See How They Do — and Don't — Measure Up
Over the past several years, fitness trackers have grown in popularity and
sophistication. If one of your New Year’s resolutions is 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
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
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
“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
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
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
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
“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