CROUTER, S. E., P. L. SCHNEIDER, M. KARABULUT, and D. R. BASSETT, JR. Validity of 10 Electronic Pedometers for Measuring Steps, Distance, and Energy Cost. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1455–1460, 2003.
Purpose: This study examined the effects of walking speed on the accuracy and reliability of 10 pedometers: Yamasa Skeletone (SK), Sportline 330 (SL330) and 345 (SL345), Omron (OM), Yamax Digiwalker SW-701 (DW), Kenz Lifecorder (KZ), New Lifestyles 2000 (NL), Oregon Scientific (OR), Freestyle Pacer Pro (FR), and Walk4Life LS 2525 (WL).
Methods: Ten subjects (33 ± 12 yr) walked on a treadmill at various speeds (54, 67, 80, 94, and 107 m·min−1) for 5-min stages. Simultaneously, an investigator determined steps by a hand counter and energy expenditure (kcal) by indirect calorimetry. Each brand was measured on the right and left sides.
Results: Correlation coefficients between right and left sides exceeded 0.81 for all pedometers except OR (0.76) and SL345 (0.57). Most pedometers underestimated steps at 54 m·min−1, but accuracy for step counting improved at faster speeds. At 80 m·min−1 and above, six models (SK, OM, DW, KZ, NL, and WL) gave mean values that were within ± 1% of actual steps. Six pedometers displayed the distance traveled. Most of them estimated mean distance to within ± 10% at 80 m·min−1 but overestimated distance at slower speeds and underestimated distance at faster speeds. Eight pedometers displayed kilocalories, but except for KZ and NL, it is unclear whether this should reflect net or gross kilocalories. If one assumes they display net kilocalories, the general trend was an overestimation of kilocalories at every speed. If one assumes they display gross kilocalorie, then seven of the eight pedometers were accurate to within ±30% at all speeds.
Conclusion: In general, pedometers are most accurate for assessing steps, less accurate for assessing distance, and even less accurate for assessing kilocalories.
The electronic pedometer is a simple device that can be used to assess physical activity. In recent years, a wide variety of new electronic pedometers have been introduced, which makes it necessary to test these new devices for accuracy and reliability. With the phasing out of older analog models, the pedometer has evolved into a device that can also estimate distance traveled and energy expenditure (kcal). Some models have internal clocks and can store information for viewing or downloading to a computer. Concerning principles of operation, electronic pedometers use three basic mechanisms for recording steps. The original and most basic is a spring-suspended horizontal lever arm that moves up and down in response to vertical displacement of the waist. The lever arm opens and closes an electrical circuit with each step, and the number of steps are counted (e.g., Yamax Digiwalker SW-701 and Sportline 345). Some newer models have incorporated a glass-enclosed magnetic reed proximity switch (e.g., Omron and Oregon Scientific). The third type has an accelerometer consisting of a horizontal beam and a piezoelectric crystal (e.g., New Lifestyles and Lifecorder); steps are determined from the number of zero-crossings of the instantaneous acceleration versus time curve.
In 1996, Bassett et al. (1) assessed the accuracy of five electronic pedometers. To date, it is the only multi-brand comparison study of electronic pedometers, and none of the pedometers they examined are currently available. Bassett et al. found that at a walking speed of 2.0 mph, pedometers underestimated steps by 50–75%, but they became more accurate as the walking speed increased. At self-selected walking speeds of 80–107 m·min−1, the Yamax Digiwalker DW-500 recorded average values for steps and distance that were within 1% of actual. Nelson et al. (9) looked at the validity of the Yamax Digiwalker DW-500 in reporting gross kilocalories. Nelson et al. showed that at walking speeds of 3–4 mph on the treadmill, it provides valid results, but it significantly underestimates gross kilocalories at 2 mph and below. However, it is possible that the kilocalorie values displayed by pedometers are supposed to reflect net kilocalories (i.e., physical activity energy expenditure, above resting).
In recent years, new recommendations have been issued concerning the amount of physical activity that one should perform on a regular basis. The current recommendation from the U.S. Surgeon General is to accumulate at least 30 min of moderate-intensity physical activity on most days of the week (16). This is also supported by the Centers for Disease Control and Prevention and the American College of Sports Medicine, which notes that the recommendation can be met by walking 2 miles briskly (10). Studies have shown that 30 min of brisk walking is equal to 3100–4000 steps, depending on the age of the population (13,17,19), which allows one to quantify a time recommendation in terms of steps taken. Others recommend a different approach to daily physical activity. Hatano (6) advocates taking a total of 10,000 steps per day for cardiovascular disease prevention. At the University of Colorado Health Sciences Center, Hill had developed a program called “Colorado On The Move” and recommends a 2000-step increase above one’s normal step count for prevention of weight gain (8).
Taking into consideration these pedometer recommendations, the increasing use of pedometers in intervention studies, and their potential for surveillance of physical activity, it is important to have valid devices for measurement. Therefore, the purpose of this study was to examine the accuracy and reliability of 10 electronic pedometers for measuring steps taken, distance traveled, and kilocalories at various treadmill walking speeds.
Department of Health and Exercise Science, The University of Tennessee, Knoxville, TN
Address for correspondence: Scott Crouter, Department of Health, Safety, and Exercise Science, The University of Tennessee, 1914 Andy Holt Ave., Knoxville, TN 37996; E-mail: email@example.com.
Submitted for publication January 2003.
Accepted for publication April 2003.