Dynamics of the body liquids and composition in long-duration space flight (Bioimpedance Analysis)

Bioimpedance measurement was used to study dynamics of human hydration status and body composition on board the International space station (ISS). At different stages of 100- to 200-day flights of 12 cosmonauts, the volume of their body liquid was reduced: the overall, intra-, and extracellular volumes became on average 5.2 to 10.4% less per group as compared to the baseline level. The in-flight changes in the body composition of the cosmonauts were also consistent: while the lean mass loss determined by impedance measurement was insignificant (on average, from 1.9 to 4.0%), the gain of the fatty mass ranged from 4.6 to 8.2% during the first three months of the flight. Thus, hydration of a human body decreased during the long-term space flight, which was accompanied by reduction of the muscular mass and the gain in fatty mass.     

Permanent depression of plasma cGMP during long-term space flight

The purpose of this study was to investigate plasma concentrations of cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP) during and after real and simulated space flight. Venous blood was obtained 3 min after the beginning and 2 min after the lower body negative pressure maneuver in two cosmonauts preflight (supine), inflight, and postflight (supine) and in five other subjects before, at the end, and 4 days after a 5-day head-down tilt (-6 degrees) bed rest. In cosmonaut 1 (10 days in space), plasma cGMP fell from preflight 4.3 to 1.4 nM on flight day 6, and was 3.0 nM on the fourth day after landing. In cosmonaut 2 (438 days in space), it fell from preflight 4.9 to 0.5 nM on on flight day 3, and stayed <0.1 nM with 5, 9, and 14 months in space, as well as on the fourth day after landing. Three months after the flight his plasma cGMP was back to normal (6.3 nM). Cosmonaut 2 also displayed relatively low inflight ANP values but returned to preflight level immediately after landing. In a ground-based simulation on five other persons, supine plasma cGMP was reduced by an average of 30% within 5 days of 6 degrees head-down tilt bed rest. The data consistently demonstrate lowered plasma cGMP with real and simulated weightlessness, and a complete disappearance of cGMP from plasma during, and shortly after long-duration space flight.     

Velocity of head movements and sensory-motor adaptation during and after short spaceflight

To investigate to time course of sensory-motor adaptation to microgravity, we tested spatially-directed voluntary head movements before, during and after short spaceflight. We also tested the re-adaptation of postural responses to sensory stimulation after space flight. The cosmonaut performed in microgravity six cycles of voluntary head rotation in pitch, roll and yaw directions. During the first days of weightlessness the angular velocity of head movements increased. Over the next days of microgravity the velocity of head movements gradually decreased. On landing day a significant decrease of head rotation velocity was observed compared to the head movement velocity before spaceflight. Re-adaptation to Earth condition measured by body sway on soft support showed similar time course, but re-adaptation measured by postural responses to vestibular galvanic stimulation was prolonged. These results showed that the angular velocity of aimed head movements of cosmonauts is a good indicator of sensory-motor adaptation in altered gravity conditions.     

Prediction of human orthostatic tolerance by changes in arterial and venous hemodynamics in the microgravity environment

In this article, we intentionally present exclusively the results of our recent studies of arterial and venous hemodynamics as predictors of human orthostatic tolerance during space flight and after the return to Earth. The possibility of in-flight orthostatic tolerance prediction by arterial hemodynamic responses to the lower body negative pressure (LBNP) and venous hemodynamic changes in response to occlusion of the lower extremities is demonstrated. For the first time, three levels of cerebral blood flow deficits during the determination of orthostatic tolerance in the course of the LBNP test performed in microgravity. We offer quantitative arguments for the dependence of the cerebral blood flow deficit on the degree of tolerance of the LBNP test. Patterns of arterial hemodynamics during LBNP were successfully used to diagnose the actual orthostatic tolerance and to follow its trend during flight, which testifies to the possibility of predicting orthostatic tolerance changes in an individual cosmonaut during space flight. Occlusion plethysmography of the legs revealed three levels of response of the most informative venous parameters (capacity, distensibility, and rate of filling) of the lower extremities correlated to the severity of decrease in orthostatic tolerance.     

Autonomic cardiovascular and respiratory control during prolonged spaceflights aboard the International Space Station.

Impaired autonomic control represents a cardiovascular risk factor during long-term spaceflight. Little has been reported on blood pressure (BP), heart rate (HR), and heart rate variability (HRV) during and after prolonged spaceflight. We tested the hypothesis that cardiovascular control remains stable during prolonged spaceflight. Electrocardiography, photoplethysmography, and respiratory frequency (RF) were assessed in eight male cosmonauts (age 41-50 yr, body-mass index of 22-28 kg/m2) during long-term missions (flight lengths of 162-196 days). Recordings were made 60 and 30 days before the flight, every 4 wk during flight, and on days 3 and 6 postflight during spontaneous and controlled respiration. Orthostatic testing was performed pre- and postflight. RF and BP decreased during spaceflight (P < 0.05). Mean HR and HRV in the low- and high-frequency bands did not change during spaceflight. However, the individual responses were different and correlated with preflight values. Pulse-wave transit time decreased during spaceflight (P < 0.05). HRV reached during controlled respiration (6 breaths/min) decreased in six and increased in one cosmonaut during flight. The most pronounced changes in HR, BP, and HRV occurred after landing. The decreases in BP and RF combined with stable HR and HRV during flight suggest functional adaptation rather than pathological changes. Pulse-wave transit time shortening in our study is surprising and may reflect cardiac output redistribution in space. The decrease in HRV during controlled respiration (6 breaths/min) indicates reduced parasympathetic reserve, which may contribute to postflight disturbances.     

Diminished plasma cGMP during weightlessness

We performed an experiment within the project "RLF" (Russian long-term flight) on a cosmonaut onboard the space station MIR. For creating an analogue to orthostatic stress, we used lower body negative pressure (LBNP) as stimulus. Decrease in central and peripheral baroreceptor load by LBNP can be used as a cardiovascular countermeasure in cosmonauts or for inducing endocrine responses. Altered steady-state plasma concentration values of volume sensitive hormones have been observed inflight as well as postflight. Within this project we measured plasma ANP and cGMP as second messenger. Changes in plasma cGMP concentration are generally considered to be a good indicator of those in ANP activity. However, in our experiments depression of cGMP during space flight was more impressive than ANP decline. We are not aware of previous measurements of plasma cGMP under these conditions, and believe to be the first to report complete suppression of plasma cGMP during long-term stay in space.     

Body composition characteristics during puberty in girls and boys from Eastern Austria

Puberty represents the final stage of sexual differentiation during which time the individual acquires reproductive capacity. Puberty is not only characterized by maturation of sexual organs and the formation of oocytes and mature spermatozoa, but also by the development of secondary sexual dimorphism. In industrialized countries the age of puberty has decreased steadily over the last 150 years in association with improved socio-economic conditions. However, the decreased onset of puberty is, especially in the female sex, associated with problematic changes in behaviour such as early onset of sexual activity and resulting in high risk teenage pregnancies. First of all, the improved nutritional status during childhood is discussed as a major cause for the decrease of puberty onset, whereas the impact of nutritional status especially on female sexual maturity is discussed controversially. In our study we analysed the association between body composition (fat tissue and fat free body mass, estimated by BIA analyses), height, Body Mass Index and fat distribution, and signs of puberty such as the timing of menarche in 228 girls and voice breaking and facial hair growth in 191 boys ageing between 10 and 15 years. In both sexes signs of puberty were highly significantly associated with body composition parameters. Nevertheless, marked differences between the two sexes were observed: Female puberty was positively associated first of all with weight status and the absolute and relative amount of body fat, while in signs of male puberty were related positively with a higher amount of fat free body mass and a decreased fat mass. Male voice breaking was significantly associated with increased stature, body weight, waist and hip circumference, lean body mass and total body water, in contrast voice breaking was significantly negatively associated with the fat percentage, the total fat mass and the waist to hip ratio. Female menarche was significantly positively associated with increased body weight, weight status, waist and hip circumference but also with increased absolute and relative fat mass, relative hip circumference, lean body mass and total body water. Only the waist to hip ratio was significantly negatively associated with the onset of menarche.     

Oogenesis-flight syndrome in crickets: age-dependent egg production, flight performance, and biochemical composition of the flight muscles in adult female Gryllus bimaculatus

Age-dependent changes in flight performance, biochemical composition of flight muscles, and fresh mass of the flight muscles and ovaries were analysed in adult female two-spotted crickets, Gryllus bimaculatus. After the final moult the flight muscle mass increased significantly to a maximum at days 2 and 3. On day 2 the highest flight activity was also observed. Between days 2 and 3 the ovary weight started to rapidly increase due to vitellogenic egg growth, which continued at a high rate until day 10. With the onset of ovarial growth, flight performance decreased and the flight muscles started to histolyse. A high correlation between flight muscle mass and the content of protein, lipid, glycogen, and free carbohydrate in the flight muscle indicated that energy-rich substrates from the degrading flight muscles were used to fuel oogenesis, although flight muscle histolysis can provide only a small fraction of the substrates needed for egg production. In general, there was a clear trade-off between egg production and flight ability. Surprisingly, however, some females possessed well-developed ovaries but displayed no signs of flight muscle histolysis. This observation was corroborated by flight experiments which revealed that, although most flying females had small ovaries, some of them carried an appreciable amount of mature eggs, and thus, somehow managed to evade the oogenesis-flight syndrome.     

Dynamics of physical performance during long-duration space flight (first results of "Countermeasure" experiment)

The efficacy of countermeasure exercise for diminishing disturbances induced by microgravity in motor system and its visceral supply during different stages of long-duration flight was evaluated. The results of both bicycle and locomotor testing indicate that physical fitness of cosmonaut does not become worse in the course of the long-duration flight. On the contrary, the lowest fitness was recorded at the first stage of mission, just after one month of flight. The "dead period" at the beginning of space flight seems to be a manifestation of the acute decrease in physical condition on transition from 1 G to microgravity, when none of the regular countermeasure regimes is sufficiently effective and acute increase of volume and intensity of training is impossible under the conditions of space flight.     

Effect of microgravity on plasma catecholamine responses to stressors during space flight

The effect of microgravity on the sympathicoadrenal system (SAS) activity in humans and animals has not yet been clarified. Our previous studies suggested that the SAS activity, evaluated by circulating and/or urinary catecholamine (CA) levels in astronauts during space flights, was found to be rather unchanged. However, CA levels were measured in astronauts only at rest conditions. The aim of the present study was to investigate effect of microgravity during space flight and post-flight readaptation on responsiveness of the SAS to somatic and psychic stressors evaluated by levels of catecholamines and their metabolite in the blood of the Slovak cosmonaut during his stay on board the space station Mir.     

The effects of space flight during gestation on rat uterine smooth muscle

Pregnant rats were flown on a NASA space shuttle during days 11-20 of gestation and the effects of pregnancy maintenance and uterine myometrial smooth muscle were evaluated. There was no effect of space flight on fetal mass in rats examined at recovery on day 20 of gestation (G-20). Rats allowed to go to term delivered vaginally at days 22-23, but space flight significantly decreased pup mass at birth. Space flight did not alter myometrial smooth muscle volume at G-20 and postpartum when compared to flight delayed synchronous controls, but flight animals showed a 37% decrease in myometrial smooth muscle volume between G-20 and postpartum. In contrast, smooth muscle volume of the myometrium of controls, postpartum, was similar to G-20. We conclude that myometrial smooth muscle, which hypertrophies during space flight similar to controls, reacclimates acutely to earth's gravity between G-20 and parturition with a dramatic reduction in volume.     

Body Composition Characteristics During Puberty in Girls and Boys from Eastern Austria

Puberty represents the final stage of sexual differentiation when the individual acquires reproductive capacity. Puberty is not only characterized by maturation of sexual organs and the formation of oocytes and mature spermatozoa, but also by the development of secondary sexual dimorphism. In industrialized countries, the age of puberty has decreased steadily over the last 150 years in association with improved socio-economic conditions. However, the decreased onset of puberty, especially in females, is associated with problematic changes in behaviour such as early onset of sexual activity resulting in high-risk teenage pregnancies. In our study, we analysed the association between body composition (fat tissue and fat-free body mass, estimated by BIA analyses), height, body mass index and fat distribution and signs of puberty such as the timing of menarche in 228 girls and voice breaking and facial hair growth in 191 boys ageing between 10 and 15 years. In both sexes, signs of puberty were associated, highly significantly, with body composition parameters. Nevertheless, marked differences between the two sexes were observed: Female puberty was positively associated with weight status and the absolute and relative amount of body fat, while in males, puberty was positively related with a higher amount of fat-free body mass and a decreased fat mass. Male voice breaking was significantly associated with increased stature, body weight, waist and hip circumference, lean body mass and total body water. In contrast, voice breaking was significantly negatively associated with the fat percentage, the total fat mass and the waist-to-hip ratio. Female menarche was significantly positively associated with increased body weight, weight status, waist and hip circumference and also with increased absolute and relative fat mass, relative hip circumference, lean body mass and total body water. Only the waist-to-hip ratio was significantly negatively associated with the onset of menarche.     

Bone biochemistry in rat femoral diaphysis after space flight

The aim of this experiment was to identify the location of the biochemical changes associated with depressed mineralization during space flight. We carried out biochemical analysis of 4 sections of the femoral diaphyses from 107 day old male rats flown aboard Cosmos 2044 Biosatellite for 16 days. Control femurs were preflight, vivarium, synchronous for feed, cage and temperature exposure, and a flight simulation model. Distal sections in both the flight and synchronous femurs showed mineral deficits associated with reduced levels of the reducible cross-link product of type I collagen, dehydro-dihydroxylysinonorleucine (deH-DHLNL) (p<.05). Unloaded bones in the ground based flight simulation model showed changes in cross-links similar to flight and synchronous controls, but were not associated with the mineral deficit. Mean values of elements measured in each section of all groups revealed significant associations (p<.005) between the non-collagenous protein, osteocalcin and calcium (r=0.774), phosphorus (r=-.624) and deH-DHLNL/deH-HLNL (r=.883). The ratio of the nonreducible cross-link, pyridinoline, to its lysl analogue, deoxypyridinoline, was consistently lower in the distal than proximal sections of the groups tested. None of the changes during space flight were unique to flight bone. The most significant and extensive changes in bone composition, i.e. mineral deficits associated with changes in both osteocalcin and reducible cross-links, were located in the distal section of the diaphysis of the femur.     

Changes in insulin sensitivity precede changes in body composition during 14 days of step reduction combined with overfeeding in healthy young men

A lifestyle characterized by inactivity and a high-calorie diet is a known risk factor for impaired insulin sensitivity and development of Type 2 diabetes mellitus. To investigate possible links, nine young healthy men (24 ± 3 yr; body mass index of 21.6 ± 2.5 kg/m(2)) completed 14 days of step reduction (10,000 to 1,500 steps/day) and overfeeding (+50% kcal). Body composition (dual X-ray absorptiometry, MRI), aerobic fitness (maximal O(2) consumption), systemic inflammation and insulin sensitivity [oral glucose tolerance test (OGTT), hyperinsulinemic euglycemic clamp] were assessed before (day 0), during (days 3 and 7), and immediately after the intervention (day 14), with follow-up tests (day 30). Body weight had increased at days 7 and 14 (P < 0.05). The amount of visceral fat had increased at day 14 compared with day 0 (P < 0.05). The insulin response to the OGTT had increased at days 7 and 14 (P < 0.05). Insulin sensitivity, estimated using the Matsuda index, had decreased at days 3 and 7 (P < 0.01). At day 14, glucose infusion rates had decreased by ～44% during the euglycemic clamps (P < 0.05). Also, plasma levels of leptin and adiponectin had increased (P < 0.05), whereas no changes were seen in inflammatory markers. At day 30, body weight and whole body adiposity were still elevated compared with day 0 (P < 0.05), whereas the insulin sensitivity as well as the insulin response to the OGTT did not differ from baseline. The glucose response to the OGTT was only affected at day 30, with a decrease compared with day 0. Our data show that insulin sensitivity was impaired after 3 days of inactivity and overfeeding. Impairments in insulin sensitivity occurred before changes in body composition, supporting the notion that the initial steps in impairment of insulin sensitivity may be linked directly to the effects of inactivity and a high calorie intake.     

Are there sex differences in the prevalence of overweight and adiposity in elementary school children in Austria

Based on the data of 203 male and 179 female schoolchildren from Eastern Austria (Burgenland), aged between 6 and 10 years, sex typical differences in body composition (absolute and relative body fat, lean body mass) and weight status were analyzed. Body composition analyses were carried out by means of BIA method, weight status was estimated using BMI percentiles (BMI > 90th percentile defined overweight, BMI > 97th percentile defined obesity). Statistically significant sex differences were found for all body composition parameters, girls exhibited a significantly higher amount of absolute and relative body fat, whereas their male counterparts exhibited a significantly higher amount of lean body mass. Regarding weight status, no statistically significant sex differences were observable, however, a higher amount of girls could be classified as overweight or obese. Evolutionary and sociocultural explanations for these observations are discussed.     

Estimation in vivo of the body composition of the ewe by measuring the diffusion space of heavy water

Relationships for estimating body lipids, energy and proteins from the deuterium-oxide (D2O) diffusion space have been determined using 38 dry, pregnant or lactating ewes. The animals were fed as usual and had free access to water up to slaughter. They were injected with deuterium-oxide in the morning, half an hour to 3 hours after being fed the whole daily ration or half of it. Blood samples were collected between 1 and 24 h after injection. The deuterium-oxide content of blood water was determined by infra-red spectrophotometry. The ewes were slaughtered 24 h after injection and their body water, protein, ash and energy were chemically determined. Different blood samples were used to measure the deuterium-oxide diffusion space (theoretical initial concentration Co method). The closest relationship between measured body water (ECM) and D2O diffusion space (ECD2O) was found when the blood sample collected 8 h after injection was discarded. Ewe body composition was estimated using a linear relationship in which ewe body weight and D2O diffusion space were two independent variable (relationship number 5). The best ewe body weight to use was the weight measured at injection time. The estimation of body lipid was significantly affected by physiological status when slaughter weight and true body water, measured at slaughter, were used. The effect of this physiological status decreased when the water content of the digestive tract was taken into account and it was no longer significant when the water content of the uterus and conceptus was considered. Body composition could always be predicted by estimating the water content; the standard error was nearly 1.4 kg. However, the method was not accurate enough to obtain a significant effect of physiological status on lipid estimation. Thus, at present we have proposed identical equations for dry, pregnant or lactating ewes.     

Laboratory evaluation of flight performance of the plum curculio (Coleoptera: Curculionidae)

Flight performance of laboratory-reared adults of the plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), was investigated under controlled conditions by using a flight mill system. Across all insects tested (n=198), median values of total distance traveled, total flight time, and maximum uninterrupted flight time were 122.7 m day(-1), 23.5 min day(-1), and 2.0 min, respectively. The latter result indicates that flight occurred primarily in short bursts. Although females had a significantly higher body mass than males, there were no significant differences in flight performance between the two sexes. Flight during the first 24-h test period (especially the first 6 h) was dominated by escape behavior, i.e., elevated levels of activity presumably associated with attempts by the insects to regain freedom of movement; during the second 24 h, flight activity was very limited throughout the late morning and afternoon, increased around sunset, and remained high during the night. All flight performance variables decreased linearly and significantly with insect age over the age range tested (2-16 d after emergence). Nutritional status also had a significant effect, whereby insects that had been provided with apples as a food source for 2 d after emergence showed considerably improved flight performance compared with those that had been given no food or only water during the same period. There was no significant effect of mating status on flight performance of male or female insects.     

Improving hydration in elite male footballers during a national team training camp – an observational case study

[Purpose] The purpose of this study was to (i) assess hydration levels in elite male football players during a national team training camp before and during qualifying matches, (ii) evaluate the effect of coaching strategies for hydration based on feedback from hydration monitoring, and (iii) assess possible relationships between hydration status and training load or wellness markers.[Methods] Thirty-one male players (age 27±4 yrs; height 185±6 cm; weight 82.9±6.7 kg; body fat 10.4±2.3%) representing a national team from the Union of European Football Associations (UEFA) participated. The players were studied during three different national team training camps related to the UEFA Nations League tournament. Urine specific gravity (U_SG) was measured to assess hydration status. During all camps, the players were actively coached on improving strategies for hydration and given individual feedback on their test results. The training load was measured using GPS technology, and wellness questionnaires were completed.[Results] U_SG decreased progressively and significantly (p<0.005) during camp 1 and hydration status improved over the three camps, with fewer dehydrated and more well-hydrated players identified during the last part of camp 3. Significantly (p<0.05) higher U_SG values were observed 2 days prior to a match (MD-2) than on match day (MD); consequently, 52% of the players were dehydrated on MD-2 and only 6% on MD. No correlations were observed between hydration status and training load or wellness markers.[Conclusion] Dehydration is a challenge in elite male football, but continuous monitoring of hydration status and coaching on hydration strategies can lead to major improvements and reduce the degree of dehydration.     

Human Physiological Responses to the G-Load Accompanying the Orbiting and Descent of Soyuz Spacecraft

Data accumulated over 25 years (from 1975 to 2000) on cosmonaut physiological reactions, subjective sensations, and general resistance to G-loads accompanying the orbiting, descent, and landing of Soyuz spacecraft during actual spaceflights are summarized. Materials on short-term (shorter than one month) and long-term (longer than one month) missions in which cosmonauts used or did not use means of preventing microgravity effects during the flight and an anti-G suit (AGS) during descent are analyzed. The physiological reactions of cosmonauts during real spaceflights and terrestrial studies using a centrifuge are compared taking into account cosmonaut ages (from 31 to 55 years). The strain on physiological systems and the reserves of the body upon exposure to +Gxregimens is estimated. A distinct trend toward a lower resistance to descent G-load (without an AGS) with an increase in the time spent in microgravity is found even in the cases when means of prevention of microgravity effects were used. The necessity of using an AGS during descent, irrespective of the flight duration, is demonstrated. The results obtained enable the resistance of cosmonauts to standard G-load conditions during real spaceflights to be predicted.     

The validity of multifrequency bioelectrical impedance measures to detect changes in the hydration status of wrestlers during acute dehydration and rehydration

The objective of this study was to examine the validity of multifrequency direct segmental bioelectrical impedance analysis (DSM-BIA) measures to detect changes in the hydration status of wrestlers after they underwent 3% acute dehydration and a 2-hour rehydration period. Fifty-six National Collegiate Athletic Association wrestlers: (mean ± SEM); age 19.5 ± 0.2 years, height 1.73 ± 0.01 m, and body mass (BM) 82.5 ± 2.3 kg were tested in euhydrated, dehydrated (-3.5%), and 2-hour rehydration conditions using DSM-BIA to detect the changes in hydration status. The hydration status was quantified by measuring the changes in plasma osmolality (P(osm)), urine osmolality (Uosm), urine specific gravity (U(sg)), BM, and weighted segmental impedance at frequencies of 5, 20, 50, 100, and 500 kHz. Weighted segmental impedance significantly increased after a 3.5% reduction in the body weight for all the 5 frequencies evaluated, but it did not return to baseline at 2-hour rehydration. P(osm) (303 ± 0.6 mOsm·L(-1)), Uosm (617 ± 47 mOsm·L(-1)), and U(sg) (1.017 ± 0.001) all significantly increased at postdehydration and returned to baseline at 2-hour rehydration. Estimations of extracellular water were significantly different throughout the trial, but there were no significant changes in the estimations of the total body water or intracellular water. The results of this study demonstrate the potential use of DSM-BIA as a field measure to assess the hydration status of wrestlers for the purpose of minimal weight certification before the competitive season. When employing DSM-BIA to assess the hydration status, the results indicated that the changes in weighted segmental impedance at the frequencies evaluated (5, 20, 50, 100, and 500 kHz) are sensitive to acute changes in dehydration but lag behind changes in the standard physiological (plasma and urinary) markers of hydration status after a 2-hour rehydration period.