Physiologia, Volume 6, Issue 3 (September 2026) – 6 articles

Background: Changes in estrogen and progesterone during the menstrual cycle could potentially influence standing-induced hemodynamic and autonomic responses. Aims and Objectives: We aimed to explore the effects of menstrual cycle phases on cardiovascular and autonomic adaptations to a virtual reality International Space Station (ISS) environment used as a microgravity analogue across varying body positions. Method: A randomized repeated-measures pilot study was conducted with two protocols (supine and standing) in an International Space Station-themed virtual reality environment involving healthy young female (n = 11, mean age 20 ± 1 years, height 160.6 ± 3 cm, weight 61.6 ± 9 kg) participants in 2 menstrual phases: follicular (n = 5, 20 ± 1 years, height 160 ± 3 cm, weight 55 ± 6 kg) and luteal phase (n = 6, mean age 20 ± 1 years, height 161.3 ± 2.4 cm, weight 67 ± 8 kg). Each protocol consisted of three stages: baseline, supine/standing, and recovery, each lasting 5 min. The data were analyzed using mixed repeated-measures analysis of variance. Results: Significant differences were observed between the two protocols from supine to standing across menstrual phases for several hemodynamic variables. Heart rate showed significant difference during the luteal phase (F(1,9) = 10.6, p = 0.01) with values from 72 bpm to 84 bpm and the follicular phase (F(1,9) = 7.4, p = 0.02) from 82 bpm to 92 bpm; diastolic blood pressure during the follicular phase (F(1,9) = 9.8, p = 0.01) from 55 mmHg to 80 mmHg; mean arterial pressure during the follicular phase (F(1,9) = 7.5, p = 0.02) from 73 mmHg to 93 mmHg; stroke index during the follicular phase (F(1,9) = 6.9, p = 0.03) from 74 mL/m² to 51 mL/m²; and systemic vascular resistance index during the follicular phase (F(1,9) = 8.0, p = 0.02), with values from 1046 dyn*sec* m²/cm⁵ to 1564 dyn*sec* m²/cm⁵, respectively. This was a preliminary pilot study, and the results need to be confirmed with larger groups and validated hormonally. Conclusions: These exploratory pilot study results show that orthostatic-induced responses are influenced by the menstrual cycle phase. Since no non-VR control condition was included, the responses observed should be considered part of the VR-based protocol, and the exact role of the immersive virtual reality environment cannot be determined. The study showed that an ISS-themed virtual reality environment led to notable changes in cardiovascular function and autonomic responses during transitions from supine to standing postures, and these responses also varied across menstrual phases. Across most epochs, the standing protocol consistently shows higher heart rate, systolic and diastolic blood pressure, mean arterial pressure, and systemic vascular resistance index than the supine protocol, reflecting the effect of orthostatic loading in an ISS-themed virtual reality environment. Full article

Background/Objectives: Previous studies have shown that excess body weight influences plantar pressure. However, the specific impact of Body Mass Index (BMI) on dynamic pressure distribution during different phases of walking, as well as its effect on load symmetry between the feet, requires further investigation. This study aimed to evaluate the effects of varying BMI categories on dynamic plantar pressure, spatiotemporal gait parameters, and load symmetry. Methods: A retrospective analysis of pre-existing records from 300 adults (2017–2025) classified as normal weight, overweight, and obese was conducted. Dynamic plantar pressure, contact time, and gait speed across four stance phases were assessed using baropodometric platforms. Bilateral differences were evaluated via the symmetry index (SI). Results: Overweight and obese individuals exhibited higher plantar pressures and prolonged contact times, particularly during the forefoot contact phase (FFCP) ($p$ < 0.001). Gait speed decreased inversely with BMI across all phases. Despite these kinematic adaptations, BMI-related load asymmetry occurred only during the initial contact phase (ICP) ($p$ < 0.001), restoring stability in subsequent phases. Conclusions: Excess body mass is associated with targeted mechanical overload of the forefoot rather than uniform stress across the foot. To manage inertia and maintain symmetry, individuals with high BMI may adopt spatiotemporal strategies that reduce speed and extend double support, potentially prioritizing stability over propulsive efficiency. These findings suggest that orthotic interventions for individuals with high BMI may benefit from prioritizing forefoot offloading, although prospective studies are needed. Full article

Background/Objectives: Chronic Kidney Disease–Mineral and Bone Disorder (CKD-MBD) is a frequent complication of chronic kidney disease, characterized by altered bone mineral density and mineral–hormonal metabolism. Therapeutic exercise may help attenuate these alterations, but evidence remains limited. This systematic review and meta-analysis evaluated the effects of therapeutic exercise on bone mineral density and mineral–bone and hormonal biomarkers in adults with CKD, focusing on CKD-MBD-related outcomes. Methods: Following a PROSPERO-registered protocol (CRD420251245021), Scopus, PubMed, Cochrane Central Register of Controlled Trials CENTRAL, and Web of Science were searched from inception to January 2026. Randomized controlled trials, including pilot randomized controlled trials, comparing therapeutic exercise with usual care or non-exercise control conditions in adults with CKD were included. Methodological quality and risk of bias were assessed with the PEDro scale and RoB 2, respectively. Results: Six studies involving 398 participants were included. Most interventions lasted 22 to 24 weeks and used resistance or combined aerobic and resistance exercise across inpatient and outpatient settings. Qualitative synthesis suggested improvements in femoral neck and lumbar spine bone mineral density and favorable biomarker changes. The assessed outcomes included femoral neck and lumbar spine BMD, calcium, phosphorus, sclerostin, PTH, FGF23, and klotho. Meta-analysis showed significant effects favoring therapeutic exercise for bone mineral density (MD = 0.05; 95% CI: 0.03 to 0.06; p < 0.00001; I² = 39%), mineral and bone-related biomarkers (SMD = 0.71; 95% CI: 0.42 to 0.99; p < 0.00001; I² = 75%), and hormonal biomarkers (SMD = 1.32; 95% CI: 0.88 to 1.77; p < 0.00001; I² = 85%). Conclusions: Therapeutic exercise may have beneficial effects on bone mineral density and selected mineral and hormonal biomarkers in adults with CKD. However, confidence in these findings is limited by the small number of studies, differences in CKD stage and exercise protocols, methodological limitations, risk of bias, and substantial heterogeneity in several pooled analyses. No definitive conclusions can currently be drawn regarding the optimal exercise modality, dose, or effects across CKD stages. Full article

Background: Secondary multiple organ dysfunction syndrome (MODS) has an excessively high fatality rate. The mechanisms by which sepsis and systemic inflammatory response syndrome (SIRS) induces organ dysfunction and their characteristic pathological findings and biomarkers are not fully understand. Methods: We examined 24 autopsy cases with secondary MODS and peripheral blood (PB) from 467 patients with SIRS and MODS. Results: PB cytology (presence of large scavenger receptor A-positive (SRA⁺) cells and an SRA index >30), systemic capillary injury, pulmonary symptoms (accumulation of neutrophils and platelet thrombi, alveolar epithelial injury and edema) and cardiac symptoms (accumulation of neutrophils and platelet thrombi, capillary injury and contraction band necrosis) were assessed for all of the cases. The 467 patients were classified into group A (negative for large SRA⁺ cells), group B (positive for large SRA⁺ cells, and SRA index <30) and group C (positive for large SRA⁺ cells, and SRA index >30). Group C patients exhibited a significantly lower survival rate (p < 0.001). Conclusions: It was concluded that: (1) the simultaneous presence of large SRA⁺ cells and an SRA index >30 appear to play a central role in the development of secondary MODS, and could be a useful predictor of poor prognosis in patients with SIRS or MODS; (2) the essential histopathological lesion associated with secondary MODS pathogenesis is systemic capillary injury; and (3) the PB, lung and heart findings mentioned above are characteristic morphological findings suggestive of secondary MODS; (4) a possible mechanism for the development of secondary MODS was proposed. Full article

Objective: This study investigated the effects of three chronic stress exposure models (permanent elimination, forced swimming, and food and water deprivation) on bone oxidative stress, structure, and metabolism in vivo. Methods: Adult rats were exposed to different stress conditions, while control animals were maintained under standard laboratory conditions. Bone morphological and histological parameters, oxidative stress biomarkers, antioxidant defense system, and mineral concentrations were assessed. Results: Stress exposure resulted in significant reductions in body weight, femur weight, and femur length compared to controls. A marked increase in oxidative stress biomarkers was observed in bone tissue, including lipid peroxidation, reactive oxygen species, hydroperoxides, hydrogen peroxide, protein carbonyls, and advanced oxidation protein products. In contrast, antioxidant defenses, including enzymatic activities and levels of glutathione, non-protein thiols, and vitamin C, was significantly decreased. Bone calcium and phosphorus levels were reduced, whereas their plasma concentrations were increased following stress exposure. Histological analysis confirmed the biochemical alterations, suggesting that chronic stress can disrupt bone integrity via oxidative mechanisms. Conclusions: These findings highlight the need for strategies to control and reduce stress-related disorders to maintain skeletal health under various chronic stress conditions. Full article

Calcium (Ca²⁺) and magnesium (Mg²⁺) are essential divalent cations whose homeostasis is essential for cardiovascular, muscular and metabolic function. Absolute or relative imbalances between Ca and Mg can lead to cardiovascular, metabolic and neurological pathologies. Ionized calcium (Ca²⁺) is a biologically active fraction of plasma calcium that is tightly regulated by protein binding, phosphate complexation, magnesium modulation and acid–base status. Ionized calcium plays a central role in multiple physiological processes and is strongly influenced by plasma pH, phosphate concentration and magnesium levels. However, the combined effects of these parameters are difficult to evaluate intuitively because of their nonlinear interactions. In this study, a numerical simulation framework was used to explore how simultaneous variations in pH, phosphate and magnesium may influence ionized calcium under typical physiological plasma conditions as a phenomenological framework linking ionic equilibrium with viscosity-dependent flow parameters under well-mixed plasma conditions. The simulations reveal phenomenological changes in which concurrent increases in pH and phosphate or reductions in magnesium produce disproportionately large decreases in ionized calcium. Within the physiological ranges examined, the results also indicate a region of relative stability for ionized calcium corresponding to Ca/Mg ratios close to 3, while this value should be interpreted as an emergent feature of the modeled parameter space rather than a universal physiological constant. These findings illustrate the importance of considering multiple electrolyte interactions simultaneously when evaluating calcium homeostasis and may provide a conceptual framework for further experimental investigation. Full article