomfort

This study investigated how driver discomfort was influenced by different types of automated vehicle (AV) controllers, compared to manual driving, and whether this response changed in different road environments, using heart-rate variability (HRV) and electrodermal activity (EDA). A total of 24 drivers were subjected to manual driving and four AV controllers: two modelled to depict “human-like” driving behaviour, one conventional lane-keeping assist controller, and a replay of their own manual drive. Each drive lasted for ~15 min and consisted of rural and urban environments, which differed in terms of average speed, road geometry and road-based furniture. Drivers showed higher skin conductance response (SCR) and lower HRV during manual driving, compared to the automated drives. There were no significant differences in discomfort between the AV controllers. SCRs and subjective discomfort ratings showed significantly higher discomfort in the faster rural environments, when compared to the urban environments. Our results suggest that SCR values are more sensitive than HRV-based measures to continuously evolving situations that induce discomfort. Further research may be warranted in investigating the value of this metric in assessing real-time driver discomfort levels, which may help improve acceptance of AV controllers.

Exercise in Thermal Inversions: PM2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance

Wintertime thermal inversions can lead to the accumulation of small particulate matter (PM2.5). Despite an association between respiratory hospital admissions and elevated PM2.5 levels, many people continue to exercise outdoors during inversions. This study compared pulmonary function and exercise performance during periods of low and high ambient PM2.5 concentrations. Forced vital capacity and forced expiratory volume in 1 s were measured outdoors before and after two 3200 m running time trials: one with low ambient PM2.5 (0.6-14.7 microgram·m-3), and the other during high PM2.5 (19.1-42.5 micrograms·m-3). A 10 cm visual analog scale (VAS) administered postexercise quantified subjective ratings of respiratory discomfort. The PM2.5 differential between trials was ≥18 micrograms·m-3 for 10 healthy runners. Despite feeling more respiratory discomfort (P=0.044) during the bad air trial (VAS: 4.6±1.8 cm) compared with the good air trial (VAS: 2.9±1.8 cm), the 3200 m run time (low PM2.5: 13:54±1:34 min:s; high PM2.5: 14:07±1:44 min:s) was not different (P=0.261) between trials. Postexercise forced vital capacity was not significantly different (P=0.846) between the low (4.86±1.00 L) and high (4.84±0.95 L) PM2.5 conditions. Similarly, the difference in postexercise forced expiratory volume in 1 s was not significant (P=0.750) between trials (4.22±0.89 L vs 4.23±0.85 L). Neither run time nor pulmonary function of healthy adults were adversely affected by an acute bout of exercise in elevated ambient PM2.5, equivalent to yellow or orange on the air quality index.

Effects of aircraft seat pitch on interface pressure and passenger discomfort

Seat pitch, defined as the distance from a point on the back of one seat to the same point on the seat in front, is one of the most important factors influencing aircraft seating comfort. This study assessed the influence of different airline seat pitches on subjective ratings of discomfort and body-seat interface contact pressures. This was a laboratory within-subjects study using an aircraft interior mock up to vary seat pitch. Twelve participants completed 1 h of sitting in each of five different seat pitches (28inches, 30inches, 32inches, 34inches, and 36inches). Interface pressure mats measured seat and backrest pressure distribution, subjective rating scales were used to measure overall and local body region discomfort. The results showed that overall body and local body region discomfort ratings tend to be lower when the seat pitch increased from 28 inches to 36 inches (p < 0.05). For pressure variables, the upper back average contact area, upper/lower back average contact pressure, upper/lower back average peak contact pressure, right buttock average contact area, left/right thigh buttock average peak contact pressure, and left buttock average peak contact pressure were significantly affected by seat pitch(p < 0.05). Separate analyses support that seat pitch was more strongly correlated with backrest interface pressure than with seat pan pressure. In conclusion, seat pitch was found to be an important factor associated with body-seat contact pressure and discomfort ratings.