INTRODUCTION: The aim was to study quadriceps muscle activation during resistance exercise using a flywheel device, developed as a gravity-independent resistance exercise device to be used during spaceflight, compared with traditional strength training exercises.METHODS: Eight healthy men experienced in resistance exercise performed the following exercises in random order: flywheel leg press (FW), knee extension isokinetic dynamometry (ID), barbell front squat (FS), weight stack leg press (LP), and weight stack knee extension (KE). They accomplished eight repetitions of coupled concentric and eccentric actions with simultaneous recordings of surface electromyography (EMG) from the three superficial quadriceps muscles and knee angles using electrogoniometry. Maximal voluntary contraction (MVC) in knee extension was performed before and after these measurements.RESULTS: EMG averaged across muscles and angles and normalized to MVC was 99/76% in FW, 48/41% FS, 65/47% LP, 81/52% KE, and 93/84% ID in concentric/eccentric phases, respectively. FW and ID showed higher mean EMG activity than LP and FS concentrically and higher than all other exercises eccentrically. No difference in activity between FW and ID was found. Pre- and post-MVC torque was comparable.DISCUSSION: Quadriceps muscle activation was superior in FW and ID exercises compared to the other exercises. The difference was most pronounced in the eccentric phase, but even concentric activation was lower in traditional closed chain exercises. This data supports that FW is an effective training tool and should be considered when designing strength training programs for spaceflights and on Earth.Alkner BA, Bring DK-I. Muscle activation during gravity-independent resistance exercise compared to common exercises. Aerosp Med Hum Perform. 2019; 90(6):506–512.

INTRODUCTION: The literature is equivocal regarding the degree of cognitive impairment incurred at the 8000-ft (2438 m) maximal cabin pressure altitude equivalence for commercial aircraft. This study elaborates upon the investigation of the 8000-ft limit by introducing the cumulative effects of repeated daily exposures thereof.METHOD: Pilots completed four daily high-altitude chamber flights at both sea level and 8000 ft. During each chamber flight, attentional processing and executive function were assessed using the Attention Network Test and the antisaccade task.RESULTS: Antisaccade task performance likely reflected a learning effect at both altitudes. Attention Network Test results, however, exhibited sensitivity to the fatigue and altitude interaction. Orienting network scores were affected by fatigue differently depending on altitude, with superior efficiency at 8000 ft compared to sea level (M = 44.9, SD = 25.0 vs. M = 29.0, SD = 18.1) in the last flight of the exposure cycle. Conflict network performance, however, suggested that while fatigue increasingly compromised executive control at both altitudes, marginally worse overall executive efficiency was observed at 8000 ft compared to sea level, notably in the last flight of the exposure cycle (M = 98.3, SD = 19.8 vs. M = 87.8, SD = 21.7).DISCUSSION: Executive control function, as measured by inhibition of interference in reconciling conflicting stimuli, degraded as a function of cumulative exposures to mild hypobaric hypoxia, though adaptive measures possibly compensated to preserve performance to a degree. This study serves as a baseline against which longer 8000-ft exposures, including long-haul flight, can be measured.Thropp JE, Buza PW. Cumulative cyclic exposures to 8000-ft pressurization equivalence and attention network responses. Aerosp Med Hum Perform. 2019; 90(6):513–523.

INTRODUCTION: The frequency of long-duration, high-altitude missions with fighter aircraft is increasing, which may increase the incidence of decompression sickness (DCS). The aim of the present study was to compare decompression stress during simulated sustained high-altitude flying vs. high-altitude flying interrupted by periods of moderate or marked cabin pressure increase.METHODS: The level of venous gas emboli (VGE) was assessed from cardiac ultrasound images using the 5-degree Eftedal-Brubakk scale. Nitrogen washout/uptake was measured using a closed-circuit rebreather. Eight men were investigated in three conditions: one 80-min continuous exposure to a simulated cabin altitude of A) 24,000 ft, or four 20-min exposures to 24,000 ft interspersed by three 20-min intervals at B) 20,000 ft or C) 900 ft.RESULTS: A and B induced marked and persistent VGE, with peak bubble scores of [median (range)]: A: 2.5 (1–3); B: 3.5 (2–4). Peak VGE score was less in C [1.0 (1–2), P < 0.01]. Condition A exhibited an initially high and exponentially decaying rate of nitrogen washout. In C the washout rate was similar in each period at 24,000 ft, and the nitrogen uptake rate was similar during each 900-ft exposure. B exhibited nitrogen washout during each period at 24,000 ft and the initial period at 20,000 ft, but on average no washout or uptake during the last period at 20,000 ft.DISCUSSION: Intermittent reductions of cabin altitude from 24,000 to 20,000 ft do not appear to alleviate the DCS risk, presumably because the pressure increase is not sufficient to eliminate VGE. The nitrogen washout/uptake rate did not reflect DCS risk in the present exposures.Ånell R, Grönkvist M, Eiken O, Gennser M. Nitrogen washout and venous gas emboli during sustained vs. discontinuous high-altitude exposures. Aerosp Med Hum Perform. 2019; 90(6):524–530.

INTRODUCTION: Working memory is an essential executive function for flying an aircraft and its limitations may jeopardize flight safety. This function is particularly critical when pilots have to struggle with spatial disorientation (SD) cues. This research aimed to assess the combined effect of the auditory N-back task (NBT) and simulator-induced SD cues on pilots’ flight performance.METHODS: Using an SD simulator, 39 male military pilots (control N = 20; age M = 31.6; SD = 8.22, experimental N = 19; age M = 26.9; SD = 8.67) were exposed to 12 flight sequences, where 6 contained an SD conflict—3 with vestibular illusions and 3 with visual illusions. Additionally, the pilots from the experimental group were asked to perform an auditory NBT involving sound stimuli (the sequential letter memory task) as they performed during oriented and disoriented flight conditions.RESULTS: Pilots’ flight performance from the NBT group were significantly worse than the control group in the approach and landing profiles involving visual illusions (for both nonconflict and conflict flight), and in the profile involving the false horizon illusion (only for the conflict flight). No increase in a pilot’s susceptibility to SD was observed with any other profiles.DISCUSSION: The current study provides support that pilots’ cognitive workload can negatively impact flight performance. Pilots are not always aware of altered flight parameters, which may indicate that they have lost spatial orientation, mainly as a result of visual illusion. If problems occur in maintaining proper flight parameters, pilots should direct all available mental resources to regain their orientation and withdraw from any other parallel tasks.Lewkowicz R, Stróżak P, Bałaj B, Francuz P. Auditory verbal working memory load effects on a simulator-induced spatial disorientation event. Aerosp Med Hum Perform. 2019; 90(6):531–539.

BACKGROUND: Extensive research has demonstrated that shift-work and time of day affect one’s ability to maintain alertness and vigilance. Research has also sought to determine ways to increase alertness and decrease the effects of fatigue in high vigilance environments, such as air traffic control. This study was designed to assess the effectiveness of video game play as a fatigue countermeasure in air traffic controllers.METHODS: We tested 22 military air traffic controllers to ascertain whether video game play prior to time in the air traffic control room heightened their alertness during their shift. An oculometer, which is an objective measure of physiological arousal and visual alertness, was used to measure pupillary diameter, amplitude, latency, and velocity. Perceived alertness was assessed using the Stanford Sleepiness Scale. Over a 4-wk period, the air traffic controllers participated in a counterbalanced, within-subjects design study with experimental (video gaming prior to control room) and control (no video gaming prior to control) conditions.RESULTS: We used a within-subjects, repeated measures MANOVA to compare differences in physiological and perceived alertness of individuals in the two conditions. Results indicated that video game play significantly increased physiological alertness in air traffic controllers, especially pupil diameter and velocity, and this effect was sustained for at least 30 min after they stopped playing. Perceived alertness was also increased by video game play.DISCUSSION: These results indicate that video game play could be an effective fatigue countermeasure in high vigilance occupations such as air traffic control.Fowler LA, Gustafson D. Video game play as a fatigue countermeasure in air traffic controllers. Aerosp Med Hum Perform. 2019; 90(6):540–545.

INTRODUCTION: Visual performance is important for safe and accurate taxiing operations. Visibility is associated with navigation errors during taxiing. The main objective of the present study was to investigate the effects of visibility on pilots’ fixation patterns during taxiing. The interaction between visibility and flight experience was also examined.METHODS: Both experienced and less experienced pilots participated in the study. They were instructed to perform simulated taxiing tasks in two visibility conditions: clear day vs. low visibility. A mixed-model analysis of variance was performed to determine the main and interaction effects of ‘visibility’ and ‘flight experience’ on fixation data in each area of interest (AOI).RESULTS: The results showed that experienced pilots’ fixation counts reduced on the electronic centralized aircraft monitoring (ECAM) area, but increased out the middle view (OTWM) and right view out of the window (OTWR) in low visibility than in clear day, while fixation counts among less experienced pilots increased on the primary flight display (PFD) and ECAM areas, but did not change significantly OTWM and OTWR in low visibility. Fixation duration increased by 59.8%, 9.8%, and 7.9% in ECAM, OTWL, and OTWR, respectively, in low visibility than in clear day.CONCLUSIONS: The findings suggest that pilots pay more attention and have higher perceptual load in the low visibility condition to maintain taxiing accuracy, and more experienced pilots make more visual efforts to extract information from AOIs outside the cockpit in the low visibility condition. These findings provide practical implications for safe and accurate taxiing operations.Zhang X, Qu X, Xue H, Liu J. Pilots’ fixation patterns during taxiing and the effects of visibility. Aerosp Med Hum Perform. 2019; 90(6):546–552.

INTRODUCTION: Although a space suit is a technological feat sustaining human life outside the spacecraft, working in the space suit environment can lead to musculotendon and soft tissue injuries in astronauts. In this literature review, we consider the injury risk mechanisms for human-space suit interactions. We first present a review of space suit injury risk founded in empirical, statistical, and experimental studies. We then review efforts in computational modeling of a human and space suit. As the interpretation of models for injury risk has not previously been defined, a review is presented of biomechanical considerations of injury risk to the tissue and joints based on previously observed space suit injuries. A review of risk assessment in occupational health in the workplace is then presented, an adjacent area that informs relevant measures of consideration for human-space suit applications. Finally, we discuss how the work-to-date can inform continued efforts in minimizing risk of musculoskeletal injury to the human when using a space suit. From the literature, this review concludes space suits cause biomechanical alterations, inducing musculoskeletal injury. Combining occupational health kinematic constraints with computational models could enable a trade space evaluation on space suited biomechanics to reduce risk mechanisms. Future work, though, is required to enable computational models to be predictive of individual injury risk. Our findings show there are significant gaps in our current knowledge on tissue injuries that preclude biomechanical models from being used directly as an injury risk assessment model. This review identifies how risk factor monitoring and modeling will enable improved space suit design and evaluation.Stirling L, Arezes P, Anderson A. Implications of space suit injury risk for developing computational performance models. Aerosp Med Hum Perform. 2019; 90(6):553–565.

BACKGROUND: Pneumocephalus is intracranial air normally occurring as a consequence of trauma or cranial surgery, but rarely has been reported following the habitual use of the Valsalva maneuver. We were unable to locate any similar cases of pneumocephalus associated with high performance aircraft flight, and this case report highlights an important consequence of the inappropriate use of Valsalva on ascent to altitude.CASE REPORT: A healthy 29-yr-old F-22 instructor pilot presented with recurrent pneumocephalus following the use of the Valsalva maneuver. These episodes started after an initial use of a forceful Valsalva during an aggressive unrestricted climb to altitude. His symptoms included facial pressure and a bubbling sensation in his head followed by a severe headache for several days. After upright CT evaluation, three small sphenoid sinus defects were discovered and repaired. There was no recurrence of pneumocephalus following provocative testing after surgical repair of the sphenoid sinus defects, and the aviator returned to flying high performance aircraft.DISCUSSION: Spontaneous or Valsalva-associated pneumocephalus is an uncommon occurrence in healthy individuals. Awareness of the pathognomonic succussion splash associated with this diagnosis as well as a presentation of facial pressure and headache following flight will lead to appropriate diagnostic investigation and management. This case highlights the importance of recognizing rare diagnoses like pneumocephalus in the flying population, and future education of aerospace physiology technicians and aviators should emphasize appropriate Valsalva technique to promote flying safety and prevent similar presentations.Woodside SS, Metzler MM. Pneumocephalus associated with inappropriate Valsalva technique. Aerosp Med Hum Perform. 2019; 90(6):566–569.

INTRODUCTION: This peer-reviewed hypothetical case was written to help the readership understand the challenges of dealing with quite common yet very debilitating diseases during space missions. This scenario is based on a real case of an astronaut who had previously flown in space and developed acute pancreatitis after being dehydrated from wilderness survival training. Many astronauts experience life threatening illness and injury before and after flight and, as space missions become longer and more remote, it is only a matter of time before these events occur during a mission. Future exploration space mission planners need to anticipate that these common catastrophic medical events will occur.CASE REPORT: You are a flight surgeon working on console at Mission Control during a long duration lunar mission. You have completed extensive space, military, and civilian aerospace medical training to address almost any anticipated medical event and can summon advice from medical experts located around the world. One crewmember is a 37-yr-old man who just completed an 8-h moonwalk and now describes a constant 7/10 dull epigastric pain with radiation around the left flank to his back. His pain is getting progressively worse and he is presently sitting with his trunk flexed and knees drawn up in extreme distress. Working with the flight director, you must decide in the next 12 h whether to recommend the multibillion-dollar mission be aborted and have the crew return to Earth immediately to save your patient.Hamilton DR, McBeth PB, Greene MR, Kirkpatrick AW, Ball CG. Hypothetical case of pancreatitis during a long duration lunar mission. Aerosp Med Hum Perform. 2019; 90(6):570–578.

Laslie WPD. You’re the flight surgeon: spontaneous diaphragmatic hemiparesis in an Air Force firefighter. Aerosp Med Hum Perform. 2019; 90(6):581–583.

Doxey RJ. You’re the flight surgeon: Ehlers-Danlos syndrome. Aerosp Med Hum Perform. 2019; 90(6):583–586.