An Evaluation of the Frequency and Severity of Motion Sickness Incidences in Personnel Within the Command and Control Vehicle (C2V)

The purpose of this study was to assess the frequency and severity of motion sickness in personnel during a field exercise in the Command and Control Vehicle (C2V). This vehicle contains four workstations where military personnel are expected to perform command decisions in the field during combat conditions. Eight active duty military men (U.S. Army) at the Yuma Proving Grounds in Arizona participated in this study. All subjects were given baseline performance tests while their physiological responses were monitored on the first day. On the second day of their participation, subjects rode in the C2V while their physiological responses and performance measures were recorded. Self-reports of motion sickness were also recorded. Results showed that only one subject experienced two incidences of emesis. However, seven out of the eight subjects reported other motion sickness symptoms; most predominant was the report of drowsiness, which occurred a total of 19 times. Changes in physiological responses were observed relative to motion sickness symptoms reported and the different environmental conditions (i.e., level, hills, gravel) during the field exercise. Performance data showed an overall decrement during the C2V exercise. These findings suggest that malaise and severe drowsiness can potentially impact the operational efficiency of the C2V crew. It was concluded that conflicting sensory information from the subject's visual displays and movements of the vehicle during the field exercise significantly contributed to motion sickness symptoms. It was recommended that a second study be conducted to further evaluate the impact of seat position or orientation and C2V experience on motion sickness susceptibility. Further, it was recommended that an investigation be performed on behavioral methods for improving crew alertness, motivation, and performance and for reducing malaise

The psychophysical function for perceived gravitational-inertial force does not depend on the orientation of the otolith organs

It has generally been believed that the perceived intensity of a gravitational-inertial force depends on both the magnitude and orientation of the force with respect to the otolith organs, as does the elevator illusion. In this study, we examine the perceived intensity of Gz force and the elevator illusion as a function of the applied force and the orientation of the subject's head. Methods: Each of 7 male subjects was seated upright in a swinging chair mounted in the Ames 20-G Human Centrifuge while he set a visual target to his apparent horizon and judged the perceived intensity of Gz forces by cross-modal matches on a hand dynamometer. Plateau Gz levels were 1.00 1.25, 1.50, 2.00, 2.25, and 2.50; a 30 second ramp to plateau was used in all cases, and the duration of exposure at each plateau was 120 seconds. All measures were obtained both with the subject's head erect and pitched forward 30 degrees. Results: Although the elevator illusion changed with head orientation (F(6,60) = 7.56; p less than 0.001) the perceived intensity of Gz was essentially the same for both orientations of the head (F (6,60) = 0.61; p greater than 50). Conclusions: The results of this experiment suggest that the perceived intensity of gravitational-inertial force does not depend on otolith mechanisms in the same way as does the elevator illusion and that somesthetic, tactile, and other proprioceptive inputs are important for the psychophysical function

The Effects of the Mars Exploration Rovers (MER) Work Schedule Regime on Locomotor Activity Circadian Rhythms, Sleep and Fatigue

This study assessed human adaptation to a Mars sol by evaluating sleep metrics obtained by actigraphy and subjective responses in 22 participants, and circadian rhythmicity in locomotor activity in 9 participants assigned to Mars Exploration Rover (MER) operational work schedules (24.65 hour days) at the Jet Propulsion Laboratory in 2004. During MER operations, increased work shift durations and reduced sleep durations and time in bed were associated with the appearance of pronounced 12-hr (circasemidian) rhythms with reduced activity levels. Sleep duration, workload, and circadian rhythm stability have important implications for adaptability and maintenance of operational performance not only of MER operations personnel but also in space crews exposed to a Mars sol of 24.65 hours during future Mars missions

The Effects of Promethazine on Human Performance, Mood States, and Motion Sickness Tolerance

Intramuscular (IM) injections of promethazine in 25 mg or 50 mg dosages are commonly used to treat space motion sickness in astronauts. The present study examined the effects of IM injections of promethazine on neuropsy-chological performance, mood states, and motion sickness tolerance in humans. Twelve men, mean age 36 plus or minus 3.1 participated in one training (no injections) and three treatment conditions: a 25 mg injection of promethazine, a 50 mg injection of promethazine, and a placebo injection of sterile saline. Each condition, spaced at 7 day intervals, required an 8-10 hr session in which subjects were given four repetitions of 12 performance tasks, and one rotating chair motion sickness test. On the training day subjects were trained on each task to establish stability and proficiency. On treatment days, the order in which the drug or placebo was assigned to subjects was counter-balanced and a double-blind technique was used. Statistically significant decrements in performance were observed on 10 of 12 tasks when subjects were given 25 mg or 50 mg of promethazine as compared to the placebo. Performance decrements were associated with mean blood alcohol dose equivalency levels of 0.085% for 25 mg and 0. 1 37% for 50 mg dosages. The mood scale results showed significant changes in individual subjective experiences with maximum deterioration in the arousal state and fatigue level. When compared to placebo significant increases in motion sickness tolerance were found for both dosages of promethazine. These data suggest that effective dosages of promethazine currently used to counteract motion sickness in astronauts may significantly impair task components of their operational performance

Effects of circadian rhythm phase alteration on physiological and psychological variables: Implications to pilot performance (including a partially annotated bibliography)

The effects of environmental synchronizers upon circadian rhythmic stability in man and the deleterious alterations in performance and which result from changes in this stability are points of interest in a review of selected literature published between 1972 and 1980. A total of 2,084 references relevant to pilot performance and circadian phase alteration are cited and arranged in the following categories: (1) human performance, with focus on the effects of sleep loss or disturbance and fatigue; (2) phase shift in which ground based light/dark alteration and transmeridian flight studies are discussed; (3) shiftwork; (4)internal desynchronization which includes the effect of evironmental factors on rhythmic stability, and of rhythm disturbances on sleep and psychopathology; (5) chronotherapy, the application of methods to ameliorate desynchronization symptomatology; and (6) biorythm theory, in which the birthdate based biorythm method for predicting aircraft accident susceptability is critically analyzed. Annotations are provided for most citations

Converging Indicators for Assessing Individual Differences in Adaptation to Extreme Environments: Preliminary Report

This paper describes the development and validation of a new methodology for assessing the deleterious effects of spaceflight on crew health and performance. It is well known that microgravity results in various physiological alterations, e.g., headward fluid shifts which can impede physiological adaptation. Other factors that may affect crew operational efficiency include disruption of sleep-wake cycles, high workload, isolation, confinement, stress and fatigue. From an operational perspective, it is difficult to predict which individuals will be most or least affected in this unique environment given that most astronauts are first-time flyers. During future lunar and Mars missions space crews will include both men and women of multi-national origins, different professional backgrounds, and various states of physical condition. Therefore, new methods or technologies are needed to monitor and predict astronaut performance and health, and to evaluate the effects of various countermeasures on crew during long duration missions. This paper reviews several studies conducted in both laboratory and operational environments with men and women ranging in age between 18 to 50 years. The studies included the following: soldiers performing command and control functions during mobile operations in enclosed armored vehicles; subjects participating in laboratory tests of an anti-motion sickness medication; subjects exposed to chronic hypergravity aboard a centrifuge, and subject responses to 36-hours of sleep deprivation. Physiological measurements, performance metrics, and subjective self-reports were collected in each study. The results demonstrate that multivariate converging indicators provide a significantly more reliable method for assessing environmental effects on performance and health than any single indicator

New findings regarding light intensity and its effects as a zeitgeber in the Sprague-Dawley rat

In most mammals, the suprachiasmatic nucleus of the anterior hypothalamus has been implicated as the central driving mechanism of circadian rhythmicity. The photic input from the retina, via the retino-hypothalamic tract, and modulation from the pineal gland help regulate the clock. In this study, we investigated the effects of low light intensity on the circadian system of the Sprague-Dawley rat. A series of light intensity experiments were conducted to determine if a light level of 0.1 Lux will maintain entrained circadian rhythms of feeding, drinking, and locomotor activity

The Effects of Ultra-Long-Range Flights on the Alertness and Performance of Aviators

This investigation assessed the impact of ultra-long-range (ULR) simulator flights, departing either in the morning or late evening, on the alertness and performance of 17 commercial aviators. Immediately prior to and throughout each flight, alertness and performance were assessed via a computerized test of sustained attention, subjective questionnaires, and "hand-flying" tasks. There were fatigue-related effects on the majority of assessments, and the nature of these effects was consistent across the vigilance and self-report measures. However, the operational "hand-flying" manuevers proved insensitive to the impact of fatigue probably due to procedural factors. Regardless, the results of the present study suggest that fatigue associated with prolonged wakefulness in ULR flight operations will interact with flight schedules due to circadian and homeostatic influences. In this study, the pilots departing at night were at a greater initial disadvantage (during cruise) than pilots who departed earlier in the day; whereas those who departed earlier tended to be most impaired towards the end of the flight prior to landing. In real-world operations, airlines should consider the ramifications of flight schedules and what is known about human sleep and circadian rhythms to optimize safety

Sleep Is Compromised in −12° Head Down Tilt Position

Recent studies are elucidating the interrelation between sleep, cranial perfusion, and cerebrospinal fluid (CSF) circulation. Head down tilt (HDT) as a simulation of microgravity reduces cranial perfusion. Therefore, our aim was to assess whether HDT is affecting sleep (clinicaltrials.gov; identifier NCT 02976168). 11 male subjects were recruited for a cross-over designed study. Each subject participated in two campaigns each comprising 3 days and 2 nights. Intervention started on the second campaign day and consisted of maintenance of horizontal position or −12° HDT for 21 h. Ultrasound measurements were performed before, at the beginning and the end of intervention. Polysomnographic measurements were assessed in the second night which was either spent in horizontal posture or at −12° HDT. Endpoints were sleep efficiency, sleep onset latency, number of sleep state changes and arousals, percentages of N3, REM, light sleep stages and subjective sleep parameters. N3 and REM sleep reduced by 25.6 and 19.1 min, respectively (P = 0.002, g = -0.898; P = 0.035, g = -0.634) during −12° HDT. Light sleep (N1/2) increased by 33.0 min at −12° HDT (P = 0.002, g = 1.078). On a scale from 1 to 9 subjective sleep quality deteriorated by 1.3 points during −12° HDT (P = 0.047, g = -0.968). Ultrasonic measurement of the venous system showed a significant increase of the minimum (P = 0.009, P < 0.001) and maximum (P = 0.004, P = 0.002) cross-sectional area of the internal jugular vein at −12° HDT. The minimum cross-sectional area of the external jugular vein differed significantly between conditions over time (P = 0.001) whereas frontal skin tissue thickness was not significantly different between conditions (P = 0.077, P = 0.811). Data suggests venous congestion at −12° HDT. Since subjects felt comfortable with lying in −12° HDT under our experimental conditions, this posture only moderately deteriorates sleep. Obviously, the human body can almost compensate the several fold effects of gravity in HDT posture like an affected CSF circulation, airway obstruction, unusual patterns of propioception and effects on the cardiovascular system