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OBJECTIVE: To assess the impact of cognitive Dual Task (DT) during walking on the energy cost of walking (Cw) in individuals with subacute stroke. The secondary objective was to determine whether there is an association between the Cw and cortical activity of the prefrontal area. METHODS: Any individual with stroke localized in the temporal-parietal regions and able to walk without human assistance was included. Cw and prefrontal cortical activity, recorded by fNIRS, were measured during simple task walking activity and cognitive dual task during walking. RESULTS: Nineteen individuals with stroke (age = 67.7 ± 9.6 yrs) were included. The cognitive DT during walking resulted in an increase in Cw of 23.1%; 95%CI [13.1%; 34.5%]. The increase in Cw in cognitive DT was correlated with the Cw for the single task walking activity (r = 0.48, p < 0.01) as well as the predominance of cortical activity of the prefrontal area in the contralesional hemisphere (r = -0.33, p < 0.01). CONCLUSION: There is an increase in Cw during the cognitive DT. This increase is even more significant, as the Cw of the single task walking activity is high, and the cortical activity of the prefrontal areas predominates in the contralesional hemisphere.
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Acidente Vascular Cerebral , Caminhada , Humanos , Pessoa de Meia-Idade , Idoso , Acidente Vascular Cerebral/psicologia , Córtex Pré-Frontal , Espectroscopia de Luz Próxima ao Infravermelho , MarchaRESUMO
This study aims to evaluate the accuracy of the Garmin Forerunner 245 heart rate (HR) and pulse O2 saturation (SpO2) sensors compared with electrocardiogram and medical oximeter, from sea level to high altitude. Ten healthy subjects underwent five tests in normoxia and hypoxia (simulated altitudes from 3000 to 5500 m), consisting in a 5-min rest phase, followed by 5-min of mild exercise. Absolute error (±10 bpm for HR and ±3% for SpO2, around criterion) and intraclass correlations (ICC) were calculated. Error rates for HR remained under 10%, except at 3000 m, and ICCs evidenced a good reliability between Garmin and criterion. Overall SpO2 was higher than criterion (P<0.001) with a >50% error rate (>80% above 4800 m), and a poor reliability with criterion. The Garmin device displayed acceptable HR data at rest and exercise for all altitudes, but failed to provide trustworthy SpO2 values, especially at high altitude, where a pronounced arterial O2 desaturation could lead to acute mountain sickness in hypoxia-sensitive subjects, and its life-threatening complications; moreover, readings of overestimated SpO2 values might induce trekkers into further hazardous behavior by pursuing an ascent while being already at risk. Therefore, its use to assess SpO2 should be proscribed in altitude for acclimatization evaluation.
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Exercício Físico , Frequência Cardíaca , Oximetria/instrumentação , Saturação de Oxigênio , Altitude , Eletrocardiografia , Humanos , Hipóxia/diagnóstico , Reprodutibilidade dos Testes , PunhoRESUMO
OBJECTIVE: To explore measures of peripheral muscular oxygenation, coupled to gait characteristics, between preterm and full-term children during a 6-minute walking test (6MWT). STUDY DESIGN: Prepubescent children performed a 6MWT. During the test, changes in muscular oxyhemoglobin, deoxyhemoglobin, and total hemoglobin were measured with Near-infrared spectroscopy technology, positioned on subjects' calves. Gait variables were monitored with the OptoGait system. RESULTS: Forty-five children (33 full-term children and 12 preterm children, mean age, 4.9 ± 0.7 and 4.6 ± 0.9 years, respectively) participated in this study. Statistical analysis highlighted a decreased walking performance for preterm children, with significantly lower walking distance (P < .05) than children born full-term (405.1 ± 91.8 m vs 461.0 ± 73.3 m respectively; -9%). A concomitant increase of oxygen extraction (over the time course of Variation of desoxyhemoglobin) was observed from the third minute of the test (P < .05). No statistically significant difference was found for other near-infrared spectroscopy measures. Finally, the analysis of gait variables highlighted a group effect for walking speed (P < .05) and stride length (P < .01). CONCLUSIONS: Premature children showed decreased walking performance and greater change in peripheral muscular oxygen extraction, associated with slower walking speed and stride length. This may point to a muscular maladjustment and reduced functional capacities for children born preterm. These phenomena could be responsible for greater muscular fatigue.
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Análise da Marcha , Músculo Esquelético/fisiologia , Fenômenos Fisiológicos Respiratórios , Teste de Caminhada/métodos , Estudos de Casos e Controles , Pré-Escolar , Estudos Transversais , Feminino , Idade Gestacional , Humanos , Masculino , Oxigênio/sangue , Espectroscopia de Luz Próxima ao InfravermelhoRESUMO
Aerobic performance is negatively impacted by tropical climate due to impairment of thermoregulatory mechanisms. We tested the hypothesis that a torso application of a 4% menthol solution would have the same effect on a best performance 10-km run as an external use of cold water. Thirteen trained male athletes completed four outdoor 10-km runs (T=29.0±1.3°C, relative humidity 59.0±13.6%) wearing a tee-shirt soaked every 2-km either in a cold (~6°C) or warm/ambient (~28°C) solution, consisting in water or in a 4% menthol solution, (CTL, MENT-Amb, CLD and MENT-CLD). Run performances were improved from 4.8 to 6.1% in CLD (51.4±5.5 min), MENT-Amb (52.2±5.9 min) and MENT-CLD (51.4±5.1 min) conditions (vs. CTL, 55.4±8.4 min, P<0.05), without differences between these three conditions, whereas heart rate (177±13bpm), body temperature (38.7±0.6°C) and drink ingestion (356±170 g) were not modified. Thermal sensation after running was lower in MENT-CLD (vs. CTL, P<0.01) and thermal acceptability was higher in CLD and MENT-Amb (vs. CTL, P<0.05), but thermal comfort, feeling scale and rate of perceived exertion remained unchanged. The use of menthol on skin enhances aerobic performance in a tropical climate, and no differences in performance were observed between menthol and traditional percooling strategies. However, combining both menthol and traditional percooling brought no further improvements.
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Desempenho Atlético/fisiologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Umidade , Mentol/administração & dosagem , Corrida/fisiologia , Clima Tropical , Administração Cutânea , Adulto , Ingestão de Líquidos , Marcha/fisiologia , Frequência Cardíaca/fisiologia , Humanos , Masculino , Percepção/fisiologia , Esforço Físico/fisiologia , Redução de Peso/fisiologia , Adulto JovemRESUMO
PURPOSE: Heart rate variability (HRV) may be influenced by several factors, such as environment (hypoxia, hyperoxia, hypercapnia) or physiological demand (exercise). In this retrospective study, we tested the hypothesis that inter-beat (RR) intervals in healthy subjects exercising under various environmental stresses exhibit oscillations at the same frequency than ventilatory oscillations. METHODS: Spectra from RR intervals and ventilation ([Formula: see text]E) were collected from 37 healthy young male subjects who participated in 5 previous studies focused on ventilatory oscillations (or periodic breathing) during exercise in hypoxia, hyperoxia and hypercapnia. Bland and Altman test and multivariate regressions were then performed to compare respective frequencies and changes in peak powers of the two signals. RESULTS: Fast Fourier analysis of RR and [Formula: see text]E signals showed that RR was oscillating at the same frequency than periodic breathing, i.e., ~ 0.09 Hz (11 s). During exercise, in these various conditions, the difference between minimum and maximum HRV peak power was positively correlated to the same change in ventilation peak power (P < 0.05). Low-frequency (LF) peak power was correlated to tidal volume (P < 0.01) and breathing frequency (P < 0.001). CONCLUSIONS: This study suggests that low-frequency ventilatory oscillations in hypoxia are a major contributor to the LF band power of heart rate variability. CLINICAL TRIAL REG. NO.: NCT02201875.
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Frequência Cardíaca , Hipóxia/fisiopatologia , Taxa Respiratória , Adulto , Humanos , MasculinoRESUMO
This study assessed the validity of a photoplethysmographic heart rate (HR) monitor, the Polar OH1 in various sports performed in ecological conditions: running, cycling, soccer, kayaking, walking, tennis and fitness. Seventy trained athletes (56 males, 14 females) wore the Polar OH1 armband and the H7 chest belt during training. A total of 390 h and 38 min of recording were compared using a 20-bpm window to assess data quality, and Bland-Altman agreements and ICC analyses were used to test accuracy. Linear regression analyses evaluated the HR accuracy and correlation with skin tone. Training loads (TRIMPs) were compared for each session. Reliability was high for endurance sports (>99%) and lower for sports involving arm movements (92~95%). Biases were slightly negative for all sports, whereas widths of limits of agreement varied from 7-20bpm. Bland-Altman agreements were all under 5% except tennis, kayak and fitness. HR accuracy was positively correlated to skin tone (p<0.05). Finally, TRIMPs from the OH1 device were inferior to criterion's (except walking and soccer), within a 3% range from reference. Hence, OH1 represents a valid tool to monitor instantaneous HR and training load, especially for endurance sports.
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Frequência Cardíaca , Monitorização Fisiológica/instrumentação , Condicionamento Físico Humano , Resistência Física/fisiologia , Esportes/fisiologia , Adolescente , Braço/fisiologia , Feminino , Humanos , Masculino , Dispositivos Eletrônicos Vestíveis , Adulto JovemRESUMO
We evaluated the mechanisms responsible for the instability of ventilation control system under simultaneous metabolic (exercise) and environmental (hypoxia) stresses, promoting the genesis of periodic breathing. A model following the main concepts of ventilatory control has been tested, including cardiovascular and respiratory parameters, characteristics of peripheral and central chemoreceptors, at mild exercise in hypoxia (FIO2=0.145). Interaction between O2 and CO2 sensing was introduced following three different modalities. A sensitivity and multivariate regression analyses closely matched with physiological data for magnitude and period of oscillations. Low FIO2 and long circulatory delay from lungs to peripheral chemoreceptors (DeltaTp) lengthen the period of oscillations, while high peripheral and central chemoresponses to O2 and CO2, low FIO2 and high DeltaTp increased their magnitude. Peripheral and central O2/CO2 interactions highlight the role of CO2 on peripheral gain to O2 and the contribution of peripheral afferences on central gain to CO2. Our model supports the key role of peripheral chemoreceptors in the genesis of ventilatory oscillations. Differences in the dynamics of central and peripheral components might be determinant for the system stability.
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Dióxido de Carbono/metabolismo , Exercício Físico/fisiologia , Modelos Teóricos , Oxigênio/metabolismo , Mecânica Respiratória/fisiologia , Algoritmos , Simulação por Computador , Humanos , Hipóxia , Cinética , Pulmão/metabolismo , Pulmão/fisiologia , Fatores de TempoRESUMO
Oxygen is vital for cellular metabolism; therefore, the hypoxic conditions encountered at high altitude affect all physiological functions. Acute hypoxia activates the adrenergic system and induces tachycardia, whereas hypoxic pulmonary vasoconstriction increases pulmonary artery pressure. After a few days of exposure to low oxygen concentrations, the autonomic nervous system adapts and tachycardia decreases, thereby protecting the myocardium against high energy consumption. Permanent exposure to high altitude induces erythropoiesis, which if excessive can be deleterious and lead to chronic mountain sickness, often associated with pulmonary hypertension and heart failure. Genetic factors might account for the variable prevalence of chronic mountain sickness, depending on the population and geographical region. Cardiovascular adaptations to hypoxia provide a remarkable model of the regulation of oxygen availability at the cellular and systemic levels. Rapid exposure to high altitude can have adverse effects in patients with cardiovascular diseases. However, intermittent, moderate hypoxia might be useful in the management of some cardiovascular disorders, such as coronary heart disease and heart failure. The aim of this Review is to help physicians to understand the cardiovascular responses to hypoxia and to outline some recommendations that they can give to patients with cardiovascular disease who wish to travel to high-altitude destinations.
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Doença da Altitude , Doenças Cardiovasculares , Insuficiência Cardíaca , Humanos , Altitude , Fenômenos Fisiológicos Cardiovasculares , Hipóxia , Doenças Cardiovasculares/etiologia , Oxigênio , Insuficiência Cardíaca/etiologia , Miocárdio , TaquicardiaRESUMO
Hermand, Eric, Léo Lesaint, Laura Denis, Jean-Paul Richalet, and François J. Lhuissier. A step test to evaluate the susceptibility to severe high-altitude illness in field conditions. High Alt Med Biol. 00:000-000, 2024.-A laboratory-based hypoxic exercise test, performed on a cycle ergometer, can be used to predict susceptibility to severe high-altitude illness (SHAI) through the calculation of a clinicophysiological SHAI score. Our objective was to design a field-condition test and compare its derived SHAI score and various physiological parameters, such as peripheral oxygen saturation (SpO2), and cardiac and ventilatory responses to hypoxia during exercise (HCRe and HVRe, respectively), to the laboratory test. A group of 43 healthy subjects (15 females and 28 males), with no prior experience at high altitude, performed a hypoxic cycle ergometer test (simulated altitude of 4,800 m) and step tests (20 cm high step) at 3,000, 4,000, and 4,800 m simulated altitudes. According to tested altitudes, differences were observed in O2 desaturation, heart rate, and minute ventilation (p < 0.001), whereas the computed HCRe and HVRe were not different (p = 0.075 and p = 0.203, respectively). From the linear relationships between the step test and SHAI scores, we defined a risk zone, allowing us to evaluate the risk of developing SHAI and take adequate preventive measures in field conditions, from the calculated step test score for the given altitude. The predictive value of this new field test remains to be validated in real high-altitude conditions.
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INTRODUCTION: The last few decades have been marked by significant advances in mechanical cardiocirculatory support. A total artificial heart (TAH) became a viable therapeutic option for numerous patients as a bridge to heart transplantation, particularly for those in end-stage heart failure. This technology aims to address the various subsequent shortfalls of organs. This report reviews the impact of a prehabilitation on a patient with an Aeson TAH (Carmat). DISCUSSION: We assessed improvements in functional capacity and quality of life (QoL) in a newly implanted patient following standard cardiac rehabilitation as a prehabilitation program, using 6-min walk test and the Short Form-12 (SF-12) health survey, respectively. Similar functional improvements were observed over a short period of 2 wk compared with a longer protocol for patients with a heart transplant, and superior effects on QoL. The patient was successfully transplanted 5 mo after the TAH implantation. SUMMARY: Prehabilitation of a patient with a TAH increased both their physical capacity and QoL.
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Reabilitação Cardíaca , Transplante de Coração , Coração Artificial , Humanos , Qualidade de Vida , Exercício Pré-OperatórioRESUMO
Breathing difficulties and exertional dyspnea are frequently reported in hypermobile Ehlers-Danlos syndrome (hEDS); however, they are not clearly explained. An impaired proprioception or the addition of a cognitive task could influence ventilatory control. How can the perception of lung volume be measured? Is lung volume perception impaired in hEDS patients? Is the breathing control impaired during a cognitive task in hEDS patients? A device was developed to assess the accuracy of lung volume perception in patients with hEDS and matched control subjects. In the second step, ventilation was recorded in both groups with and without a cognitive task. Two groups of 19 subjects were included. The accuracy of lung volume perception was significantly (P < 0.01) lower at 30% of inspired vital capacity in patients with hEDS in comparison to the control group, and they showed erratic ventilation (based on spatial and temporal criteria) when performing a cognitive task. These data support the influence of the proprioceptive deficit on ventilatory control in hEDS patients. These elements may help to understand the respiratory manifestations found in hEDS. Future research should focus on this relationship between lung volume perception and ventilation, and could contribute to our understanding of other pathologies or exercise physiology.Trial registration number: ClinicalTrials.gov, NCT05000151.
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Síndrome de Ehlers-Danlos , Humanos , Síndrome de Ehlers-Danlos/patologia , Pulmão/patologia , Dispneia , Medidas de Volume Pulmonar , PercepçãoRESUMO
The main objective of this study was to investigate the effect of mixed cooling techniques (combination of internal and external strategies, with and without menthol) during warm-up for a time trial in tropical climate. Seven heat-acclimatized trained male road cyclists participated in three experimental sessions consisting of 20-min cycling performances on a velodrome track in ecological hot and humid conditions (Guadeloupe, French West Indies; WBGT: 27.64±0.27°C; relative humidity: 76.43±2.19%), preceded by a standardized 30-min warm-up and the ingestion of cold menthol water (1) with a cooling vest soaked in ice water (ICE-VEST), (2) with a cooling vest soaked in ice menthol water (MEN-VEST), and (3) without a vest (NO-VEST). Cycling performance (total distance, distance traveled per 2-min block), physiological parameters (core body temperature recorded, heart rate) and perceptions (exertion, thermal comfort, thermal sensation) were assessed. No between-condition differences were found for physiological parameters, the total covered distance or the distance traveled per 2-min block. However, distance traveled per 2-min decreased with time (p = 0.03), with no difference between conditions, suggesting a variation in pace during the cycling performance trial (e.g., mean±SD: 1321±48.01m at T2; 1308±46.20m at T8, 1284±78.38m at T14, 1309±76.29m at T20). No between-condition differences were found for perception of exertion, thermal comfort and thermal sensation during the warm-up (11.83±3.34; 2.58±1.02; 4.39±0.94, respectively) and the performance (17.85±0.99; 2.70±1.25; 5.20±1.20, respectively) but the pairwise comparisons within condition revealed a significant increase of TS values from T0 (4.57±1.13) to T20 (6.00±0.58) only in NO-VEST condition (p = 0.04). The absence of modification of thermal sensation at the end of the cycling test under the mixed conditions (ICE-VEST and MEN-VEST) suggests a beneficial effect of wearing a cooling vest on thermal sensation although it had no effect on performance.
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Desempenho Atlético , Temperatura Corporal , Humanos , Masculino , Temperatura Corporal/fisiologia , Clima Tropical , Mentol , Temperatura Baixa , Temperatura Alta , Frequência Cardíaca/fisiologia , Água , Regulação da Temperatura Corporal/fisiologia , Desempenho Atlético/fisiologiaRESUMO
OBJECTIVE: This study aimed to investigate the effect of balance rehabilitation on postural control in both low and increased cognitive load conditions in two children with Autism Spectrum Disorders (ASD). METHODS: Two children diagnosed with ASD participated in a 4-week personalized balance rehabilitation program with two sessions per week. We assessed postural control in two single task (ST) conditions with low cognitive load: Eyes Closed (EC), Eyes Open (EO); and in five increased cognitive load conditions. Those dual task (DT) conditions consisted of presenting images representing a neutral condition, sadness, anger, happiness, and fear. Postural control parameters (surface, velocity, medio-lateral and antero-posterior sway amplitudes of the center of pressure (CoP)) were collected by a posturographic platform before and after the balance rehabilitation. RESULTS: The rehabilitation program resulted in a 30-96% improvement of postural control parameters in the ST condition for both participants. In DT, participant 1 progressed on all conditions while participant 2 progressed on 3 of the 5 conditions (sadness, anger and fear). CONCLUSION: This suggests that these two children with ASD improved their balance control in both low and increased cognitive load conditions. These encouraging results need to be replicated before recommending balance rehabilitation as standard health rehabilitation in children with ASD.
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Transtorno do Espectro Autista , Humanos , Criança , Equilíbrio Postural , MedoRESUMO
BACKGROUND: Exercise represents a viable non-pharmacological intervention to help treating insomnia but the interaction mechanisms between sleep and physical activity still remain poorly understood. The aim of this study was to investigate the effect of a aerobic exercise training intervention on sleep and core temperature. METHODS: Twenty-four adult women suffering from insomnia participated in this study. They were randomized into an exercise group and a control group. Aerobic exercise training consisted in moderate to vigorous aerobic exercise training for 12 weeks. Outcome measures included both subjective (Insomnia Severity Index, ISI) and objective (actigraphy recordings) sleep quality assessments, and core body temperature continuously recorded for a minimum 24 h. RESULTS: The exercise group showed a decrease in ISI (p < 0.001) and in various objective sleep parameters. The core temperature batyphase value was lowered (p = 0.037) whereas its amplitude was larger (p = 0.002). We also found a tight correlation between the evolution of insomnia and the evolution of mean night-time core temperature and batyphase values. CONCLUSIONS: A moderate to vigorous aerobic exercise program appears to be an effective non-drug therapy for improving sleep in women with insomnia. In addition, exercise programs should aim to increase core body temperature during practice to induce sleep-promoting adaptations and rebound.
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Distúrbios do Início e da Manutenção do Sono , Adulto , Pessoa de Meia-Idade , Humanos , Feminino , Distúrbios do Início e da Manutenção do Sono/terapia , Temperatura , Sono , Exercício Físico , Terapia por Exercício , Resultado do TratamentoRESUMO
INTRODUCTION: Achieving our daily tasks depends on the speed-accuracy conflict. Physical activity plays a role in the development of our motor skills. However, the relationship between physical activity level (PAL) and fine motor skills remains largely unexplored.
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Destreza Motora , Ácidos Ftálicos , Desempenho Psicomotor , Exercício Físico , Resinas AcrílicasRESUMO
Exposure to high altitude induces a decrease in oxygen pressure and saturation in the arterial blood, which is aggravated by exercise. Heart rate (HR) at maximal exercise decreases when altitude increases in prolonged exposure to hypoxia. We developed a simple model of myocardial oxygenation in order to demonstrate that the observed blunting of maximal HR at high altitude is necessary for the maintenance of a normal myocardial oxygenation. Using data from the available scientific literature, we estimated the myocardial venous oxygen pressure and saturation at maximal exercise in two conditions: (1) with actual values of maximal HR (decreasing with altitude); (2) with sea-level values of maximal heart rate, whatever the altitude (no change in HR). We demonstrated that, in the absence of autoregulation of maximal HR, myocardial tissue oxygenation would be incompatible with life above 6200 m-7600 m, depending on the hypothesis concerning a possible increase in coronary reserve (increase in coronary blood flow at exercise). The decrease in maximal HR at high altitude could be explained by several biological mechanisms involving the autonomic nervous system and its receptors on myocytes. These experimental and clinical observations support the hypothesis that there exists an integrated system at the cellular level, which protects the myocardium from a hazardous disequilibrium between O2 supply and O2 consumption at high altitude.
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Altitude , Consumo de Oxigênio , Frequência Cardíaca/fisiologia , Humanos , Hipóxia , Miocárdio/metabolismo , Oxigênio/metabolismo , Consumo de Oxigênio/fisiologiaRESUMO
Periodic breathing is a respiratory phenomenon frequently observed in patients with heart failure and in normal subjects sleeping at high altitude. However, until recently, periodic breathing has not been studied in wakefulness and during exercise. This review relates the latest findings describing this ventilatory disorder when a healthy subject is submitted to simultaneous physiological (exercise) and environmental (hypoxia, hyperoxia, hypercapnia) or pharmacological (acetazolamide) stimuli. Preliminary studies have unveiled fundamental physiological mechanisms related to the genesis of periodic breathing characterized by a shorter period than those observed in patients (11~12 vs. 30~60 s). A mathematical model of the respiratory system functioning under the aforementioned stressors corroborated these data and pointed out other parameters, such as dead space, later confirmed in further research protocols. Finally, a cardiorespiratory interdependence between ventilatory oscillations and heart rate variability in the low frequency band may partly explain the origin of the augmented sympathetic activation at exercise in hypoxia. These nonlinear instabilities highlight the intrinsic "homeodynamic" system that allows any living organism to adapt, to a certain extent, to permanent environmental and internal perturbations.
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INTRODUCTION: Visuo-spatial working memory (VSWM) performances undergo a decline throughout aging and are affected by the space in which the task is performed (reaching or navigational). Cerebral oxygenation and cognitive capabilities could explain this decline. We assessed the effects of age on cerebral oxygenation of the dorsolateral prefrontal cortex (dlPFC) in VSWM tasks in reaching and navigational space. We also assessed cognitive correlates of VSWM performance in each space. METHOD: Thirty-one (31) young adults (YA) and 24 healthy older adults (OA) performed a battery of neuropsychological tests and the electronic Corsi Block-tapping Test in reaching space (e-CBT) and in navigational space on the "Virtual Carpet" (VWCT). Participants were asked to memorize and recall a sequential pathway, progressively increasing from 2 to 9 blocks. Their span score reflected VSWM performance. The dlPFC oxygenation (oxyhaemoglobin: ΔO2Hb and deoxyhaemoglobin: ΔHHb) was measured by using functional Near-Infrared Spectroscopy (fNIRS) during the encoding of the sequential pathway in both tasks. RESULTS: YA had higher span scores than OA in both spaces. We identified a significantly stronger decrease of ΔHHb in YA compared to OA during encoding in VWCT. OA also exhibited significantly lower cerebral oxygenation in VWCT compared to e-CBT. A decrease of ΔHHb was also associated with a better performance in VWCT. Finally, we identified the association of mental rotation and executive functions with VSWM performance in both tasks. CONCLUSION: VSWM performance and cerebral oxygenation during encoding are impacted by aging. Space in which the task was performed was found to be associated with different cognitive functions and revealed differences in cerebral oxygenation.
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Envelhecimento/fisiologia , Cognição/fisiologia , Função Executiva/fisiologia , Memória de Curto Prazo/fisiologia , Rememoração Mental/fisiologia , Córtex Pré-Frontal/fisiologia , Percepção Espacial/fisiologia , Memória Espacial/fisiologia , Percepção Visual/fisiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Neuroimagem Funcional , Humanos , Masculino , Córtex Pré-Frontal/diagnóstico por imagem , Espectroscopia de Luz Próxima ao Infravermelho , Adulto JovemRESUMO
Increasing cerebral oxygenation, more precisely the overactivation of the prefrontal cortex (PFC), reflects cortical control of gait in stroke disease. Studies about the relationship between brain activation and the functional status in stroke patients remain scarce. The aim of this study was to compare brain activation, gait parameters, and cognitive performances in single and dual tasks according to the functional status in subacute stroke patients. Twenty-one subacute stroke patients were divided in two groups according to Barthel Index ("low Barthel" and "high Barthel") and randomly performed ordered walking, cognitive task (n-back task), and dual tasks (walking + n-back task). We assessed gait performances (speed, variability) using an electronic walkway system and cerebral oxygenation (ΔO2Hb) by functional near-infrared spectroscopy. Patients with better functional status (high Barthel) showed a lower PFC activation (ΔO2Hb) and better gait parameters in single and dual tasks compared to low-Barthel patients, who exhibited decreased gait performances despite a higher PFC activation, especially in the unaffected side (P < 0.001). PFC overactivation in less functional subacute stroke patients may be due to the loss of stepping automaticity. Our results underline the interest of proposing rehabilitation programs focused on walking, especially for patients with low functional capacity.
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Endurance and prolonged exercise are altered by hot climate. In hot and dry climate, thermoregulation processes, including evapotranspiration, normally maintain a relatively constant body core temperature. In hot and wet climate (usually called "tropical"), the decrease in evapotranspiration efficacy increases the sweating rate, which can rapidly induce severe hypohydration without efficiently reducing core temperature. The negative effects of tropical environment on long-duration exercise have been well documented, with clear demonstrations that they exceed the acclimation possibilities: both acclimated athletes and natives to tropical climate show impaired performances compared with that in neutral climate. New countermeasures, applicable during competitive events, are therefore needed to limit these negative effects. We studied the effects of several countermeasures in outdoor or natural tropical climates and noted that the easiest method to apply is cooling with cold (-1 to 3°C) beverage. Moreover, adding menthol increased the cold sensation induced by the beverage temperature, optimizing the positive effects on performance. We also demonstrated that efficient pre-cooling with cold menthol beverage requires drinking for 1 h instead of 30 min before the exercise. The optimal cooling method seems to be 1 h of cold + menthol pre-cooling ingestion followed by menthol + ice-slurry per-cooling. However, limitations should be noted: (1) the menthol concentration seems to be crucial, with positive effects for a 0.05% solution, whereas higher concentrations need to be explored; and (2) because it acts as a cold adjuvant without decreasing core temperature, menthol can lead to decreased thermoregulatory processes, thus inducing hyperthermia. Last, if menthol is added to cooling processes, athletes should first test them in training conditions for the maximal cooling effect to ensure optimal performance in competition in tropical climate.