INTRODUCTION: Hearing loss can compromise U.S. Army aviators’ performance, safety, and situational awareness, resulting in increasing mental workload and listening effort. This study evaluated simulated hearing loss on performance and cognitive workload among Army aviators.

METHODS: A mixed-effects linear regression study design was used. A total of 21 aviators underwent clinical audiological testing and simulated flight performance assessments. Simulated hearing loss and workload were manipulated to investigate their effects on speech recognition, flight performance, and subjective workload. Flight simulator routes included normal hearing and simulated hearing loss conditions for both high and low workloads. Task load questionnaires were administered for subjective workload assessments and compared across conditions.

RESULTS: Speech recognition scores decreased with increasing levels of hearing loss. In-flight speech intelligibility declined in high workload conditions, with a 26% decrease for mild hearing loss and a 40% decrease for severe hearing loss. High workload conditions degraded flight performance and response times to a secondary task which was exacerbated by simulated hearing loss. Workload scores validated increased workload with simulated hearing loss. No significant findings were observed on the hearing assessment.

DISCUSSION: Findings suggest hearing loss negatively impacts speech recognition and flight performance, especially under high workloads. These results support the importance of addressing hearing loss in aviators. Further research is needed to determine if the clinically adapted Modified Rhyme Test can reflect the impact of hearing loss on aviator performance.

Noetzel J, Henry P, Mackie R, Cave K, Stefanson JR, Hale JK, Andres K, Jones H. Simulated hearing loss on speech recognition, flight performance, and workload in aviators. Aerosp Med Hum Perform. 2025; 96(4):269–278.

INTRODUCTION: Warning information is mainly transmitted to pilots through visual and auditory forms in flight, with only a small portion transmitted through vibration. Poorly designed flight deck warnings have negative effects on pilot performance and safety. This study aimed to give insights into how different encoding forms of warnings act on pilot performance from a cognitive modeling perspective.

METHODS: Four encoding forms were designed using voice prompts and flashing messages. An Adaptive Control of Thought–Rational based model was built to simulate the perception process. Flight simulator tests were carried out with four types of warnings triggered randomly for comparison with simulation results and thereby performed model validation. Statistical tests were performed to examine the significant differences and effect sizes.

RESULTS: Both cognitive models (response time 0.82 ± 0.06 s with voice vs. 1.37 ± 0.09 s without voice in static forms; 1.35 ± 0.56 s with voice vs. 1.83 ± 0.32 s without voice in flashing forms) and subjects’ response time (1.42 ± 0.37 s with voice vs. 1.53 ± 0.42 s without voice in static forms; 1.43 ± 0.44 s with voice vs. 1.65 ± 0.43 s without voice in flashing forms) suggest the benefits of using voice prompts to improve performance, while flashing forms of warnings may impose an extra burden on cognition even though they bring the benefit of attracting attention.

DISCUSSION: By carrying out a joint analysis with cognitive modeling and flight simulator tests, this work shows that designers can make use of alternative sensory channels for achieving a timely transfer of attention, but with a risk of increasing cognitive load.

Zhang X, Li C, Sun Y, Yan C. Cognitive response efficiency under varying audiovisual display modalities of flight deck warnings. Aerosp Med Hum Perform. 2025; 96(4):279–286.

INTRODUCTION: New computerized color vision tests are gaining popularity in the aviation community. These tests determine color vision status by measuring chromatic sensitivity and they can effectively classify color vision as normal vs. abnormal. However, little information is available regarding their repeatability. We evaluated the repeatability of two such tests: the Operational Based Visual Assessment Cone Contrast Test (OCCT) and the Rabin Cone Contrast Test (RCCT).

METHODS: A total of 56 subjects with normal color vision and 63 subjects with defective color vision completed both tests twice over 2 sessions. We determined the repeatability for a normal/abnormal result, between-eye differences in thresholds within a session, and between-session results for each eye.

RESULTS: Both tests had excellent repeatability for normal vs. abnormal color vision (i.e., using a cutoff score of 75 Rabin Color Contrast Sensitivity Units). The OCCT also had excellent repeatability for acceptable vs. unacceptable color discrimination (i.e., a cutoff score of 55), whereas the RCCT repeatability was lower. The RCCT’s lower repeatability was because the between-eye and between-session Limits of Agreement for the color-defective subjects were approximately ±40 relative sensitivity units. In contrast, the Limits of Agreement for the OCCT ranged from ±10 to ±15.

DISCUSSION: These results reinforce the advantage of using a finer stimulus change when estimating cone thresholds in the clinical setting.

Hovis JK, Almustanyir A, Glaholt M. Repeatability of cone contrast color vision tests. Aerosp Med Hum Perform. 2025; 96(4):287–295.

INTRODUCTION: Spatial disorientation and stress pose significant threats to flight safety. The attitude indicator (AI) is crucial for pilots to maintain spatial orientation. This study aims to investigate pilot performance with the original and a modified AI under stress and nonstress conditions.

METHODS: There were 52 pilots recruited and divided into a control group and a stress group. The stress group underwent the Trier Social Stress Test to induce acute stress, while the control group performed a nonstress task. Both groups then completed flight attitude recovery tasks using the original and a modified AI. The modified AI featured two white bars added around the original AI to enhance the display of the aircraft’s attitude.

RESULTS: The stress group exhibited significantly higher heart rates (88.01 ± 14.03 bpm) and subjective anxiety scores (35.82 ± 9.41) compared to the control group (83.22 ± 6.57 bpm; 32.26 ± 5.81). In the control group, accuracy with the modified AI (94.9% ± 5.1%) was significantly higher than with the original AI (91.8% ± 6.6%). Additionally, the modified AI reduced pitch reversal errors and roll reversal errors. In the stress group, the modified AI increased accuracy for smaller initial pitch and bank angles and reduced roll reversal errors.

DISCUSSION: The addition of visual cues in the periphery of the AI improved performance under nonstressed conditions. Under stress, the visual cues enhanced accuracy for smaller pitch and bank angles and reduced roll reversal errors. These findings provide insights for the ergonomic design of cockpit instruments.

Jiang H, Liu X, Peng X, Zhu Q, Wang Q, Yang J. Pilot performance on original and modified attitude indicators with and without acute stress. Aerosp Med Hum Perform. 2025; 96(4):296–303.

INTRODUCTION: The present study aimed to investigate changes in risky behavior in a sample of 36 healthy men during a 90-d head-down bed rest (HDBR) experiment and examined whether psychological factors—general self-efficacy, stress, and recovery—could influence these changes.

METHODS: Subjects completed the Balloon Analog Risk Task (BART) and two psychological scales once during the acclimation period, six times during the HDBR period, and twice during the recovery period. During the HDBR period, subjects were required to maintain a −6° head-down position for most daily activities and only permitted to change positions around the longitudinal axis of their bodies.

RESULTS: The results demonstrated that subjects’ risk-taking behaviors were significantly affected by bed rest, with an increased propensity to engage in risky activities during the head-down stage. In addition, BART scores did not return to baseline when subjects entered the recovery stage. In terms of psychological variables, the results indicated that scores of general self-efficacy and recovery were negatively correlated with BART indicators, while stress levels were positively correlated with risky behaviors. Compared to other psychological variables, the perceived physical stress, including fatigue, somatic complaints, and sleep quality, exhibited the strongest correlations with BART indicators.

DISCUSSION: The findings of this study implied that prolonged exposure to a simulated microgravity environment and confined isolation conditions may have a sustained impact on risk-taking tendencies, with changes in risky behaviors in the head-down state more closely associated with physiological symptoms.

He X, Lei Y, Xu Z, Li K, Nicolas M, Wu R, Li Y. Changes in risky behavior in long-term head-down bed rest and relation to psychological status. Aerosp Med Hum Perform. 2025; 96(4):304–313.

INTRODUCTION: Operators of rotary wing aircraft and high-performance jet aircraft often face musculoskeletal pain and cervical spine injury risks due to flight-related factors, including heavy vibrational and g-loading, abrupt head maneuvering, and a large number of flight hours. This study explores the use of a portable lightweight resistance band exercise device (PLED) to strengthen and stretch neck musculature, potentially mitigating these risks.

METHODS: A multi-aircraft study building on an initial pilot study of 10 high-performance jet aircraft aviators involved both active-duty aviators and civilians. Over 6 wk, subjects engaged in targeted PLED-based exercises. Baseline and endpoint measurements were obtained. Quantitative measurements assessed range of motion (ROM) and endurance, while Visual Analog Scale reports tracked pain. A total of 47 subjects consented, with 26 completing the protocol. There were 21 subjects who were either lost to follow-up or withdrew due to scheduling conflicts.

RESULTS: Analysis of this interventional study showed significant ROM improvement, increased muscular endurance, and reductions in pain magnitude. Subjects reported improvements in flexibility, strength, stiffness, and pain relief. Active-duty aviators noted improved ROM, quicker postflight recovery, and reduced in-flight pain.

DISCUSSION: This collaborative Department of Defense-academia-Department of Veterans Affairs research highlights the effectiveness of regular PLED-based cervical musculature exercises in enhancing ROM and endurance. While promising, further research with larger datasets is needed to support definitive recommendations. Moreover, the study’s findings may benefit a broad population engaging in activities that stress the cervical spine and surrounding musculature.

Keller RJ, Rosenthal R, Dalal S, O’Conor D, Ramachandran V, Vandeven S, Butler N, Shivers B, Shender B, Jones JA. Exercise regimen for mitigation of neck pain in military aircrew and support personnel. Aerosp Med Hum Perform. 2025; 96(4):314–321.

INTRODUCTION: Facial hair is prohibited for most airline pilots because of the widespread belief that the seal on oxygen masks might be rendered ineffective, preventing aircrew from performing their duties during emergencies.

METHODS: Continuous oximetry recordings were made every second from 24 volunteers wearing a standard commercial airline mask in 1 of 3 beard conditions: no beards, short beards (<10 mm in length), and long beards (>10 mm in length) in a normobaric hypoxia chamber at 30,000 ft (10,000 m). Masks were worn in the chamber for about 10 min before being removed for about 2 min to experience hypoxia. Once returned to normoxia, volunteers were exposed to smelling salts held directly under the chin.

RESULTS: None of the beard conditions differed in the time to don the masks. There were no differences in the arterial saturation percent of oxygen (S_po₂) between beard conditions for either mask-on or mask-off segments in the chamber. There were significant differences in S_po₂ between the mask-on segment and the mask-off segment, indicating that hypoxemic conditions would have been detected had the masks been ineffective.

DISCUSSION: Using a current on-demand airline oxygen mask, S_po₂ levels were never compromised by any of the beard conditions. Because the highly volatile smelling salts were imperceptible through the masks, smoke and other noxious irritants would not be perceived. These results support the contention that airline pilots with beards of any length would not be impaired by hypoxia or smoke while dealing with an in-flight emergency.

French J, Wagner SD. Beard length and the efficacy of an aviator oxygen mask. Aerosp Med Hum Perform. 2025; 96(4):322–326.

INTRODUCTION: Despite significant advancements in aerospace engineering and safety protocols over the last decade, U.S. Naval mishap rates have remained essentially unchanged. This paper explores how researchers may leverage current artificial intelligence (AI) technologies to enhance aviation safety.

METHODS: A critical review was performed identifying aviation research protocols which have incorporated machine learning (ML) to enhance the accuracy of detecting common aviation hazards leading to cognitive decrements. The review proposes a three-step methodology for creating protocols to identify cognitive decrements in aviators: 1) sensor selection; 2) preprocessing techniques; and 3) ML algorithm development. Natural language processing was utilized to assist with the development of aviation-related denoising and ML algorithm tables.

RESULTS: Several psychophysiological biosensors, enhanced by ML modeling, show promise in identifying cognitive deficits secondary to fatigue, hypoxia, and spatial disorientation. The most cited biosensors integrated with ML models include electroencephalographic, electrocardiographic, and eye-tracking devices. The application of preprocessing techniques to biosensor data is a critical methodological step prior to applying ML algorithms for data training and classification. ML algorithms utilized were categorized into supervised, unsupervised, and semi-supervised types, often used in combination for more accurate predictions.

DISCUSSION: Current literature suggests that AI, when used in conjunction with various psychophysiological sensors, can predict and potentially mitigate common aeromedical hazards such as fatigue, spatial disorientation, and hypoxia in simulated settings. The miniaturization of preprocessing and ML algorithmic hardware is the next phase of transitioning AI to operational environments for real-time continuous monitoring.

Rice GM, Linnville S, Snider D. Methodologies using artificial intelligence to detect cognitive decrements in aviation environments. Aerosp Med Hum Perform. 2025; 96(4):327–338.

INTRODUCTION: This study systematically explores the effects of self-administered physical exercise training on alleviating flight-associated neck pain and improving functional outcomes in military pilots.

METHODS: PubMed, Cochrane Library, Web of Science, Embase, Scopus, China National Knowledge Infrastructure, and the Chinese biomedical literature service system (SinoMed) were searched from inception to September 18, 2024. Standardized mean differences (SMD) or mean differences (MD) and 95% confidence intervals (95% CI) were calculated and data pooled using fixed or random effects models.

RESULTS: Included were 7 studies involving 366 patients having neck pain. Military pilots who underwent self-administered physical exercise training showed a significant reduction in their Visual Analog Scale scores (SMD = −0.25, 95% CI: −0.47 to −0.03). The maximum voluntary contraction (MVC) of neck extension and flexion in military pilots did not increase significantly after self-administered physical exercise training (extension MVC, MD = 3.00, 95% CI: −1.33 to 7.33; flexion MVC, MD = 1.12, 95% CI: −2.12 to 4.36).

DISCUSSION: Self-administered physical exercise training is an effective method for alleviating flight-associated neck pain in military pilots. However, its effectiveness in improving neck function among military pilots remains uncertain.

Chen H, Wang M, Li J, Wang X, Fu Y, Gao B. Self-administered physical exercise training and flight-associated neck pain in military pilots. Aerosp Med Hum Perform. 2025; 96(4):339–349.

INTRODUCTION: Fiber-reinforced composites are widely used in the aircraft industry, including in helicopters. When exposed to fire, airborne fibers can be released from the composite and pose a risk to exposed humans—the fear being that it may pose a similar health hazard as asbestos fibers, particularly the pulmonary damage.

METHODS: A systematic literature review was performed in the PubMed database. Four search strings were made deliberately extensive to find relevant articles on the narrow subject.

RESULTS: The search resulted in a total of 330 titles. Of these, 73 abstracts were found relevant, of which 28 articles and finally 18 articles were included.

DISCUSSION: The health hazards of the different fiber types were found to be as follows: fiberglass has been classified by the International Agency for Research on Cancer as: “Not classifiable as to their carcinogenicity in humans”, with no later studies indicating that decision as being inaccurate. Studies on p-aramid have found a transient pulmonary inflammatory response which is not present 1 mo after exposure. Carbon/graphite has not been thoroughly investigated, but temporary lung inflammation, reversible after 10 d, has been described. Studies have not agreed on the number of fibers released in a fire, but many factors play an important role as to how many are produced, such as high temperatures (>600–850°C), turbulence, and situations like pool fire and a flashover. The knowledge on long-term outcomes after short-term exposures of fibers is scarce, and studies following up victims from aircraft incidents and firefighters as well as next-in-line helpers would be highly relevant.

Laugesen M, Lindgaard K. Potential pulmonary damage from exposure to composite fibers in helicopter fires. Aerosp Med Hum Perform. 2025; 96(4):350–355.

INTRODUCTION: We previously published a model of how calcium from resorbing bone can enter and persist in the circulation with consequent precipitation in coronary arteries. The model was based on chronic inflammation as the source of continued bone resorption. We asked whether other forms of resorptive bone loss such as microgravity (disuse) might also be associated with bone calcium accumulation in coronary arteries.

METHODS: We analyzed a de-identified database provided by NASA consisting of 52 astronauts who had flown a space mission around two determinations of coronary artery calcium (CAC) scores at 5-yr intervals and bone density determinations in the year prior to and 10 d and 1 yr following a space mission.

RESULTS: We found that in 38.5% of the astronauts, their CAC scores changed between pre- and postflight, with 95% of the CAC scores increasing. These astronauts were significantly older than the 61.5% whose CAC scores did not change, although the mission length was not different between the groups. Both groups lost bone acutely but had partial recovery over the year postflight.

DISCUSSION: Due to lack of uniform sampling times, we could not correlate changes in CAC score with bone loss and would advocate for synchronous determinations of CAC and bone density pre- and postflight.

Klein GL, Jupiter DC. Elevated coronary artery calcium scores in astronauts. Aerosp Med Hum Perform. 2025; 96(4):356–359.

INTRODUCTION: The original spacecraft maximum allowable concentrations (SMACs) for 2-propanol were established by NASA in 1996. 2-propanol is an irritant that may also cause central nervous system effects at high concentrations. Limits for 1 and 24 h were set at 400 and 100 ppm based on human exposure data. Limits for 7, 30, and 180 d were set at 60 ppm using the same human data but further accounting for the small number of subjects.

METHODS: A literature search was conducted using keywords “isopropyl alcohol” and further narrowed with keywords “toxicity” and “inhalation.” Additionally, studies cited in the development of occupational and acute exposure limits were assessed.

RESULTS: While no new toxicity studies were identified since the SMACs were established, a study that was not previously discussed in the existing documentation was identified. The data suggest that the original SMACs remain relevant, and we chose only to increase the 24-h limit from 100 to 200 ppm, the current occupational limit. We also determined that it is appropriate to apply the existing nominal SMAC of 60 ppm to missions of 1000 d.

DISCUSSION: NASA is committed to ensuring that spacecraft limits for chemicals in air and water are based on the most recent evidence and risk assessment methodologies. As such, we periodically review historical limits to ensure they are both adequately protective and not overly restrictive. For this compound, there is no new evidence to indicate significant change is required.

Ryder VE. Revisions to limits for 2-propanol in spacecraft air. Aerosp Med Hum Perform. 2025; 96(4):360–362.