Two studies at the McMaster University Department of Kinesiology Exercise and Metabolism Research Group sought to confirm earlier findings related to risk factors for cardiovascular disease (CVD), as well as to uncover some of the underlying mechanisms. Both studies used similar methodology and isometric handgrip (IHG) exercise three times a week for eight weeks at 30% of maximal voluntary contraction.
IHG's effect on carotid distensibility
Adrienne Visocchi led a group studying whether arterial distensibility (AD, or the ability of arteries to stretch) contributed to the reduction in resting blood pressure (RBP). They compared the impact of isometric arm and leg exercise on RBP as well as central (carotid) and peripheral (arm and leg arteries) AD in persons who were already taking medication for hypertension, or high blood pressure. Her group consisted of Cheri L.M. McGowan, Martha Faulkner, Robin Verduyn, Neil McCartney and Maureen J. MacDonald.
Results indicated that following IHG exercise systolic blood pressure decreased significantly, while carotid AD improved significantly. IHG didn't affect either diastolic BP or peripheral AD. The study also tested isometric leg press exercise, but it had no effect on any of the parameters being studied.
IHG's effect on endothelial function
Hypertension is associated with endothelial dysfunction and development of cardiovascular disease, noted Cheri L.M. McGowan, who led the other McMaster study. Her group studied endothelial function after IGH to see if it played a role in the reduction of blood pressure in people taking anti-hypertensive medication. Other group members included Adrienne Viscocchi, Martha Faulkner, Mark Rakobowchuk, Neil McCartney and Maureen J. MacDonald. Both McMaster studies were undertaken in Dr. MacDonald's laboratory.
Prior to beginning the exercise regimen, vascular reactivity, which is a measure of an artery's ability to dilate in response to an increase in blood flow, was measured in both arms using a technique called flow-mediated dilation (FMD). This technique involves stopping blood flow to the forearm for 5 minutes then measuring the artery's internal diameter with ultrasound after blood flow is reintroduced. After training, systolic blood pressure decreased significantly, while FMD increased (both relative and normalized to average shear rate). Average resting diameter and resting flow remained unchanged.
The researchers also noted that following training there was a reduced reactive hyperemic flow (blood flow after cuff deflation). Although the amount of blood flowing through the artery was less than before training, the artery still dilated more. This suggests a heightened vasoactive sensitivity to the reactive hyperemic stimulus. These findings suggest that the reduction of blood pressure with IHG may be due to improvements of endothelial function.
The Austin exercise meeting is cosponsored by APS, the American College of Sports Medicine and the Canadian Society for Exercise Physiology. Additional support through unrestricted educational grants came from: the National Aeronautics and Space Administration (NASA), the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMSD), Gatorade Sports Sciences Institute, Pfizer Inc. and the U.S. Army Research Institute of Environmental Medicine (USARIEM).
Editors note: Participants from both studies are speaking at the American Physiological Society's 2004 Intersociety Meeting, "The Integrative Biology of Exercise," Oct. 6-9 in Austin. Information about the meeting can be found at (http://www.the-aps.org/meetings/aps/austin/). A detailed program, including abstracts, for the entire meeting is available upon request to members of the media.
Arrangements for on-site interviews, or telephone interviews during the meeting can be arranged through APS from Mayer Resnick (cell: 301-332-4402, mresnick@the-aps.org) or Stacy Brooks 301-634-7253 (sbrooks@the-aps.org). From Oct. 6 (2 p.m.) – Oct. 9, the onsite phone number in Austin is 512-482-8000, room 602, or 512-682-2950 direct.
The American Physiological Society was founded in 1887 to foster basic and applied bioscience. The Bethesda, Maryland-based society has more than 10,000 members and publishes 14 peer-reviewed journals containing almost 4,000 articles annually.
APS provides a wide range of research, educational and career support and programming to further the contributions of physiology to understanding the mechanisms of diseased and healthy states. In May, APS received the Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring (PAESMEM).