ECSS Paris 2023: CP-PN11
INTRODUCTION: Living in a hypoxic environment combined with physical training in a normoxic condition (living high-training low, LH-TL) is widely studied in exercise physiology, with emphasis on its metabolic adaptations [1]. With growing interest in the topic, advanced analytical approaches that transcend conventional statistics are needed [2]. This study aimed to analyze the effects of 6-week LH-TL on muscles and tissues in C57BL/6J mice, using the complex network model. METHODS: Forty animals were grouped according environmental condition (normoxia-Nx or hypoxia-Hx) and training (non-N or trained-T) totaling 4 groups (Nx-N, Nx-T, Hx-N and Hx-T). Hx mice were exposed to 14.5% inspired oxygen (~3,000m) for 18h/day. T mice underwent 6-week treadmill running (80% of the critical velocity, 40min/day, 5 days/week) in normoxia. Euthanasia occurred 48h after the last training session. Data corresponding to the mass of muscles, liver, heart, kidney, brain and adipose tissues, and the stores of glycogen in muscles, liver and heart tissues, as well as body composition measurements, were analyzed by the Scheirer-Ray-Hare test, with Dunns post hoc. Undirected weighted graphs (G=V,E,w) of the complex network were constructed from the 4 scenarios (groups) to analyze the degree (number of connections) and eigenvector (prestige of the node related to the prestige of its neighbors) centrality metrics. The graphs were composed of 27 vertices (V, nodes) and the edges (E) denoted interactions based on Spearmans correlation coefficients (r≥0.5) to construct the weight function (w) [3]. RESULTS: The density of the graphs for the 4 scenarios studied were 0.27, 0.18, 0.16, and 0.25, respectively. For degree, the complex network highlighted muscle glycogen nodes among all parameters. In Nx-N and Hx-T scenarios, there was high centrality for white gastrocnemius glycogen. Furthermore, aerobic training promoted highlights for oxidative parameters, such vastus lateralis mass, gluteus glycogen, and, especially in the Hx-T group, soleus glycogen (11 connections). Hypoxia increased the centrality of carcass mass, an effect enhanced by training. Only in Hx-T was the hypothalamus mass highlighted (10 connections). Interestingly, eigenvector centrality reinforced the degree findings. Nonparametric statistics showed differences in some parameters, especially for brown adipose tissue and femur masses, and liver glycogen, but these do not seem to be, at least in our conditions, integrated with the other parameters studied, since they did not reveal prominent complex networks centralities. However, gastrocnemius and triceps glycogen stores were highlighted in both analyses. CONCLUSION: The complex network model was sensitive to the isolated and combined effects of physical training and hypoxia, which were not fully represented by conventional statistics. This approach may refine data interpretation in investigations involving LH-TL. 1.Girard et al.,2023, 2.Beck et al.,2024, 3.Brandes,2001 Support: FAPESP, CNPq, CAPES, FAEPEX
Read CV Juan OrsiECSS Paris 2023: CP-PN11
INTRODUCTION: The growth of global adventure tourism has led to millions of travellers visiting areas of high-altitude for recreational trekking, charity fundraising challenges and/or cultural immersion over several days to weeks annually. These activities necessitate carrying backpacks that contain hiking provisions of additional weight without understanding how increased load carriage may affect physiological responses at altitude, nor whether they may increase the risk of experiencing symptoms of acute mountain sickness (AMS) - a common altitude illness typically observed above 2500m. There is limited understanding whether existing backpack load recommendations used at sea-level (maximum load equating to 1/3 of body weight) apply at altitude, or whether increasing loads exacerbate symptoms of AMS. The purpose of the study was to therefore assess backpack weight of 10%, 20% and 30% of body weight on physiological and perceptual strain and symptoms of AMS, during a simulated hillwalking test in hypoxia. METHODS: Thirteen physically active males and females (23±1 years) completed three intermittent walking tests (including: 35-mins rest, 60-min walk [3x20-min intervals with 5-min rest] at 4km.hr-1 at 10% gradient, followed by 15-mins recovery) within normobaric hypoxia (FIO2: 0.13). These were conducted within a randomised order whilst carrying a backpack loaded with additional weight that was either 10%, 20% or 30% relative to the participants’ body mass. Physiological, perceptual and Lake Louise Questionnaire (LLQ) scores were assessed throughout. RESULTS: Heart rate and ventilation were higher (both p<0.05) during the 30% backpack test compared to 10% (+13±11 b.min-1 and +9.4±7.6 L.min-1), but no differences were found between 10% and 20%. LLQ scores were higher (p<0.05) during the 30% backpack test compared to the 10% (+2±1 A.U.) and 20% (+1±1 A.U.), but no differences (p>0.05) were found between 10% and 20%. Rating of perceived exertion (RPE: 6-20 Borg [1982]) were higher (all p<0.05) during the 20% and 30% trials compared to 10% (+2±2 and +4±2 A.U.), and also during the 30% compared to 20% trial (+2±2 A.U.). No differences in pulse oxygen (O2) saturation, nor volume of O2 uptake (all p>0.05) were found between tests. CONCLUSION: Carrying additional backpack weight increases markers of physiological and perceptual strain and may augment AMS symptoms. Altitude travellers without prior experience of hiking and who are carrying a backpack for an extended period of time should understand these responses and potential risks to health, as well as educate themselves on safe altitude knowledge/travel and contributing risk factors.
Read CV Ashley WillmottECSS Paris 2023: CP-PN11
INTRODUCTION: Executive function has been shown to be improved after acute light exercise, and limited research suggests these beneficial effects remain even after breakfast omission (1). In contrast, executive function is impaired in hypoxia at rest, during and after exercise (2,3). This study aimed to determine the interactive effects of exercise, and breakfast consumption on executive function after light exercise. We hypothesized executive function would be improved after light exercise in normoxia, but reduced after exercise in hypoxia, with or without breakfast. METHODS: Twelve healthy young adults (10 men and 2 women with a mean age of 21 years) participated in this study. All participants completed four morning experimental conditions in a random order; i) breakfast omission (overnight fasting) in normoxia (20.9% O2), ii) having breakfast in normoxia (20.9% O2), iii) breakfast omission in hypoxia (13% O2), and iv) having breakfast in hypoxia (13% O2). In each condition, participants arrived after an overnight fast and had or did not have a standard breakfast, and then rested for 60 min, which was followed by 20 minutes of light-intensity leg cycling exercise (80 watts for men and 60 watts for women). Cerebral oxygenation (COX) was assessed by near-infrared spectroscopy pre-, during exercise, and post-exercise. Blood glucose, blood lactate, and executive function such as Digit span task (DST) and Hopkins verbal learning test (HVLT) were assessed pre-and post-exercise, respectively. RESULTS: At rest, blood glucose was lower after breakfast omission regardless of normoxia or hypoxia (delta -20% and P<0.001). After exercise, blood lactate in hypoxia was significantly higher than in normoxia (delta 2 mmol/L in normoxia vs. 4 mmol/L in hypoxia, P<0.001). A significant interaction (oxygen×time, P<0.001) in COX was found, where regardless of breakfast, COX was unchanged in normoxia (1.8% increase during exercise compared to pre-exercise) but decreased by 3.8% in hypoxia. In normoxia and hypoxia, the DST backward score was improved post-exercise compared to pre-exercise (P=0.02) but was impaired by breakfast omission (P=0.03). In contrast, the DST forward score, and HVLT were unaffected by exercise, oxygen level, or breakfast (all P>0.05). CONCLUSION: Acute moderate exercise improved backward scores of DST, but not forward scores and HVLT irrespective of oxygen levels or breakfast. Breakfast omission impaired only backward scores of DST. Hypoxia did not influence both DTS and HVLT. These results suggest that exercise improved short-term and working memory, but, breakfast omission impaired working memory. Moreover, hypoxic-induced reductions in cerebral oxygen hemodynamics did not affect executive function. Reference (1) Komiyama et al. (2016) Physiology & Behavior. 157:178–184. (2) Ando et al. (2020) Scand J Med Sci Sports. 30:384–398. (3) McMorris et al. (2017) Neuroscience & Biobehavioral Reviews. 74:225–232.
Read CV Masahiro HoriuchiECSS Paris 2023: CP-PN11