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Study examines safest time to exercise

04/02/2019

Eleanor Roberts and her father, Glyn RobertsVancouver, BC – Kinesiologist Eleanor Roberts is constantly moving. She teaches soccer and yoga and cycles to work. Admittedly, she is an unlikely candidate for a heart attack. Yet, Eleanor is part of a study linking the heart and exercise. "This is an opportunity to manage something I cannot see," says Eleanor.

Researchers from Vancouver Coastal Health (VCH), UBC, and SportsCardiologyBC are in the final phase of recruiting for a study that will follow 126 recreational and competitive athletes for 10 years. The Time of Day Study will determine the safest time of day to exercise based on the presence of arrhythmia—or irregular heartbeats—during exercise.

"There is no disputing the tremendous benefits of exercise," says Dr. James McKinney, the study's lead author and cardiologist. "But we want to find out if there is a time of day when moderate to vigorous exercise is safest, from a cardiac standpoint."

The biological process responsible for our physical, mental and behavioral changes in a 24-hour period is known as circadian rhythm. External factors like sunlight and temperature affect our circadian rhythms. Research suggests that sudden cardiac death may also be linked to circadian rhythm. A study of more than 2,000 people in Massachusetts who died of sudden cardiac arrest found the patients' circadian rhythms were more varied in the morning.

"There is a body of research that shows a higher rate of sudden cardiac death in the general population in the early morning," says Dr. Saul Isserow, cardiologist and founder of SportsCardiologyBC. "We want to find out in our study whether the circadian rhythms of healthy people who exercise at moderate to high intensity at certain times of the day have any influence on myocardial infarction (heart attack) and sudden cardiac death. In a nutshell, we're looking at whether the risk of a cardiac event—albeit already very low because the people in the study exercise—is greater in the morning or the evening."

The Time of Day Study is open to competitive and recreational athletes over the age of 18 who engage in four hours of endurance exercise per week and are able to reach a target heart rate of 60 to 70 percent. Participants fill out a questionnaire and undergo an electrocardiogram (ECG) and stress test. The participants are then outfitted with a Holter monitor to record their heartbeats for 24 hours. They exercise with the Holter monitor in the morning and the evening, so the results can be compared. They will be retested after the first year, then again in five and 10 years.

"Being part of this study gives me a sense of comfort," says Eleanor. "I would probably never undergo cardiac screening, so I see this as an opportunity to evaluate myself as an athlete and get a head start on my heart health."

SportsCardiologyBC is a nonprofit-organization dedicated to making sports safer for athletes through research and education. The SportCardiologyBC clinic at UBC Hospital plays a leading role in sports cardiology research.

"VGH & UBC Hospital Foundation is a proud long-term partner of SportsCardiologyBC and Dr. Saul Isserow, having provided over $4.4 million in philanthropic support over the last five years," says Barbara Grantham, President & CEO of VGH & UBC Hospital Foundation.

Vancouver Coastal Health is responsible for the delivery of $3.3 billion in community, hospital and residential care to more than one million people in communities including Richmond, Vancouver, the North Shore, Sunshine Coast, Sea to Sky corridor, Powell River, Bella Bella and Bella Coola. VCH also provides specialized care and services for people throughout BC, and is the province's hub of health care education and research. 

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