Pedometers

Pedometers may help track your physical activity.

Pedometers provide objective measurement of physical activity and are one potential remedy to the problem of inaccurate activity recall. They can also be fun!

In this article, I'll review how pedometers work, how to use one, how accurate they are, how many steps are good for you, and where to buy one.

A pedometer is a small, beeper-sized device you wear on your waist that counts the number of steps you take.

There are two types of pedometers, spring-levered and piezoelectric.

• Spring-levered pedometers use a spring-suspended horizontal lever arm that moves up and down in response to the movement (vertical accelerations) of your hips as you walk or run. The movement opens and closes an electrical circuit, and as the lever arm makes contact, a step is registered. Spring-levered pedometers must be placed in a vertical plane, perpendicular to the ground, for them to work. They don't work if they tip forward to a horizontal plane.
• Piezoelectric is a material that generates an electric charge when it is mechanically deformed. Piezoelectric pedometers use a horizontal cantilevered beam with a weight on the end that compresses a piezoelectric crystal when subjected to movement like walking (acceleration). This generates a voltage proportional to the acceleration and the voltage oscillations are used to record steps.

Pedometers work when you dance, climb stairs, or walk outdoors or on a treadmill, but they don't work if you're biking, skiing, rowing, or swimming.

The benefits of exercise are well known. Decreased risk of and management of chronic diseases like diabetes and heart disease, improvements in bone density, decreases in blood pressure, reduction in certain types of cancer, increases in muscle strength and endurance, alleviation of symptoms of depression, and elevation of mood are just some.

The quantity of exercise necessary to accrue these benefits is also well known. There are two national recommendations to choose from. First, the Surgeon General recommends 30 minutes or more of moderate-intensity physical activity on five or more days per week to improve health and fitness. You can accumulate it in 10- to 15-minute bouts throughout the day or do it all at once. "Moderate intensity" physical activity means you feel warm and slightly out of breath when you do it. And second, the American College of Sports Medicine recommends a more formal, workout prescription of 20-60 minutes of continuous activity, three to five times a week (at 60%-90% of maximum heart rate reserve) and 2-3 days of resistance training.

Thirty minutes of exercise is good for you, but objective measurement of how much activity you do can be elusive. Research shows that it's possible to overestimate your activity level or calorie expenditure by as much as 51%! Overestimating your activity or calorie expenditure level can have undesirable consequences; it can mislead you into thinking that you're doing enough physical activity to improve your health or that you're doing enough activity to burn off extra calories from a weekend binge. Overestimation of physical activity is also a problem for exercise scientists; subjects who overestimate their activity level confound the results of research.

Piezoelectric pedometers tend to be more sensitive than spring-levered at slower speeds so they may be preferable for individuals who walk slowly. In addition, the tilt of the pedometer is critical for performance with spring-levered devices, but not so with piezoelectric devices (the piezoelectric mechanism is not position-dependent). For example, a pedometer may tilt forward into the horizontal plane if an overweight individual with excess abdominal fat wears one on their waist. Tilt in a spring-levered pedometer can throw off the accuracy by as much as 20% at fast speeds and 60% at slow speeds. A piezoelectric pedometer does not have this tilt error except at the slowest speed (less than 2 mph), and the error is less than 10%.

The accuracy of pedometers has been carefully studied because they are frequently used in studies and researchers demand to know if they are reliable and accurate. Research shows that pedometers tend to count steps more accurately at speeds greater than 3 miles per hour (mph) than at slower speeds. Accuracy can exceed 96% when speeds exceed 3 mph, whereas the accuracy drops to between 74%-91% at speeds from 2 mph to 3 mph, and it drops even further to between 60%-71% at speeds below 2 mph. The error has to do with the insensitivity of pedometers to detect steps when people shuffle or drag their feet at slow speeds. Detectable vertical movement of the hips is necessary for pedometers to work well.

Accurate pedometers are those with step-count errors less than 10%, high or low. Your pedometer should not count more than 110 steps, or fewer than 90 steps if you walk 100 steps. The accuracy of 13 popular pedometers was studied in 2003 (see pedometer list below). Results from this study showed the Kenz Lifecorder, New-Lifestyles NL-2000 (piezoelectric), and Yamax Digi-Walkers SW-200 and SW-70 to be the most accurate of the various models tested. The Colorado on the Move, Sportline 330 and 345, and Yamax Skeletone EM-180 were within acceptable high or low error limits of 10%. The Accusplit and Freestyle underestimated steps by 20% and 25%, respectively, and the Walk4Life, Omron, and Oregon Scientific overestimated steps by 20%, 30%, and 45%, respectively. Here are the pedometers that were studied with their rank marked with an asterisk (*).

• Accusplit Alliance 1510***
• Freestyle Pacer Pro***
• Kenz Lifecorder*
• New-Lifestyles NL-2000 (piezoelectric)*
• Omron HJ-105****
• Oregon Scientific PE316CA****
• Sportline 330 & 345**
• Walk4Life LS 2525****
• Yamax Digi-Walker SW-200*
• Yamax Digi-Walker SW-701*

* most accurate

** within acceptable high or low error limits of 10%

*** underestimated steps by 20% (AA) and 25% (FPP)

**** overestimated steps by 20% (W4L), 30% (Omron) and 45% (OS)

The Kenz costs hundreds of dollars, which is probably more than you want to spend, but the Yamax SW-200 and SW-70, as well as many of the others, range in price from $20 to $30.

Pedometers don't measure distance or calories burned accurately. They can be off by as much as 10% with distance and 30% with calories, which means the error could be half a mile if you walk 5 miles and 150 calories if you burn 500. They tend to overestimate distance at slower speeds, underestimate distance at faster speeds, and they're simply not sensitive or smart enough to detect and factor in all the variables that determine how many calories you burn when you exercise.

Due to these various errors to which pedometers are prone, I recommend a simple pedometer that measures only steps. Tell a salesman who wants to sell you a pedometer with all the bells and whistles that you prefer the simple one. The bells and whistles will cost you extra money for features that don't work.

The precise number of steps per day necessary for health and fitness is unknown. Ten thousand steps per day is the popular recommendation, and there is accumulating evidence that this number of steps is associated with health benefits (lower blood pressure, improvements in blood glucose and insulin sensitivity), but it may not be appropriate for everyone (children, older adults, and individuals with chronic diseases). As for meeting the Surgeon General and ACSM guidelines by accumulating 10,000 steps per day, research suggests that the chances are good but it is not a guarantee. Until we know more it's reasonable to shoot for 10,000 steps per day if you are a healthy adult.

So Many Choices

There were 1,970,000 results in my most recent Google search for "pedometers." Not that there are more than 1 million different pedometers on the market, but there are certainly hundreds. They come as promotions in McDonald's Happy Meals and cereal boxes, they're given away at conferences, and they are readily available through sporting goods stores and many online vendors. There are talking pedometers, pedometers that use GPS technology to measure distance, and pedometers that measure heart rate and calories burned. They come in all shapes, sizes, and colors. Some have happy faces painted on them, some have corporate logos (you can have one customized), some are oval, some are square, and some are round. I even found pedometers on eBay from the 1940s that were used to promote radio shows from that era! Who knows, by the time you read this, there may even be a pedometer that does the walking for you!

I recommend wearing your pedometer from the moment you wake up in the morning until the moment you go to sleep at night for 1-2 weeks, record the steps, and then calculate your average daily steps. Once you know your average, you can make efforts to increase your average daily count by 250-500 each week until you reach an average of 10,000 steps per day.

Pedometers should be worn on your waist in a line straight up from the middle of your knee. They can be worn on either side of the body. You can wear it on your underwear if you're wearing a dress without a waistband, and you can wear it on your sock if you have excess abdominal fat and can't keep your spring-levered pedometer upright. My clients who can't keep the pedometer vertical on their waistband have had good results wearing their pedometer on their socks.

Set your pedometer to 0, and then walk and count off 100 steps to determine if your pedometer is accurate. Remember that it's accurate if the error is within 10% of your count (90-110 steps if you walk 100 steps). Move the pedometer forward or backward on your waist or even switch sides and walk another 100 steps if the error is more than 10%. Repeat these trials until you find the right position. Call the manufacturer or return the pedometer if you can't get accurate readings after repeated attempts.

Figure 1,900-2,600 steps per mile depending on your stride length. Stride length is dependent on (1) your leg length, and (2) how fast you're moving. It's longer when you jog or run, compared with walking, which means your step count will be different for the same distance depending on your mode of activity. For example, it could take 2,400 steps to walk a mile and 2,100 steps to jog it. Power- and speed-walkers take smaller, more rapid steps to go faster, and so they will take more steps in a mile than when walking slower. Likewise, you will take more steps walking uphill than when walking on flat ground and so you need to consider that when assessing your activity level with a pedometer.

Set your pedometer to 0 and walk, jog, or run a measured mile, or half a mile, and multiply by 2, to determine how many steps you take per mile for each mode of activity that you're interested in.

Looking for ideas to increase your steps? A researcher asked 34 employees of a small northeastern college what strategies they used to increase their steps. Below are the results (numbers in parentheses are the percentage of participants who used the strategies). The employees said that they had increased their steps by taking the time to walk:

• To a meeting or work-related errand (65%)
• After work (50%)
• Before work (35%)
• At lunch (47%)
• On the weekend (32%)
• While traveling (32%)
• With the dog (32%)
• To a destination (work/store) (29%)
• Parked farther away (50%)
• Used the stairs rather than an elevator (24%)
• Performed other cardiovascular activity (539%)

If you scanned your week, you would find times and opportunities when you could walk a little more. I also suggest pedometer contests at your office or even at home. Divide your office colleagues into teams and post a big chart in a conspicuous place with the cumulative number of steps that all of you take each week, and then at the end of the month, give awards to the members of the team with the highest step count and give a special award to the individual who takes the most steps. At home, post a chart on the fridge and see who takes the most steps. The winner doesn't have to do dishes for a week! Make the contests fun. The good news is that anyone with a pedometer can participate.

Pedometers are available online, at sporting goods stores, and at large retail outlets. Look for pedometers that were reviewed in the study I presented in this article, but keep in mind that new models of pedometers have emerged over the years and that some vendors sell the same brands under different names. For instance, the Accusplit Eagle 120XL, although not reviewed in the study, is the same as the Yamax Digi-Walker. Ask the vendor for details, and make sure that you can return it if it's not accurate, no matter which one you buy.

Some pedometers have a safety strap or leash that loops around a belt or belt loop so if your pedometer pops off you won't lose it. These are good to have because it's not uncommon to hear stories about pedometers falling off and breaking or even popping into the toilet! Also, make sure that your pedometer has a cover (most do). This will prevent you from accidentally hitting the reset button in the middle of the day. It's frustrating to hit the button and reset your pedometer to zero when you've worked so hard to accumulate 5,000 steps!

Below are two reliable vendors that sell pedometers online, but you can find others if you search.

• http://www.accusplit.com
• http://www.digiwalker.com

Go for it!

Don't expect a pedometer to zap you into walking like crazy the moment you put one on, but they do provide objective, accurate, and reliable data to help you assess how many steps you're taking. My experience is that individuals are shocked when they see how few steps they take and that the feedback from the pedometer is a motivator to increase steps during the day. Most Americans don't take close to 10,000 steps per day, so if this device gives you a little oomph to move more, then it's worth the investment! Go for it!