| Grant number: | 15/15466-0 |
| Support type: | Scholarships abroad - Research Internship - Doctorate |
| Effective date (Start): | January 15, 2016 |
| Effective date (End): | July 14, 2016 |
| Field of knowledge: | Health Sciences - Physical Education |
| Principal Investigator: | Cláudia Lúcia de Moraes Forjaz |
| Grantee: | Tiago Peçanha de Oliveira |
| Supervisor abroad: | David Andrew Low |
| Home Institution: | Escola de Educação Física e Esporte (EEFE). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
| Local de pesquisa : | Liverpool John Moores University (LJMU), England |
| Associated to the scholarship: | 13/05519-4 - Heart rate recovery after exercise: regulatory mechanisms in normotensives and hypertensives, BP.DR |
Abstract Post-exercise heart rate recovery (HRR) is a practical tool for the assessment of cardiac autonomic recovery after exercise. Accordingly, HRR in the first minute after exercise is mainly determined by parasympathetic reactivation, while HRR after this period is determined by a sum of parasympathetic reactivation and sympathetic withdrawal. In addition of being an index of autonomic function, HRR has also proved to be sensitive to cardiovascular morbidity and mortality, a fact that highlights the clinical importance of this variable as a prognostic tool. Several studies have investigated the mechanisms that regulate HRR, and thermoregulation has been suggested as a promising one. Data of my current PhD project indicates that a post-exercise cooling using a fan is able to accelerate HRR after aerobic exercise. Unexpectedly, however, despite of improving HRR, the cooling protocol did not decrease the internal temperature, which raises the question if HRR is under control of other aspects of thermoregulation instead of internal temperature, such as skin temperature and blood flow. Thus, the aim of the current project is to assess the influence of exercise-induced thermoregulatory responses on HRR. For this purpose, 12 healthy men will perform two sessions (random order) of 10 min of sub-maximal exercise on a cycle ergometer followed by recovery in seated position. In one session, the subjects will perform the exercise in a normothermic state, while in the second, they will perform the exercise after being submitted to a whole-body heat stress protocol (water-perfused tube-lined suit) aiming to increase their internal temperature in 1°C. From the heart rate (HR) collected during the whole protocol, HRR will be assessed using the following indexes: a) HRR30s, HRR60s and HRR300s - i.e. absolute HR reduction after 30, 60 and 300s of exercise in relation to peak HR of the exercise; b) T30 - i.e. the negative reciprocal of the slope of the regression line between the natural logarithm of HR of the first 30s after exercise and the time; c) HRRt - i.e. time constant of the first order exponential fitting of the HRR curve of the five min after exercise. Additionally, post-exercise HR variability will be assessed in segments of 30s during the whole recovery period through the calculation of the root mean square residual (RMS) and the root mean square of successive differences between adjacent RR intervals (rMSSD). Apart from the HR measurements, finger blood pressure, intenal and skin temperatures, and skin blood flow and conductance will be continuously measured throughout the experimental protocol. Data will be expressed as mean ± standard deviation. HRR and other variables will be compared between exercise bouts using paired Student's t test or repeated measure ANOVA (p < 0.05). The associations between HRR and thermoregulatory indices will be tested using single and multiple regression analysis. | |