Regulation of Breathing During Exercise

‭Chemical modifications.‬ ‭ ny‬‭increase‬‭in‬‭CO2,‬‭any‬‭increase‬‭in‬‭H+‬‭ions‬‭and‬‭therefore‬‭any‬‭drop‬‭in‬‭pH‬ A ‭will‬ ‭result‬ ‭in‬ ‭a‬ ‭command‬ ‭from‬ ‭the‬ ‭central‬ ‭chemoreceptors‬ ‭to‬ ‭the‬ ‭respiratory‬ ‭centers‬ ‭to‬ ‭increase‬ ‭ventilation‬ ‭(allows‬ ‭excess‬ ‭CO2‬ ‭to‬ ‭be‬ ‭eliminated and the pH to be restored).‬ ‭ eripheral‬‭chemoreceptors‬‭which‬‭are‬‭located‬‭at‬‭the‬‭level‬‭of‬‭the‬‭aortic‬‭arch‬ P ‭and‬ ‭at‬ ‭the‬ ‭level‬ ‭of‬ ‭the‬ ‭carotid‬ ‭artery‬ ‭are‬ ‭sensitive‬ ‭to‬ ‭variations‬ ‭in‬ ‭PO2,‬ ‭PCO2‬‭and‬‭pH.‬‭Furthermore,‬‭its‬‭sensitive‬‭fibers‬‭from‬‭these‬‭chemoreceptors‬ ‭will‬ ‭therefore‬ ‭transmit‬ ‭information‬ ‭to‬ ‭the‬ ‭inspiratory‬ ‭center‬ ‭which‬ ‭will‬ ‭increase‬ ‭diaphragmatic‬ ‭and‬ ‭intercostal‬ ‭muscle‬ ‭contraction‬ ‭(main‬‭muscles‬ ‭of respiration) to restore PCO2 and pH.‬ I‭ n‬ ‭addition‬ ‭to‬ ‭these‬ ‭central‬ ‭and‬ ‭peripheral‬ ‭chemoreceptors,‬ ‭there‬ ‭are‬ ‭mechanical‬‭receptors‬‭that‬‭are‬‭sensitive‬‭to‬‭stretch.‬‭They‬‭are‬‭located‬‭at‬‭the‬ ‭level‬ ‭of‬ ‭the‬ ‭pleura,‬ ‭at‬ ‭the‬ ‭level‬ ‭of‬ ‭the‬‭bronchioles‬‭and‬‭at‬‭the‬‭level‬‭of‬‭the‬ ‭pulmonary‬ ‭alveoli.‬ ‭These‬ ‭receptors‬ ‭sensitive‬ ‭to‬ ‭stretching‬ ‭will‬ ‭stimulate‬ ‭the‬ ‭expiratory‬ ‭centers‬ ‭and‬ ‭will‬ ‭be‬ ‭responsible‬ ‭for‬ ‭an‬ ‭increase‬ ‭in‬ ‭respiration.‬‭They‬‭will‬‭therefore‬‭stimulate‬‭the‬‭expiratory‬‭muscles‬‭which‬‭are‬ ‭the abs and the external intercostal muscles.‬ ‭Regulation of breathing during exercise.‬ ‭ espiration‬ ‭can‬ ‭be‬ ‭measured‬ ‭during‬ ‭exercise‬ ‭using‬ ‭a‬ ‭mask‬ ‭that‬ ‭is‬ R ‭connected‬‭to‬‭oxygen‬‭and‬‭carbon‬‭dioxide‬‭analyzers.‬‭We‬‭then‬‭measure‬‭what‬ ‭happens during breathing.‬ ‭ uring‬ ‭an‬ ‭exercise‬ ‭gradually‬ ‭increasing‬ ‭in‬ ‭intensity‬ ‭we‬ ‭observe‬ ‭that‬ D ‭ventilation‬ ‭first‬ ‭evolves‬ ‭in‬ ‭a‬ ‭linear‬ ‭manner‬ ‭then‬ ‭from‬ ‭a‬ ‭certain‬ ‭intensity,‬ ‭ventilation‬ ‭decreases‬ ‭(this‬ ‭is‬ ‭the‬ ‭first‬ ‭threshold‬ ‭for‬ ‭adaptation‬ ‭of‬ ‭breathing)‬ ‭until‬ ‭to‬ ‭reach‬ ‭a‬ ‭second‬ ‭threshold‬ ‭(the‬ ‭ventilation‬ ‭mismatch‬ ‭threshold) where a new breakdown in ventilation is observed.‬ ‭ uring‬ ‭the‬ ‭first‬ ‭exercise‬ ‭period,‬ ‭ventilation‬ ‭increases‬ ‭linearly‬ ‭as‬ ‭needed.‬ D ‭Oxygenation is sufficient and reaches the muscles.‬ ‭ ut‬‭from‬‭the‬‭first‬‭dropout,‬‭we‬‭observe‬‭a‬‭first‬‭increase‬‭in‬‭acid‬‭waste‬‭in‬‭the‬ B ‭blood,‬ ‭we‬ ‭observe‬ ‭a‬‭first‬‭increase‬‭in‬‭CO2‬‭produced‬‭and‬‭from‬‭SV1‬‭we‬‭see‬ ‭that‬‭the‬‭intensity‬‭is‬‭such‬‭that‬‭there‬‭is‬‭a‬‭first‬‭observation‬‭of‬‭lactates‬‭blood‬ ‭(we‬ ‭enter‬ ‭anaerobic‬ ‭metabolism).‬ ‭At‬ ‭this‬ ‭intensity‬ ‭the‬ ‭quantity‬ ‭of‬ ‭acid‬ ‭waste‬ ‭(H+‬ ‭ions)‬ ‭is‬ ‭not‬ ‭significant‬ ‭and‬ ‭they‬ ‭are‬‭therefore‬‭buffered‬‭by‬‭the‬ ‭arrival of bicarbonates in the blood.‬ ‭ t‬‭the‬‭SV2‬‭level,‬‭the‬‭increase‬‭in‬‭acid‬‭waste‬‭and‬‭the‬‭intensity‬‭of‬‭the‬‭effort‬ A ‭is‬ ‭such‬ ‭that‬ ‭bicarbonates‬ ‭are‬ ‭no‬ ‭longer‬ ‭sufficient‬ ‭to‬ ‭buffer‬ ‭lactates‬ ‭and‬ ‭acid‬‭waste.‬‭There‬‭is‬‭therefore‬‭a‬‭strong‬‭increase‬‭in‬‭H+‬‭ions‬‭and‬‭therefore‬‭a‬ ‭drop‬ ‭in‬ ‭pH,‬ ‭which‬ ‭will‬ ‭stimulate‬ ‭the‬‭nerve‬‭centers‬‭which‬‭will‬‭lead‬‭to‬‭very‬ ‭significant hyperventilation.‬ ‭How does the tidal volume and respiratory rate change?‬ ‭ t‬ ‭rest,‬ ‭the‬ ‭ventilatory‬ ‭flow‬ ‭is‬ ‭around‬ ‭6l‬ ‭per‬ ‭minute.‬ ‭In‬ ‭fact,‬ ‭the‬ ‭tidal‬ A ‭volume‬ ‭is‬ ‭500‬ ‭ml‬ ‭and‬ ‭the‬ ‭respiratory‬ ‭frequency‬ ‭is‬ ‭around‬ ‭12‬ ‭to‬ ‭16‬ ‭respiratory cycles per minute.‬ ‭ ith‬‭exercise,‬‭the‬‭ventilatory‬‭flow‬‭will‬‭increase‬‭thanks‬‭to‬‭an‬‭increase‬‭first‬ W ‭of‬ ‭all‬ ‭in‬ ‭the‬ ‭tidal‬ ‭volume.‬ ‭This‬ ‭tidal‬ ‭volume‬ ‭impinges‬ ‭on‬‭the‬‭VRI‬‭and‬‭the‬ ‭ERV‬ ‭then,‬ ‭when‬ ‭the‬ ‭tidal‬ ‭volume‬ ‭can‬ ‭no‬ ‭longer‬ ‭increase,‬ ‭the‬ ‭respiratory‬ ‭rate‬ ‭accelerates.‬ ‭The‬ ‭second‬ ‭threshold‬ ‭(SV2)‬ ‭appears‬ ‭when‬ ‭the‬ ‭tidal‬ ‭volume‬ ‭no‬ ‭longer‬ ‭increases.‬ ‭Tidal‬ ‭volume‬ ‭increases‬ ‭only‬ ‭up‬ ‭to‬ ‭50%‬ ‭of‬ ‭vital capacity (VRI + ERV + VC).‬ ‭ raining‬ ‭is‬ ‭therefore‬ ‭an‬ ‭important‬ ‭factor‬ ‭which‬ ‭improves‬ ‭breathing‬ ‭in‬ T ‭quality‬ ‭and‬ ‭quantity.‬ ‭Training‬ ‭improves‬ ‭the‬ ‭number‬ ‭of‬ ‭functional‬ ‭alveoli.‬ ‭The‬ ‭more‬ ‭we‬ ‭train,‬ ‭the‬ ‭greater‬ ‭the‬ ‭alveolar-capillary‬ ‭exchange‬ ‭surface.‬ ‭Ventilation‬ ‭is‬ ‭then‬ ‭more‬ ‭efficient,‬ ‭more‬ ‭profitable‬ ‭and‬ ‭more‬ ‭economical.‬ ‭We are therefore pushing back the threshold of shortness of breath.‬