Do Fitness Trackers Really Work? See How They Do — and Don’t — Measure Up

By Beth Israel Deaconess Medical Center Correspondent

Over the past several years, fitness trackers have grown in popularity and sophistication. If one of your New Year’s resolutions was to step up your exercise regimen, you might be considering adding one of these wearable devices to your wardrobe.

A number of recent studies have looked at the benefits and limitations of fitness trackers. Here’s a summary of the findings and tips on how to get the most from your device.

How Fitness Trackers Work

Fitness trackers, also known as activity trackers, burst on the scene several years ago. These devices, typically worn around the wrist, keep track of a number of key movements. Like a pedometer, they measure the number of footsteps a person takes, and many of today’s devices also record distance traveled and specific type of movement (walk or run, for example.)

In addition, through sophisticated sensors contained in many new versions of activity trackers, the devices can monitor a user’s heart rate, blood pressure and blood oxygen levels, and count calories and record sleep. Data from the trackers can often be transferred to a smartphone or computer to help users record and monitor their fitness progress.

A Motivating Factor

As their name implies, fitness trackers have proven successful at helping users stay on top of their exercise goals and routines.

A study in the Journal of the American Medical Association (JAMA) in 2015 found that fitness trackers were more successful than standard pedometers in helping exercisers stay motivated.

“By helping you monitor your activity patterns, these devices may encourage regular exercise,” reports JAMA Cardiology.

Nurse Practitioner Lorraine Britting, MS, NP-C, SFHM, Clinical Director of Advanced Practice in Cardiology Medicine in the CardioVascular Institute at Beth Israel Deaconess Medical Center, works with patients who have heart disease or have undergone a cardiac procedure such as a cardiac catheterization or device implantation.

“When I talk to patients about risk factor modification, one thing I ask them is how much exercise they’re getting,” says Britting. “Some people say they exercise regularly but most people say they don’t get any exercise at all.”

For the latter individuals, she recommends activity trackers.

“Patients who have had a heart attack or undergone a procedure can’t undertake any strenuous physical activity right away,” explains Britting. “But, generally, within a week or so, these patients can start walking. Using a fitness tracker to monitor their progress gives patients concrete information and can empower them to start making changes to help improve their heart health.”

Britting suggests her patients exercise 30 minutes and walk 10,000 steps — the equivalent of five miles — every day. This also meets the guideline from the Centers for Disease Control and Prevention that adults should get at least 150 minutes of moderate exercise per week.

Britting also finds the calorie-counting feature of fitness trackers to be helpful.

“Many people have no idea how much they’re eating and totally underestimate how many calories they’re taking in,” Britting says. “You can actually track how many calories your expending and how many calories you eat, and then ask yourself if you have enough calories left for that dessert.”

Taking her own advice, Britting herself has worn a fitness tracker for the past two years.

“I find myself consciously thinking about how to get in 10,000 steps each day,” she notes. “I almost always take the stairs and take the long way to or from work if I need to increase steps. I also enjoy other aerobic activities including biking and hiking — and that activity is tracked as well.”

A Tool for Weight Loss?

Like Britting, Jean Beach, a pharmacy supervisor at BIDMC, has worn a fitness tracker for the past several years.

“I have a sedentary job, so for me to reach 10,000 steps in a day, I need to plan,” says Beach. “I take a shuttle bus to work in the morning and always get off three stops early. And at the end of the day, instead of taking the shuttle bus, I take the green line to Arlington Street and I walk to South Station. It’s an enjoyable walk and a chance to get the rest of my steps in.”

Since Beach began her walking routine, aided by the fitness tracker, she has lost 20 pounds.

“I have also been a runner, but found that walking was more effective in helping me lose weight,” says Beach.

However, as recent research reminds us, wearing an activity tracker does not in itself lead to weight loss. A large study in JAMA compared weight loss between two groups of overweight adults — one of which wore fitness trackers, while the other logged their daily exercise sessions on a website. The results showed that the participants wearing the devices lost an average of five pounds less than those who did not wear the devices.

The reason for this difference is not immediately clear, say the study’s authors, but they speculate that one possible reason might be because participants focused on the technology and forgot to focus on their behaviors.

Fitness Trackers and Heart Health

Heart rate reflects the amount of blood being pumped by the heart to supply the body’s oxygen needs. Measurements are generally categorized as resting heart rate — the lowest amount of blood being pumped — and maximum heart rate, which indicates that the heart is working its hardest to meet the body’s oxygen needs, as is the case during exercise.

Many of the fitness trackers on the market today measure heart rate. But a new study looking at four popular fitness trackers found that there was significant variability in the measurements of heart rate among the different devices — and that none were as accurate as a chest strap monitor.

The researchers compared the trackers’ heart rate measurements with measurements taken with standard electrocardiographic (ECG) electrodes by way of a chest strap monitor. (Chest strap monitors are used in doctors’ offices and often used by elite runners to accurately track heart rate. Fitness trackers assess heart rate through optical sensors to detect the blood moving through the veins.)

All of the study participants were assessed at rest, and then again while walking or running on a treadmill at various speeds. In the final analysis, none of the trackers proved as accurate as the ECG in recording heart rate.

For cardiac patients who need to stay within physician-recommended heart-rate thresholds during rehabilitation and exercise, a chest strap monitor may be preferable, according to the study. But, says Britting, for many patients, the need to have specific heart rate information is less critical than the need to add exercise to their routines.

“You put can put a fitness tracker on in the morning and forget about it, and at the end of the day, you can figure out how many steps you took,” says Britting. “Being more active and changing habits is important, but it can be hard to do. Wearing an activity tracker can be a helpful motivator.”

Beach also discovered an unexpected health benefit from regularly using her fitness tracker.

“I love to take pictures,” says Beach. “During my walks, I always find something to take a picture of and I post it as my walk picture of the day. It helps take the stress out of the day.”

Above content provided by the CardioVascular Institute at Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.
Posted February 2017

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