Fitbit, Apple Watch, and other wearable fitness trackers are increasingly popular worldwide. As medical practitioners, we of course want to encourage more physical activity in our patients. Do fitness trackers have a place in the clinical setting? Read on to learn more about the relationship between physical activity and health and to discover if fitness trackers are effective at getting patients moving.
The Origin of the Link between Physical Activity and Health
Jeremy Morris was the pioneer researcher who examined the relationship between physical activity and health in the 1950s and 1960s. In 1953, he published an article that classified thousands of men’s occupations into heavy, intermediate, and light, based on physical intensity. Mortality from coronary heart disease in heavy workers was less than half that of light workers, hinting that physical activity was heart-protective. (1, 2)
The following year, he published the London Transport study, in which he showed that conductors, who spent time walking to collect tickets from passengers on double-decker buses, were less likely to develop cardiovascular disease than drivers, who spent the majority of their days sitting. (3)
In a later study, Morris looked at the self-reported leisure time activities of 17,000 men. In line with his previous findings, the men who reported being more active had fewer electrocardiographic abnormalities. (4) With Morris’s research as a springboard, an association between staying active and staying healthy emerged.
The Benefits of Being Active
Research since Morris’s day has only strengthened the notion that physical activity is good for health. Today, we know that staying active is correlated with reduced risk of cardiovascular disease and lower all-cause mortality. (5) However, in our modern era of desk jobs and constant electronic entertainment, people spend approximately 4.2 hours per day sitting at work and 2.9 hours per day of leisure time sitting. (6) Although it is only one contributing factor to modern-day diseases, time spent sedentary is associated with metabolic risk factors. (7, 8)
10,000 Steps as a Cut-Off for Health Benefits
The idea of walking 10,000 steps each day for overall well-being is traceable to the 1960s in Japan. Does it have any merit?
Steps per day in several observational studies was predictive of BMI and/or body fat. (9, 10, 11) Not coincidentally, higher step count is correlated with fewer cardiometabolic risk factors, especially in men, with the “cut-off” for major benefits estimated at 8,000 or 10,000 steps per day. (10, 12)
Inflammation, which is at the root of most modern diseases, is also inversely correlated with step count. The expression of many inflammatory markers, including TNF-alpha, IL-15, plasma C-reactive protein, and IL-6, were lower in people who logged more steps per day. (13, 14) Even cognitive benefits are seen with higher daily step counts. In older adults who were monitored with pedometers, those who achieved over 10,000 steps vs. less than 7,000 steps per day had better mental health scores. (15)
Health benefits may continue well beyond 10,000 steps per day. In postmenopausal women, only those who walked over 12,500 steps daily had BMI levels within the healthy range. (16) In a study of postal workers who wore activity monitors for seven days, the only subjects without any markers of metabolic syndrome walked 15,000 steps per day or spent over seven hours per day upright. (6) Waist circumference, triglycerides, and HDL cholesterol were all favorably associated with stepping time.
The physical activity needs of children and adolescents are greater than that of older populations. Sixteen thousand steps for boys and 13,000 steps for girls were better cut-offs for predicting body fat and BMI. (17)
Is Step Count the Cause of Good Health, or Are Healthy People More Active Because They Are Physically More Able to Be?
If you are thinking, “correlation doesn’t necessarily equal causation,” you would be correct. So far, these studies are just looking at associations and cannot prove a cause-effect relationship between step counts and health outcomes. Designing a double-blind, placebo-controlled trial for step count would be impossible, but there is evidence that people who increase their step count improve their health.
In overweight people assigned to a 12-week pedometer intervention program, those who increased daily step count to over 10,000 steps had lower anxiety, depression, waist circumference, and body fat. (18) In a longer intervention study lasting 36 weeks, walking 10,000 steps per day lowered blood pressure in middle-aged men. (19)
In a study that observed people’s step count over several years, those who increased their daily steps from a sedentary level at the beginning of the study to over 10,000 steps per day by the end of the study decreased their mortality risk by 46 percent. (20)
Fitness Trackers Modestly Increase Physical Activity
Over the short-term, fitness trackers can increase participants’ physical activity, but average daily step changes are modest at best. (21, 22) Intervention studies on adults report average daily step count increases of 2,000 to 2,500. (23) Considering that the average American adult only walks a little over 5,000 steps per day, this isn’t enough of an increase to reach the cardiovascular benefits and other benefits that occur at 8,000, 10,000, or even 12,500 steps per day. In older adults, the increase in daily step count averages only 775 steps in fitness tracker intervention studies. (24)
Follow-up and accountability are key. Although the sales for fitness trackers are very high, about one-third of people abandon them after six months. Wearable fitness trackers are well tolerated and generally well received in scientific studies, but the novelty often wears off.
Can fitness trackers improve patient health?
Fitness Trackers Aren’t Accurate for All Measures
An accelerometer, the technology found in most fitness tracking devices, can record more than step count from three-dimensional acceleration measurements. Heart rate, sleep duration and quality, steps climbed, and energy expenditure are examples of other outputs from these devices. However, these measurements have shortcomings:
- Accelerometers can’t distinguish standing from sedentary The metabolic cost of an upright posture is one-third greater than that of sitting, (25) but this won’t be taken into account in the tracker’s “energy expenditure” algorithm.
- Swimming, yoga, tai chi, cycling, and many other forms of physical activity aren’t properly accounted for in a fitness tracker, but these obviously contribute to good health.
- Accelerometers aren’t great at estimating sleep. One study compared the Fitbit to polysomnography and actigraphy in children and adolescents and found that total sleep time and sleep efficiency were either over- or underestimated depending on the Fitbit’s settings. (26) If patients have sleep concerns, don’t rely too heavily on their fitness tracker data.
- Heart rate measurements in accelerometers aren’t accurate, and there is actually a lawsuit concerning this. For patients with heart conditions who need to pay extra attention to heart rate, a fitness tracker is a poor substitute for a heart rate monitor.
- Measurements of energy expenditure are highly variable and probably not accurate. (27) Too many variables are involved in this sort of calculation.
Encourage Your Patients to Move
In many of the observational and intervention studies mentioned above, health benefits from higher step count are often also explained by waist circumference alone. Therefore, it’s more about being active and maintaining a healthy weight than step count per se. Since U.S. adults average only a little over 5,000 steps per day, increasing physical activity for most patients is vital to their health.
Humans aren’t meant to sit for as long as most do today in the Western world. In lieu of chronic cardio programs, I instead encourage my patients to move like our ancestors, including moving frequently at a slow pace, lifting heavy things, and sprinting occasionally. Fitness trackers can be one tool to help patients achieve more movement, but with all the shortcomings and high abandonment rates, they may not be the best option for everyone. They especially should not be used as a replacement for clinical data such as heart rate or sleep efficiency.
The best exercise is one that the participant actually enjoys and will continue to do, whether it is getting 10,000 steps each day with a fitness tracker, walking with friends at night, or Zumba class at the local gym. Another key aspect for successful exercise is accountability in some form. Some thrive on social media networks, while others do better keeping track of their efforts with a close friend.