Publications by authors named "Leah M Mann"

At rest, the menstrual cycle phase impacts ventilation and chemosensitivity. However, during exercise there is inconclusive evidence that the menstrual cycle phase affects ventilation or chemosensitivity. We sought to examine the influence of menstrual phase and hormonal birth control (BC) on chemosensitivity.

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  • Acute mountain sickness (AMS) can result from quick ascents to high altitudes and insufficient acclimatization, with acetazolamide (AZ) often prescribed for prevention but negatively affecting exercise performance.
  • This study compared the effects of AZ, methazolamide (MZ), and a placebo on whole-body exercise performance in hypoxic conditions using a cycling time trial with fifteen participants.
  • Results showed that both AZ and MZ impaired exercise performance compared to the placebo group, as indicated by longer times to complete a 5-km trial, while MZ did not show a significant performance advantage over AZ.
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We recently explored the cardiopulmonary interactions during partial unloading of the respiratory muscles during exercise. Expanding upon this work, we present a noteworthy case study whereby we eliminated the influence of respiration on cardiac function in a conscious but mechanically ventilated human during exercise. This human was a young healthy endurance-trained male who was mechanically ventilated during semi-recumbent cycle exercise at 75 Watts (W) (∼30% W).

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Peripheral hypercapnic chemosensitivity (PHC) is assessed as the change in ventilation in response to a rapid change in carbon dioxide pressures (Pco). The increase in chemoresponse from rest to subrespiratory compensation point (RCP) exercise intensities is well-defined but less clear at intensities above the RCP when changes in known ventilatory stimulants occur. Twenty healthy subjects ( = 10 females) completed a maximal exercise test on 1 day, and on a subsequent day, transient hypercapnia was used to test PHC at multiple exercise stages.

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  • A study was conducted with 20 participants to explore the relationship between peripheral hypercapnic chemosensitivity and expiratory flow limitation (EFL) during exercise.
  • Participants underwent both chemosensitivity testing and a maximal exercise test, which involved assessing how their bodies reacted to increased levels of carbon dioxide (CO2) during different exercise intensities.
  • The findings indicated that there was no significant difference in the hypercapnic chemoresponse between those who experienced EFL and those who did not, suggesting that peripheral hypercapnic chemosensitivity during mild exercise is not linked to the occurrence of EFL.
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Peripheral hypercapnic chemosensitivity (PHC) is the ventilatory response to hypercapnia and is enhanced with acute whole body exercise. However, little is known about the mechanism(s) responsible for the exercise-related increase in PHC and if progressive exercise leads to further augmentation. We hypothesized that unloaded cycle exercise (0 W) would increase PHC but progressively increasing the intensity would not further augment the response.

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Purpose: We sought to determine if supramaximal exercise testing confirms the achievement of V̇O 2max in acute hypoxia. We hypothesized that the incremental and supramaximal V̇O 2 will be sufficiently similar in acute hypoxia.

Methods: Twenty-one healthy adults (males n = 13, females n = 8) completed incremental and supramaximal exercise tests in normoxia and acute hypoxia (fraction inspired oxygen = 0.

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Intrathoracic pressure (ITP) swings that permit spontaneous ventilation have physiological implications for the heart. We sought to determine the effect of respiration on cardiac output ( ) during semi-supine cycle exercise using a proportional assist ventilator to minimize ITP changes and lower the work of breathing (W ). Twenty-four participants (12 females) completed three exercise trials at 30%, 60% and 80% peak power (W ) with unloaded (using a proportional assist ventilator, PAV) and spontaneous breathing.

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The perception of dyspnea is influenced by both physiological and psychological factors. We sought to determine whether exertional dyspnea perception could be experimentally manipulated through prior exposure to heightened dyspnea while exercising. We hypothesized that dyspnea perception during exercise would be lower following an induced dyspnea task (IDT).

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  • The study investigates whether the benefits of inspiratory muscle training (RMT) on respiratory muscle strength and metaboreflex are maintained after a period of detraining.
  • Main findings show that after 5 weeks of detraining, respiratory muscle strength remained elevated and the metaboreflex was still attenuated, indicating lasting benefits from RMT.
  • This suggests that the positive effects of inspiratory muscle training persist even after training cessation, highlighting its importance for respiratory health.
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Quantifying diaphragm neuromuscular function using cervical magnetic stimulation (CMS) typically uses only a single stimulator (1-Stim) which may be inadequate to maximally stimulate the phrenic nerves. We questioned if using two stimulators (2-Stim) together alters diaphragm neuromuscular function at baseline and following inspiratory pressure threshold loading. Six (n = 3 female) healthy young participants were instrumented with esophageal and gastric balloon tipped catheters and electrodes over the 7-8th intercostal space.

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Hypercapnic chemosensitivity is the response to the increased partial pressure of carbon dioxide and results from central and peripheral chemosensor stimulation. The hypercapnic chemosensitivity of the peripheral chemoreceptors is potentially impacted by acute exercise, aerobic fitness, and sex. We sought to determine the peripheral chemoresponse to transient hypercapnia at rest and during exercise in males and females of various fitness.

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Rationale: It is unclear whether the frequency and mechanisms of expiratory flow limitation (EFL) during exercise differ between males and females.

Purpose: This study aimed to determine which factors predispose individuals to EFL during exercise and whether these factors differ based on sex. We hypothesized that i) EFL frequency would be similar in males and females and ii) in females, EFL would be associated with indices of low ventilatory capacity, whereas in males, EFL would be associated with indices of high ventilatory demand.

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Recent evidence suggests healthy females have significantly smaller central conducting airways than males when matched for either height or lung volume during analysis. This anatomical sex-based difference could impact the integrative response to exercise. Our review critically evaluates the literature on direct and indirect techniques to measure central conducting airway size and their limitations.

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We sought to determine the impact of wearing cloth or surgical masks on the cardiopulmonary responses to moderate-intensity exercise. Twelve subjects ( = 5 females) completed three, 8-min cycling trials while breathing through a non-rebreathing valve (laboratory control), cloth, or surgical mask. Heart rate (HR), oxyhemoglobin saturation (SpO), breathing frequency, mouth pressure, partial pressure of end-tidal carbon dioxide (PCO) and oxygen (PO), dyspnea were measured throughout exercise.

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New Findings: What is the central question of this study? What is the relative contribution of a putative tonic splenic contraction to the haematological acclimatization process during high altitude ascent in native lowlanders? What is the main finding and its importance? Spleen volume decreased by -14.3% (-15.2 ml) per 1000 m ascent, with an attenuated apnoea-induced [Hb] increase, attesting to a tonic splenic contraction during high altitude ascent.

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Smaller airways increase resistance and the propensity toward turbulent airflow, both of which are thought to be mechanisms behind greater resistive and total work of breathing (Wb) in females. Previous research examining the effect of airway size on the Wb between the sexes is limited by the inability to experimentally manipulate airway size. Heliox (21% oxygen, balance helium) is less dense than room air, which reduces turbulent airflow and airway resistance.

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New Findings: What is the central question of this study? We assessed the utility of a new metric for quantifying ventilatory acclimatization to high altitude, derived from differential ascent and descent steady-state cardiorespiratory variables (i.e. hysteresis).

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The pressure-passive cerebrovasculature is affected by alterations in cerebral perfusion pressure (CPP) and arterial blood gases (e.g., pressure of arterial [Pa]CO), where acute changes in either stimulus can influence cerebral blood flow (CBF).

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