| Grant number: | 23/07135-0 |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |
| Start date: | November 01, 2023 |
| Status: | Discontinued |
| Field of knowledge: | Biological Sciences - Physiology - Physiology of Effort |
| Principal Investigator: | Bruno Moreira Silva |
| Grantee: | Felipe Silva Gomes |
| Host Institution: | Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil |
| Associated scholarship(s): | 24/15796-0 - Cerebral blood flow regulation by the muscle metaboreflex during hypocapnic exercise in healthy humans, BE.EP.DD |
Abstract Pulmonary ventilation increases during exercise as the metabolic demand imposed by muscle contractions increases, allowing maintenance of arterial gas homeostasis at moderate (i.e., below the lactate threshold) and heavy (i.e., between the lactate threshold and critical power) exercise intensities. Several humoral and neural mechanisms are capable of regulating pulmonary ventilation. However, in isolation, none of the known mechanisms can explain the enormous increase in pulmonary ventilation observed during exercise in healthy humans ( = 15 to 20 times the resting values). Even more importantly, the sum of the isolated effects of these mechanisms does not explain the exercise hyperpnoea. Therefore, it has been hypothesized that the involved mechanisms interact synergistically. In this sense, this project aims to investigate the interaction between efferent signals triggered in brain areas involved in skeletal muscles' motor control (i.e., central command) which also influences the ventilation control and afferent signals originating in skeletal striated muscles by the accumulation of metabolites related to muscle contractions (i.e., muscle metaboreflex). For the first study, healthy adults will perform active or involuntary muscle contractions to activate the central command and the muscle metaboreflex in separation or combination. All protocols will be conducted under isocapnia. We expect that central command and muscle metaboreflex co-activation will generate a ventilatory response superior to the sum of separated central command and muscle metaboreflex responses, thus supporting a synergistic interaction between the mechanisms addressed for the control of ventilation during exercise. Such a result would be similar to the synergistic interaction already reported between other mechanisms that participate in the control of ventilation in humans, which would therefore strengthen the theoretical model proposing that the precise adjustment of ventilation during exercise depends on synergistic, and possibly redundant, interactions between multiple neural and humoral mechanisms. For the second study, healthy young adults will perform handgrip exercise with the non-dominant hand, succeeded by post-exercise circulatory occlusion of that same arm, to trap metabolites produced during the handgrip, which will maintain the activation of the muscle metaborreflex. The handgrip exercise will be done at 4 different intensities, so that there will be 4 intensities of muscle metaborreflex. After 1 min post circulatory occlusion of the non-dominant arm, an incremental handgrip exercise with the dominant hand will be started, until exhaustion. The incremental exercise will have 4 intensity stages, each lasting 1 min. During the protocols, lung ventilation (pneumotachograph) and respiratory gas exchange (O2 and CO2 sensors), contraction force (dynamometers), muscle electrical activity (surface electromyography), muscle oxygenation (near-infrared spectroscopy), and sensations related to breathing and exercise (Borg scale) will be measured. The additional effect of metaborreflex activation on ventilation during incremental handgrip exercise is expected to emerge at higher intensities only. The slope of the ventilatory response will be expected to be greater at higher metabolic stress intensities compared to mild metabolic stresses. This finding would support the relevance of the magnitude of a given stimulus for eliciting a ventilatory response and thus the recently proposed sigmoid theoretical model of ventilation regulation during exercise. (AU) | |
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