Featured Research

from universities, journals, and other organizations

Finding May Explain Biggest Cause Of Post-exercise Fainting

Date:
October 13, 2006
Source:
University of Oregon
Summary:
Overactivation of two receptors for histamine, normally associated with common allergies and acid reflux, may explain why some people, including highly trained athletes, pass out soon after heightened physical activities, according to researchers at the University of Oregon.

Overactivation of two receptors for histamine, normally associated with common allergies and acid reflux, may explain why some people, including highly trained athletes, pass out soon after heightened physical activities, according to researchers at the University of Oregon.

A series of studies led researchers in incremental steps to the discovery that the use of two commonly used antihistamines (fexofenadine and ranitidine) prior to exercise dramatically lower or completely eliminate low blood pressure following exertion. The drugs worked by preventing post-exercise hyperemia, an increased flow of blood, in the skeletal muscle during the critical 90-minute recovery period after exercise. In all, the pre-exercise consumption of the two antihistamines reduced the blood flow that occurs during recovery by 80 percent.

The study, funded by the American Heart Association, was posted online ahead of regular publication in the Journal of Applied Physiology. While fainting after exercise, a condition called syncope, can indicate a serious heart disorder, most cases are linked to low blood pressure and low blood flow to the brain.

"There is reason to believe that histamine is the primary vasodilator contributing to post-exercise hypotension, but we cannot say for certain," cautioned principal investigator John R. Halliwill, a professor of human physiology. "Some people have problems regulating blood pressure during and after exercise. Trained athletes have had fainting bouts at the end of exercise. It may be that these result from a natural overactivation of these two receptors for histamine."

The histamine receptors involved are known as H1 and H2. Fexofenadine, which is the generic name for Allegra, works against H1, reducing the occurrence of such allergy symptoms as sneezing and runny nose. Ranitidine, or Zantac, acts against H2 in the treatment of acid reflux.

For the study, 28 sedentary and endurance-trained men and women were monitored closely throughout a session that covered a pre-exercise period, a 60-minute ride on a cycling machine and a 90-minute recovery period. The participants were all non-smokers without blood pressure problems and between the ages of 19 and 34. The group given the histamine blockers consumed them with water 60 minutes before beginning the exercise regimen.

The studies in Halliwill's Exercise and Environmental Physiology Laboratories were designed to pursue the mechanisms involved in the exercise recovery period. The findings that the two antihistamine products worked as they did do not mean that athletes or sedentary-turned-active people should head to their medicine cabinets before exercising.

The amount of fexofenadine used in the study was almost three times the strongest dose used for respiratory allergies, while the dosage for ranitidine matched the common starting dose for battling heartburn. Also, there may be a benefit to the normal activation of these receptors during physical activity, because routine exercise helps to reduce or prevent the development of hypertension, or high blood pressure. "Activating these receptors might be an important part of the health benefits of daily exercise," Halliwill said.

The two drugs, however, did not appear to affect the central nervous system or cause sedation during the exercise experiments, Halliwill and co-author Jennifer L. McCord, a doctoral student, noted in the study.

The big question now, Halliwill said, is what triggers the histamine responses during exercise.

"The body tends to be very good at recycling mechanisms," he said. "The body may be using these same receptors for other things. A bout of exercise appears to turn on a program for remodeling blood vessels in the body, and these receptors may be an important part of that program."


Story Source:

The above story is based on materials provided by University of Oregon. Note: Materials may be edited for content and length.


Cite This Page:

University of Oregon. "Finding May Explain Biggest Cause Of Post-exercise Fainting." ScienceDaily. ScienceDaily, 13 October 2006. <www.sciencedaily.com/releases/2006/10/061012185827.htm>.
University of Oregon. (2006, October 13). Finding May Explain Biggest Cause Of Post-exercise Fainting. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2006/10/061012185827.htm
University of Oregon. "Finding May Explain Biggest Cause Of Post-exercise Fainting." ScienceDaily. www.sciencedaily.com/releases/2006/10/061012185827.htm (accessed July 28, 2014).

Share This




More Health & Medicine News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

$15B Deal on Vets' Health Care Reached

$15B Deal on Vets' Health Care Reached

AP (July 28, 2014) A bipartisan deal to improve veterans health care would authorize at least $15 billion in emergency spending to fix a veterans program scandalized by long patient wait times and falsified records. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
West Africa Gripped by Deadly Ebola Outbreak

West Africa Gripped by Deadly Ebola Outbreak

AFP (July 28, 2014) The worst-ever outbreak of the deadly Ebola epidemic grips west Africa, killing hundreds. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins