Impact du diabète de type 2 sur la physiologie intégrée du système cardiorespiratoire à l'exercice chez l'humain

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2007-2008

Uncoupling between cerebral perfusion and oxygenation during incremental exercise in an athlete with postconcussion syndrome: a case report

High‐intensity exercise may pose a risk to patients with postconcussion syndrome (PCS) when symptomatic during exertion. The case of a paralympic athlete with PCS who experienced a succession of convulsion‐awakening periods and reported a marked increase in postconcussion symptoms after undergoing a graded symptom‐limited aerobic exercise protocol is presented. Potential mechanisms of cerebrovascular function failure are then discussed

Sex differences in effects of mental work and moderate-intensity physical activity on energy intake in young adults

The aim of this study was to examine the acute effects of mental work and moderate-intensity physical activity on various components of energy balance in young and healthy adults. With the use of a randomized crossover design, 35 participants aged 24 ± 3 years completed three 45-min conditions, namely, (i) resting in a sitting position (control), (ii) reading and writing (mental work (MW)), and (iii) exercising on a treadmill at 40% of peak oxygen uptake (exercise), followed by an ad libitum lunch. The endpoints were spontaneous energy intake (EI), energy expenditure (EE), appetite sensations, and EI for the remainder of the day. We observed that the energy cost of the control and MW conditions was about the same whereas the exercise condition increased EE to a greater extent in men than women. Exercise induced a decrease in EI relative to EE compared to the control condition that was more pronounced in men than women. However, women tended to increase their energy intake after the MW condition compared to the control one whereas an opposite trend was observed in men. None of the appetite sensation markers differed significantly between both sexes. In conclusion, men and women have specific food intake patterns when submitted to cognitive and physical stimuli

Mental work stimulates cardiovascular responses through a reduction in cardiac parasympathetic modulation in men and women

Mental Work (MW) stimulates Cardiovascular (CV) functions in healthy adults and a reduction in cardiac parasympathetic modulation could be one mechanism involved in such a response. The influence of sex on these CV responses remains ambiguous. The aim of the study was to evaluate CV impacts of MW in healthy individuals and whether sex influences CV responses induced by MW. The impact of a 45-min reading and writing session vs. a control condition, on Blood Pressure (BP), Heart Rate (HR), and Heart Rate Variability (HRV), was evaluated in 44 healthy adults with the use of a randomized crossover design. The influence of sex on those variables was then evaluated. Diastolic BP (74 ± 1 vs. 69 ± 1 mmHg; p < 0.05) and mean arterial pressure (MAP; 87 ± 7 vs. 83 ± 8 mmHg; p < 0.005), HR (68 ± 1 vs. 62 ± 1 bpm; p < 0.0001) and low frequency/high frequency ratio (2.8 ± 0.1 vs. 2.0 ± 0.1; p < 0.0001) were higher, while global HRV (SDNN: 84 ± 3 vs.104 ± 3 ms; p < 0.0001) and cardiac parasympathetic activity were lower during MW (p < 0.0001) vs. the control condition in the whole sample. During both experimental conditions, HR was higher (p < 0.0001), while BP, rMSSD, pNN50 and low frequency component of HRV were lower in women compared to men (all p < 0.05). The intensity of the cognitive demand and its influence on CV variables were comparable between men and women. These results support that MW increases BP and HR through decrement in cardiac parasympathetic modulation in healthy subjects and suggest that sex does not influence CV responses induced by cognitive demand of similar intensity

Mental work stimulates cardiovascular responses through a reduction in cardiac parasympathetic modulation in men and women

Mental Work (MW) stimulates Cardiovascular (CV) functions in healthy adults and a reduction in cardiac parasympathetic modulation could be one mechanism involved in such a response. The influence of sex on these CV responses remains ambiguous. The aim of the study was to evaluate CV impacts of MW in healthy individuals and whether sex influences CV responses induced by MW. The impact of a 45-min reading and writing session vs. a control condition, on Blood Pressure (BP), Heart Rate (HR), and Heart Rate Variability (HRV), was evaluated in 44 healthy adults with the use of a randomized crossover design. The influence of sex on those variables was then evaluated. Diastolic BP (74 ± 1 vs. 69 ± 1 mmHg; p < 0.05) and mean arterial pressure (MAP; 87 ± 7 vs. 83 ± 8 mmHg; p < 0.005), HR (68 ± 1 vs. 62 ± 1 bpm; p < 0.0001) and low frequency/high frequency ratio (2.8 ± 0.1 vs. 2.0 ± 0.1; p < 0.0001) were higher, while global HRV (SDNN: 84 ± 3 vs.104 ± 3 ms; p < 0.0001) and cardiac parasympathetic activity were lower during MW (p < 0.0001) vs. the control condition in the whole sample. During both experimental conditions, HR was higher (p < 0.0001), while BP, rMSSD, pNN50 and low frequency component of HRV were lower in women compared to men (all p < 0.05). The intensity of the cognitive demand and its influence on CV variables were comparable between men and women. These results support that MW increases BP and HR through decrement in cardiac parasympathetic modulation in healthy subjects and suggest that sex does not influence CV responses induced by cognitive demand of similar intensity

Trans-cerebral HCO3- and PCO2 exchange during acute respiratory acidosis and exercise-induced metabolic acidosis in humans

This study investigated trans-cerebral internal jugular venous-arterial bicarbonate ([HCO(3)(−)]) and carbon dioxide tension (PCO(2)) exchange utilizing two separate interventions to induce acidosis: 1) acute respiratory acidosis via elevations in arterial PCO(2) (PaCO(2)) (n = 39); and 2) metabolic acidosis via incremental cycling exercise to exhaustion (n = 24). During respiratory acidosis, arterial [HCO(3)(−)] increased by 0.15 ± 0.05 mmol ⋅ l(−1) per mmHg elevation in PaCO(2) across a wide physiological range (35 to 60 mmHg PaCO(2); P < 0.001). The narrowing of the venous-arterial [HCO(3)(−)] and PCO(2) differences with respiratory acidosis were both related to the hypercapnia-induced elevations in cerebral blood flow (CBF) (both P < 0.001; subset n = 27); thus, trans-cerebral [HCO(3)(−)] exchange (CBF × venous-arterial [HCO(3)(−)] difference) was reduced indicating a shift from net release toward net uptake of [HCO(3)(−)] (P = 0.004). Arterial [HCO(3)(−)] was reduced by −0.48 ± 0.15 mmol ⋅ l(−1) per nmol ⋅ l(−1) increase in arterial [H(+)] with exercise-induced acidosis (P < 0.001). There was no relationship between the venous-arterial [HCO(3)(−)] difference and arterial [H(+)] with exercise-induced acidosis or CBF; therefore, trans-cerebral [HCO(3)(−)] exchange was unaltered throughout exercise when indexed against arterial [H(+)] or pH (P = 0.933 and P = 0.896, respectively). These results indicate that increases and decreases in systemic [HCO(3)(−)] – during acute respiratory/exercise-induced metabolic acidosis, respectively – differentially affect cerebrovascular acid-base balance (via trans-cerebral [HCO(3)(−)] exchange)

Compromised cerebrovascular regulation and cerebral oxygenation in pulmonary arterial hypertension

Background : Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. Methods and Results : Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure‐flow relationship (assessed at rest and during squat‐stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls. Both groups also completed an incremental ramp exercise protocol until exhaustion, during which MCAvmean, mean arterial pressure, cardiac output (photoplethysmography), end‐tidal partial pressure of CO2, and cerebral oxygenation (near‐infrared spectroscopy) were measured. Patients were characterized by a significant decrease in resting MCAvmean (P<0.01) and higher transfer function gain at rest and during squat‐stand maneuvers (both P<0.05). Cerebrovascular reactivity to CO2 was reduced (P=0.03), whereas central chemoreceptor sensitivity was increased in PAH (P<0.01), the latter correlating with increased resting ventilation (R2=0.47; P<0.05) and the exercise ventilation/CO2 production slope (Embedded Image slope; R2=0.62; P<0.05) during exercise for patients. Exercise‐induced increases in MCAvmean were limited in PAH (P<0.05). Reduced MCAvmean contributed to impaired cerebral oxygen delivery and oxygenation (both P<0.05), the latter correlating with exercise capacity in patients with PAH (R2=0.52; P=0.01). Conclusions : These findings provide comprehensive evidence for physiologically and clinically relevant impairments in cerebral hemodynamic regulation and oxygenation in PAH