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.

Physiological Responses at Rest and Exercise to High Altitude in Lowland Children and Adolescents.

During the last decades, the number of lowland children exposed to high altitude (HA) has increased drastically. Several factors may influence the development of illness after acute HA exposure on children and adolescent populations, such as altitude reached, ascent velocity, time spent at altitude and, especially, their age. The main goal of this study was to evaluate the resting cardiorespiratory physiological and submaximal exercise responses under natural HA conditions by means of the six-minute walking test (six MWT). Secondly, we aimed to identify the signs and symptoms associated with acute mountain sickness (AMS) onset after acute HA exposure in children and adolescents. Forty-two children and adolescents, 18 boys and 24 girls aged from 11 to 15 years old, participated in this study, which was performed at sea level (SL) and during the first 42 h at HA (3330 m). The Lake Louise score (LLS) was recorded in order to evaluate the evolution of AMS symptoms. Submaximal exercise tests (six MWT) were performed at SL and HA. Physiological parameters such as heart rate, systolic and diastolic blood pressure, respiratory rate and arterialized oxygen saturation were measured at rest and after ending exercise testing at the two altitudes. After acute HA exposure, the participants showed lower arterial oxygen saturation levels at rest and after the submaximal test compared to SL (p < 0.001). Resting heart rate, respiratory rate and diastolic blood pressure presented higher values at HA (p < 0.01). Moreover, heart rate, diastolic blood pressure and dyspnea values increased before, during and after exercise at HA (p < 0.01). Moreover, submaximal exercise performance decreased at HA (p < 0.001). The AMS incidence at HA ranged from 9.5% to 19%, with mild to moderate symptoms. In conclusion, acute HA exposure in children and adolescent individuals produces an increase in basal cardiorespiratory parameters and a decrement in arterial oxygen saturation. Moreover, cardiorespiratory parameters increase during submaximal exercise at HA. Mild to moderate symptoms of AMS at 3330 m and adequate cardiovascular responses to submaximal exercise do not contraindicate the ascension of children and adolescents to that altitude, at least for a limited period of time.

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.

Effects of Plyometric Training on Explosive and Endurance Performance at Sea Level and at High Altitude.

Plyometric training performed at sea level enhance explosive and endurance performance at sea level. However, its effects on explosive and endurance performance at high altitude had not been studied. Therefore, the aim of this study was to determine the effects of a sea level short-term (i.e., 4-week) plyometric training program on explosive and endurance performance at sea level and at high altitude (i.e., 3,270 m above sea level). Participants were randomly assigned to a control group (n = 12) and a plyometric training group (n = 11). Neuromuscular (reactive strength index - RSI) and endurance (2-km time-trial; running economy [RE]; maximal oxygen uptake - VO2max) measurements were performed at sea level before, at sea level after intervention (SL +4 week), and at high altitude 24-h post SL +4 week. The ANOVA revealed that at SL +4 week the VO2max was not significantly changed in any group, although RE, RSI and 2-km time trial were significantly (p < 0.05) improved in the plyometric training group. After training, when both groups were exposed to high altitude, participants from the plyometric training group showed a greater RSI (p < 0.05) and were able to maintain their 2-km time trial (11.3 ± 0.5 min vs. 10.7 ± 0.6 min) compared to their pre-training sea level performance. In contrast, the control group showed no improvement in RSI, with a worse 2-km time trial performance (10.3 ± 0.8 min vs. 9.02 ± 0.64 min; p < 0.05; ES = 0.13). Moreover, after training, both at sea level and at high altitude the plyometric training group demonstrated a greater (p < 0.05) RSI and 2-km time trial performance compared to the control group. The oxygen saturation was significantly decreased after acute exposure to high altitude in the two groups (p < 0.05). These results confirm the beneficial effects of sea level short-term plyometric training on explosive and endurance performance at sea level. Moreover, current results indicates that plyometric training may also be of value for endurance athletes performing after an acute exposure to high altitude.

Melatonin Relations With Respiratory Quotient Weaken on Acute Exposure to High Altitude.

High altitude (HA) exposure may affect human health and performance by involving the body timing system. Daily variations of melatonin may disrupt by HA exposure, thereby possibly affecting its relations with a metabolic parameter like the respiratory quotient (RQ). Sea level (SL) volunteers (7 women and 7 men, 21.0 ± 2.04 y) were examined for daily changes in salivary melatonin concentration (SMC). Sampling was successively done at SL (Antofagasta, Chile) and, on acute HA exposure, at nearby Caspana (3,270 m asl). Saliva was collected in special vials (Salimetrics Oral Swab, United Kingdom) at sunny noon (SMCD) and in the absence of blue light at midnight (SMCN). The samples were obtained after rinsing the mouth with tap water and were analyzed for SMC by immunoassay (ELISA kit; IBL International, Germany). RQ measurements (n = 12) were realized with a portable breath to breath metabolic system (OxiconTM Mobile, Germany), between 8:00 PM and 10:00 PM, once at either location. At SL, SMCD, and SMCN values (mean ± SD) were, respectively, 2.14 ± 1.30 and 11.6 ± 13.9 pg/ml (p < 0.05). Corresponding values at HA were 8.83 ± 12.6 and 13.7 ± 16.7 pg/ml (n.s.). RQ was 0.78 ± 0.07 and 0.89 ± 0.08, respectively, at SL and HA (p < 0.05). Differences between SMCN and SMCD (SMCN-SMCD) strongly correlate with the corresponding RQ values at SL (r = -0.74) and less tight at HA (r = -0.37). Similarly, mean daily SMC values (SMC) tightly correlate with RQ at SL (r = -0.79) and weaker at HA (r = -0.31). SMCN-SMCD, as well as, SMC values at SL, on the other hand, respectively, correlate with the corresponding values at HA (r = 0.71 and r = 0.85). Acute exposure to HA appears to loosen relations of SMC with RQ. A personal profile in daily SMC variation, on the other hand, tends to be conserved at HA.

Circadian and Sex Differences After Acute High-Altitude Exposure: Are Early Acclimation Responses Improved by Blue Light?

OBJECTIVE: The possible effects of blue light during acute hypoxia and the circadian rhythm on several physiological and cognitive parameters were studied. METHODS: Fifty-seven volunteers were randomly assigned to 2 groups: nocturnal (2200-0230 hours) or diurnal (0900-1330 hours) and exposed to acute hypoxia (4000 m simulated altitude) in a hypobaric chamber. The participants were illuminated by blue LEDs or common artificial light on 2 different days. During each session, arterial oxygen saturation (Spo2), blood pressure, heart rate variability, and cognitive parameters were measured at sea level, after reaching the simulated altitude of 4000 m, and after 3 hours at this altitude. RESULTS: The circadian rhythm caused significant differences in blood pressure and heart rate variability. A 4% to 9% decrease in waking nocturnal Spo2 under acute hypoxia was observed. Acute hypoxia also induced a significant reduction (4%-8%) in systolic pressure, slightly more marked (up to 13%) under blue lighting. Women had significantly increased systolic (4%) and diastolic (12%) pressures under acute hypoxia at night compared with daytime pressure; this was not observed in men. Some tendencies toward better cognitive performance (d2 attention test) were seen under blue illumination, although when considered together with physiological parameters and reaction time, there was no conclusive favorable effect of blue light on cognitive fatigue suppression after 3 hours of acute hypobaric hypoxia. CONCLUSIONS: It remains to be seen whether longer exposure to blue light under hypobaric hypoxic conditions would induce favorable effects against fatigue.

Age-related arrhythmogenesis on ascent and descent: "autonomic conflicts" on hypoxia/reoxygenation at high altitude?

PURPOSE: To discern whether arrhythmogenesis at high-altitude (HA) may differ depending on ascent or descent, as well as on age. METHODS: Male subjects (37.9±12.0 SD y, n=33) were separated into a young (Y) group (29.6±5.73 SD y, n=18) and an older (O) one (47.9±9.83 SD y, n=15). All subjects were monitored by Holter electrocardiography while successively ascending (41.2±7.51 SD min) and descending (38.7±6.68 SD min) between 2950 and 5050 m as car passengers on a 25 km road in Northern Chile. Arrhythmic events (AE) ensued when the difference between two consecutive RR intervals exceeded 0.16 sec. RESULTS: From 311 AE registered, 29% occurred on ascent and 71% on descent, the sinusal type predominating in both age groups. AE incidence, RR interval duration, and heart rate variability (HRV) in the time domain (RMSSD) increased during descent, as compared to ascent, in the Y group (p<0.05), but not in the O one. Independently of age, AE incidence along descent associates with the time previously spent at 5050 m (p<0.001). CONCLUSIONS: Rapid transitions at HA favor arrhythmogenesis, the latter becoming evident particularly in the Y group on descent. Age-dependent changes of autonomic activity appear to be involved in arrhythmogenesis on transitions at HA.

The effects of interset rest on adaptation to 7 weeks of explosive training in young soccer players.

The aim of the study was to compare the effects of plyometric training using 30, 60, or 120 s of rest between sets on explosive adaptations in young soccer players. Four groups of athletes (age 10.4 ± 2.3 y; soccer experience 3.3 ± 1.5 y) were randomly formed: control (CG; n = 15), plyometric training with 30 s (G30; n = 13), 60 s (G60; n = 14), and 120 s (G120; n = 12) of rest between training sets. Before and after intervention players were measured in jump ability, 20-m sprint time, change of direction speed (CODS), and kicking performance. The training program was applied during 7 weeks, 2 sessions per week, for a total of 840 jumps. After intervention the G30, G60 and G120 groups showed a significant (p = 0.0001 - 0.04) and small to moderate effect size (ES) improvement in the countermovement jump (ES = 0.49; 0.58; 0.55), 20 cm drop jump reactive strength index (ES = 0.81; 0.89; 0.86), CODS (ES = -1.03; -0.87; -1.04), and kicking performance (ES = 0.39; 0.49; 0.43), with no differences between treatments. The study shows that 30, 60, and 120 s of rest between sets ensure similar significant and small to moderate ES improvement in jump, CODS, and kicking performance during high-intensity short-term explosive training in young male soccer players. Key pointsReplacing some soccer drills by low volume high-intensity plyometric training would be beneficial in jumping, change of direction speed, and kicking ability in young soccer players.A rest period of 30, 60 or 120 seconds between low-volume high-intensity plyometric sets would induce significant and similar explosive adaptations during a short-term training period in young soccer players.Data from this research can be helpful for soccer trainers in choosing efficient drills and characteristics of between sets recovery programs to enhance performances in young male soccer players.

Effects of oxygen supplementation on acute mountain sickness symptoms and functional capacity during a 2-kilometer walk test on Chajnantor plateau (5050 meters, Northern Chile).

OBJECTIVE: The aim of this study was to test the hypothesis that administration of low-flow oxygen will improve physical performance in subjects unacclimatized to altitude. We evaluated the effects of oxygen supplementation on functional capacity and acute mountain sickness (AMS) symptoms in young, healthy male and female subjects who performed a 2-km fast walk test following rapid ascent to the Chajnantor plateau (5050 m above sea level) in Northern Chile. METHODS: The participants were randomly distributed into 2 groups according to oxygen supplementation levels: 1 or 3 L O(2) · min(-1). Within each group, males and females were evaluated separately. A preliminary walk test was carried out at sea level on a 100-m long, flat track with 10 U-turns. For the first walk at altitude, subjects carried the supplementary oxygen system but did not breathe the oxygen. Subjects received oxygen through a facemask the following day during the second test. The nights prior to altitude tests were spent at 2400 m in San Pedro de Atacama. RESULTS: Supplementary oxygen administration during a 2-km walk test significantly improved walking times at 5050 m. We also observed a significant improvement in AMS symptoms. As expected, however, performance was poorer at altitude compared to test values at sea level, despite supplementary oxygen administration. CONCLUSIONS: Our findings demonstrate the beneficial effects of supplementary oxygen administration on physical capacity, reducing the incidence of AMS and, thus, improving health and safety conditions for high altitude workers following rapid ascent, when adequate acclimatization is not possible.

Knowledge, attitudes, and practices evaluation about travel medicine in international travelers and medical students in Chile.

Because information about travel medicine in Chile is lacking, a knowledge, attitudes, and practices evaluation in international travelers and medical students was done. The travelers and medical students did not know the travel medicine and sanitary conditions of their destinations, although they perceived travel-associated health risks, but <10% had any vaccination and 5% got sick during international trips.

El desafío de caminar a 5.050 m de altitud en el llano de Chajnantor / The challenge of walking at 5050 m of altitude in Chajnantor plateau

La capacidad aeróbica máxima individual (VO2 máx) declina con la altitud, por eso el esfuerzo para cumplir con las demandas energéticas de una caminata representa una fracción cada vez mayor del VO2 máx a mayor altitud; entonces, a un individuo le “cuesta más caminar”, sin que haya cambiado su peso corporal, la longitud de sus pasos, su masa muscular, ni su sistema cardiorrespiratorio. En el llano de Chajnantor, a 5.050 m, se construirá el proyecto de radiotelescopios más grande del mundo y a esa altitud llegarán trabajadores de la construcción, ingenieros, científicos y visitantes de todas las edades, etc.; todos con mayor o menor carga genética y ambiental para cumplir sus tareas a una altitud casi extrema. Este estudio evaluó una prueba de caminata de 2 Km en 7 hombres y 7 mujeres, universitarios, jóvenes, sanos, a nivel del mar y a 5.050 m. El deterioro significativo del tiempo de caminata, la caída en la saturación de O2, aumento del porcentaje carga cardiovascular, del mal agudo de montaña y la percepción del esfuerzo, fundamentan que a 5.050 m un esfuerzo tan cotidiano como caminar, si se realiza en forma brusca y enérgica, es una actividad de alta exigencia cardiorrespiratoria.