Time course of neuromuscular fatigue after exercise in the heat: are heart rate variability and blood markers sensitive?

• Grant number: 22/01173-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2022
• End date: February 28, 2023
• Field of knowledge: Biological Sciences - Physiology - Physiology of Effort
• Principal Investigator: Alessandro Moura Zagatto
• Grantee: João Pedro Fialho Lopes
• Host Institution: Faculdade de Ciências (FC). Universidade Estadual Paulista (UNESP). Campus de Bauru. Bauru , SP, Brazil

Abstract

Fatigue can be defined as a temporary decline in the ability to voluntarily produce force and power at levels adequate for task maintenance (GANDEVIA, 2001). A detriment in the function of the neuromuscular system is one of the possible components of fatigue, which can affect peripheral mechanisms and the central nervous system. This mechanism is measured by the decrease in force signals and electromyographic signal amplitude during a maximum voluntary contraction (MVC) and the percentage of voluntary activation (VA) respectively. Physical exertion under conditions of hyperthermia may be capable of imposing great stresses on the cardiovascular system, due to changes in physiological and metabolic factors (HARGREAVES, 2008). With this, the main objective of this project is to verify the impact of exercise in the heat, on indicators of global, central, and peripheral neuromuscular function, and on markers of damage to heart rate variability (HRV) and blood immediately, 24h, 48h, and 72h after exercise. For this purpose, ten healthy men will be recruited, who will make nine visits to perform the experiments in a controlled environment, performed on separate days to carry out a crossover study, in which the participants will perform a running effort, on a treadmill, until exhaustion, in a thermally insulated room, keeping the temperature at (43ºC) or in neutral temperature conditions (24ºC), separated by one week, at an intensity of 100% of the respiratory compensation point (RCP). For the strength data, the participants will perform two MVCs, to extend the dominant leg, separated by 1 minute, under the two environmental conditions, after the effort, as well as the blood collection, while the HRV will be measured during rest before any effort.(AU)