Baroreflex and chemoreflex interaction in high-altitude exposure: possible role on exercise performance.

The hypoxic chemoreflex and the arterial baroreflex are implicated in the ventilatory response to exercise. It is well known that long-term exercise training increases parasympathetic and decreases sympathetic tone, both processes influenced by the arterial baroreflex and hypoxic chemoreflex function. Hypobaric hypoxia (i.e., high altitude [HA]) markedly reduces exercise capacity associated with autonomic reflexes. Indeed, a reduced exercise capacity has been found, paralleled by a baroreflex-related parasympathetic withdrawal and a pronounced chemoreflex potentiation. Additionally, it is well known that the baroreflex and chemoreflex interact, and during activation by hypoxia, the chemoreflex is predominant over the baroreflex. Thus, the baroreflex function impairment may likely facilitate the exercise deterioration through the reduction of parasympathetic tone following acute HA exposure, secondary to the chemoreflex activation. Therefore, the main goal of this review is to describe the main physiological mechanisms controlling baro- and chemoreflex function and their role in exercise capacity during HA exposure.

Quality of life, exercise capacity, cognition, and mental health of Chilean patients after COVID-19: an experience of a multidisciplinary rehabilitation program at a physical and rehabilitation medicine unit.

Background: Post-COVID disabilities, encompassing physical, cognitive, and psychological aspects, constitute the primary health sequelae for survivors. While the rehabilitation needs post COVID-19 are now well understood, each country possesses unique characteristics in terms of populations, healthcare systems, social dynamics, and economic profiles, necessitating context-specific recommendations. This study aims to address two main objectives: (1) analyze the impact of an 8-week multidisciplinary rehabilitation program on the quality of life, functional capacity, cognition, and mental health adaptations in adults recovering from COVID-19 in northern Chile, and (2) propose a personalized model for predicting program dropouts and responses. Methods: A total of 44 subjects were enrolled, forming two groups during the study: a treatment group (n = 32) and a dropout group (n = 12). The treatment group participated in the 8-week multidisciplinary rehabilitation program. Results: The results indicate that (1) After 8 weeks, the quality of life of the patients in the treatment group exhibited significant improvements reflected in all aspects of the Short Form-36 Health Survey (SF36, p < 0.005) and the total score (p < 0.001), with a concurrent decrease in dysfunctionality (p < 0.001). (2) Significant improvements were also observed in various physical performance tests, including the: 6-minute walk test, 1-min sit-to-stand, dynamometry, Tinetti balance, and Berg score (p < 0.001). Moreover, physical therapy led to a reduction in neuropathic symptoms and pain, psychological therapy reduced anxiety and depression, and language therapy enhanced memory and speech (all p < 0.05). (3) Demographic and clinical history characteristics did not predict responses to rehabilitation. (4) A regression model for predicting changes in SF-36 total score, based on physical function, physical role, general health, and mental health, was established based on the data from study (p < 0.01, adjusted R2 = 0.893). (5) Classification models for predicting dropouts achieved 68% accuracy, with key predictors of treatment adherence including diabetes, hypertension, and dyslipidemia, Tinetti balance, physical role, and vitality of SF36, and performance on the 6-minute walk test and 1-minute sit-to-stand. Conclusions: This study demonstrates significant enhancements in quality of life, improved functional performance, and reductions in mental and cognitive burdens within an 8-week rehabilitation program. Additionally, it is possible to identify patients at risk of dropping out using cost-effective, outpatient, and clinically applicable tests.

Maximal pulmonary ventilation and lactate affect the anaerobic performance in young women exposed to hypobaric hypoxia.

Background: Athletes, tourists, and mining workers from all over the world ascend daily to an altitude greater than 3.000 meters above sea level to perform different activities, all of which demand physical effort. A ventilation increase is the first mechanism once the chemoreceptors perceive hypoxia, and is key to maintaining blood oxygen levels during acute exposure to high altitudes and to buffering lactic acidosis during exercise. It has been observed that gender is a variable that can influence the ventilatory response. Still, the available literature is limited due to the few studies considering women as study subjects. The influence of gender on anaerobic performance and its effects under high altitudes (HA) environments have been poorly studied. Objective: The objectives of this study were to evaluate anaerobic performance in young women exposed to high altitudes and to compare the physiological response to multiple sprints between women and men measured by ergospirometry. Methodology: Nine women and nine men (22.9 ± 3.2 years old) carried out the multiple-sprint anaerobic tests under two conditions, sea level and high altitudes. Results: In the first 24 h of exposure to a high altitudes, lactate levels were higher in women than those in men (2.57 ± 0.4 Mmol/L, 2.18 ± 0.3 Mmol/L, respectively; p < 0.05). Second, women had a decreased ventilatory response in exposure to high altitudes compared to men (p > 0.005). Third, there is a positive correlation between lactate levels prior to an anaerobic test and the ventilatory response developed by subjects at high altitudes (R2 = 0.33, slope = -41.7, and p < 0.05). Lastly, this ventilatory response can influence VO2peak (R2 = 0.60, slope = 0.02, and p < 0.001). Conclusion: This study provides insights into the mechanisms behind the reduced respiratory capacity observed in women during an anaerobic exercise test at high altitudes. An acute response to HA showed a greater work of breathing and increased the drive ventilatory response. It is possible to postulate the differences in the fatigue-induced metaboreflex of the respiratory muscles and aerobic-anaerobic transition between genders. These results on multiple sprint performance and the influences of gender in hypoxic environments deserve further investigation.

Efectos del apoyo social percibido sobre el estrés materno y lactancia materna: Una revisión narrativa / Effects of perceived social support on maternal stress and breastfeeding: A narrative review

RESUMEN Introducción: Los organismos de salud recomiendan la lactancia materna exclusiva hasta los 6 meses de vida y lactancia materna (LM) continuada hasta los 2 años de edad. Objetivo: Realizar una revisión narrativa de los efectos del apoyo social sobre el estrés materno y la LM. Método: Se realizó una revisión narrativa y no sistemática en la cual se seleccionó artículos de la literatura en PubMed, Redalyc y BVS y en páginas web de entidades como la OMS y la UNICEF. Resultados: Los resultados reflejan que el escaso apoyo social se asocia con un incremento del estrés materno e impacta en el inicio y sostenimiento de la LM. El apoyo social actúa atenuando los niveles de estrés. Conclusión: Se concluye que el apoyo social es un factor que ha de ser considerado como una estrategia para disminuir los niveles de estrés materno y la promoción de la LM. Es necesario enfatizar el importante rol de los equipos de salud en torno a la promoción de la LM, especialmente en madres que ofrecen crianza monoparental, al proveer apoyo social y formación para la lactancia.

ABSTRACT Background: Health authorities recommend exclusive breastfeeding until six months of age and continued breastfeeding (BF) until two years. Objective: To conduct a narrative review of the effects of social support on maternal distress and BF. Method: A narrative and non-systematic review was conducted, selecting articles from the literature in PubMed, Redalyc, BVS, and from websites of organisations such as WHO and UNICEF. Results: The results show that low social support is associated with increased maternal stress and affects the initiation and maintenance of breastfeeding. Social support acts to reduce stress levels. Conclusion: Social support is a factor to be considered as a strategy to reduce maternal stress and promote BF. It is necessary to emphasise the role of healthcare teams in promoting BF, especially among single-parent mothers, by providing social support and breastfeeding education.

Chemoreflex Control as the Cornerstone in Immersion Water Sports: Possible Role on Breath-Hold.

Immersion water sports involve long-term apneas; therefore, athletes must physiologically adapt to maintain muscle oxygenation, despite not performing pulmonary ventilation. Breath-holding (i.e., apnea) is common in water sports, and it involves a decrease and increases PaO2 and PaCO2, respectively, as the primary signals that trigger the end of apnea. The principal physiological O2 sensors are the carotid bodies, which are able to detect arterial gases and metabolic alterations before reaching the brain, which aids in adjusting the cardiorespiratory system. Moreover, the principal H+/CO2 sensor is the retrotrapezoid nucleus, which is located at the brainstem level; this mechanism contributes to detecting respiratory and metabolic acidosis. Although these sensors have been characterized in pathophysiological states, current evidence shows a possible role for these mechanisms as physiological sensors during voluntary apnea. Divers and swimmer athletes have been found to displayed longer apnea times than land sports athletes, as well as decreased peripheral O2 and central CO2 chemoreflex control. However, although chemosensitivity at rest could be decreased, we recently found marked sympathoexcitation during maximum voluntary apnea in young swimmers, which could activate the spleen (which is a reservoir organ for oxygenated blood). Therefore, it is possible that the chemoreflex, autonomic function, and storage/delivery oxygen organ(s) are linked to apnea in immersion water sports. In this review, we summarized the available evidence related to chemoreflex control in immersion water sports. Subsequently, we propose a possible physiological mechanistic model that could contribute to providing new avenues for understanding the respiratory physiology of water sports.

Cardiac Autonomic Modulation and Response to Sub-Maximal Exercise in Chilean Hypertensive Miners.

Cardiac autonomic modulation in workers exposed to chronic intermittent hypoxia (CIH) has been poorly studied, especially considering hypertensive ones. Heart rate variability (HRV) has been proven as valuable tool to assess cardiac autonomic modulation under different conditions. The aim of this study is to investigate the cardiac autonomic response related to submaximal exercise (i.e., six-minute walk test, 6MWT) in hypertensive (HT, n = 9) and non-hypertensive (NT, n = 10) workers exposed for > 2 years to CIH. Participants worked on 7-on 7-off days shift between high altitude (HA: > 4.200 m asl) and sea level (SL: < 500 m asl). Data were recorded with electrocardiography (ECG) at morning upon awakening (10 min supine, baseline), then at rest before and after (5 min sitting, pre and post) the 6MWT, performed respectively on the first day of their work shift at HA, and after the second day of SL sojourn. Heart rate was higher at HA in both groups for each measurement (p < 0.01). Parasympathetic indices of HRV were lower in both groups at HA, either in time domain (RMSSD, p < 0.01) and in frequency domain (log HF, p < 0.01), independently from measurement's time. HRV indices in non-linear domain supported the decrease of vagal tone at HA and showed a reduced signal's complexity. ECG derived respiration frequency (EDR) was higher at HA in both groups (p < 0.01) with interaction group x altitude (p = 0.012), i.e., higher EDR in HT with respect to NT. No significant difference was found in 6MWT distance regarding altitude for both groups, whereas HT covered a shorter 6MWT distance compared to NT (p < 0.05), both at HA and SL. Besides, conventional arm-cuff blood pressure and oxygen blood saturation values (recorded before, at the end and after 5-min recovery from 6MWT), reported differences related to HA only. HA is the main factor affecting cardiac autonomic modulation, independently from hypertension. However, presence of hypertension was associated with a reduced physical performance independently from altitude, and with higher respiratory frequency at HA.

Blood Pressure Response in Miners Exposed to Chronic Intermittent Hypoxia in Chile.

Introduction: Limited information is available on blood pressure (BP) behavior in workers exposed to chronic intermittent hypoxia (CIH), and even less is known regarding effects of CIH on 24-h ambulatory BP in those affected by arterial hypertension at sea level (SL). The aims of this study were to assess clinic and 24-h ambulatory BP at SL and at high altitude (HA; 3,870 m above SL) in workers exposed to CIH, and to compare BP response to HA exposure between normotensive and hypertensive workers. Methods: Nineteen normotensive and 18 pharmacologically treated hypertensive miners acclimatized to CIH were included, whose work was organized according to a "7 days-on-7 days-off" shift pattern between SL and HA. All measurements were performed on the second and seventh day of their HA shift and after the second day of SL sojourn. Results: Compared to SL, 24-h systolic BP (SBP) and diastolic BP (DBP) increased at HA [+14.7 ± 12.6 mmHg (p < 0.001) and +8.7 ± 7.2 mmHg (p < 0.001), respectively], and SBP nocturnal fall decreased consistently (-4.1 ± 9.8%; p < 0.05) in all participants, with hypertensives showing higher nocturnal DBP than normotensives (p < 0.05) despite the current therapy. Also, heart rate (HR) nocturnal fall tended to be reduced at HA. In addition, the 24-h SBP/DBP hypertension threshold of ≥130/80 mmHg was exceeded by 39% of workers at SL and by 89% at HA. Clinic HR, SBP, and DBP were significantly higher on the second day of work at HA compared with SL, the increase being more pronounced for SBP in hypertensives (p < 0.05) and accompanied by, on average, mild altitude sickness in both groups. These symptoms and the values of all cardiovascular variables decreased on the seventh day at HA (p < 0.05) regardless of CIH exposure duration. Conclusion: Long history of work at HA according to scheduled CIH did not prevent the occurrence of acute cardiovascular changes at HA during the first days of exposure. The BP response to HA tended to be more pronounced in hypertensive than in normotensive workers despite being already treated; the BP changes were more evident for 24-h ambulatory BP. Twenty-four-hour ABP monitoring is a useful tool for an appropriate evaluation of BP in CIH workers.

ESTUDIOS MORFO-ANATÓMICOS, CITOGENÉTICOS Y MOLECULARES EN Talinum (TALINACEAE): UNA NUEVA ENTIDAD PARA EL NOROESTE ARGENTINO / Morfo-anatomical, cytogenetic and molecular studies in Talinum (TALINACEAE): a new entity from the northwest of Argentina

RESUMEN Talinum paniculatum es una hierba adventicia ampliamente distribuida en Argentina, que tiene importancia económica como maleza de cultivos resistente a herbicidas. Esta especie se presenta en el campo con dos morfotipos y ellos se distinguen por la forma, tamaño y color de sus flores, frutos y hojas. El objetivo de este trabajo fue determinar las características morfo-anatómicas (de hoja y tallo), citogenéticas y moleculares en dos morfotipos de la provincia de Tucumán (Argentina), y establecer diferencias entre ellos. Se utilizaron técnicas morfo-anatómicas y citogenéticas clásicas y se realizaron análisis moleculares con el marcador ITS2. Los resultados evidencian que las características morfológicas, anatómicas, citogenéticas y moleculares de Talinum paniculatum permitieron diferenciar los morfotipos MT1 y MT2. Se concluye que el MT1 corresponde a T. paniculatum y el MT2 a un taxón diferente que aún no se mencionó para la flora de Argentina.

ABSTRACT Talinum paniculatum is an adventitious herb widely distributed in the Argentina. This plant is considered as an economically important herbicide-resistant weed. This species shows two morphotypes in the field which are differentiated by shape, size and colour of their flowers leaves and fruits. The aims of this work were to determinate morpho-anatomical (leave and stem), cytogenetic and molecular traits of two morphotypes from Tucumán province (Argentina) and to establish differences between them. Classical morpho-anatomical and cytogenetic techniques were used, molecular analysis based on the ITS2 marker were performed. The results showed that morphological, anatomical, cytogenetic and molecular traits of T. paniculatum allow us to differentiate the MT1 and MT2 morphotypes. We concluded that MT1 match with T. paniculatum and MT2 is a different taxon still not described for the flora of Argentina.