Human Physiological Limitations Research Articles

Downscaled climate change threats to United States freshwater finfish aquaculture

Climate change threatens food production, yet gaps remain in our understanding of these threats to aquaculture, the fastest growing food production subsector. To build climate-resilient practices and policies we need to quantify and map current and future climate threats to aquaculture. Here, we explore how downscaled climate change [SSP 2 (eq. RCP 4.5) and SSP 5 (eq. RCP8.5), CMIP6] threats – including water scarcity, flooding, and increasing temperature – may directly affect United States (US) freshwater farmed fish (N = 7) based on their biological thermal tolerances and indirectly challenge the operations required for production, including to the human workforce. Aquaculture in the US is dominated by catfish, trout, and tilapia production and is widespread, with some form of finfish aquaculture present in every state and nearly half of all counties across the country. Given the current location of catfish, tilapia, bass, and carp in the US and their tolerance to warmer conditions, we find increasing temperatures are less likely to biologically impact these species negatively. In contrast, current trout, sturgeon, and perch production will be biologically threatened by rising temperatures. With respect to operational needs for facilities, increases in ‘wet bulb’ temperatures in the Southeast will regularly challenge human physiological limits and constrain worker capacity. Drought in the Southwest will also limit an intrinsically water dependent system, affecting nearly all taxa. While current areas of aquaculture will tend to become increasingly challenging for farmed fishes, new potential habitats will open up for nearly all species. Overall, in the absence of immediate greenhouse gas mitigation, there are several non-mutually exclusive climate adaptations, yet these adaptations can be extremely costly. Ultimately, freshwater aquaculture in the US is going to be under intense climate pressure, which may drive out small operations and cause the country to further increase dependence on international aquatic food imports.

Exploring the dynamics of sports records evolution through the gembris prediction model and network relevance analysis

Background Sports records hold valuable insights into human physiological limits. However, presently, there is a lack of integration and evolutionary patterns in the recorded information across various sports. Methods We selected sports records from 1992 to 2018, covering 24 events in men’s track, field, and swimming. The Gembris prediction model calculated performance randomness, and Pearson correlation analysis assessed network relevance between projects. Quantitative study of model parameters revealed the impact of various world records’ change range, predicted value, and network correlation on evolutionary patterns. Results 1) The evolution range indicates that swimming events generally have a larger annual world record variation than track and field events; 2) Gembris’s predictions show that sprint, marathon, and swimming records outperform their predicted values annually; 3) Network relevance analysis reveals highly significant correlations between all swimming events and sprints, as well as significant correlations between marathon and all swimming events. Conclusion Sports record evolution is closely linked not only to specific sports technology but also to energy expenditure. Strengthening basic physical training is recommended to enhance sports performance.

The potential impact of advanced footwear technology on the recent evolution of elite sprint performances.

Elite track and field sprint performances have reached a point of stability as we near the limits of human physiology, and further significant improvements may require technological intervention. Following the widely reported performance benefits of new advanced footwear technology (AFT) in road-running events, similar innovations have since been applied to sprint spikes in hope of providing similar performance enhancing benefits. However, it is not yet clear based on current evidence whether there have been subsequent improvements in sprint performance. Therefore, the aims of this study were to establish if there have been recent year-to-year improvements in the times of the annual top 100 and top 20 athletes in the men's and women's sprint events, and to establish if there is an association between the extensive use of AFT and potential recent improvements in sprint performances. For the years 2016-19 and 2021-2022, the season best performances of the top 100 athletes in each sprint event were extracted from the World Athletics Top lists. Independent t-tests with Holm corrections were performed using the season's best performance of the top 100 and top 20 athletes in each year to identify significant differences between years for each sprint discipline. Following the classification of shoes worn by the top 20 athletes in each event during their annual best race (AFT or non-AFT), separate linear mixed-model regressions were performed to determine the influence of AFT on performance times. For the top 100 and top 20 athletes, there were no significant differences year-to-year in any sprint event prior to the release of AFT (2016-2019). There were significant differences between AFT years (2021 or 2022) and pre-AFT years (2016-2019) in eight out of 10 events. These differences ranged from a 0.40% improvement (men's 100 m) to a 1.52% improvement (women's 400 m hurdles). In the second analysis, multiple linear mixed model regressions revealed that the use of AFT was associated with improved performance in six out of ten events, including the men's and women's 100 m, women's 200 m, men's 110 m hurdles, women's 100 m hurdles and women's 400 m hurdles (estimate range: -0.037 - 0.521, p = <0.001 - 0.021). Across both analyses, improvements were more pronounced in women's sprint events than men's sprint events. Following a period of stability, there were significant improvements in most sprint events which may be partly explained by advances in footwear technology. These improvements appear to be mediated by event, sex and potentially level of athlete.

Metabolomics of Endurance Capacity in World Tour Professional Cyclists.

The study of elite athletes provides a unique opportunity to define the upper limits of human physiology and performance. Across a variety of sports, these individuals have trained to optimize the physiological parameters of their bodies in order to compete on the world stage. To characterize endurance capacity, techniques such as heart rate monitoring, indirect calorimetry, and whole blood lactate measurement have provided insight into oxygen utilization, and substrate utilization and preference, as well as total metabolic capacity. However, while these techniques enable the measurement of individual, representative variables critical for sports performance, they lack the molecular resolution that is needed to understand which metabolic adaptations are necessary to influence these metrics. Recent advancements in mass spectrometry-based analytical approaches have enabled the measurement of hundreds to thousands of metabolites in a single analysis. Here we employed targeted and untargeted metabolomics approaches to investigate whole blood responses to exercise in elite World Tour (including Tour de France) professional cyclists before and after a graded maximal physiological test. As cyclists within this group demonstrated varying blood lactate accumulation as a function of power output, which is an indicator of performance, we compared metabolic profiles with respect to lactate production to identify adaptations associated with physiological performance. We report that numerous metabolic adaptations occur within this physically elite population (n = 21 males, 28.2 ± 4.7 years old) in association with the rate of lactate accumulation during cycling. Correlation of metabolite values with lactate accumulation has revealed metabolic adaptations that occur in conjunction with improved endurance capacity. In this population, cycling induced increases in tricarboxylic acid (TCA) cycle metabolites and Coenzyme A precursors. These responses occurred proportionally to lactate accumulation, suggesting a link between enhanced mitochondrial networks and the ability to sustain higher workloads. In association with lactate accumulation, altered levels of amino acids before and after exercise point to adaptations that confer unique substrate preference for energy production or to promote more rapid recovery. Cyclists with slower lactate accumulation also have higher levels of basal oxidative stress markers, suggesting long term physiological adaptations in these individuals that support their premier competitive status in worldwide competitions.

Understanding Human Physiological Limitations and Societal Pressures in Favor of Overeating Helps to Avoid Obesity.

Fat gain in our United States (US) environment of over-abundant, convenient, and palatable food is associated with hypertension, cardiovascular disease, diabetes, and increased mortality. Fuller understanding of physiological and environmental challenges to healthy weight maintenance could help prevent these morbidities. Human physiological limitations that permit development of obesity include a predilection to overeat palatable diets, inability to directly detect energy eaten or expended, a large capacity for fat storage, and the difficulty of losing body fat. Innate defenses resisting fat loss include reduced resting metabolism, increased hunger, and high insulin sensitivity, promoting a regain of fat, glycogen, and lean mass. Environmental challenges include readily available and heavily advertised palatable foods, policies and practices that make them abundant, less-than-ideal recommendations regarding national dietary macronutrient intake, and a frequently sedentary lifestyle. After gaining excess fat, some metabolic burdens can be mitigated though thoughtful selection of nutrients. Reduced dietary salt helps lower hypertension, less dietary sugar lowers risk of cardiovascular disease and obesity, and reducing proportion of dietary carbohydrates lowers post-meal insulin secretion and insulin resistance. Food intake and exercise should also be considered thoughtfully, as exercise in a fasted state and before the meals raises glucose intolerance, while exercising shortly after eating lowers it. In summary, we cannot directly detect energy eaten or expended, we have a genetic predisposition to eat palatable diets even when not hungry, and we have a large capacity for fat storage and a difficult time permanently losing excess fat. Understanding this empowers individuals to avoid overeating and helps them avoid obesity.

The 2-hour marathon: what do students think?

### Overview this educational activity is designed to enhance teaching and learning of physiology by connecting the limits of human physiology to one of the most coveted barriers in athletic performance: the 2-h marathon. Moreover, investigation into the possibility of achieving this athletic feat

The Vanity and Entombment of Marie Antoinette

In his fifteenth century treatise on building, De re aedificatoria, Leon Battista Alberti argued for the expansion of architectural purview through the inclusion of objects such as sundials and dovecotes on the grounds that the former marks and fundamentally registers human beings in time and space, while the latter acknowledges the possibility of constructed environments for other species. The long march of coincidence that denoted the inimitable life of Marie Antoinette has provided cover for leveraging subjects that have not yet been mined as architecture; much less as possibilities for critical exploration. The Vanity and Entombment of Marie Antoinette attempts to goad the limits of critical spatial inquiry by examining a series of salient artefacts from the queen’s monarchical life: the guillotine as incontrovertible threshold, cleaving life from death, mind from body, thought from matter; the carriage, which widened the experience of the world past the limits of human physiology, and placed architecture on the move; curtains and crinolines, those soft precincts between body and berth, which beg the question, ‘Is there architecture in the occupation of a material condition, however tight the stays of the corset may be?’ The Vanity is a conceptual project imagined for the Hall of Mirrors; an object that is indeterminately a diminutive architecture, occupiable furniture, and a sculptural deviation made to house the remains of Marie Antoinette and her lost wedding trousseau. The essay that follows is a fictional test of The Vanity’s measure – of its elasticity as a demarcation of narrative and milieu.

Neonatology Specialty Grand Challenge

Neonatology Specialty Grand Challenge

Circadian Rhythms as a Basis for Work Organization

With the assumption that circadian rhythms influence human performance, the work of live line electricians was reorganized and evaluated. The hypothesis was that in highly physical and attention-demanding work, the organization of tasks, according to the ideal period of day and day of week, should diminish stress and consequent work risks. There are only a few studies reporting the work of electricians and even fewer approaching work organization. Moreover, these investigations often do not consider human physiological limitations and capabilities as well as task demands. A new work system was proposed with consideration of (a) the circadian cycles and homeostatic processes; (b) the effect of heat, which is a zeitgeber (synchronizer) for the biological clocks; and (c) the degree of physical and mental demands of the different performed tasks, which was assessed on the basis of opinions of the electricians and physiological markers of stress that are controlled by circadian rhythms. The traditional and new systems were compared on the basis of two cognitive indices (the arrangement of matchsticks and the perception of a minute) and three physiological markers of mental-to-physical loads (heart frequency and the level of adrenaline and noradrenaline). Both physical and mental loads were reduced in the new system. Work organization should include consideration of human circadian rhythms, mainly when stressful and high-risk tasks are involved. The findings can be applied in any work design, but they are especially suited for highly demanding work carried out outdoors.

The pulmonary system during exercise in hypoxia and the cold

The demands for pulmonary O(2) and CO(2) transport in the exercising human are substantial. Fortunately, the regulatory and architectural limits of the pulmonary system meet the requirements of heavy exercise in most individuals. However, in some highly trained athletes the high metabolic demand of intense exercise is in excess of the capacity of the pulmonary system. Environmental considerations, in addition to those imposed by the demands of exercise, provide further physiological challenges that must be met. Winter athletes often encounter high-altitude hypoxia and cold, either transiently during competition or repeatedly during training. In this brief review, we examine the pulmonary system during acute and chronic exercise in hypoxic and cold environmental conditions. Observations from studies conducted in humans are emphasized in order to ask questions about regulation, plasticity and the limits of human physiology. We also highlight new findings and controversial questions that would benefit from additional study.

Athlete atypicity on the edge of human achievement: performances stagnate after the last peak, in 1988.

The growth law for the development of top athletes performances remains unknown in quantifiable sport events. Here we present a growth model for 41351 best performers from 70 track and field (T&F) and swimming events and detail their characteristics over the modern Olympic era. We show that 64% of T&F events no longer improved since 1993, while 47% of swimming events stagnated after 1990, prior to a second progression step starting in 2000. Since then, 100% of swimming events continued to progress.We also provide a measurement of the atypicity for the 3919 best performances (BP) of each year in every event. The secular evolution of this parameter for T&F reveals four peaks; the most recent (1988) followed by a major stagnation. This last peak may correspond to the most recent successful attempt to push forward human physiological limits. No atypicity trend is detected in swimming. The upcoming rarefaction of new records in sport may be delayed by technological innovations, themselves depending upon economical constraints.

Success in Developing Regions: World Records Evolution through a Geopolitical Prism

A previous analysis of World Records (WR) has revealed the potential limits of human physiology through athletes' personal commitment. The impact of political factors on sports has only been studied through Olympic medals and results. Here we studied 2876 WR from 63 nations in four summer disciplines. We propose three new indicators and show the impact of historical, geographical and economical factors on the regional WR evolution. The south-eastward path of weighted annual barycenter (i.e. the average of country coordinates weighting by the WR number) shows the emergence of East Africa and China in WR archives. Home WR ratio decreased from 79.9% before the second World War to 23.3% in 2008, underlining sports globalization. Annual Cumulative Proportions (ACP, i.e. the cumulative sum of the WR annual rate) highlight the regional rates of progression. For all regions, the mean slope of ACP during the Olympic era is 0.0101, with a maximum between 1950 and 1989 (0.0156). For European countries, this indicator reflects major historical events (slowdown for western countries after 1945, slowdown for eastern countries after 1990). Mean North-American ACP slope is 0.0029 over the century with an acceleration between 1950 and 1989 at 0.0046. Russia takes off in 1935 and slows down in 1988 (0.0038). For Eastern Europe, maximal progression is seen between 1970 and 1989 (0.0045). China starts in 1979 with a maximum between 1990 and 2008 (0.0021), while other regions have largely declined (mean ACP slope for all other countries = 0.0011). A similar trend is observed for the evolution of the 10 best performers. The national analysis of WR reveals a precise and quantifiable link between the sport performances of a country, its historical or geopolitical context, and its steps of development.

Computer simulation of driver working memory processing

In general, using simulations to solve problems of human behaviour, as is done in engineering, is particularly difficult. Making use of research into motor vehicle manoeuvrability, this article studies, from the engineering perspective, a computer simulation of working memory processing disabilities of automobile drivers. Firstly, utilizing theories drawn from cognitive psychology, motor vehicle manoeuvrability dynamics, and fuzzy control theory, a driver working memory simulation model is advanced. The model integrates working memory, which is a critical factor in predicting complex cognitive manipulation activities. Secondly, the driver's working memory processing is simulated using the model, and its effects on motor vehicle manoeuvrability and stability are assessed. The test result shows that there is an optimal range of processing time for driving. The lower limit of the range is limited by human physiological limits. The upper limit is defined by the task's complexity. The task could not be finished if the information processing time for finishing the complex task is greater than the upper limit.

Frequency of Use of Automotive Stereo Controls

The primary determinants of control location are human physiological limitations, spatial relationship to the functions controlled, functional groupings, sequential arrangements, and priority of usage/frequency of use. The first four of these are relatively easy to determine, whether through anthropometrics or task/function analyses, but the final consideration is often less straightforward. The relative frequency of use of a set of controls that are primarily driven not by need, but by user preference are often almost impossible to determine before a product is actually put into use. This paper describes a study designed to evaluate the relative frequency of use of the controls available on automotive stereo products. The study focused on experienced users over an extended period of time and a relatively wide age range. Results indicated that control usage fell into several broad groups, with volume control being the most commonly used function.

Analysis of cannabis smoke obtained under different combustion conditions.

The recovery of cannabinoids was investigated by combustion of marihuana cigarettes in a specially constructed smoking machine, with air flow parameters varying within potential human physiological limits. Combustion temperature was found to be about 600°. Percentage recovery of tetrahydrocannabinol in the smoke increased slightly but significantly with increasing air flow rate, but was unaffected by continuous versus intermittent flow. Maximum recovery after complete combustion was about 60%, with negligible change in cannabinoid ratios. Synthetic tetrahydrocannabinol applied to tobacco or alfalfa cigarettes was less completely recovered. Total dry residue (tar content) of the cannabis smoke was somewhat greater than that of tobacco smoke.

Obsessive-compulsive aspects of obesity.

Obesity is related in some ways to the range of disorders which are compulsively produced and sustained. Like drug or alcohol addiction, obesity may be the consequence of a personality configuration that compels some individuals to overeat as a way of dealing with emotional distress. Such individuals feel exempt from the human physiological limitations and feel they can eat without gaining weight, or they perceive their body image as slender rather than obese. Any therapeutic program must take into account this aspect of grandiosity, which is at the core of many addictive processes. Obesity therefore is viewed here as an addictive disorder in which physiological factors may initiate or sustain the psychological processes.

Einleitung in die physiologische Zoologie (Physikalische und chemische Funktionen des Tierkörpers)

THE increasing tendency of zoology to turn from the more purely morphological towards the functional aspects of the subject, and to utilise the data of chemistry and physics in their study, has induced Prof. Przibram to write an introduction to physiological zoology which can act as a companion to his introduction to experimental morphology, and enable the student to gain a comprehensive outline of the subject before turning to one of the larger treatises. The work is divided into some thirty short chapters arranged in pairs, and dealing respectively with the physical and chemical properties of the different organs of the body: numerous references are given throughout the text: notes on the chemical composition, including formuhe, of substances referred to in the text are collected together in an appendix. In a small space the author has succeeded in covering a very large field and in giving an excellent outline of the subject of general physiology. The work could be read with profit by all students of physiology or zoology, but in the short time at their disposal will probably be found to range the field too widely to appeal to those studying within the narrower limits of human physiology. However, for all those who wish to know something of how animals of different species live, of their varying types of respiratory apparatus, of their modes of digesting and assimilating their food, of their secretions and excretions, their sense organs, or their reproduction, this short treatise can be thoroughly recommended for perusal.