A comparison of exercise interventions from bed rest studies for the prevention of musculoskeletal loss.

Musculoskeletal loss in actual or simulated microgravity occurs at a high rate. Bed rest studies are a reliable ground-based spaceflight analogue that allow for direct comparison of intervention and control participants. The aim of this review was to investigate the impact of exercise compared to no intervention on bone mineral density (BMD) and muscle cross-sectional area (muscle CSA) in bed rest studies relative to other terrestrial models. Eligible bed rest studies with healthy participants had an intervention arm with an exercise countermeasure and a control arm. A search strategy was implemented for MEDLINE. After screening, eight studies were identified for inclusion. Interventions included resistive exercise (RE), resistive vibration exercise (RVE), flywheel resistive exercise, treadmill exercise with lower body negative pressure (LBNP) and a zero-gravity locomotion simulator (ZLS). Lower limb skeletal sites had the most significant BMD losses, particularly at the hip which reduced in density by 4.59% (p < 0.05) and the tibial epiphysis by 6% (p < 0.05). Exercise attenuated bone loss at the hip and distal tibia compared to controls (p < 0.05). Muscle CSA changes indicated that the calf and quadriceps were most affected by bed rest. Exercise interventions significantly attenuated loss of muscle mass. ZLS, LBNP treadmill and RE significantly attenuated bone and muscle loss at the hip compared to baseline and controls. Despite exercise intervention, high rates of bone loss were still observed. Future studies should consider adding bisphosphonates and pharmacological/nutrition-based interventions for consideration of longer-duration missions. These findings correlate to terrestrial bed rest settings, for example, stroke or spinal-injury patients.

Sleep and Fatigue Differences in the Two Most Common Types of Commercial Flight Operations.

BACKGROUND: Sleep and fatigue management is one of the main challenges in airline operations scheduling. Our aim was to compare the differences regarding fatigue, sleep, and labor specificities between the two most common types of flight, short/medium haul (SM-H) and long haul (L-H), in a large sample of airline pilots. METHODS: A self-report questionnaire was developed, composed of socio-economic and labor questions, and psychological assessment scales for fatigue and sleep. Associations of these variables and type of flight were tested. RESULTS: Of the total sample of Portuguese airline pilots (N = 435), 313 (72%) were from SM-H and 122 (28%) were from L-H. For SM-H, the values obtained for sleep complaints were 34.2%, daytime sleepiness 61.6%, and fatigue 93.0%. For L-H, 36.9%, 53.3%, and 84.4%, respectively. Looking at labor variables, the differences between the two types of flights were evident, with SM-H pilots' having statistically significant higher mean values of duty and flight hours, numbers of sectors, and early mornings. Only the mean number of night periods was higher in L-H pilots. All values were reported for 28 consecutive scheduling days. CONCLUSION: Night periods and time-zone crossing may explain higher prevalence levels of sleep disturbances in L-H pilots. However, the values for daytime sleepiness were higher in SM-H pilots, which may be attributed to diminished sleep caused by a combination of frequent early starts and long duty periods. Taking into account the large differences between the two types of flights, different regulatory limits should be considered by aviation authorities. Reis C, Mestre C, Canhão H, Gradwell D, Paiva T. Sleep and fatigue differences in the two most common types of commercial flight operations. Aerosp Med Hum Perform. 2016; 87(9):811-815.

Sleep complaints and fatigue of airline pilots.

This work aimed to determine daytime sleepiness and sleep complaints prevalence and the corresponding influence on perceived fatigue and to evaluate the influence of sociodemographic parameters and labour variables on sleep complaints, sleepiness and fatigue. A questionnaire was developed including socio-economic and labour issues and instruments, focused in sleep and fatigue. The response rate was 32% and the final sample had 435 pilots. The prevalence of sleep complaints was 34.9%, daytime sleepiness 59.3% and fatigue 90.6%. The high prevalence of sleep complaints, sleepiness and fatigue was disclosed in pilots, with those who fly short/medium having an added risk of fatigue.

Effect of hypobaric hypoxia, simulating conditions during long-haul air travel, on coagulation, fibrinolysis, platelet function, and endothelial activation.

CONTEXT: The link between long-haul air travel and venous thromboembolism is the subject of continuing debate. It remains unclear whether the reduced cabin pressure and oxygen tension in the airplane cabin create an increased risk compared with seated immobility at ground level. OBJECTIVE: To determine whether hypobaric hypoxia, which may be encountered during air travel, activates hemostasis. DESIGN, SETTING, AND PARTICIPANTS: A single-blind, crossover study, performed in a hypobaric chamber, to assess the effect of an 8-hour seated exposure to hypobaric hypoxia on hemostasis in 73 healthy volunteers, which was conducted in the United Kingdom from September 2003 to November 2005. Participants were screened for factor V Leiden G1691A and prothrombin G20210A mutation and were excluded if they tested positive. Blood was drawn before and after exposure to assess activation of hemostasis. INTERVENTIONS: Individuals were exposed alternately (> or =1 week apart) to hypobaric hypoxia, similar to the conditions of reduced cabin pressure during commercial air travel (equivalent to atmospheric pressure at an altitude of 2438 m), and normobaric normoxia (control condition; equivalent to atmospheric conditions at ground level, circa 70 m above sea level). MAIN OUTCOME MEASURES: Comparative changes in markers of coagulation activation, fibrinolysis, platelet activation, and endothelial cell activation. RESULTS: Changes were observed in some hemostatic markers during the normobaric exposure, attributed to prolonged sitting and circadian variation. However, there were no significant differences between the changes in the hypobaric and the normobaric exposures. For example, the median difference in change between the hypobaric and normobaric exposure was 0 ng/mL for thrombin-antithrombin complex (95% CI, -0.30 to 0.30 ng/mL); -0.02 [corrected] nmol/L for prothrombin fragment 1 + 2 (95% CI, -0.03 to 0.01 nmol/L); 1.38 ng/mL for D-dimer (95% CI, -3.63 to 9.72 ng/mL); and -2.00% for endogenous thrombin potential (95% CI, -4.00% to 1.00%). CONCLUSION: Our findings do not support the hypothesis that hypobaric hypoxia, of the degree that might be encountered during long-haul air travel, is associated with prothrombotic alterations in the hemostatic system in healthy individuals at low risk of venous thromboembolism.