Respostas agudas de pressão arterial e variabilidade da frequência cardíaca são dependentes do volume total do exercício aeróbio em adultos saudáveis

Abstract

Postexercise hypotension (PEH) is a phenomenon of clinical relevance, but doubts persist regarding the effect of the mode and manner of execution (continuous vs. cumulative) of aerobic exercise for its manifestation, as well as the role of cardiac autonomic control as physiological mechanisms associated with PEH. Thus, this thesis aimed to: a) investigate the PEH elicited by isocaloric bouts of continuous and accumulative aerobic exercise; b) to compare the acute responses of systolic (SBP) and diastolic blood pressure (DBP) after maximal cardiopulmonary exercise tests (CPET) performed using three exercise modalities; and c) to determine the influence of exercise mode and cardiac autonomic control at rest on the vagal reactivation after CPET. In the first study, ten healthy men (age: 27.6 ± 3.5 yrs) performed maximal CPETs to determine the peak oxygen uptake (VO2peak), and continuous (400 kcal) and accumulated (2 x 200 kcal) exercise bouts of running and cycling at 75% VO2reserve. The SBP and DBP decreased similarly after continuous and accumulated exercise (4.6 ± 2.3 vs. 5.2 ± 2.3 mmHg, 2.6 ± 2.5 vs. 3.6 ± 2.5 mmHg, respectively, P > 0.05). However, running elicited greater SBP reductions than cycling (P < 0.05). The sympathetic (low frequency component, LF) and parasympathetic (high frequency component, HF) activity increased (P < 0.001) and decreased (P < 0.001) from baseline, increasing the sympathovagal balance (LF:HF ratio) (P < 0.001) that was inversely related to ΔSBP and ΔDBP (r = -0.41 to -0.70; P < 0.05). In the second and third studies, 20 healthy men (age: 21.2 ± 3.0 yrs) performed three CPETs (cycling, walking and running). The second study investigated the acute response of BP, cardiac output (Q), peripheral vascular resistance (PVR), spontaneous baroreflex sensitivity (SBR), heart rate variability (HRV) and energy expenditure during 60 min after exercise and a control session. Compared to the control, only running the exercise mode involving greater energy expenditure (P <0.001) - was able to reduce the SBP after exercise (P <0.001). Changes in SVR, BRS, LF, and LF:HF ratio were negatively correlated to variations in SBP (range -0.69 to -0.91; P < 0.001) and DBP (range -0.58 to -0.93; P &#8804; 0.002). The third study examined the parasympathetic reactivation after each CPET by the root mean square of successive R-R differences calculated for consecutive 30-s windows (rMSSD30s). Despite lower HRpeak, VO2peak and energy expenditure in cycling vs. walking and running (P < 0.001), parasympathetic reactivation was significantly faster after cycling (P < 0.05). Furthermore, ΔrMSSD30-180s was positively related to the HF (rs = 0.90 to 0.93; P < 0.001) and negatively related to the LF and LF:HF ratio (rs = -0.73 to -0.79 and -0.86 to -0.90, respectively; P < 0.001) assessed at rest. In conclusion, continuous or accumulated bouts of aerobic exercise do not affect the magnitude of PEH; but the PEH is dependent on exercise mode or the total volume of exercise. The results also indicate that the recovery pattern of HRV may have an important role in eliciting PEH.