Active Voice: Voice: What Type of Exercise Training Most Improves Artery Health in Older Adults?
By Myles W. O達rien, M.Sc., and Derek S. Kimmerly, Ph.D.

Myles W. O達rien Derek S. Kimmerly
It is well-established that engaging in regular aerobic exercise training helps to prevent age-related declines in arterial health. Part of this protection relates to an improvement in the ability of the artery inner lining (i.e., endothelium) to produce and release chemicals that cause them to relax and get bigger. This training-induced response in the brachial artery is highly predictive of better heart artery health. Our current understanding of arterial health has primarily been limited to arteries in the upper body (e.g., brachial artery). How the endothelium in lower body arteries (e.g., popliteal) respond to aerobic exercise training in older adults is less clear. Compared to the brachial artery, the popliteal artery is more likely to develop plaque with aging. It also directly experiences increases and decreases in blood flow in response to physical activity and sedentary behaviors, respectively. There has been renewed interest in examining how well the endothelium responds to decreases in blood flow, which causes the artery to get smaller. This is also a healthy response that we have shown to be enhanced in the brachial and popliteal arteries of older adults with higher cardiorespiratory fitness. High-intensity interval training (HIIT) is a popular, effective and time-efficient way to improve cardiorespiratory fitness and many aspects of health. However, whether HIIT improves these aspects of arterial health more than traditional types of training has yet to be studied.

In our study, published in the May 2020 issue of Medicine & Science in Sports & Exercise®, we examined whether six weeks of HIIT would increase brachial and popliteal artery endothelial-dependent dilation and constriction responses more than moderate-intensity continuous training or whole-body resistance training in healthy older adults (mean age: 67 years). Arterial responses to induced increases (dilation) and decreases (constriction) in blood flow were conducted using high-resolution ultrasound. Changes in cardiorespiratory fitness were assessed by measuring peak oxygen consumption during a cardiopulmonary exercise test. All training programs increased cardiorespiratory fitness. Popliteal and brachial artery dilation, as well as popliteal constriction responses, were similarly improved following both types of aerobic training. However, only HIIT increased resting brachial artery blood flow and constriction response. Resistance training did not enhance any of these measures of brachial or popliteal health.

A key takeaway from this study was that HIIT and moderate-intensity continuous training, but not whole-body resistance training, increased the ability of arteries to relax in response to an increase in blood flow. However, only HIIT enhanced resting blood flow in the brachial artery. Furthermore, exercise training-induced improvements in endothelial function differed between upper arm versus leg arteries. Altogether, engaging in HIIT resulted in the greatest improvements in artery health versus moderate-intensity aerobic training or resistance training. However, moderate-intensity training also improved cardiorespiratory fitness in older adults. Our findings highlight the impact that exercise training has on lower-limb arteries, which are more susceptible to plaque development. We encourage the assessment of leg arterial health in future studies in populations with, or at-risk for, cardiovascular disease. It is our hope that these findings may help inform the design of rehabilitation and active aging programs.

About the authors:
Myles W. O達rien, M.Sc., is a Ph.D. candidate in the health program at Dalhousie University in Halifax, Nova Scotia in Canada. He is a clinical exercise physiologist. Mr. O達rien痴 research seeks to examine the influence of physical activity, sedentary behaviors and cardiorespiratory fitness on vascular endothelial function in older adults. Connect with Mr. O達rien at myles.obrien@dal.ca.

Derek S. Kimmerly, Ph.D., is an associate professor in the Division of Kinesiology at Dalhousie University in Halifax. He also serves as the director of the Autonomic Cardiovascular Control of Exercise Laboratory, which conducts research focusing on the impact that gender, aging and/or aerobic fitness have on heart and blood vessel health. Connect with Dr. Kimmerly at dskimmerly@dal.ca.

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