Author(s): KOBAYASHI, M., IMAI, A., FURUKAWA, H., TOMIISHI, C., ONISHI, K., GOTO, K., Institution: RITSUMEIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 1265

INTRODUCTION:
A single bout of exercise decreases blood pressure (BP) transiently, which is called as “post-exercise hypotension (PEH)”. Repetition of PEH contributes to reducing BP chronically. A previous study revealed that endurance exercise reduced markedly systolic BP (SBP) compared to resistance exercise (Ramis et al. 2014). In addition, resistance exercise under hypoxic environment caused greater PEH compared to the same exercise under normoxic condition (Horiuchi et al. 2018). Therefore, combination of “endurance exercise” and “hypoxia” may facilitate PEH. However, PEH after endurance exercise in hypoxia has not been fully elucidated. Therefore, the aim of the present study was to compare PEH between endurance exercise in hypoxia and the same exercise in normoxia.
METHODS:
Eighteen young men (22 ± 2 years) conducted three trials on different days with a randomized order of trial: (1) pedaling exercise in hypoxia (FiO2: 14.5%; HYP), (2) pedaling exercise in normoxia (FiO2: 20.9%; NOR), and (3) rest in normoxia (REST). Exercise trials (HYP and NOR) consisted of 60 min of pedaling exercise at 55% of maximal oxygen uptake in normoxia. During each trial, heart rate (HR), rating of perceived exertion, and arterial oxygen saturation (SpO2) were determined. Following each intervention (60 min of exercise or rest), BP and cardiac output (CO), stroke volume (SV), total peripheral vascular resistance (TPR) were measured every 15min for 3h. Also, HR variability (HRV) was continuously monitored for 3h.
RESULTS:
During exercise, HR was significantly higher in HYP compared to NOR and REST (p<0.001). SpO2 was significantly lower in HYP (82.7 ± 3.6%) than in NOR (95.7 ± 1.7%) and REST (97.3 ± 0.5%, p<0.001). During 3 h of post-exercise period, reduction of mean arterial pressure (ΔMAP) was significantly profound in HYP (-4.2 ± 4.8mmHg) and NOR (-3.2 ± 3.2mmHg) compared to REST (1.3 ± 2.7mmHg, p<0.05). Moreover, the duration of PEH was longer in HYP than NOR. However, average ΔMAP did not differ significantly between HYP and NOR (p>0.05). During post-exercise period (NOR, HYP), CO increased until 30 min whereas SV and TPR decreased between 15-165 min after the exercise with no significant difference between the trials (p>0.05). Also, time-domain HRV parameters (i.e., SDNN, RMSSD, NN50, pNN50) returned to baseline levels within approximately 2 h with no significant difference between NOR and HYP.
CONCLUSION:
Although both HYP and NOR significantly reduced MAP compared to REST, the magnitude of PEH (ΔMAP) did not differ significantly between NOR and HYP. Furthermore, CO was transiently elevated during post-exercise, but the reductions of SV, TPR, and HRV parameters lasted over 2 h. These findings suggest that endurance exercise causes PEH regardless of oxygen concentration during the exercise.