This preview of Gravity explores the design opportunities found in a unique and evolving theory of gravity. If confirmed, it will dramatically change – and.
Table of contents
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The exact value for Martian gravity is 0. The ranges that were considered acceptable for Lunar- and Martian gravity in the present study are shown in gray. The exact values for Lunar and Martian gravity and each unit are depicted through solid diamonds and circles. Out of these 29 studies, 18 applied actual Lunar gravity of 0. Seventeen studies were conducted in the range of Martian gravity and nine applied the actual value for Martian gravity. In the range between Lunar and Martian gravity 10 studies applied 0.
Gravity levels and simulation models of included studies. The ranges that were considered acceptable for Lunar- and Martian gravity in the present review are shown in gray. The exact values for Lunar and Martian gravity are depicted through dashed and dotted lines. Control conditions and measured gravity levels outside the defined range of 0. The age of participants across the studies ranged from 18—63 years. Studies recruited predominantly men. Taken together men and 88 women participated in total. For 19 adults gender was not indicated. The highest number of participants within one study was 21, the lowest number was two.
Some of the investigated partial gravity simulation models did not allow movements. When movements were not possible e. Included locomotion types were walking w , running r , skipping s , and hopping h at different velocities or the preferred walk-to-run transition speed PTS. The overall risk of bias see Table 3 was very low.
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Most studies were case series and did not have control groups, therefore, some aspects of the Cochrane risk of bias tool which was designed for controlled clinical trials were not relevant. This includes randomization and allocation concealment.
In addition to this, many studies failed to give sufficient detail to assess their potential risk of bias including blinding of participants, personnel and outcome assessment. Therefore, only conclusions about incomplete outcome data and selective reporting could be drawn. The majority of included studies were case series. The number of participants in the included studies was comparably low and therefore often no adequate statistical analysis in consistency with the research question was performed. This reduces the quality of most of the included studies with respect to the authors' research question.
In the following the clinical relevance of available data is presented. Main effects of outcome parameters and their bias corrected effect sizes Hedge's g are depicted in Figures 5 — 9. Please note that since the scale we used to define effect sizes as per Hopkins et al. Effect sizes Hedge's g and confidence intervals for cardiopulmonary parameters in Lunar gravity compared to 1 g.
In the following, if effects were similar in direction and magnitude, then these effects were generalized and body postures and simulation models were not further considered. Heart rate, stroke volume, cost of transport, efficiency except of the hopping condition in Pavei and Minetti, as measured in Lunar and Martian gravity conditions revealed the most pronounced changes compared to 1 g Figures 5 , 6.
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Effect sizes Hedge's g and confidence intervals for cardiopulmonary parameters in Martian gravity compared to 1 g. For cardiac output as measured using the lower body positive pressure model, Kostas et al. The effects for cardiac output as measured during head-up tilt revealed moderate changes in Lunar and small changes in Martian gravity compared to 1 g. For blood pressure parameters, inconsistent results between the different included studies were found. The study of Kostas et al. Using the lower body positive pressure model, effects for total peripheral resistance were reported to be moderate Lunar vs.
For thoracic impedance, data published by Kostas et al. Effect sizes Hedge's g and confidence intervals for biomechanical parameters in Lunar gravity compared to 1 g. Effect sizes Hedge's g and confidence intervals for biomechanical and cardiopulmonary parameters in 0. Effect sizes Hedge's g and confidence intervals for biomechanical parameters in Martian gravity compared to 1 g.
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For the biomechanical parameter recovery ability of the human body to safe energy by behaving like a pendulum-like system , especially in Martian gravity different effects and direction of changes were found ranging from small to extremely large changes depending on locomotion modes and velocities Figure 9. For joint kinematics only effect sizes for Lunar gravity compared to 1 g are presented and indicate reductions with extremely large effects for hip and knee range of motion using the tilted and vertical body weight support systems.
For ankle range of motion, effect sizes cover the whole range from small to extremely large Figure 7. Most of the spatio temporal parameters showed extremely large effects in all defined gravity ranges Figures 7 — 9. Examples of these effects include increased swing phase and cycle duration in Lunar gravity, increased Froude number and decreased preferred walk-to-run transition speeds in Lunar and Martian gravity. One exception for the overall extremely large reduced stride frequency was found in the study of Pavei et al. In partial gravity, stride length is mostly reduced during walking Donelan and Kram, and increased during running Donelan and Kram, ; Cutuk et al.
Stride length data from Ivanenko et al. Duty Factor is reduced in partial gravity compared to 1 g but beside extremely large effects, also moderate effects are presented by Donelan and Kram for walking at fixed Froude numbers in 0. Ground reaction forces GRF except relative values and impulses are reduced in partial gravity compared to 1 g and involve extremely large effects. Contrary, the time to impact peak force is increased in 0.
The main findings of this study were the heterogeneity of results across studies, the extremely large effect sizes within a wide range of effect sizes, the low quality of applied methodologies as well as the discovery of a significant lack of knowledge concerning long-term adaptations in partial gravity. The longest continuous exposure to partial gravity reported in one of the included studies was a period of 2 weeks, with 9. The reasons for the heterogeneous findings across studies can be explained as follows: For example Evans et al.
While some authors reported absolute values, some others reported relative values using different normalization reference values; 4 Gravity levels were inconsistent between studies because not all studies used the exact gravity levels of 0. Donelan and Kram , found significant different results for relative stride length at same speed depending on walking or running protocols; 7 Varying experimental conditions were reported between studies.
For instance not all simulation models are suitable to expose the whole body to a partial gravity environment or to simulate realistic hemodynamic changes e. In all included studies the cardiopulmonary parameters heart rate, oxygen consumption, respiratory rate, expired minute volume, net metabolic rate, locomotion efficiency, cost of transport and bioelectrical thoracic impedance revealed either decreasing trends or significant reductions with decreasing gravity levels.
On the other hand, stroke volume seems to increase with decreasing gravity levels. For blood pressure parameters, no consistent results were found. Some studies reported increasing values Cutuk et al. However, effect sizes for most of the cardiac as well as metabolic outcomes and for two exceptions concerning blood pressure parameters were extremely large. Data obtained during the Apollo missions 11—17 reveal that during actual Lunar surface explorations mean heart rates were 90— beats per minute bpm with maximum values of bpm Kopanev and Yuganov, Metabolic rates had a total mean of kilocalories per hour within a total time of h of Lunar Extravehicular Activities EVA; Waligora and Horrigan, Importantly, data from the Apollo missions have to be interpreted with caution as Apollo astronauts were restricted in their movements through their space suits, making it impossible to compare Apollo data to most of the data obtained in lab conditions.
The biomechanical data of the included studies duty factor, vertical impact loading rate, active force peaks, peak vertical and horizontal impulses, horizontal and vertical work as well as the resultant total external, internal and mechanical work per unit distance decreased significantly with decreasing gravity levels. All included studies presented increasing trends for the Froude number, vertical spring stiffness and with one exception during walking; Sylos Labini et al.
Further, a significant increase for time to impact force peak vertical GRF with decreasing gravity levels was shown. For Electromyography EMG amplitude and activation patterns inconsistent results were reported, with studies reporting changes in all directions depending on locomotion velocity Ivanenko et al. The largest effect sizes were associated with parameters influencing the center of mass oscillation such as internal, external and mechanical work and for GRF and impulses where extremely large effects were presented.
These outcomes together with cardiac and metabolic parameters are therefore the main areas that operational guidelines and decision making need to consider. Future research should attempt to address these same issues ahead of upcoming exploration missions to minimize risks to the astronauts. Terrestrial partial gravity simulation models seek to simulate reduced gravity and its impact on human physiology as close as possible to the actual Lunar or Martian environment. Nevertheless, a quality appraisal of included technical principles to create partial gravity conditions was performed by the authors see Table 4.
Partial gravity as created through parabolic flights was set as a gold standard with the highest possible rating. Obviously, considering the very short exposure times during parabolic flights, the model validity must only refer to immediate physiological adaptations. Slow reacting systems cannot be studied using parabolic flights and require different models. Thus, considering the aim of the present quality appraisal all methods were rated as per how accurate they can mimic the effects of partial gravity for relevant physiological and biomechanical categories. The ratings are based on the advantages and limitations of the included simulation models and were performed in agreement with physiological and biomechanical experts from ESA's Space Medicine Office and from the German Sport University.
As shown in Table 4 , all models are suitable to manipulate GRF very accurately whereas cardiovascular responses are dependent on the posture of the body e. Kinematics were only rated as quite accurate because movements are influenced by the set-up of the included simulation systems which may limit natural friction-free movements e. As GRF can be mimicked very precisely and kinematics are quite accurate, biomechanics can be investigated in all included simulation models quite accurately.
Respiratory and metabolic properties were rated as quite accurate but not perfect due to the movement constraining nature of all partial gravity simulators. Different simulation models affect different physiological systems in different ways. This may explain, why for cardiopulmonary outcomes within this review, mainly partial gravity parabolic flights, head-up tilt or lower body positive pressure models were used.
In agreement with the rating performed by Chappell and Klaus the vertical body weight support system was only used to investigate metabolic or respiratory changes but not for cardiovascular properties. Biomechanical outcomes within this review were mainly investigated using a vertical body weight support system as it is a valid method to reduce GRF while almost preserving natural movements. Results from different models may therefore vary and comparisons between models should be made with caution.
Statistical analyses of included studies were in many cases deficient or not performed at all. The reason for this is probably the often very limited number of participants without normal distributed data. Therefore, the sample sizes probably failed to provide adequate power to draw conclusions about all outcome parameters using traditional significance testing.
Furthermore, almost all studies had no separate control group and several studies did not involve both genders equally. Unfortunately, in most of the included studies means and standard deviations for the experimental as well as for control conditions were not presented and had to be requested.
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Hence, the authors of this article were limited by the data available and in some cases only visual inspection of figures was possible. Additionally, statistics sometimes failed to address the research questions of this study and therefore some of the presented p -values could not be used. Some parameters such as the arterio-venous oxygen difference are missing and diverse respiratory parameters except of oxygen consumption are very sparse being only investigated in one study Robertson and Wortz, The same can be said for venous hemodynamics.
Morphological parameters such as fiber type composition, muscle fiber length, physiological and anatomical cross sectional areas, muscle pennation angles, tendon function and material properties as well as bone mineral density are completely missing but are important indicators for physiological deconditioning and very relevant for space flight operations. Obviously, changes of these parameters can only be investigated during long-term exposure to partial gravity, and as already mentioned there is a lack of long-term partial gravity studies.
Furthermore, muscle force, angular velocities and joint torques have not been investigated but are important measures for the mechanical strain in the musculoskeletal system. Of all included technical principles to simulate partial gravity only supine suspension systems are missing. The strict methodology of this review with clearly defined inclusion criteria as well as a comprehensive search strategy minimized the potential for bias. The literature research was hindered by the design of some databases.
Obviously, this increases the risk of failing to include relevant studies. Furthermore, misleading or wrong terminology may have led to the undesired exclusion of relevant studies. In some cases the authors had to obtain data from figures instead of numeric tables e. Therefore, smallest differences from control were defined as changes, even if statistically no significant results were reported.
In the result Supplementary Tables 1 — 6 , arrows without an asterisk indicate this fact and should be interpreted with caution. Due to the comprehensive literature research there are almost no experimental studies left to which the present results can be compared. The kinematic model of Raichlen which predicts the effects of gravity on human locomotion matches the data as presented in this review.
For Froude number, the same increasing tendency was estimated from audio transcripts and video clips of Lunar EVA's as well as by the astronauts and space suit characteristics by Carr and Mcgee The latter study also found out, that wearing a spacesuit appears to lower the Froude number and the walk-to-run transition will occur at lower velocities. Ackermann and van Den Bogert predicted values for different locomotion types in partial gravity through a computational simulation using a realistic musculoskeletal model. They calculated reduced vertical GRF for each gait type compared to terrestrial gravity which is in agreement with the present findings.
They also predicted skipping as the preferred gait mode in Lunar gravity because their results suggest that skipping is more efficient and less fatiguing compared to walking or running Ackermann and van Den Bogert, Keller and Strauss predicted bone mineral density changes in partial gravity using modeled data. They predicted a weekly loss of 0. Unfortunately, no included study of the present review investigated changes in bone mineral density. Nevertheless, it should be pointed out that this model predicted that bone mineral density loss will not be prevented in a partial gravity environment.
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Centre of gravity of MNCs shifting to India as tech becomes core to business. The future strategies of these companies are being invented here. Ahuja, who started his career in the Indian Navy before retiring as a Lieutenant Commander, runs a unique venture out of Bengaluru called Ansr that has been funded by Infosys , Accel Partners and others. After establishing them, it runs these centres for some time and, once they achieve a level of maturity, hands them back to the parent companies.
One of the first companies he did this for was US retail giant Target. For eight years, he was the head of the centre, built it to significant scale both in the number of people and capabilities, and then got out of it to focus on bringing more such ventures. Since , the pace has accelerated significantly. But in the early years, the work largely involved low-end transaction processing and IT work that could be done far more cheaply out of India than in the home countries.
But today, an increasing amount of the work in the older centres and much of the work in the newer centres are absolutely at the cutting edge of technology.