scholarly journals Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Giovanni Taibbi ◽  
Millennia Young ◽  
Ruchi J. Vyas ◽  
Matthew C. Murray ◽  
Shiyin Lim ◽  
...  
Keyword(s):  
Space Station ◽  
Bed Rest ◽  
Vascular Density ◽  
Vascular Response ◽  
Mixed Effects Modeling ◽  
Long Duration ◽  
Fluid Shifts ◽  
Before And After ◽  
And Performance ◽  
The One

AbstractThe Spaceflight Associated Neuro-ocular Syndrome (SANS), associated with the headward fluid shifts incurred in microgravity during long-duration missions, remains a high-priority health and performance risk for human space exploration. To help characterize the pathophysiology of SANS, NASA’s VESsel GENeration Analysis (VESGEN) software was used to map and quantify vascular adaptations in the retina before and after 70 days of bed rest at 6-degree Head-Down Tilt (HDT), a well-studied microgravity analog. Results were compared to the retinal vascular response of astronauts following 6-month missions to the International Space Station (ISS). By mixed effects modeling, the trends of vascular response were opposite. Vascular density decreased significantly in the 16 retinas of eight astronauts and in contrast, increased slightly in the ten retinas of five subjects after HDT (although with limited significance). The one astronaut retina diagnosed with SANS displayed the greatest vascular loss. Results suggest that microgravity is a major variable in the retinal mediation of fluid shifts that is not reproduced in this HDT bed rest model.

Determining the Optimal Interval Exercise Intensity Dose for Improving Exercise Performance

2016 ◽  
Author(s):  
Norah MacMillan
Keyword(s):  
Interval Training ◽  
Active Recovery ◽  
Performance Variables ◽  
Interval Exercise ◽  
Optimal Interval ◽  
Positive Effects ◽  
Long Duration ◽  
Before And After ◽  
And Performance ◽  
Type Of Exercise

Short duration interval training is a time-efficient exercise strategy that can improve fitness through changes in metabolic, cardiovascular and performance related variables. Studies have examined the positive effects of maximal intensity exercise (≥100% VO2max) on metabolic and performance variables in recreationally active individuals and trained athletes. The intensity of interval training required to cause improvements in aerobic fitness is unknown. This study will look at the performance related adaptations that occur with three different exercise intensities of interval training matched in terms of duration, frequency and type of exercise. Sixteen recreationally active individuals, both males (n=9, age = 23.3±3.3, VO2max = 44.2±6.5) and females (n=6, age = 21.5±0.7, VO2max = 39.7±5.4) were randomly assigned to one of three groups who trained using intervals at 120% VO2max (n=5), 90% VO2max (n=4) or 65% VO2max (n=7). The participants performed 14 days of training spread over 4 weeks that consisted of 8-12 repeats of 1-minute cycling at the prescribed intensity with 1-minute active recovery between intervals. Training increased time to fatigue in the 90% VO2max and 120% VO2max group however not in the 65% VO2max group. The changes in VO2max before and after training were significant in the 90% VO2max group and the 120% VO2max group, however not between the 120% VO2max and 90% VO2max group (p≤0.05). Interval training at 90% and 120% VO2max stimulates analogous improvements in fitness. These results may be important for diseased or sedentary populations where very high-intensity and long duration exercise may not be well tolerated.

scholarly journals Effects of Spaceflight Stressors on Brain Volume, Microstructure and Intracranial Fluid Distribution

2021 ◽  
Author(s):  
Jessica K Lee ◽  
Vincent Koppelmans ◽  
Ofer Pasternak ◽  
Nichole E Beltran ◽  
Igor S Kofman ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Space Station ◽  
Free Water ◽  
Bed Rest ◽  
Fluid Distribution ◽  
Functional Changes ◽  
Brain Changes ◽  
And Performance ◽  
Underlying Mechanisms ◽  
The Brain

Abstract Astronauts are exposed to elevated CO2 levels onboard the International Space Station (ISS). Here, we investigated structural brain changes in 11 participants following 30-days of head-down tilt bed rest (HDBR) combined with 0.5% ambient CO2 (HDBR+CO2) as a spaceflight analog. We contrasted brain changes observed in the HDBR+CO2 group with those of a previous HDBR sample not exposed to elevated CO2. Both groups exhibited a global upward shift of the brain and concomitant intracranial free water (FW) redistribution. Greater gray matter changes were seen in the HDBR+CO2 group in some regions. The HDBR+CO2 group showed significantly greater FW decrements in the posterior cerebellum and the cerebrum than the HDBR group. In comparison to the HDBR group, the HDBR+CO2 group exhibited greater diffusivity increases. In half of the participants, the HDBR+CO2 intervention resulted in signs of Spaceflight Associated Neuro-ocular Syndrome (SANS), a constellation of ocular structural and functional changes seen in astronauts. We therefore conducted an exploratory comparisoncompared between subjects that did and did not develop SANS and found asymmetric lateral ventricle enlargement in the SANS group. These results enhance our understanding of the underlying mechanisms of spaceflight-induced brain changes, which is critical for promoting astronaut health and performance.

Induced venous pooling and cardiorespiratory responses to exercise after bed rest

1982 ◽  
Vol 52 (5) ◽  
pp. 1343-1348 ◽  
Author(s):  
V. A. Convertino ◽  
H. Sandler ◽  
P. Webb ◽  
J. F. Annis
Keyword(s):  
Bed Rest ◽  
Control Group ◽  
O2 Uptake ◽  
Vo2 Max ◽  
Endurance Time ◽  
Venous Pooling ◽  
Fluid Shifts ◽  
Before And After ◽  
Male Subjects ◽  
Experimental Group

The purpose of this study was to deliberately induce venous pooling the lower extremities of bed-rested subjects to determine whether such distention may reverse the reduction in maximal O2 uptake that has regularly been observed. Bed-rest deconditioning was assessed in eight healthy male subjects by measuring submaximal and maximal O2 uptake (VO2 max), ventilation, and heart rate (HRmax) before and after 15 days of bed rest. During bed rest four subjects in the experimental group received daily treatments of venous pooling for 210 min/day with a reverse gradient garment (RGG), whereas the four subjects in the control group received no treatment. Compared with prebed-rest values, VO2max was reduced by 14.0 (P less than 0.05), HRmax was increased by 4.2 (P less than 0.05), and endurance time for the exercise test was decreased by 9.2% (P less than 0.05) in the control group. In the RGG group, VO2max, HRmax, and endurance time were essentially unchanged after bed rest. The plasma volume (PV) of the control group decreased by 16.7 (P less than 0.05) after bed rest compared with a 10.3% (not significant) reduction in the RGG group. The percent delta PV was related to the percent delta VO2 max (r = 0.75, P less than 0.05) and percent delta HR max (r = 0.65, P less than 0.05). The data support the hypothesis that the lack of venous pooling and associated fluid shifts contribute the decrement in VO2 max associated with bed-rest deconditioning.

scholarly journals The effect of using Electrical Flipping Model Learning to improve the performance of student in Electric and Electronic of Automobiles

2018 ◽  
Vol 226 (3) ◽  
pp. 229-248
Author(s):  
Lecturer: Majida Waheeb Irzooqi
Keyword(s):  
Control Group ◽  
Model Learning ◽  
Traditional Course ◽  
Significant Difference ◽  
Before And After ◽  
Training Of Trainers ◽  
And Performance ◽  
The One ◽  
And Control ◽  
Experimental Group

   The aim of the study was to uncover the effectiveness of the inverted learning model in the achievement and performance of e-learning skills in the students of the department of machinery and equipment . The semi experimental approach design was used with before and after test measurement. The study sample consisted of students of the first stage of the equipment and equipment department of the Institute of training of trainers (70) students divided into two groups: experimental group (35) students were taught the subject of electricity and electronic cars. And a control group (35) students were taught with a traditional course. The tools of the study were applied before and after the two groups. The data were analyzed using the one-way contrast test and  Gohen Standard  equation  to  effective  size . The results of the study were statistically significant difference at (α = 0.05k) between the average of the experimental and control groups in the post application of both the achievement test and the skill performance observation card for the benefit of the experimental group.                                                                                                                            

scholarly journals Long-duration bed rest as an analog to microgravity

2016 ◽  
Vol 120 (8) ◽  
pp. 891-903 ◽  
Author(s):  
Alan R. Hargens ◽  
Laurence Vico
Keyword(s):  
Bone Loss ◽  
Orthostatic Intolerance ◽  
Bed Rest ◽  
Strength Exercise ◽  
Radiation Hazards ◽  
Cardiac Atrophy ◽  
Earth Gravity ◽  
Long Duration ◽  
Microgravity Simulation ◽  
Fluid Shifts

Long-duration bed rest is widely employed to simulate the effects of microgravity on various physiological systems, especially for studies of bone, muscle, and the cardiovascular system. This microgravity analog is also extensively used to develop and test countermeasures to microgravity-altered adaptations to Earth gravity. Initial investigations of bone loss used horizontal bed rest with the view that this model represented the closest approximation to inactivity and minimization of hydrostatic effects, but all Earth-based analogs must contend with the constant force of gravity by adjustment of the G vector. Later concerns about the lack of similarity between headward fluid shifts in space and those with horizontal bed rest encouraged the use of 6 degree head-down tilt (HDT) bed rest as pioneered by Russian investigators. Headward fluid shifts in space may redistribute bone from the legs to the head. At present, HDT bed rest with normal volunteers is the most common analog for microgravity simulation and to test countermeasures for bone loss, muscle and cardiac atrophy, orthostatic intolerance, and reduced muscle strength/exercise capacity. Also, current physiologic countermeasures are focused on long-duration missions such as Mars, so in this review we emphasize HDT bed rest studies with durations of 30 days and longer. However, recent results suggest that the HDT bed rest analog is less representative as an analog for other important physiological problems of long-duration space flight such as fluid shifts, spinal dysfunction and radiation hazards.

scholarly journals Regular exercise counteracts circadian shifts in core body temperature during long-duration bed rest

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Stefan Mendt ◽  
Hanns-Christian Gunga ◽  
Dieter Felsenberg ◽  
Daniel L. Belavy ◽  
Mathias Steinach ◽  
...  
Keyword(s):  
Body Temperature ◽  
Core Body Temperature ◽  
Space Station ◽  
Bed Rest ◽  
Resistive Exercise ◽  
Long Duration ◽  
Human Exploration ◽  
Core Body

AbstractWith NASA’s plans for the human exploration of Mars, astronauts will be exposed to mission durations much longer than current spaceflight missions on the International Space Station. These mission durations will increase the risk for circadian misalignment. Exercise has gained increasing interest as a non-pharmacological aid to entrain the circadian system. To assess the potential of exercise as a countermeasure to mitigate the risk for circadian disorders during spaceflight, we investigated the effects of long-term head-down tilt bed rest (HDBR) with and without exercise on the circadian rhythm of core body temperature. Core body temperature was recorded for 24 h using a rectal probe in sixteen healthy men (age: 30.5 ± 7.5 years (mean ± SD)) after 7 days and 49 days of HDBR. Five participants underwent HDBR only (CTR), five participants underwent HDBR and performed resistive exercises (RE), and six participants underwent HDBR and performed resistive exercises superimposed with vibrations (RVE). The exercise was scheduled three times per week. CTR showed a phase delay of 0.69 h. In contrast, both exercise groups were characterized by a phase advance (0.45 h for RE and 0.45 h for RVE; p = 0.026 for interaction between time and group). These findings suggest that resistive exercise (with or without vibration) may also serve as a countermeasure during spaceflight to mitigate circadian misalignments. The results could also be important for increasing awareness about the role of circadian disorders in long-term bedridden patients.

scholarly journals Clinical and Optical Coherence Tomography Angiographic Features in Patients with Postcataract Stenotrophomonas maltophilia Endophthalmitis

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Lu Chen ◽  
Dahui Ma ◽  
Jieting She ◽  
Miaohong Chen ◽  
Jian Zeng ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Stenotrophomonas Maltophilia ◽  
Vascular Density ◽  
Ophthalmological Examination ◽  
Optical Coherence ◽  
Before And After ◽  
Capillary Plexus ◽  
Pars Plana ◽  
The One ◽  
Perfusion Density

Purpose. To report the clinical presentations and optical coherence tomography (OCT) angiographic features of patients with postcataract surgery endophthalmitis due to Stenotrophomonas maltophilia. Methods. A retrospective observational study of 4 patients who developed S. maltophilia endophthalmitis after cataract surgery. Pars plana vitrectomy (PPV) was performed to control the infection. Patients were followed up for six months. Complete ophthalmological examination results were collected before and after PPV. Results. Patients’ response to PPV therapy was excellent and the infection was cured in all cases. OCTA showed that, at the one-month follow-up, the vascular density (VD) and perfusion density (PD) in the superficial capillary plexus (SCP) were significantly lower than those in healthy collateral eyes. As time went on, the SCP-VD and SCP-PD values gradually improved. Conclusions. With early PPV, the infection caused by S. maltophilia can be cured. OCTA provides a quantitative noninvasive assessment to evaluate the severity and prognosis of patients with S. maltophilia endophthalmitis.

Effect of long-duration spaceflight on postural control during self-generated perturbations

2001 ◽  
Vol 90 (3) ◽  
pp. 997-1006 ◽  
Author(s):  
Charles S. Layne ◽  
Ajitkumar P. Mulavara ◽  
P. Vernon McDonald ◽  
Casey J. Pruett ◽  
Innessa B. Kozlovskaya ◽  
...  
Keyword(s):  
Postural Control ◽  
Center Of Pressure ◽  
Space Station ◽  
Arm Movement ◽  
Systematic Evaluation ◽  
Neuromuscular Activation ◽  
Long Duration ◽  
Before And After ◽  
Upper Limb Movements ◽  
Rapid Arm Movements

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure (COP) motion associated with arm movement of eight subjects who experienced long-duration spaceflight (3–6 mo) aboard the Mir space station. Surface electromyography, arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions before and after spaceflight. Subjects generally displayed compromised postural control after flight, as evidenced by modified COP peak-to-peak anterior-posterior and mediolateral excursion, and pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e., when subjects were attempting to maintain upright posture in response to self-generated perturbations). These findings suggest that, although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long-duration spaceflight.

Protein kinetics during and after long-duration spaceflight on MIR

1999 ◽  
Vol 276 (6) ◽  
pp. E1014-E1021 ◽  
Author(s):  
T. P. Stein ◽  
M. J. Leskiw ◽  
M. D. Schluter ◽  
M. R. Donaldson ◽  
I. Larina
Keyword(s):  
Protein Synthesis ◽  
Dietary Intake ◽  
G Protein ◽  
Energy Intake ◽  
Space Station ◽  
Bed Rest ◽  
Whole Body ◽  
Protein Kinetics ◽  
Body Protein ◽  
Long Duration

Human spaceflight is associated with a loss of body protein. Bed rest studies suggest that the reduction in the whole body protein synthesis (PS) rate should be ∼15%. The objectives of this experiment were to test two hypotheses on astronauts and cosmonauts during long-duration (>3 mo) flights on MIR: that 1) the whole body PS rate will be reduced and 2) dietary intake and the PS rate should be increased postflight because protein accretion is occurring. The15N glycine method was used for measuring whole body PS rate before, during, and after long-duration spaceflight on the Russian space station MIR. Dietary intake was measured together with the protein kinetics. Results show that subjects lost weight during flight (4.64 ± 1.0 kg, P < 0.05). Energy intake was decreased inflight (2,854 ± 268 vs. 2,145 ± 190 kcal/day, n = 6, P < 0.05), as was the PS rate (226 ± 24 vs. 97 ± 11 g protein/day, n = 6, P < 0.01). The reduction in PS correlated with the reduction in energy intake ( r 2 = 0.86, P < 0.01, n = 6). Postflight energy intake and PS returned to, but were not increased over, the preflight levels. We conclude that the reduction in PS found was greater than predicted from ground-based bed rest experiments because of the shortfall in dietary intake. The expected postflight anabolic state with increases in dietary intake and PS did not occur during the first 2 wk after landing.

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