Effects of Bicycle Ergometer Exercise on Cerebral Blood Flow Velocity and Electroencephalogram Response in Normoxia and Hypoxia

Article information

Korean J Health Promot. 2019;19(1):59-67

Publication date (electronic) : 2019 March 31

doi : https://doi.org/10.15384/kjhp.2019.19.1.59

Seong Dae Kim ¹, Myung Wha Kim ², Il Gyu Jeong ¹

¹Department of Sports Science, Hannam University, Daejeon, Korea.

²Department of Sports Rehabilitation, Woosong University, Daejeon, Korea.

Corresponding author: Il Gyu Jeong, PhD. Department of Sports Science, Hannam University, 70 Hannam-ro, Daedeok-gu, Daejeon 34430, Korea. Tel: +82-42-629-7653, Fax: +82-42-629-8402, jig1229@hanmail.net

Received 2019 February 26; Revised 2019 March 21; Accepted 2019 March 22.

Abstract

Background

The cerebral blood flow velocity (CBFV) has been known to increase in response to acute hypoxia. However, how CBFV might respond to exercise in hypoxic conditions and be associated with electroencephalogram (EEG) remains unclear. The purpose of this study was to evaluate the effect of exercise in hypoxic conditions corresponding to altitudes of 4,000 m on CBFV and EEG.

Methods

In a randomized, double-blind, balanced crossover study, ten healthy volunteers (19.8±0.4 years) were asked to perform the incremental bicycle ergometer exercise twice in hypoxic and control (sea level) conditions with a 1-week interval, respectively. Exercise intensity was set initially at 50 W and increased by 25 W every 2 minutes to 125 W. Acute normobaric hypoxic condition was maintained for 45 minutes using low oxygen gas mixture. CBFV in the middle cerebral artery (MCA) and EEG were measured at rest 5 minutes, rest 15 minutes, immediately after exercise, and 15 minutes recovery using transcranial-Doppler sonography and EEG signal was recorded from 6 scalp sites leading to analysis of alpha and beta wave relative activities. All data were analyzed using two-way repeated-measures analysis of variance and Pearson's correlation.

Results

CBFV in the MCA in the hypoxic condition was significantly higher than that in the control condition at rest 5 minutes (83±9 vs. 69±9 cm/s, P<0.01), rest 15 minutes (87±8 vs. 67±7 cm/s, P<0.001), immediately after exercise (112±9 vs. 97±9 cm/s, P<0.01), and 15 minutes recovery (91±11 vs. 74±7 cm/s, P<0.01). However, no significant correlation was found between the changes of CBFV and EEG wave activities.

Conclusions

These results suggest that the drastic change of CBFV observed during exercise with hypoxia might appear independently with EEG wave activities.

Keywords: Exercise; Hypoxia; Cerebrovascular circulation; Electroencephalogram

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Korean Society for Health Promotion and Disease Prevention

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This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Figure 1

Experimental procedures.

Abbreviations: CBF, cerebral blood flow; EEG, electroencephalography; HR, heart rate; SaO₂, arterial oxygen saturation.

Figure 2

Correlation between changes in mean flow velocity of middle cerebral artery (MCA) and changes in Beta activity for resting 15 minutes after hypoxic exposure. P values are calculated by Pearson correlation analysis. r represents a negative correlation of changes in mean flow velocity of MCA and changes in Beta activity.

Table 1

Characteristics of participants

Values are presented as mean±standard deviation.

Table 2

Changes of cerebral blood flow velocity in the middle cerebral artery

Values are presented as mean±standard deviation.

F values are calculated by two-way repeated-measures ANOVA.

Abbreviations: EDV, maximum end-diastolic velocity; G, group; Mean, mean flow velocity; Peak, peak systolic velocity; T, time.

^aSignificantly different from rest (P<0.05).

^bSignificantly different from control group (P<0.05).

^cSignificantly different from control group (P<0.01).

^dSignificantly different from control group (P<0.001).

Table 3

Changes of electroencephalogram in the temporal lobe

Values are presented as mean±standard deviation.

F values are calculated by two-way repeated-measures ANOVA.

Abbreviations: G, group; T, time.

^aSignificantly different from rest 5 minutes (P<0.05).

Table 4

Changes of arterial oxygen saturation and heart rate

Values are presented as mean±standard deviation.

F values are calculated by two-way repeated-measures ANOVA.

Abbreviations: G, group; SaO₂, arterial oxygen saturation; T, time.

^aSignificantly different from rest (P<0.05).

^bSignificantly different from control group (P<0.05).

^cSignificantly different from control group (P<0.01).

^dSignificantly different from control group (P<0.001).