| 1. |
- Alricsson, Marie, et al.
(författare)
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Mobility, muscular strength and endurance in the cervical spine in Swedish air force pilots
- 2001
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 72:4, s. 336-342
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Muscle strength, endurance and range of movement of the cervical spine in a group of Swedish Air Force jet pilots (AF) and in a reference group of conscripts doing their military service (RG) were compared. METHODS: We tested 30 (AF) 24-42 yr and 33 (RG) 19-22 yr. A questionnaire was used to document complaints. Maximum voluntary isometric muscle strength of the flexor and extensor muscles of the cervical spine and sub-maximum isometric endurance in the flexor and extensor muscles were measured. RESULTS: Eleven AF (37%) and four RG (12%) had experienced discomfort in the neck within the previous year. The pilots' flexor and extensor muscle strength (47 Nm and 65 Nm) was superior to that of the conscripts (36 Nm and 59 Nm) (p = 0.0001, p = < 0.05, respectively). However, the RG group had greater isometric endurance in the flexor muscles than AF (p = < 0.05) and greater neck rotation (p = <0.005). There was no difference between the two groups in the other variables. CONCLUSION: Differences between the groups with regard to muscle strength and endurance might depend on variations in work-related physical muscle strain, and/or differences in fiber composition in the muscles, which might be reflected by pilot selection procedures.
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| 2. |
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| 4. |
- Balldin, Ulf, et al.
(författare)
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Color vision with rapid-onset acceleration
- 2003
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 74:1, s. 29-36
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Eiken, Ola, et al.
(författare)
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A new hydrostatic anti-G suit vs. a pneumatic anti-G system : Preliminary comparison
- 2002
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 73:7, s. 703-708
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: A newly developed hydrostatic anti-G suit is now commercially available. The suit is said to offer a high level of protection against +Gz acceleration. However, past experience shows that it is difficult to produce a hydrostatic suit with effective high-G protection. Careful testing is, therefore, needed to verify its efficacy. Methods: The G-protective properties of the hydrostatic anti-G suit (Libelle, L) were compared with those of a pneumatic anti-G ensemble (AGE-39) used in the Swedish JAS 39 Gripen aircraft. Three pilots were studied during vertical (+Gz) acceleration in a centrifuge using the following: 1) the L-suit with varied straining maneuvers, 2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver, FM), and 3) the ACE-39 in combination with AGSM during the initial part of each high-G exposure (reduced maneuver, RM). G-intensity tolerance was established during exposures to rapid onset rate (ROR) profiles with C-plateau levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during simulated aerial combat maneuvers (SACM) consisting of 10 cycles of 5.5 to 7.5 G. Results: All three pilots tolerated 9.0 C with the pneumatic system both in the RM and FM conditions, their tolerances averaged 6.3 G (range 6.0 to 7.0 G) for the L suit. Thus, during the ROR exposures only the 6.0 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition. Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L condition. In the RM condition all subjects completed the SACM profile and in the FM condition two subject completed the SACM. Conclusions: Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. While wearing the L-suit, G-tolerance was 6.3 G. Thus, under the conditions tested, the C-protection afforded by the L-suit is not adequate for use in a 9-G aircraft.
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| 6. |
- Eiken, Ola, et al.
(författare)
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Relationship between arm pain and distension of arteries and veins caused by elevation of transmural pressure in local vascular segments
- 2001
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 72:5, s. 427-431
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Exposure to high +Gz forces may induce arm pain, which has been hypothesized to be caused by pressure-induced overdistension of local blood vessels. The purpose of the present investigation was to study the pressure-distension relation of veins and arteries in the human arm and the relation between arm pain and distension of local vessels. METHODS: Increased distending pressures (DP) in the vasculature of the arm were accomplished by placing the subject (n = 8) in a pressure chamber with one arm positioned through a port in the chamber door, and increasing chamber pressure to +180 mm Hg in a stepwise manner. Diameters in the brachial artery and in the brachial, radial and cephalic veins were measured by ultrasonography. Changes in forearm volume were estimated from measurement of tissue impedance. Perceived pain was rated using a 10-point scale. RESULTS: Arm pain increased with pressure to a maximum rating of 8.5 (= median; range: 4-10). Increasing DP from 30 to 180 mm Hg resulted in a steady increase (p < 0.05) in venous diameter which varied from 12 +/- 8% (mean +/- SD) in the brachial vein to 23 +/- 14% in the radial vein. Inthe brachial vein diameter increases were most pronounced at the sites of the venous valves. Arterial diameter was unchanged up to a DP of about 200 mm Hg (calculated as diastolic arterial pressure + applied chamber pressure), but then increased by 32 +/- 9% (p < 0.001). Forearm impedance dropped with increasing pressure (delta = 23 +/- 5%; p < 0.01); the rate of change was non-linear with a faster change at the highest DP which may indicate pressure distension of precapillary resistance vessels. CONCLUSIONS: Elevation of pressure in arm vessels to levels that may occur in pilots flying high-performance aircraft results in distension not only of veins but also of arteries and probably of smaller precapillary vessels. Therefore, and because these changes coincide with the development of severe arm pain, local overdistension of blood vessels remains a plausible cause of G-induced arm pain.
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| 7. |
- Eiken, Ola, et al.
(författare)
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The effect of straining maneuvers on G-protection during assisted pressure breathing
- 2003
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 74:8, s. 822-826
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Pilots flying high-performance aircraft increase their acceleration tolerance by using straining maneuvers and anti-G suits. Recently, assisted positive pressure breathing has been added in some aircraft systems. This study assessed the effect of anti-G straining maneuvers on the G-protective properties of one such system, the AGE-39 anti-G ensemble used in the Swedish JAS 39 Gripen aircraft. METHODS: Ten subjects were studied in a centrifuge using each of the following: 1) the AGE-39 in combination with anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); 2) the AGE-39 in combination with AGSM only during the initial part of each high-G exposure (reduced maneuver; RM). G-tolerance was established during exposures to rapid onset rate (ROR) G profiles with plateau levels ranging from 6.5 to 9.0 G. RESULTS: Mean G-tolerance was > or = 8.8 G (range: 8.5 to > or = 9.0 G) in the RM condition and > or = 9.0 G in all subjects in the FM condition. Mean arterial pressure was 30-50 mm Hg higher (p < 0.001) in the FM than in the RM condition at any given ROR G-load. CONCLUSIONS: AGE-39 in combination with a brief period of straining provide efficient G-protection as illustrated by the finding that all subjects could tolerate 8.5 G while performing AGSM during the initial part of the high-G exposures. However, at 9.0 G, 40% of the subjects had to perform AGSM throughout the duration of the G-exposure. That arterial pressure was only 30-50 mm Hg higher in the FM than RM condition suggests that in the presence of straining maneuvers, pressure breathing makes only a minute contribution to the arterial-pressure response.
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| 8. |
- Eklundh, Thomas, et al.
(författare)
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Cerebrospinal fluid levels of monoamine compounds and cholecystokinin peptides after exposure to standardized barometric pressure
- 2000
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 71:11, s. 1131-1136
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Connections between mood changes and weather have been described throughout the ages, and in more recent years, there have been reports on a relationship between atmospheric pressure and neurotransmitter levels in cerebrospinal fluid.METHODS: To further investigate this issue under strictly standardized conditions, we have lumbar-punctured 8 healthy males under low (963 hPa) and high (1064 hPa) barometric pressure, using a pressure chamber.RESULTS: Under high pressure, the tyrosine concentrations in the cerebrospinal fluid (CSF) were lower, while the cholecystokinin tetrapeptide (CCK-4) levels were higher. No differences between low and high pressure were found for tryptophan, 5-hydroxyindolacetic acid (5-HIAA), dopamine (DA), and sulphated cholecystokinin octapeptide (CCK-8S). The serum level of CCK-8S was higher under high pressure. On comparing concentration ratios between the second and the first CSF fraction, we found significantly increased ratios for homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylglycol (HMPG), but a decreased ratio for tyrosine under high pressure. The difference in the concentration ratios of HVA between low and high pressure correlated negatively with age. Intraspinal pressure correlated negatively with tapping time at low pressure.CONCLUSION: Our results are in line with the hypothesis that atmospheric pressure influences CSF levels of monoamine compounds and cholecystokinin peptides.
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