Heart-Rate Activity Tracker Helps Gauge Healthy Exercise Level

August 28, 2016

ROME, ITALY — A new device that measures changes in heart rate during exercise could be a more scientific way than current methods of gauging how much physical activity individuals need to do to cut their risks of cardiovascular disease (CVD), a new study suggests[1].

Presenting the data at the European Society of Cardiology (ESC) 2016 Congress, Dr Javaid Nauman (Norwegian University of Science and Technology, Trondheim) said: "We need to know how much physical activity we need to engage in to stay healthy, but so far there hasn't been a simple formula for this. We investigated whether changes in heart rate could be used as a guide to how the body responds to physical activity. We wanted to see whether we could make a meaningful formula to translate changes in heart rate into a guide to how much physical activity we need to do. "

The researchers formulated an algorithm based on gender, age, and the difference between maximum heart rate during exercise and resting heat rate (heart rate reserve), in a group of 5000 healthy people and developed a physical-activity index (PAI) score. PAI scores can range from zero to infinity, with higher scores signifying higher levels of activity.

They then applied the PAI scores to 39,298 healthy Norwegian men and women who had been followed for 28 years as part of the Hunt epidemiological study. They found that people who had PAI scores over 100 (during 1 week) had a lower risk of cardiovascular death. "We found that an individual with a PAI score of 100 lived an average of 5 years longer than someone with a PAI score of 30," Nauman said.

Dr Javaid Nauman

He explained that PAI translates heart-rate data from any physical activity and personal information (age, gender, resting and maximum heart rate) into one simple score. "The goal is to keep your PAI score above 100 over a 7-day rolling window to protect yourself from premature death related to heart disease."

Nauman said the PAI scores could be particularly attractive for unfit individuals as they generate PAI quite easily. "So this is very rewarding for people who don't do much exercise to start with.

"You can generate PAI by doing simple things like walking, playing with your grandchildren. The more activity you do, the higher your PAI score will be," he explained.

While each person will have different PAI scores for any set exercise, as each individual's heart-rate change during exercise is different, a typical unfit individual could generate about 40 PAI by walking for 150 minutes. But a 40-minute vigorous run could generate 100 PAI, he suggested.

He added "PAI is for everyone, young and old, fit and unfit, and it's an easy-to-understand number. Regardless of the physical activity, every time you raise your heart rate, you contribute to your PAI score, which can be calculated with the PAI app. The more elevated your heart rate is during exercise, the more quickly you accumulate PAI points, but you can also work out at lower intensities for longer durations to earn PAI. Our research shows that keeping your PAI score at 100 or above could prevent premature death."

Commenting for heartwire from Medscape, Dr Joep Perk (Linnaeus University, Sweden) said: "This seems to be useful tool, particularly in more unfit individuals as they can achieve 100 PAI weekly with relatively modest levels of activity. As people become more fit they have to work harder to get the same PAI scores. This could be a valuable tool to get people off the couch and onto their feet." But Perk wondered whether an increase in heart rate due to stress may affect the results and give a false impression that enough physical activity had been done.

Another outside commentator, Dr Pedro Marques-Vidal (Lausanne University Hospital, Switzerland), was also enthusiastic about the study. "This is something that can make people understand that even a little bit of physical activity regularly can be beneficial. This might help convince people who are not willing to go to the gym that they can still make meaningful changes."

He noted that devices that record an individual's physical-activity levels are becoming very popular and that in Switzerland insurance companies have even started discounting premiums if an individual submits data from such devices showing good levels of activity. "So far they are based on the 10,000-steps model, but this is a similar idea," he said.

For the analysis, participants in the Hunt study were divided into four groups according to their PAI score (0, 1–50, 51–99, >100). A score of 0 was considered inactive and used as the reference group for comparison. After a median follow-up of 28.7 years, there were 10,062 deaths, including 3867 deaths from CVD.

Results showed that men with a PAI level >100 had 17% reduced risk of CVD mortality compared with the inactive group, and women with a score over 100 had a 23% reduced risk, after adjustment for multiple confounders. The corresponding risk reduction for all-cause mortality was 13% and 17% for men and women, respectively. PAI level >100 was associated with similar reductions in all-cause and CVD mortality, regardless of age and risk factors such as smoking, hypertension, or overweight or obesity.

The reductions in risk of all-cause and CVD mortality compared with the inactive group were dose dependent by PAI score, with those achieving the recommended level of >100 PAI having the highest reductions in risk.

A watchlike device that calculates PAI scores has been developed by Mio Global and has recently reached the market.

The study was sponsored by grants from the KG Jebsen Foundation and the liaison committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology. Nauman reports no relevant financial relationships.

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