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Eccentric upper‐body exercise performed 24 h prior to high‐altitude decompression has previously been shown to aggravate venous gas emboli (VGE) load. Yet, it is unclear whether increasing the muscle mass recruited (i.e., upper vs. whole‐body) during eccentric exercise would exacerbate the decompression strain. Accordingly, this study aimed to investigate whether the total muscle mass recruited during eccentric exercise influences the decompression strain. Eleven male participants were exposed to a simulated altitude of 24,000 ft for 90 min on three separate occasions. Twenty‐four hours before each exposure, participants performed one of the following protocols: (i) eccentric whole‐body exercise (ECCw; squats and arm‐cycling exercise), (ii) eccentric upper‐body exercise (ECCu; arm‐cycling), or (iii) no exercise (control). Delayed onset muscle soreness (DOMS) and isometric strength were evaluated before and after each exercise intervention. VGE load was evaluated at rest and after knee‐ and arm‐flex provocations using the 6‐graded Eftedal–Brubakk scale. Knee extensor (−20 ± 14%, P = 0.001) but not elbow flexor (−12 ± 18%, P = 0.152) isometric strength was reduced 24 h after ECCw. ECCu reduced elbow flexor isometric strength at 24 h post‐exercise (−18 ± 10%, P < 0.001). Elbow flexor DOMS was higher in the ECCu (median 6) compared with ECCw (5, P = 0.035). VGE scores were higher following arm‐flex provocations in the ECCu (median (range), 3 (0–4)) compared with ECCw (2 (0–3), P = 0.039) and control (0 (0–2), P = 0.011), and in ECCw compared with control (P = 0.023). VGE were detected earlier in ECCu (13 ± 20 min) compared with control (60 ± 38 min, P = 0.021), while no differences were noted between ECCw (18 ± 30 min) and control or ECCu. Eccentric exercise increased the decompression strain compared with control. The VGE load varied depending on the body region but not the total muscle mass recruited. Highlights: What is the central question of this study?Does exercise‐induced muscle damage (EIMD) resulting from eccentric exercise influence the presence of venous gas emboli (VGE) during a 90 min continuous exposure at 24,000 ft?What is the main finding and its importance?EIMD led to an earlier manifestation and greater VGE load compared with control. However, the decompression strain was dependent on the body region but not the total muscle mass recruited. [ABSTRACT FROM AUTHOR]

During coordinated flight and centrifugation, pilots show interindividual variability in perceived roll tilt. The study explored how this variability is related to perceptual and cognitive functions. Twelve pilots underwent three 6-min centrifugations on two occasions (G levels: 1.1G, 1.8G, and 2.5G; gondola tilts: 25°, 56°, and 66°). The subjective visual horizontal (SVH) was measured with an adjustable luminous line and the pilots gave estimates of experienced G level. Afterward, they were interrogated regarding the relationship between G level and roll tilt and adjusted the line to numerically mentioned angles. Generally, the roll tilt during centrifugation was underestimated, and there was a large interindividual variability. Both knowledge on the relationship between G level and bank angle, and ability to adjust the line according to given angles contributed to the prediction of SVH in a multiple regression model. However, in most cases, SVH was substantial smaller than predictions based on specific abilities. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pilots undergoing coordinated flight turns or centrifugation, whilst devoid of visual cues, exhibit substantial interindividual variation in their perception of roll tilt. The objectives of this study were to investigate whether, and to what extent, specific perceptual and cognitive abilities can account for this inter-individual variability. METHODS: Twelve experienced fixed-wing pilots were subjected to centrifuge tests on two separate occasions, with a six-month interval between them. The subjective visual horizon (SVH) was measured in darkness using an adjustable luminous line during three 6-minute centrifuge runs, each involving different roll tilts: 25° (1.1 G), 56° (1.8 G), and 66° (2.5 G). Initial and final SVH settings were recorded for each G plateau. During the second occasion, the SVH settings were temporarily interrupted at each plateau (visual distraction task). In addition, verbal estimations of experienced G loads were provided by the pilots. After the centrifuge tests, 1-g environment, the pilots were questioned about the relationship between G load and roll tilt, and they were asked to adjust the luminous line so that its slope corresponded with specified angles. RESULTS: The pilots underestimated their roll tilt throughout each G plateau, average SVH being 4° to 28° less than the actual roll angle at the different G loads. The visual distraction task did not affect the SVH settings. A multiple regression analysis indicated that the chain of tested capacities - perception of G load, knowledge of relation between G load and bank angle, accuracy when indicating angles in 1 g - significantly contributed to the SVH. DISCUSSION: Thus, the tested chain of skills appears to influence the pilots' ability to assess the degree of roll tilt during simulated coordinated flight turns. Notwithstanding, SVH was typically markedly smaller than predictions based on the specific abilities. Presumably, SVH is also dependent on subconscious processing, linking the sensation of bodily weight to a visually imagined horizon. Learning Objectives 1. Participants will gain insight into the role of the vestibular system in pilots' perception of roll tilt during coordinated flight turns and centrifugation, and how it interfaces with cognitive processes, shedding light on the complexities of pilot perception. 2. Participants will understand the challenges posed by the nonlinear relationship between G load and bank angle perception, and how the brain's reliance on otolith information for spatial orientation can affect pilots' ability to accurately estimate roll tilt, highlighting the need for potential training regimens to improve this capability. [ABSTRACT FROM AUTHOR]

Resistance exercise on Earth commonly involves both body weight and external load. When developing exercise routines and devices for use in space, the absence of body weight is not always adequately considered. This study compared musculoskeletal load distribution during two flywheel resistance knee-extension exercises, performed in the direction of (vertical squat; S) or perpendicular to (horizontal leg press; LP) the gravity vector. Eleven participants performed these two exercises at a given submaximal load. Motion analysis and musculoskeletal modelling were used to compute joint loads and to simulate a weightless situation. The flywheel load was more than twice as high in LP as in S (p < 0.001). Joint moments and forces were greater during LP than during S in the ankle, hip and lower back (p < 0.01) but were similar in the knee. In the simulated weightless situation, hip and lower-back loadings in S were higher than corresponding values at Earth gravity (p ≤ 0.01), whereas LP joint loads did not increase. The results suggest that LP is a better terrestrial analogue than S for knee-extension exercise in weightlessness and that the magnitude and direction of gravity during resistance exercise should be considered when designing and evaluating countermeasure exercise routines and devices for space. [ABSTRACT FROM AUTHOR]

The present investigation concerns the integrity of a primary mental function, the egocentric frame of reference and the sense of polarity of one's own head. The visually perceived eye level (VPEL) and the subjective antero-posterior axis of the head were measured by means of a visual indicator in darkness during two stimulus conditions: static pitch (sagittal-plane) tilting in the 1-g environment and gondola centrifugation (2G). It is demonstrated that an increase in the magnitude of the gravitoinertial (G) force, acting in the direction of the head and body long (z) axis, causes a substantial change not only in the VPEL but also in the perceived direction of the antero-posterior axis of the head.

It is anticipated that flywheel-based leg resistance exercise will be implemented in future long-duration space missions, to counter deconditioning of weight-bearing bones and postural muscles. The aim was to examine low back loads and muscle engagements during flywheel leg press (FWLP) and flywheel squat (FWS) and, for comparisons, free-weight barbell back squat (BBS). Eight resistance-trained subjects performed 8 repetition maximums of FWLP, FWS, and BBS. Motion analysis and inverse dynamics-based musculoskeletal modeling were used to compute joint loads and muscle forces. Muscle activities were measured with electromyography (EMG). At the L4-L5 level, peak vertebral compression force was similarly high in all exercise modes, whereas peak vertebral posteroanterior shear force was greater (p < 0.05) in FWLP and BBS than in FWS. Among the back-extensor muscles, the erector spinae longissimus exerted the greatest peak force, with no difference between exercises. Peak force in the lumbar multifidus was lower (p < 0.05) during FWLP than during FWS and BBS. Peak EMG activity in the lumbar extensor muscles ranged between 31 and 122% of maximal voluntary isometric contraction across muscles and exercise modes, with the greatest levels in the lumbar multifidus. The vertebral compression forces and muscle activations during the flywheel exercises were sufficiently high to presume that when implementing such exercise in space countermeasure regimens, they may be capable of preventing muscle atrophy and vertebral demineralization in the lumbar region. [ABSTRACT FROM AUTHOR]