The effect of underwater massage during hot water immersion on acute cardiovascular and mood responses.

PURPOSE: There is emerging evidence that demonstrates the health benefits of hot water immersion including improvements to cardiovascular health and reductions in stress and anxiety. Many commercially available hot tubs offer underwater massage systems which purport to enhance many benefits of hot water immersion, however, these claims have yet to be studied. METHODS: Twenty participants (4 females) completed three, 30-min sessions of hot-water immersion (beginning at 39 °C) in a crossover randomized design: with air massage (Air Jet), water massage (Hydro Jet) or no massage (Control). Cardiovascular responses comprising; heart rate, blood pressure and superficial femoral artery blood flow and shear rate were measured. State trait anxiety, basic affect, and salivary cortisol were recorded before and after each trial. Data were analysed using a mixed effects model. RESULTS: Post immersion, heart rate increased (Δ31bpm, P < 0.001, d = 1.38), mean arterial blood pressure decreased (Δ16 mmHg, P < 0.001, d = -0.66), with no difference between conditions. Blood flow and mean shear rate increased following immersion (P < 0.001, Δ362 ml/min, d = 1.20 and Δ108 s-1, d = 1.00), but these increases were blunted in the Air Jet condition (P < 0.001,Δ171 ml/min, d = 0.43 and Δ52 s-1, d = 0.52). Anxiety and salivary cortisol were reduced (P = 0.003, d = -0.20, P = 0.014, d = -0.11), but did not vary between conditions. Enjoyment did not vary between conditions. CONCLUSION: These data demonstrate positive acute responses to hot water immersion on markers of cardiovascular function, anxiety, and stress. There was no additional benefit of water-based massage, while air-based massage blunted some positive vascular responses due to lower heat conservation of the water.

Evaluation of eye and serum findings in different waters in rabbits by drowning and submersion modeling.

Background/aim: This study investigated serum, vitreous, and anterior chamber fluid electrolyte changes, corneal thickness (CT), corneal volume (CV), anterior chamber volume (ACV), and anterior chamber depth (ACD) as an auxiliary diagnostic method in the identification of drowning in fresh or salt water. Materials and methods: The study used 35 healthy, adult, male, white New Zealand rabbits, seperated into five groups (control, saltwater drowning (SWD), saltwater immersion (SWI), freshwater drowning (FWD), freshwater immersion (FWI)). CT, CV, ACV, and ACD measurements were made with Pentacam topography at 0, 2, and 4 h in all groups. Magnesium (mg), sodium (Na), and chlorine (Cl) were measured in the blood at 0 and 2 h, and in blood, vitreous fluid, and humor aqueous at 4 h. Results: It was determined that CT, CV, ACV, and ACD are not of great value in drowning diagnosis and are affected by the fresh or salt water rather than drowning. Vitreous Na, Cl, and Mg levels are ineffective in determining drowning after one h. Anterior chamber fluid may provide valuable information in the differentiation freshwater - saltwater drownings at the 4th h in corpses retrieved from water. Conclusion: Anterior chamber fluid Na and Cl levels, especially in corpses removed from salt water, can be an easily used test that can help diagnose drowning.

Redox profile of silver catfish challenged with Aeromonas hydrophila and treated with hexane extract of Hesperozygis ringens (Benth.) Epling through immersion bath.

The growing increase in the fish farming sector has favored the establishment of bacterial outbreaks caused by Aeromonas hydrophila in several species. The hexane extract of Hesperozygis ringens (HEHR) (Lamiaceae) leaves increased the survival rate of silver catfish (Rhamdia quelen) experimentally infected by A. hydrophila. However, it is noteworthy that no reports have been found on the possible mechanisms of action of this extract in infected fish. This study aimed to evaluate the effect of the HEHR, administered through single immersion bath, on lipid peroxidation and antioxidant defenses in muscle and liver tissue of silver catfish challenged with A. hydrophila. The results showed that the oxidative status of silver catfish was altered, although oxidative stress was not triggered during the experiment. HEHR at 30 mg/L (HEHR30) was not characterized as a pro-oxidant agent in the presence of infection, unlike florfenicol and HEHR at 15 mg/L treatments in some cases. In short, HEHR30 provided an important increase in hepatic catalase activity, characterizing one of the possible mechanisms involved in the greater survival of fish experimentally infected by A. hydrophila. Additionally, HEHR30 did not induce lipid peroxidation, nor reduced antioxidant defenses of silver catfish infected or not by A. hydrophila.

Health Care Innovation for Low-Resource Settings: The Value of Local Immersion and Partnership.

Health Care Innovation is the creation, development, and translation of new and better solutions to health care challenges. At its core, this endeavor does not require extending the frontiers of science or the creation of new fundamental technologies. Rather, it is primarily focused on the use of existing science and established technologies in the design of new solutions to problems in health care. Successfully innovating for low- and middle-income countries (LMICs) requires a needs and stakeholder-driven approach to enable development and adoption of available, accessible, and acceptable solutions tailored to the specific need and context of care.

The effects of cold exposure (cold water immersion, whole- and partial- body cryostimulation) on cardiovascular and cardiac autonomic control responses in healthy individuals: A systematic review, meta-analysis and meta-regression.

BACKGROUND: Cryostimulation and cold-water immersion (CWI) have recently gained widespread attention due to their association with changes in cardiovascular and cardiac autonomic control responses. Therefore, the aim of the present systematic review and meta-analysis was to identify the global impact of such cold exposures on cardiovascular and cardiac autonomic activity. METHODS: Three databases (PubMed, Embase, Web-of-Science) were used. Studies were eligible for inclusion if they were conducted on healthy participants using cryostimulation and/or CWI. The outcomes included measurements of blood pressure (BP), heart rate (HR), and heart rate variability (HRV) indices: RR interval (RR), Root mean square of successive RR interval differences (RMSSD), low frequency band (LF), high frequency band (HF), and LF/HF ratio. RESULTS: Among the 27 articles included in our systematic literature review, only 24 were incorporated into the meta-analysis. Our results reveal a significant increase in HRV indices: RMSSD (Standardized mean difference (SMD) = 0.61, p < 0.001), RR (SMD = 0.77, p < 0.001), and HF (SMD = 0.46, p < 0.001), as well as significantly reduced LF (SMD = -0.41, p < 0.001) and LF/HF ratio (SMD = -0.25, p < 0.01), which persisted up to 15 min following cold exposure. Significantly decreased heart rate (SMD = -0.16, p < 0.05), accompanied by slightly increased mean BP (SMD = 0.28, p < 0.001), was also observed. These results seem to depend on individual characteristics and the cooling techniques. CONCLUSION: Our meta-analysis suggests that cryostimulation and/or CWI exposure enhance parasympathetic nervous activity. There is scarce scientific literature regarding the effect of individual characteristics on cold-induced physiological responses.

Acute moderate normobaric hypoxia does not modify circulating thyroid hormone concentrations induced by 1 h of head-out cold-water immersion.

This study tested the hypothesis that acute moderate normobaric hypoxia augments circulating thyroid hormone concentrations during and following 1 h of cold head-out water immersion (HOWI), compared with when cold HOWI is completed during normobaric normoxia. In a randomized crossover single-blind design, 12 healthy adults (27 ± 2 yr, 2 women) completed 1 h of cold (22.0 ± 0.1°C) HOWI breathing either normobaric normoxia ([Formula: see text] = 0.21) or normobaric hypoxia ([Formula: see text] = 0.14). Free and total thyroxine (T3) and triiodothyronine (T4), and thyroid-stimulating hormone (TSH) concentrations were measured in venous blood samples obtained before (baseline), during (15-, 30-, and 60 min), and 15 min following HOWI (post-), and were corrected for changes in plasma volume. Arterial oxyhemoglobin saturation and core (rectal) temperature were measured continuously. Arterial oxyhemoglobin saturation was lower during hypoxia (90 ± 3%) compared with normoxia (98 ± 1%, P < 0.001). Core temperature fell from baseline (normoxia: 37.2 ± 0.4°C, hypoxia: 37.2 ± 0.4°C) to post-cold HOWI (normoxia: 36.4 ± 0.5°C, hypoxia: 36.3 ± 0.5°C, P < 0.001) in both conditions but did not change differently between conditions (condition × time: P = 0.552). Circulating TSH, total T3, free T4, total T3, and free T4 concentrations demonstrated significant main effects of time (all P ≤ 0.024), but these changes did not differ between normoxic and hypoxic conditions (condition × time: all P ≥ 0.163). These data indicate that acute moderate normobaric hypoxia does not modify the circulating thyroid hormone response during 1 h of cold HOWI.NEW & NOTEWORTHY Acute head-out cold (22°C) water immersion (HOWI) decreased core temperature and increased thermogenesis. This thermogenic response was paralleled by the activation of the hypothalamic-pituitary-thyroid axis, as evidenced by changes in thyroid hormones. However, cold HOWI in combination with moderate normobaric hypoxia did not modify the thermogenic nor the circulating thyroid hormone response. This finding suggests that hypoxia-induced alterations in thyroid hormone concentrations are unlikely to acutely contribute to adaptations resulting from repeated cold-water exposures.

The interprofessional practice experiences of final-semester prelicensure BSN students completing clinical immersion: A descriptive qualitative study.

BACKGROUND: The goal of interprofessional practice experiences in health professions programs is to develop interprofessional collaborative practice skills. PURPOSE: The purpose of the study was to explore the meaning final-semester Bachelor of Science in Nursing students attributed to interprofessional practice experiences during clinical immersion. METHODS: The theoretical framework for this descriptive qualitative study was experiential learning theory. A sample of 12 participants was drawn from final-semester prelicensure Bachelor of Science in Nursing students at a college of nursing at a public research university. Data were collected through one-on-one semi-structured interviews and analyzed through inductive thematic analysis. RESULTS: The analysis yielded four themes: professional and interprofessional identity, working with team members, communication practices, and trusting relationships. Patterns across themes were clinical environment culture, nursing school preparation, nurse preceptor role, fear/concern/worry, and night shift. CONCLUSION: Consistency in preceptors, welcoming clinical environments, and opportunities to practice communicating with team members contributed to interprofessional collaborative practice skill development and improved perceptions of readiness for practice. Academic and clinical educators may use findings to (a) identify immersion placements for interprofessional practice experiences, (b) design curricula reflective of interprofessional practice, (c) advance teaching strategies to promote interprofessional practice, and (d) create learning environments that aid in professional and interprofessional identity formation.

Effect of a single immersion in cold water below 4 °C on haemorheological properties of blood in healthy men.

Cold water immersion (CWI) involves rapid cooling of the body, which, in healthy individuals, triggers a defence response to an extreme stimulus, to which the body reacts with stress. The aim of the study was to determine the effect of CWI on hemorheological blood indicators. The study group consisted of 13 young males. Blood samples were collected before and after CWI. The assessed parameters included the complete blood count, fibrinogen, hs-C-reactive protein (CRP), proteinogram, and blood rheology factors, such as erythrocyte elongation index (EI), half-time of total aggregation, and aggregation index. Additionally, the effect of reduced temperature on primary human vascular endothelium was investigated in vitro. CWI resulted in the decrease of body temperature to 31.55 ± 2.87 °C. After CWI, neutrophil count and mean corpuscular volume (MCV) were significantly increased in the study group, while lymphocyte count was significantly decreased. Significantly higher levels of total blood protein and albumin concentration were detected after the immersion. Among hemorheological characteristics, erythrocyte EIs at shear stress values ranging from 2.19 to 60.30 Pa were significantly lower after CWI. No significant changes in other rheological, morphological or biochemical parameters were observed. In vitro, human umbilical vein endothelial cells responded to 3 h of temperature decrease to 25 °C with unchanged viability, but increased recruitment of THP-1 monocytic cells and changes in cell morphology were observed. This was the first study to evaluate the effect of single CWI on rheological properties of blood in healthy young men. The results indicate that a single CWI may increase blood protein concentrations and worsen erythrocyte deformability parameters.

Differential tissue immune stimulation through immersion in bacterial and viral agonists in the Antarctic Notothenia rossii.

The genome evolution of Antarctic notothenioids has been modulated by their extreme environment over millennia and more recently by human-caused constraints such as overfishing and climate change. Here we investigated the characteristics of the immune system in Notothenia rossii and how it responds to 8 h immersion in viral (Poly I:C, polyinosinic: polycytidylic acid) and bacterial (LPS, lipopolysaccharide) proxies. Blood plasma antiprotease activity and haematocrit were reduced in Poly I:C-treated fish only, while plasma protein, lysozyme activity and cortisol were unchanged with both treatments. The skin and duodenum transcriptomes responded strongly to the treatments, unlike the liver and spleen which had a mild response. Furthermore, the skin transcriptome responded most to the bacterial proxy (cell adhesion, metabolism and immune response processes) and the duodenum (metabolism, response to stress, regulation of intracellular signal transduction, and immune system responses) to the viral proxy. The differential tissue response to the two proxy challenges is indicative of immune specialisation of the duodenum and the skin towards pathogens. NOD-like and C-type lectin receptors may be central in recognising LPS and Poly I:C. Other antimicrobial compounds such as iron and selenium-related genes are essential defence mechanisms to protect the host from sepsis. In conclusion, our study revealed a specific response of two immune barrier tissue, the skin and duodenum, in Notothenia rossii when exposed to pathogen proxies by immersion, and this may represent an adaptation to pathogen infective strategies.

Combined cold-water immersion and breathwork may be associated with improved mental health and reduction in the duration of upper respiratory tract infection - a case-control study.

A polar plunge is a term referring to an ice-cold water immersion (CWI), usually in the winter period. It is also a part of a specific training program (STP) which currently gains popularity worldwide and was proven to display paradigm-shifting characteristics. The aim of this study was to compare the indices of mental functioning (including depression, anxiety, mindfulness) and duration of upper respiratory tract infection (URTI) measured among the study participants. A set of questionnaires was distributed via the Internet. Participants declaring regular STP practice were selected (N = 77). Two groups were matched based on a case-control principle: the first one (the control group) comprised participants who did not declare nor CWI practice, nor STP practice. The second one comprised participants declaring regular CWI practice only. The CWI only group displayed better mental health indices and shorter URTIs compared to the control group. Moreover, the STP group also displayed better general mental health, less somatic complaints, and shorter URTIs compared to the CWI only group. This study suggests the existence of CWI's potential in boosting mental health and immune system functioning, however when complemented by a specific breathwork, this potential can be increased. However, further research is required.

Does dietary total antioxidant capacity relate to oxidative stress levels in water immersion during labor? A case-control study.

OBJECTIVE: The aim of this study was to investigate the effect of water immersion during the first stage of labor on maternal and neonatal oxidative stress and the association between serum and dietary total antioxidant capacity. METHODS: Women were divided into two groups: those immersed in water during the first stage of labor (n=30) and those who had conventional birth (n=33). Total oxidative stress and total antioxidant status levels were examined in antepartum and postpartum maternal serum and neonatal cord blood samples. Dietary total antioxidant capacity was determined by the food frequency questionnaire. RESULTS: Vitamin C and dietary total antioxidant capacity consumption were found to be higher in the water immersion group (106.92 mg/day and 18.94 mmol/gün, respectively) than the conventional birth group (92.69 mg/day and 15.99 mmol/gün, respectively) (p<0.05). Women immersed in water during the first stage of labor had lower total oxidative stress levels in antepartum and postpartum maternal serum and neonatal cord blood samples than those who had conventional birth (5.43±2.42 mmol/L and 5.59±3.35 mmol/L vs. 8.58±5.53 mmol/L and 12.68±16.58 mmol/L; p<0.05). Dietary total antioxidant capacity was found to be negatively correlated with total oxidative stress levels in antepartum and postpartum maternal serum and neonatal cord blood samples (p=0.012, p=0.047, p=0.035, and p<0.05). CONCLUSION: Women immersed in water during the first stage of labor had lower total oxidative stress levels in their postnatal maternal serum and neonatal cord blood samples and dietary total antioxidant capacity was also a factor associated with low total oxidative stress levels.

Mannose modified targeted immersion vaccine delivery system improves protective immunity against Infectious spleen and kidney necrosis virus in mandarin fish (Siniperca chuatsi).

Vaccination is an effective method to prevent viral diseases. However, the biological barrier prevents the immersion vaccine from achieving the best effect without adding adjuvants and carriers. Researches on the targeted presentation technology of vaccines with nanocarriers are helpful to develop immersion vaccines for fish that can break through biological barriers and play an effective role in fish defense. In our study, functionally modified single-walled carbon nanotubes (SWCNTs) were used as carriers to construct a targeted immersion vaccine (SWCNTs-M-MCP) with mannose modified major capsid protein (MCP) to target antigen-presenting cells (APCs), against iridovirus diseases. After bath immunization, our results showed that SWCNTs-M-MCP induced the presentation process and uptake of APCs, triggering a powerful immune response. Moreover, the highest relative percent survival (RPS) was 81.3% in SWCNTs-M-MCP group, which was only 41.5% in SWCNTs-MCP group. Altogether, this study indicates that the SWCNTs-based targeted immersion vaccine induces strong immune response and provided an effective protection against iridovirus diseases.

Cool head-out water immersion does not alter cerebrovascular reactivity to hypercapnia despite elevated middle cerebral artery blood velocity: A pilot study.

Episodic increases in cerebral blood flow (CBF) are thought to contribute to improved cerebrovascular function and health. Head-out water immersion (HOWI) may be a useful modality to increase CBF secondary to the hydrostatic pressure placed on the body. However, it is unclear whether water temperatures common to the general public elicit similar cerebrovascular responses. We tested the hypothesis that mean middle cerebral artery blood velocity (MCAvmean) and cerebrovascular reactivity to CO2 (CVRCO2) would be higher during an acute bout of thermoneutral (TN; 35°C) vs. cool (COOL; 25°C) HOWI. Ten healthy participants (age: 23±3 y; 4 women) completed two randomized HOWI visits. Right MCAvmean, end-tidal CO2 (PETCO2) mean arterial pressure (MAP), and MCA conductance (MCAvmean/MAP) were continuously recorded. CVRCO2 was assessed using a stepped hypercapnia protocol before (PRE), at 30 minutes of HOWI (HOWI), immediately after HOWI (POST-1), and 45 minutes after HOWI (POST-2). Absolute values are reported as mean ± SD. MCAvmean, PETCO2, MAP, and CVRCO2 were not different between conditions at any timepoint (all P≥0.17). In COOL, MCAvmean increased from PRE (61±9 cm/s) during HOWI (68±11 cm/s), at POST-1 (69±11 cm/s), and POST-2 (72±8 cm/s) (all P<0.01), and in TN from PRE to POST-1 (66±13 vs. 71±14 cm/s; P = 0.05). PETCO2 did not change over time in either condition. In COOL, MAP increased from PRE (85±5 mmHg) during HOWI (101±4 mmHg), at POST-1 (97±7 mmHg), and POST-2 (96±9 mmHg), and in TN from PRE (88±5 mmHg) at HOWI (98±7 mmHg) and POST-1 (99±8 mmHg) (all P<0.01). In COOL, CVRCO2 increased from PRE to HOWI (1.66±0.55 vs. 1.92±0.52 cm/s/mmHg; P = 0.04). MCA conductance was not different between or within conditions. These data indicate that 30 minutes of cool HOWI augments MCAvmean and that the increase in MCAvmean persists beyond cool HOWI. However, cool HOWI does not alter CVRCO2 in healthy young adults.

Post exercise hot water immersion and hot water immersion in isolation enhance vascular, blood marker, and perceptual responses when compared to exercise alone.

Exercise and passive heating induce some similar vascular hemodynamic, circulating blood marker, and perceptual responses. However, it remains unknown whether post exercise hot water immersion can synergise exercise derived responses and if they differ from hot water immersion alone. This study investigated the acute responses to post moderate-intensity exercise hot water immersion (EX+HWI) when compared to exercise (EX+REST) and hot water immersion (HWI+HWI) alone. Sixteen physically inactive middle-aged adults (nine males and seven females) completed a randomized cross-over counterbalanced design. Each condition consisted of two 30-min bouts separated by 10 min of rest. Cycling was set at a power output equivalent to 50% V̇o2 peak . Water temperature was controlled at 40°C up to the mid sternum with arms not submerged. Venous blood samples and artery ultrasound scans were assessed at 0 (baseline), 30 (immediately post stressor one), 70 (immediately post stressor two), and 100 min (recovery). Additional physiological and perceptual measures were assessed at 10-min intervals. Brachial and superficial femoral artery shear rates were higher after EX+HWI and HWI+HWI when compared with EX+REST (p < 0.001). Plasma nitrite was higher immediately following EX+HWI and HWI+HWI than EX+REST (p < 0.01). Serum interleukin-6 was higher immediately after EX+HWI compared to EX+REST (p = 0.046). Serum cortisol was lower at 30 min in the HWI+HWI condition in contrast to EX+REST (p = 0.026). EX+HWI and HWI+HWI were more enjoyable than EX+REST (p < 0.05). Irrespective of whether hot water immersion proceeded exercise or heating, hot water immersion enhanced vascular and blood marker responses, while also being more enjoyable than exercise alone.

A 3D-simulation study of the deformation, tension, and stress of 3D-printed and conventional denture base materials after immersion in artificial saliva.

INTRODUCTION: The worldwide application of digital technology has presented dentistry with transformative opportunities. The concept of digital dentures, incorporating computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques, holds the promise of improved precision, customization, and overall patient satisfaction. However, the shift from traditional dentures to their digital counterparts should not be taken lightly, as the intricate interplay between oral physiology, patient comfort, and long-term durability requires thorough examination.

Impact of pre-meal immersion on multi-scale structural changes and starch digestibility of cooked dried noodles.

Pre-meal immersion is a common process for both the consumption of dried noodles and development of takeaway noodles, but its impact on the structure and digestibility of dried noodles is still unclear. In this study, dried noodles cooked for the optimal time were immersed at 80 °C for different time durations. Multi-scale structural changes, including texture, molecular structure, microstructure, and in vitro starch digestibility were studied using a combination of kinetic (first-order exponential decay function, the Peleg model, and LOS plots), physicochemical, and microscopic analysis. The relationship between multi-scale structural changes and starch digestibility was derived. As the immersion progressed, the hardness first rapidly decayed and then reached equilibrium. The decay rate in the initial stage depended on the gluten content. In most cases, the immersion process caused depolymerization of gluten proteins and further gelatinization of starch granules, which was observed from an increase in the free -SH content and decrease in the short-range ordered structure, although there were fluctuations over immersion time. Structural changes resulted in the corresponding changes in substance migration. However, a high gluten content (∼15% w/w) imparted a denser microstructure to the noodles, weakening the deterioration effects compared with a low gluten content (∼10% w/w). In vitro digestion experiments proved that samples with higher gluten content had higher starch digestion rates and lower starch digestion extent during immersion. Correlation analysis revealed that there was a negative correlation between k1 and the tightness of the gel. This study helps to reveal the structural mechanisms of starch digestibility in cooked noodles during immersion.

Insights into the enhancement mechanism of immersion resistance of cooked noodles induced by wheat flour post-ripening: The view from protein cross-linking.

To overcome the problem that takeaway noodles possessed poor immersion resistance, in this study noodles were prepared from post-ripened wheat flour, and changes in textural properties, protein components, and water status of noodles were determined. The firmness and tensile distance of noodles were gradually increased by 7.40%-35.88% when wheat flour was post-ripened for 20-40 d. Afterwards, noodle textural qualities were slightly decreased. Compared with control groups, contents of glutenin macropolymer (GMP) and disulfide bonds were significantly (p<0.05) increased and protein network was also more compact, whereas the Glutenin/Gliadin ratio and free sulfhydryl groups content were significantly (p<0.05) reduced. Contents of sodium dodecyl sulfate extractable protein (SDSEP) were reduced by 3.22%-6.23%. Meanwhile, the decrease in A23 indicated that wheat flour post-ripening limited water-absorbing capacity of noodles during immersion. In conclusion, wheat flour post-ripening promoted the immersion resistance of noodles by inducing protein cross-linking, and the best post-ripening time was 20-40 d.

Repeated short cold-water immersions are sufficient to habituate to the cold, but do not lead to adaptations during exercise in normobaric hypoxia.

We sought to assess the effects of repeated cold-water immersions (CWI) on respiratory, metabolic, and sympathoadrenal responses to graded exercise in hypoxia. Sixteen (2 female) participants (age: 21.2 ± 1.3 years; body fat: 12.3 ± 7.7%; body surface area 1.87 ± 0.16 m2, VO2peak: 48.7 ± 7.9 mL/kg/min) underwent 6 CWI in 12.0 ± 1.2 °C. Each CWI was 5 min, twice daily, separated by ≥4 h, for three consecutive days, during which metabolic data were collected. The day before and after the repeated CWI intervention, participants ran in normobaric hypoxia (FIO2 = 0.135) for 4 min at 25%, 40%, 60%, and 75% of their sea level peak oxygen consumption (VO2peak). CWI had no effect on VO2 (p > 0.05), but reduced the VE (CWI #1: 27.1 ± 17.8 versus CWI #6: 19.9 ± 12.1 L/min) (p < 0.01), VT (CWI #1: 1.3 ± 0.4 vs CWI #6: 1.1 ± 0.4 L) (p < 0.01), and VE:VO2 (CWI #1: 53.5 ± 24.1 vs CWI #6: 41.6 ± 20.5) (p < 0.01) during subsequent CWI. Further, post exercise plasma epinephrine was lower after CWI compared to before (103.3 ± 43.1; 73.4 ± 34.6 pg/mL) (p = 0.03), with no change in pre-exercising values (75.4 ± 30.7; 72.5 ± 25.9 pg/mL). While these changes were noteworthy, it is important to acknowledge there were no changes in pulmonary (VE, VT, and VE:VO2) or metabolic (VO2, SmO2, and SpO2) variables across multiple hypoxic exercise workloads following repeated CWI. CWI habituated participants to cold water, but this did not lead to adaptations during exercise in normobaric hypoxia.

Effect of chitosan crosslinking time on the structure and antifouling performance of polyvinylidene fluoride membrane by surface gelation-immersion precipitation phase inversion.

Polyvinylidene fluoride (PVDF) porous membrane was prepared by a two-step method of surface gelation-immersion precipitation phase inversion. Chitosan/acetic acid solution and glutaraldehyde aqueous solution were sequentially sprayed onto the surface of the PVDF solution film, with chitosan crosslinking and gelation occurring simultaneously on the film surface. The solution film was then immersed in a coagulation bath to obtain a modified PVDF porous membrane. The effect of the crosslinking time of chitosan and glutaraldehyde on the structure and properties of the PVDF porous membrane was discussed. The results showed that with the prolongation of crosslinking time, the surface structure of the membrane changed from a dense skin layer to a porous structure; the porosity and the mean pore size of the modified PVDF membranes increased first and then decreased, and the contact angle gradually decreased. When the crosslinking time extended to 15 min, the water flux of modified membrane (M153) reached a maximum value. BSA dynamic cyclic filtration experiment showed that the retention rate (R) of the modified membrane was significantly improved, compared to 68.3% retention rate of the blank membrane (M000), but the crosslinking time had little effect on the retention rates of the four modified membranes. The antifouling data showed that the flux recovery rate of the blank membrane was 73.0%, while the flux recovery rate of the modified membrane can reach as high as 84.40%, and the irreversible pollution rate of the blank membrane was 27.7%, while the irreversible pollution rate of the modified membrane reduced to 15.6%. These results indicated that, after surface chitosan crosslinking, the hydrophilicity and antifouling properties of PVDF membranes were improved. PRACTITIONER POINTS: Modified PVDF membranes with crosslinking CS coating were prepared by a two-step method of surface gelation-immersion precipitation phase inversion. -OH groups and -NH2 groups of CS coating improve the hydrophilicity and the antifouling property of modified PVDF membranes. Modified PVDF membranes had larger mean pore size and higher porosity than unmodified membrane. Flux recovery rates of the modified membranes were higher than that of unmodified membrane. Pollution degree, reversible pollution rate, and irreversible pollution rate of modified membranes were lower than those of unmodified membrane.