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Papachatzis N, Slivka DR, Pipinos II, Schmid KK, Takahashi KZ. Does the Heel’s Dissipative Energetic Behavior Affect Its Thermodynamic Responses During Walking? Front Bioeng Biotechnol 2022; 10:908725. [PMID: 35832413 PMCID: PMC9271620 DOI: 10.3389/fbioe.2022.908725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/06/2022] [Indexed: 11/13/2022] Open
Abstract
Most of the terrestrial legged locomotion gaits, like human walking, necessitate energy dissipation upon ground collision. In humans, the heel mostly performs net-negative work during collisions, and it is currently unclear how it dissipates that energy. Based on the laws of thermodynamics, one possibility is that the net-negative collision work may be dissipated as heat. If supported, such a finding would inform the thermoregulation capacity of human feet, which may have implications for understanding foot complications and tissue damage. Here, we examined the correlation between energy dissipation and thermal responses by experimentally increasing the heel’s collisional forces. Twenty healthy young adults walked overground on force plates and for 10 min on a treadmill (both at 1.25 ms−1) while wearing a vest with three different levels of added mass (+0%, +15%, & +30% of their body mass). We estimated the heel’s work using a unified deformable segment analysis during overground walking. We measured the heel’s temperature immediately before and after each treadmill trial. We hypothesized that the heel’s temperature and net-negative work would increase when walking with added mass, and the temperature change is correlated with the increased net-negative work. We found that walking with +30% added mass significantly increased the heel’s temperature change by 0.72 ± 1.91 ℃ (p = 0.009) and the magnitude of net-negative work (extrapolated to 10 min of walking) by 326.94 ± 379.92 J (p = 0.005). However, we found no correlation between the heel’s net-negative work and temperature changes (p = 0.277). While this result refuted our second hypothesis, our findings likely demonstrate the heel’s dynamic thermoregulatory capacity. If all the negative work were dissipated as heat, we would expect excessive skin temperature elevation during prolonged walking, which may cause skin complications. Therefore, our results likely indicate that various heat dissipation mechanisms control the heel’s thermodynamic responses, which may protect the health and integrity of the surrounding tissue. Also, our results indicate that additional mechanical factors, besides energy dissipation, explain the heel’s temperature rise. Therefore, future experiments may explore alternative factors affecting thermodynamic responses, including mechanical (e.g., sound & shear-stress) and physiological mechanisms (e.g., sweating, local metabolic rate, & blood flow).
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Affiliation(s)
- Nikolaos Papachatzis
- Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, United States
| | - Dustin R. Slivka
- School of Health and Kinesiology, University of Nebraska at Omaha, Omaha, NE, United States
| | - Iraklis I. Pipinos
- Department of Surgery, University of Nebraska Medical Center, Omaha, NE, United States
| | - Kendra K. Schmid
- Department of Biostatistics, University of Nebraska Medical Center, Omaha, NE, United States
| | - Kota Z. Takahashi
- Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, United States
- *Correspondence: Kota Z. Takahashi,
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Urban Climate Risk Mitigation via Optimal Spatial Resource Allocation. ATMOSPHERE 2022. [DOI: 10.3390/atmos13030439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Decision makers (DMs) who are involved in urban planning are often required to allocate finite resources (say, money) to improve outdoor thermal comfort (OTC) levels in a region (e.g., city, canton, country). In this paper, for the first time, we address the following two questions, which are directly related to this requirement: (1) How can the statistical properties of the spatial risk profile of an urban area from an OTC perspective be quantified, no matter which OTC index the DM chooses to use? (2) Given the risk profile, how much and where should the DM allocate the finite resources to improve the OTC levels? We answer these fundamental questions by developing a new and rigorous mathematical framework as well as a new class of models for spatial risk models. Our approach is based on methods from machine learning: first, a surrogate model of the OTC index that provides both accuracy and mathematical tractability is developed via regression analysis. Next, we incorporate the imperfect climate model and derive the statistical properties of the OTC index. We present the concept of spatio-temporal aggregate risk (STAR) measures and derive their statistical properties. Finally, building on our derivations, we develop a new algorithm for spatial resource allocation, which is useful for DMs and is based on modern portfolio theory. We implemented the tool and used it to illustrate its operation on a practical case of the large-scale area of Singapore using a WRF climate model.
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Presbitero A, Melnikov VR, Krzhizhanovskaya VV, Sloot PMA. A unifying model to estimate the effect of heat stress in the human innate immunity during physical activities. Sci Rep 2021; 11:16688. [PMID: 34404876 PMCID: PMC8371171 DOI: 10.1038/s41598-021-96191-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/30/2021] [Indexed: 02/07/2023] Open
Abstract
Public health is threatened by climate change and extreme temperature events worldwide. Differences in health predispositions, access to cooling infrastructure and occupation raises an issue of heat-related health inequality in those vulnerable and disadvantaged demographic groups. To address these issues, a comprehensive understanding of the effect of elevated body temperatures on human biological systems and overall health is urgently needed. In this paper we look at the inner workings of the human innate immunity under exposure to heat stress induced through exposure to environment and physical exertion. We couple two experimentally validated computational models: the innate immune system and thermal regulation of the human body. We first study the dynamics of critical indicators of innate immunity as a function of human core temperature. Next, we identify environmental and physical activity regimes that lead to core temperature levels that can potentially compromise the performance of the human innate immunity. Finally, to take into account the response of innate immunity to various intensities of physical activities, we utilise the dynamic core temperatures generated by a thermal regulation model. We compare the dynamics of all key players of the innate immunity for a variety of stresses like running a marathon, doing construction work, and leisure walking at speed of 4 km/h, all in the setting of a hot and humid tropical climate such as present in Singapore. We find that exposure to moderate heat stress leading to core temperatures within the mild febrile range (37, 38][Formula: see text], nudges the innate immune system into activation and improves the efficiency of its response. Overheating corresponding to core temperatures beyond 38[Formula: see text], however, has detrimental effects on the performance of the innate immune system, as it further induces inflammation, which causes a series of reactions that may lead to the non-resolution of the ongoing inflammation. Among the three physical activities considered in our simulated scenarios (marathon, construction work, and walking), marathon induces the highest level of inflammation that challenges the innate immune response with its resolution. Our study advances the current state of research towards understanding the implications of heat exposure for such an essential physiological system as the innate immunity. Although we find that among considered physical activities, a marathon of 2 h and 46 min induces the highest level of inflammation, it must be noted that construction work done on a daily basis under the hot and humid tropical climate, can produce a continuous level of inflammation triggering moieties stretched at a longer timeline beating the negative effects of running a marathon. Our study demonstrates that the performance of the innate immune system can be severely compromised by the exposure to heat stress and physical exertion. This poses significant risks to health especially to those with limited access to cooling infrastructures. This is due in part to having low income, or having to work on outdoor settings, which is the case for construction workers. These risks to public health should be addressed through individual and population-level measures via behavioural adaptation and provision of the cooling infrastructure in outdoor environments.
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Affiliation(s)
- Alva Presbitero
- grid.464507.40000 0001 2219 7447Asian Institute of Management, Makati, Philippines ,grid.35915.3b0000 0001 0413 4629National Center of Cognitive Research, ITMO University, St. Petersburg, Russian Federation
| | - Valentin R. Melnikov
- grid.7177.60000000084992262Institute for Advanced Study, University of Amsterdam, Amsterdam, The Netherlands ,grid.59025.3b0000 0001 2224 0361Complexity Institute, Nanyang Technological University, Singapore, Singapore ,Future Cities Laboratory, Singapore-ETH Centre, Singapore, Singapore
| | - Valeria V. Krzhizhanovskaya
- grid.35915.3b0000 0001 0413 4629National Center of Cognitive Research, ITMO University, St. Petersburg, Russian Federation ,grid.7177.60000000084992262Informatics Institute, University of Amsterdam, Amsterdam, The Netherlands
| | - Peter M. A. Sloot
- grid.35915.3b0000 0001 0413 4629National Center of Cognitive Research, ITMO University, St. Petersburg, Russian Federation ,grid.7177.60000000084992262Institute for Advanced Study, University of Amsterdam, Amsterdam, The Netherlands ,grid.484678.1Complexity Science Hub Vienna, Vienna, Austria
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Lippke S, Schalk TM, Kühnen U, Shang B. Pace of life and perceived stress in international students. Psych J 2021; 10:425-436. [PMID: 33511764 DOI: 10.1002/pchj.426] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/12/2022]
Abstract
An accelerated pace of life greatly impacts individuals' health and lifestyles. However, this imposition has not been systematically researched within a culturally diverse sample. Thus, this study aimed to explore the subjective experience of the pace of life and its correlates in a culturally diverse sample within a German university context. This was done to test whether students (N = 156) with a migration background from other countries (n = 105) differ from students without migration background (n = 51). The pace of life, life satisfaction, stress, work-life balance, and health were measured on an individual level along with sociodemographic variables through online questionnaires. The pace of life was found to be invariant across students from different cultural backgrounds and unrelated to the length of stay at the current university. Interrelations were found between pace of life and work-life balance, r = .21, p < .05. While this study revealed perceived stress to be generally prevalent among students, the relationship between a slower pace of life and increased stress levels, ß = -.17, p < .05, disappears when controlling for health, ß = -.26, p < .01, work-life balance, ß = -.28, p < .01, and life satisfaction, ß = -.25, p < .01, as well as sociodemographic variables (only gender and medium length of stay were significant.) Furthermore, a mediation effect, b = -1.89, 95% CI [-3.598, -0.463], revealed that students cope with a faster pace of life by effective time management, which also leads to better work-life balance and in turn reduces the experienced level of stress. Future research should examine psychological mechanisms more extensively in longitudinal research and apply interventional designs to help students prevent and manage stress in the era of a fast-paced life.
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Affiliation(s)
- Sonia Lippke
- Department of Psychology and Methods, Jacobs University Bremen, Bremen, Germany
| | - Torven M Schalk
- Department of Psychology and Methods, Jacobs University Bremen, Bremen, Germany.,School of Psychology, Victoria University of Wellington, Wellington, New Zealand
| | - Ulrich Kühnen
- Department of Psychology and Methods, Jacobs University Bremen, Bremen, Germany
| | - Borui Shang
- Department of Social Sciences, Hebei Sport University, Shijiazhuang, China
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