Influence of inspiratory resistive loading on expiratory muscle fatigue in healthy humans

Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel co-activation of the inspiratory muscles during expiration. It is unknown whether the expiratorymuscles are similarly co-activated to the point of fatigue during inspiratory resistive loading (IRL).The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n=9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths∙min-1, 0.7 inspiratory duty cycle) to task failure. Abdominal and diaphragm contractile function was assessed at baseline and at 3, 15 and 30 min post-IRL by measuring gastric twitch pressure (Pga,tw) and transdiaphragmatic twitch pressure (Pdi,tw) in response to potentiated magnetic stimulation of the thoracic and phrenic nerves, respectively. Fatigue was defined as a significant reduction from baseline in Pga,tw or Pdi,tw. Throughout IRL, there was a time-dependent increase in cardiac frequency and mean arterial blood pressure, suggesting activation of the respiratory muscle metaboreflex. Pdi,tw was significantly lower than baseline (34.3 9.6 cmH2O) at 3min (23.2 5.7 cmH2O, P<0.001), 15 min (24.2 5.1 cmH2O, P<0.001) and 30 min post-IRL (26.3 6.0 cmH2O, P<0.001). Pga,tw was not significantly different from baseline (37.6 17.1 cmH2O) at 3min (36.5 14.6 cmH2O), 15 min (33.7 12.4 cmH2O) and 30 min post-IRL (32.9 11.3 cmH2O). IRL elicits objective evidence of diaphragm, but not abdominal, muscle fatigue. Agonist-antagonist interactions for the respiratory muscles appear to be more important during expiratory versus inspiratory loading.The Natural Sciences and Engineering Research Council (NSERC) of Canada supported this study. C.M. Peters, P.B. Dominelli, and Y. Molgat-Seon were supported by NSERC postgraduate scholarships. J.F Welch was supported by a University of British Columbia graduate fellowship

Effects of Age and Sex on Inspiratory Muscle Activation Patterns During Exercise

Purpose: Characterize the effects of age, sex, and their interaction on inspiratory muscle activation patterns during exercise. Methods: Twenty younger (20-30y, n=10 women) and twenty older (60-80y, n=10 women) subjects performed an incremental cycle exercise test. Electromyography of the scalene (EMGsca) and sternocleidomastoid (EMGscm) muscles were measured using skin surface electrodes, while diaphragm electromyography (EMGdi) and esophageal and transdiaphragmatic pressures were measured using an esophageal catheter. Electromyography data were transformed into root-mean-square with a 100ms time constant. Esophageal (PTPes) and diaphragmatic (PTPdi) pressure-time products were used as indices of total inspiratory muscle pressure production and diaphragmatic pressure production, respectively. Results: At absolute minute ventilations (V E), women and older subjects had greater EMGdi than men and younger subjects, respectively (all p<0.05), but no differences were noted when V E was expressed in relative terms (all p>0.05). Women had greater EMGsca activity than men at absolute and relative levels of V E (all p<0.05). Older subjects had greater EMGsca than younger subjects when V E was expressed relative (all p<0.05) but not absolute terms (all p>0.05). At absolute and relative levels of V E, women and older subjects had greater EMGscm than men and younger subjects, respectively (all p<0.05). Women and older subjects had a greater PTPdi/PTPes at a V E of 70 l·min-1 than men and younger subjects, respectively (both p<0.05), but no differences were noted when V E was expressed in relative terms (all p>0.05). No significant interactions between age and sex were noted (all p>0.05). Conclusion: Age and sex significantly affect inspiratory muscle activation patterns during exercise; however, the extent of the effects depends on whether comparisons are made at a solute or relative V E.This study was supported by the British Columbia Lung Association (BCLA). YMS, PBD, and AHR were supported by graduate scholarships from the Natural Sciences and Engineering Research Council of Canada (NSERC). PBD and MRS were supported by fellowships from the University of British Columbia and BCLA. JAG was supported by a Scholar Award from the Michael Smith Foundation for Health Research, a New Investigator Award from the Providence Health Care Research Institute and St. Paul’s Hospital Foundation, and a Canadian Institutes of Health Research Clinical Rehabilitation New Investigator Award

Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women

© 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society. KEY POINT SUMMARY:The perceived intensity of exertional breathlessness (i.e. dyspnoea) is higher in older women than in older men, possibly due to sex-difference respiratory system morphology. During exercise at a given absolute intensity or minute ventilation, older women have a greater degree of mechanical ventilatory constraint (i.e. work of breathing and expiratory flow limitation) than their male counterparts, which may lead to a greater perceived intensity of dyspnoea. Using a single-blind randomized study design, we experimentally manipulated the magnitude of mechanical ventilatory constraint during moderate-intensity exercise at ventilatory threshold in healthy older men and women. We found that changes in the magnitude of mechanical ventilatory constraint within the physiological range had no effect on dyspnoea in healthy older adults. When older men and women perform submaximal exercise at a moderate intensity, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea. We sought to determine the effect of manipulating mechanical ventilatory constraint during submaximal exercise on dyspnoea in older men and women. METHODS:Eighteen healthy subjects (60-80 y; 9 men, 9 women) completed two days of testing. On Day 1, subjects performed pulmonary function testing and a maximal incremental cycle exercise test. On Day 2, subjects performed three 6-min bouts of cycling at ventilatory threshold, in a single-blind randomized manner, while breathing: i) normoxic helium-oxygen (HEL) to reduce the work of breathing (Wb ) and alleviate expiratory flow limitation (EFL); ii) through an inspiratory resistance (RES) of ∼5 cmH2 O·l-1 ·s-1 to increase Wb ; and iii) ambient air as a control (CON). Oesophageal pressure, diaphragm electromyography, and sensory responses (using the category-ratio 10 Borg scale) were monitored throughout exercise. RESULTS:During the HEL condition, there was a significant decrease in Wb (men: -21 ± 6%, women: -17 ± 10%) relative to CON (both p < 0.01). Moreover, if EFL was present during CON (4 men, 5 women), it was alleviated during HEL. Conversely, during the RES condition, Wb (men: 42 ± 19%, women: 50 ± 16%) significantly increased relative to CON (both p < 0.01). There was no main effect of sex on Wb (p = 0.59). Across conditions, women reported significantly higher dyspnoea intensity than men (2.9 ± 0.9 vs. 1.9 ± 0.8 Borg scale units, p < 0.05). Despite significant differences in the degree of mechanical ventilatory constraint between conditions, dyspnoea intensity was unaffected, independent of sex (p = 0.46). CONCLUSION:When older men and women perform submaximal exercise at a moderate intensity, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea. This article is protected by copyright. All rights reserved.Natural Science and Engineering Research Council of Canada (NSERC) British Columbia Lung Association (BCLA

Thoracic load carriage-induced respiratory muscle fatigue.

We investigated the effect of carrying a 25 kg backpack upon exercise-induced respiratory muscle fatigue, pulmonary function and physiological and perceptual responses to exercise.N/

Вплив тренувань на розвиток артеріальної гіпоксемії, спричиненої фізичними вправами, у волейболістів

Background and Study Aim. The purpose of this study was to examine the effect of volleyball training on the development of exercise-induced arterial hypoxemia during incremental exercise in male competitive volleyball players. Material and Methods. &nbsp;Eight male amateur volleyball players (age 21±1.3 years) participated in a 6-week volleyball training program three times a week in the pre-season preparatory period. Before and after the training period, all players performed an incremental treadmill test to determine maximal oxygen uptake (VO2max), and oxyhemoglobin saturation (SaO2) was continuously measured using a pulse oximeter during the test. Maximal values of minute ventilation (VEmax), respiratory exchange ratio (RERmax), ventilatory equivalent for oxygen (VE/VO2) and carbon dioxide (VE/VCO2) were determined. Exercise-induced arterial hypoxemia (EIAH) was defined as a SaO2 decreased by at least 4% (ΔSaO2≤ −4%) from resting level. Results.&nbsp;All the players exhibited exercise-induced arterial hypoxemia before (ΔSaO2= –8.8±3.3%) and after (ΔSaO2= –8.31.5%) the training period. SaO2 was significantly decreased from 97.6±1% at rest to 88.7±2.7% at exhaustion before the training period, and from 97.2±1.1% at rest to 88.8±2.1% at exhaustion after training period (p &lt; 0.001). There was no significant difference in resting and lowest SaO2 values by comparison between the before and after training (p &gt; 0.05). There were no significant changes in VO2max, VEmax, RERmax, VE/VO2 and VE/VCO2 after training period (p &gt; 0.05). Conclusions.&nbsp;The results of this study showed that volleyball players with a history of anaerobic training may exhibit EIAH, but that 6-week volleyball training has no effect on the degree of exercise-induced arterial hypoxemia.Предпосылки и цель исследования. Целью данного исследования было изучить влияние тренировок по волейболу на развитие артериальной гипоксемии, вызванной физической нагрузкой, во время дополнительных физических нагрузок у соревнующихся волейболистов-мужчин.Материал и методы. Восемь волейболистов-любителей (возраст 21 ± 1,3 года) участвовали в 6-недельной программе волейбольных тренировок три раза в неделю в предсезонный подготовительный период. До и после периода тренировки все игроки выполняли пошаговый тест на беговой дорожке, чтобы определить максимальное потребление кислорода (VO2max), и во время теста постоянно измеряли насыщение оксигемоглобином (SaO2) с помощью пульсоксиметра. Определяли максимальные значения минутной вентиляции (VEmax), коэффициента дыхательного обмена (RERmax), эквивалента вентиляции по кислороду (VE / VO2) и диоксиду углерода (VE / VCO2). Артериальная гипоксемия, вызванная физической нагрузкой (EIAH), определялась как снижение SaO2 как минимум на 4% (ΔSaO2≤ −4%) от уровня покоя.Результаты.&nbsp;У всех игроков наблюдалась артериальная гипоксемия, вызванная физической нагрузкой, до (ΔSaO2 = –8,8 ± 3,3%) и после (ΔSaO2 = –8,31,5%) периода тренировки. SaO2 значительно снизился с 97,6 ± 1% в покое до 88,7 ± 2,7% при истощении перед тренировочным периодом и с 97,2 ± 1,1% в покое до 88,8 ± 2,1% при истощении после тренировочного периода (p &lt;0,001). Не было существенной разницы между значениями SaO2 в состоянии покоя и самыми низкими значениями SaO2 до и после тренировки (p&gt; 0,05). Не было значительных изменений VO2max, VEmax, RERmax, VE / VO2 и VE / VCO2 после периода тренировки (p&gt; 0,05).Выводы. Результаты этого исследования показали, что у волейболистов с анаэробными тренировками может наблюдаться EIAH, но что 6-недельные тренировки по волейболу не влияют на степень артериальной гипоксемии, вызванной физической нагрузкой.Передумови та мета дослідження. Метою даного дослідження було вивчити вплив тренувань з волейболу на розвиток артеріальної гіпоксемії, викликаної фізичним навантаженням, під час додаткових фізичних навантажень у змагаються волейболістів-чоловіків.Матеріал і методи. Вісім волейболістів-любителів (вік 21 ± 1,3 року) брали участь в 6-тижневій програмі волейбольних тренувань три рази в тиждень в передсезонний підготовчий період. До і після періоду тренування всі гравці виконували покроковий тест на біговій доріжці, щоб визначити максимальне споживання кисню (VO2max), і під час тесту постійно вимірювали насичення оксигемоглобіном (SaO2) за допомогою пульсоксиметра. Визначали максимальні значення хвилинної вентиляції (VEmax), коефіцієнта дихального обміну (RERmax), еквівалента вентиляції по кисню (VE / VO2) і діоксиду вуглецю (VE / VCO2). Артеріальна гіпоксемія, викликана фізичним навантаженням (EIAH), визначалася як зниження SaO2 як мінімум на 4% (ΔSaO2≤ -4%) від рівня спокою.Результати. У всіх гравців спостерігалася артеріальна гіпоксемія, викликана фізичним навантаженням, до (ΔSaO2 = -8,8 ± 3,3%) і після (ΔSaO2 = -8,31,5%) періоду тренування. SaO2 значно знизився з 97,6 ± 1% в спокої до 88,7 ± 2,7% при виснаженні перед тренувальним періодом і з 97,2 ± 1,1% в спокої до 88,8 ± 2,1% при виснаженні після тренувального періоду (p &lt;0,001). Не було суттєвої різниці між значеннями SaO2 в стані спокою і найнижчими значеннями SaO2 до і після тренування (p&gt; 0,05). Не було значних змін VO2max, VEmax, RERmax, VE / VO2 і VE / VCO2 після періоду тренування (p&gt; 0,05).Висновки. Результати цього дослідження показали, що у волейболістів з анаеробними тренуваннями може спостерігатися EIAH, але що 6-тижневі тренування з волейболу не впливають на ступінь артеріальної гіпоксемії, викликаної фізичним навантаженням

The effects of age and sex on mechanical ventilatory constraint and dyspnea during exercise in healthy humans

Natural Science and Engineering Research Council of Canada 590 (NSERC); British Columbia Lung Association (BCLA); University of British Columbia; Michael Smith Foundation for Health Research; Providence Health Care Research Institute; St. Paul’s Hospital Foundation; Canadian 595 Institutes of Health Research Clinical Rehabilitation

Effect of Resistive Load on the Inspiratory Work and Power of Breathing during Exertion

Resistive loads are used to train respiratory muscles in athletes and in rehabilitation of people with pulmonary disease or spinal injuries [1–3]. Other studies use external resistive load detection as a tool to study dyspnoea sensitivity [4]. Resistive work is dependent on ventilation, and different exercise modes, for example walking and cycling place different metabolic demands on the body. A measure of the work performed during breathing can be derived from the product of the volume and pressure change generated during the respiratory cycle. The mechanical work of breathing which includes the elastic and resistive components, defined per litre of ventilation in resting healthy subjects is around 0.3560.1 JL21 while the power generated is around 2.460.7 W [5]. The power generated is thus influenced by respiratory rate and volume of air moved. Measuring these parameters often involve using invasive techniques and require an estimate of chest wall compliance [6]. At rest the inspiratory work of breathing is consistently larger than expiratory work. However this changes with exercise when expiration also becomes an active process. Measuring work only during the inspiratory phase of the respiratory cycle provides a simple index of the muscle-driven work irrespective of the expiratory phase. This study aims to use a new non-invasive method to measure the resistive work of breathing and the subsequent power generated (WRI and PRI respectively) while breathing against added resistive loads and explore this relationship with ventilation during sub-maximal exercise, sitting, walking or cycling. This study while observational is unique in that the loading was applied in ‘‘real-time’’ using a servo-controlled variable orifice pneumotachograph allowing both resistive inspiratory work and power to be assessed simultaneously