Accuracy of Five Talking Pedometers under Controlled Conditions

By Gerald J. Jerome, Carolyn Albright


Abstract

Background: This study examined the reliability and accuracy of five talking pedometers: Brookstone Talking Pedometer, Voice Zone, Sportline 343, Accusplit Alliance AL390, and Oregon Scientific PE829. All pedometers announced cumulative step count when the talk button was pressed.

Methods: Ten older adults (73 ± 5.5 years old), and 13 adults with visual impairments (42.4 ± 13.6 years old) wore the pedometers during a 50-step walk, ascending and descending stairs. Pedometer step counts were compared to hand-tally counts.

Results: All pedometers underestimated actual steps with higher prevalence of under-counting when ascending stairs and descending stairs. Average absolute errors follow: Brookstone (13.0%±13.8), Accusplit (18.7%±21.7), Voice Zone (20.2%±18.1), Oregon Scientific (25.7%±24.3) and Sportline (33.7±25.5).

Conclusions: The Brookstone and Accusplit pedometers were the most accurate models. None of the talking pedometers tested appeared appropriate for research (maximum of 5% error) or general use (maximum of 10% error).

Keywords

low vision, pedometer, motion sensor, physical activity, walking

 

Introduction

Public health recommendations to increase regular physical activity for primary and secondary disease prevention (e.g. cardiovascular disease, diabetes, obesity) highlight the need for objective measures of physical activity (Centers for Disease Control and Prevention, 1996; U.S. Department of Health and Human Services, 2008). Objective measures of physical activity are important in assessing physical activity levels of various populations and evaluating the effectiveness of physical activity promotion efforts. Pedometers provide an objective measure of daily step counts, and have been shown to be both an accurate and reliable tool for assessing physical activity (Schneider, Crouter, Lukajic, & Bassett, 2003). Additionally, pedometers can be used in conjunction with daily step goals as a motivational tool to increase physical activity levels. Examples of step goals have included 10,000 steps per day and more recently, 3,000 steps in 30 minutes, which targets both the intensity and duration of the physical activity guidelines (Marshall et al., 2009; Tudor-Locke & Bassett, 2004). Pedometers used in conjunction with step goals have been found effective in increasing physical activity levels and have been associated with corresponding positive health outcomes (Bravata et al., 2007).

Pedometers are widely available to the general public and most models are small enough to be worn inconspicuously. One limitation associated with the pedometer's unobtrusive profile is a small screen, or step count readout which presents usability issues for those with low vision. In the United States there are an estimated 2.4 million adults age 40 and older with low vision and an additional 937,000 adults who are blind (Congdon et al., 2004). Due to the increasing number of adults over the age 65, the incidence of low vision has been estimated to increase by 240,000 cases per year over the next 20 years (Massof, 2002). The need for health promotion efforts among this group is punctuated by low physical activity levels and co-morbidity (e.g. obesity, diabetes) associated with low vision (Capella-McDonnall, 2007). Because of the small screen, traditional pedometers have limited value in efforts to promote independence and self reliance toward increasing daily physical activity among adults with low vision or blindness.

This investigation identified five commercially available talking pedometers, or devices providing cumulative step counts both visually on a screen and audibly when a talk button is pressed. Each of the talking pedometers examined in this study had a unique combination of features; however, all of them had the ability to provide an audible step count. Theoretically, this talking feature would allow for those with vision impairments to use these pedometers in order to track their daily physical activity levels. The accuracy of talking pedometers has been evaluated in adolescents; however, few efforts have been made to examine the reliability of these devices under controlled conditions among adults (Beets, Foley, Tindall, & Lieberman, 2007). Evaluating pedometers under controlled conditions allows researchers to report standardized evaluations of pedometer accuracy, which provides an additional benefit of facilitating comparisons between models.

The purpose of this study is to examine the accuracy of five commercially available talking pedometers (Brookstone Talking Pedometer, Voice Zone, Sportline 343, Accusplit Alliance AL390, and Oregon Scientific PE829) during a 50-step walk, ascending stairs, and descending stairs. Specifically we wanted to provide recommendations to both researchers and consumers regarding the accuracy of these pedometers.

Methods

Participants

Ten older adults (=60 years old) and 14 adults with visual impairments (=18 years old) were recruited for the study. Approval for the study was obtained from the appropriate institutional review board and all participants provided written informed consent. The older adults were recruited from the university wellness center. The adults with visual impairments were recruited from a local advocacy group and a rehabilitation center. Inclusion criteria included self-reported ability to climb stairs without holding on to a railing. Exclusion criteria included the need for a load-bearing assistive walking device, planned pregnancy in the next 3 months, psychiatric hospitalization in the last year, history of seizures, and contra indicants to physical activity.

Talking Pedometers

Five commercially-available talking pedometers were selected for this study including: Brookstone Talking Pedometer, Voice Zone, Accusplit Alliance AL390, Sportline 343, and Oregon Scientific PE829. This was a selection of pedometers that were reasonably priced (retail prices ranged between $15 and $50), were readily available to Internet shoppers, and were distributed by reputable companies. All pedometers had a feature which announced the cumulative step count when a talk button was pressed. The Oregon Scientific PE8289 pedometer did not have a speaker and required the use of headphones.

Pedometers were attached to a 2-inch-wide belt of double-thickness elastic that fastened with a quick-release buckle, adjusted to fit snuggly just above the participant's iliac crest. When determining reliability and accuracy during normal-paced walking, pedometers were worn in pairs with left- and right-side pedometers aligned with the midline of the thigh, approximately equidistant from the participant's midline. The belt was fitted with up to two pairs of pedometers at a time for each of the tests.

Procedures

Walking 50 steps: The participants stood at one end of a long, straight hallway or walkway while the researcher zeroed the pedometers. The participants were then instructed to walk 50 steps at a normal, or usual pace and a researcher signaled the participants to stop once the hand-tally counter indicated 50 steps. The researcher then recorded steps from both the counter and the pedometer.

Ascending/descending stairs: Stairwells with at least 10 steps were selected for this portion of the study. When possible, the same stairwell was chosen; however, some of the data was collected in the field and therefore the most appropriate set of stairs with at least 10 steps was chosen. The participants stood at the bottom/top of the steps while the researcher zeroed the pedometers. Then participants were instructed to ascend/descend the stairs without holding on to the railing and stop at the bottom/top of the stairs. The researcher followed the participants using a hand-tally counter to track the number of observed steps. After the researcher recorded the number of steps from both the counter and the pedometer, the participants were instructed to turn around, and the procedure was repeated in the opposite direction.

Data Analysis

Due to the modest sample size and the desire for increased generalizability, all analyses were conducted using the entire data set. Descriptive data including means and standard deviations were reported. All analyses were performed using PASW version 18.0 (Chicago, IL). Intra-class correlation coefficients (ICC) and 95% confidence intervals (95% CI) comparing steps registered by pedometers on the right and left sides of the body were reported as a measure of intra-instrument reliability (Schneider et al., 2003). Separate ICCs were calculated for each pedometer model corresponding with the 50-step walk, ascending stairs, and descending stairs. Previous research has described ICC below 0.80 as low agreement between left-and right-side pedometers (Crouter et al., 2003; Tudor-Locke et al., 2006).

Both net error and absolute error have been reported. Net error indicates if the pedometer, on average, under- or over-counted. However, if a particular model both under- and over-counts, the net error may not reflect the true magnitude of error. Consequently absolute error, which is an average of the absolute value of the error, is also reported.

Net error (steps registered-steps taken)/steps taken*100%) was reported for both left- and right-side pedometers (Cyarto, Myers, & Tudor-Locke, 2004; Horvath, Taylor, Marsh, & Kriellaars, 2007; Leicht & Crowther, 2009; Shepherd, Toloza, McClung, & Schmalzried, 1999; Tudor-Locke et al., 2006). Net error was also classified as under- (<-5%), exact- (±5%) or over- (>5%) counting. Prevalence of under-, exact- and over-counting included results from both the left- and right-side pedometers. These categories have been reported for treadmill walking using a 1% cut-point (Le Masurier & Tudor-Locke, 2003; Tudor-Locke et al., 2006), however a 5% error rate has been indicated as an appropriate cut-point when walking across ground (Tudor-Locke et al., 2006).

Absolute error [absolute difference(steps registered-steps taken)/steps taken*100%] was reported for the left- and right-side pedometer during the 50-step walk, ascending stairs, and descending stairs (Le Masurier, Lee, & Tudor-Locke, 2004; Leicht & Crowther, 2009). Total absolute error was the average across left- and right-side pedometers in all activities. Absolute error at or below 5% was considered acceptable for research purposes and error at or below 10% was considered acceptable for general use (Crouter et al., 2003; Tudor-Locke et al., 2006).

Results

Ten older adults (see Table 1) ranged in age from 64-82 years (M=73.0±5.5 years), were 30% female, and had an average BMI of 25.7±3.3 kg/m2. The 13 adults with visual impairments ranged in age from 20-64 years (M=42.4±13.6 years), were 46% female, and had an average BMI of 32.3±7.4 kg/m2. All of the adults with visual impairment were legally blind, used a long cane, and described themselves as confident travelers or walkers.

 

Table 1: Selected characteristics of participants

 

Total

Older Adults

Adults with Visual Impairments

 

 

n= 23

n =10

n = 13

 

 

M±SD

M±SD

M±SD

p*

Age (yrs)

55.7±18.8

73.0±5.5

42.4±13.6

0.000

Height (inches)

170.0±9.5

170.5±8.0

169.6±10.8

0.818

Weight (lbs)

187.2±52.0

162.1±30.0

206.5±57.9

0.039

BMI

29.2±6.9

25.2±3.3

32.4±7.4

0.009

Female (%)

39%

30%

46%

0.431

Note: *p indicates between-group comparison

The intraclass correlation coefficients (ICC) between scores from the left-and right-side pedometers were reported in Table 2 and ICC = 0.80 were considered as acceptable agreement between pedometers. During the 50-step task the Voice Zone (0.88), Sportline (0.84), and Oregon Scientific (.82) pedometers had acceptable ICC. None of the pedometers had ICC = 0.80 when ascending stairs and only the Accusplit (0.88) and Sportline (0.80) pedometers had acceptable ICC when descending stairs.

 

Table 2: Intraclass correlation coefficient and 95% confidence interval for five talking pedometers worn on the left and right sides of the body

 

Brookstone

Voice Zone

Accusplit

Sportline

Oregon Scientific

 

ICC(95%CI)

ICC(95%CI)

ICC(95%CI)

ICC(95%CI)

ICC(95%CI)

50 Steps

0.01(-0.40,0.41)

0.88(0.75-0.95)

0.75(0.49,0.88)

0.84(0.67,0.93)

0.82(0.63,0.92)

Ascending Stairs

0.20(-0.22,0.56)

0.61(0.28,0.81)

0.66(0.35,0.84)

0.63(0.32,0.83)

0.42(0.02,0.70)

Descending Stairs

0.27(-0.15,0.61)

0.59(0.26,0.80)

0.88(0.75,0.95)

0.80(0.59,0.91)

0.38(-0.23,0.68)

 

Table 3: Net error for five talking pedometers when walking 50 steps, ascending stairs, and descending stairs

 

Brookstone

Voice Zone

Accusplit

Sportline

Oregon Scientific

 

M±SD

M±SD

M±SD

M±SD

M±SD

50 Steps

 

 

 

 

 

Left side

-29.6±36.5

-15.4±27.5

-14.9±25.8

-29.6±36.5

-18.2±31.8

Right side

-25.8±34.9

-18.9±32.2

-13.7±29.0

-25.8±34.9

-26.5±39.8

Ascending Stairs

 

 

 

 

 

Left side

-14.5±22.5

-22.2±25.5

-25.2±29.5

-43.2±38.5

-26.1±37.7

Right side

-17.7±35.2

-20.5±27.5

-16.2±30.7

-41.9±39.7

-23.4±38.3

Descending Stairs

 

 

 

 

 

Left side

-8.7±22.0

-14.6±16.1

-16.1±24.6

-24.6±24.8

-14.7±20.5

Right side

-13.3±23.7

-13.6±18.7

-13.6±25.0

-20.7±28.1

-19.5±29.4

Table 3 indicates that all pedometers had negative average net errors across all tasks. Table 4 shows the prevalence of under-, accurate-, and over-counting by each of the pedometers for each task. During the 50-step walk the pedometers with the highest prevalence of accurate-counting were the Brookstone (67%) and the Accusplit pedometers (67%), followed by the Oregon Scientific (52%), Voice Zone (46%), and Sportline (41%) pedometers. Accurate counting occurred less frequently for all pedometers when ascending stairs (9-28%) and descending stairs (11-41%).

 

Table 4: Frequency of under-,accurate and over-counting for five talking pedometers when walking 50 steps, ascending stairs, and descending stairs

 

50 Steps

Ascending Stairs

Descending Stairs

 

under-
report

accurate

over-
report

under-
report

accurate

over-
report

under-
report

accurate

over-
report

 

%

%

%

%

%

%

%

%

%

Brookstone

33

67

0

54

28

17

57

24

20

Voice Zone

48

46

7

72

22

7

72

17

11

Accusplit

33

67

0

67

20

13

50

41

9

Sportline

54

41

4

83

9

9

76

11

13

Oregon Scientific

41

52

7

65

15

20

74

17

9

Note: Under-counting was defined as net error <-5%, accurate was within 5% error and over-counting was >5% error. Due to rounding not all percentage totals equal 100%.

Table 5 shows absolute error for each pedometer. All pedometers exceeded 10% absolute error in each of the tasks. The Brookstone had the lowest average absolute error (13.0±13.8), followed by the Accusplit (18.7±21.7), Voices Zone (20.2±18.1), Oregon Scientific (25.7±24.3), and Sportline (33.7±25.5) pedometers.

Table 5: Absolute error for five talking pedometers when walking 50 steps, ascending stairs, and descending stairs

 

Brookstone

Voice Zone

Accusplit

Sportline

Oregon Scientific

 

M±SD

M±SD

M±SD

M±SD

M±SD

50 Steps

 

 

 

 

 

Left side

10.1±21.9

17.8±25.9

15.7±25.2

31.7±34.6

19.8±30.7

Right side

14.7±27.9

21.4±30.5

15.0±28.3

28.4±32.7

28.0±38.7

Ascending Stairs

 

 

 

 

 

Left side

16.3±21.2

22.5±25.1

26.5±28.3

47.0±33.6

35.0±29.2

Right side

24.3±29.7

25.3±23.0

20.6±27.8

44.5±36.6

30.2±33.0

Descending Stairs

 

 

 

 

 

Left side

13.6±19.3

16.4±14.1

17.5±23.6

26.2±23.0

17.4±18.1

Right side

18.1±20.1

18.0±14.3

16.9±22.8

24.6±24.6

24.0±25.7

Average

13.0±13.8

20.2±18.1

18.7±21.7

33.7±25.5

25.7±24.3

Note: Absolute error is an average of both left- and right-side values for all three activities

Discussion

This was the first study to examine the accuracy of talking pedometers among adults during three different free-living activities: walking 50 steps, ascending stairs, and descending stairs. This selection of over-ground activities was chosen to correspond with a variety of walking activities likely to be encountered during a typical day. There have been a number of criteria suggested for the evaluation of pedometers, including maximum of 5% error for research devices and a maximum of 10% error for general use (Crouter et al., 2003; Tudor-Locke et al., 2006). Based on these criteria, none of the pedometers tested appeared appropriate for either research or general use.

The most accurate counting appeared when walking 50 steps (41-67%) compared to ascending stairs (9-28%) and descending stairs (11-41%). All pedometers consistently under-reported during all three activities. The under-counting during ascending and descending stairs is congruent with previous research (Cyarto et al., 2004; Horvath et al., 2007; Leicht & Crowther, 2009; Shepherd et al., 1999; Tudor-Locke et al., 2006). It has been suggested that altered lower-limb biomechanics during ascent and descent may contribute to the differences in accuracy (Cyarto et al., 2004; Horvath et al., 2007; Leicht & Crowther, 2009; Shepherd et al., 1999; Tudor-Locke et al., 2006).

Additionally, it appeared that a range of techniques were differentially used among individuals during ascent and descent in the current study. For example one strategy was to advance to a new stair with each step and both feet were never on the same stair. Another strategy was to consistently use the same leg when advancing to a new stair and the second step brought both feet together before advancing again.

Net error was used to provide information regarding the direction of the error; however averaging net errors can result in underestimating the magnitude of the counting error (Le Masurier et al., 2004; Leicht & Crowther, 2009; Schmalzried et al., 1998). As previously suggested we used the absolute error as an indicator of the error magnitude (Le Masurier et al., 2004; Leicht & Crowther, 2009; Schmalzried et al., 1998). Absolute error at or below 5% was considered acceptable for research purposes and error at or below 10% was considered acceptable for general use (Crouter et al., 2003; Tudor-Locke et al., 2006). Only the left-side Brookstone pedometer during the 50-step walk indicated an absolute error that met the general use criteria. None of the values met the research criteria of absolute error less than or equal to 5% error. The average absolute error for all five pedometers exceeded both the research and general use criteria (13-34%). These results support the conclusion that the talking pedometers in this study were not sufficiently accurate for either research purposes or general use.

This study did not include measurement of gait speed or gait quality, which would have allowed for the assessment of ambulation variables in relation to pedometer accuracy. Given the consistency in literature indicating that pedometers are more accurate at moderate walking speeds and among those with regular gait, these results may overestimate accuracy for groups with a markedly slow or irregular gait due to functional limitations or low confidence in traveling (Le Masurier et al., 2004; Leicht & Crowther, 2009; Schmalzried et al., 1998). A second potential limitation was the small sample size, which precluded the examination of differences in pedometer performance between participant characteristics such as gender or BMI. However we believe the study design is appropriate for the stated objective of evaluating the accuracy of these pedometers. Additionally, the general recommendation generated from these results may be more helpful to a consumer compared to a range of results associated with individual characteristics (e.g. BMI, gender) requiring further interpretation from a consumer to determine the most relevant finding.

Intraclass correlation coefficients were reported as an indicator of inter-unit reliability, with higher scores indicating a stronger association between steps registered on left- and right-side pedometers. In the current sample, the Voice Zone, Sport Line and Oregon Scientific pedometers had ICC = 0.80 when walking 50 steps, indicating acceptable agreement. The ICC data for these models during this task were similar to those reported from traditional non-talking pedometers worn during varying treadmill speeds and were higher than the ICC reported for talking pedometers worn by children with visual impairments (Crouter et al., 2003; Tudor-Locke et al., 2006). On average ICC was < 0.80 for ascending stairs and only the Accusplit and Sport Line models had ICC = 0.80 when descending stairs. The generally low agreement between units corresponds with an earlier study examining inter-unit agreement of talking pedometers among children, reporting ICC between 0.32-0.76 (Crouter et al., 2003; Tudor-Locke et al., 2006).

Freedson and Miller have suggested that pedometers used to objectively measure physical activity should be easy to administer to large groups, inexpensive, unobtrusive, and accurate (Freedson & Miller, 2000). We believe usability should be added to the list of criteria if the device is to convey information to the wearer. Consequently, six of the adults with visual impairments who were familiar with usability evaluation volunteered to wear the pedometers during their daily activities and provide feedback. After one week of using the pedometers, the participants provided general qualitative usability feedback concerning talking pedometers.

As indicated previously, the Oregon Scientific model required a headset to hear the speech function. One of the participants enjoyed the privacy of the headset on the Oregon Scientific model; another indicated that it was a neutral feature; and four others viewed it as a safety concern, as the headset decreased their awareness of their surroundings. Participants preferred a clip that was both sturdy and provided a tight fit; however, there was no consensus on the best clip. They also indicated preference for pronounced buttons that were easy to identify yet resistant to inadvertent activation, and none of the pedometers were noted as having these features.

Additionally there was preference for loud crisp speech, yet there was no consensus on the best model related to speech. A more controlled study is needed to determine if talking pedometer functions such as strength and clarity of speech are related to battery strength. Many of the talking pedometers appeared to need new batteries more frequently than the traditional pedometers. Unfortunately, none of the talking pedometers provided feedback on battery charge; and changing the button cell batteries could present a usability challenge, as the task required fine motor control and the ability to read fine print to properly align the batteries.

The talking feature appeared to be accurate for all of the talking pedometers, with regards to the number of steps reported on the speaker relative to that on the readout. There was only one instance where the audio reported 1 fewer steps that the readout indicated. This may have been due to researcher error, as it was challenging to record readouts and manipulate the speech buttons while others were wearing the pedometers. These usability reviews clarified the need to identify potential challenges in using talking pedometers and to develop strategies to overcome these potential barriers before using pedometers for physical activity interventions.

Implications for Practitioners and Families

We believe this was the first study to examine the accuracy of talking pedometers among older adults and adults with visual impairments during specific over-ground walking tasks (walking 50 steps, ascending stairs, and descending stairs). None of the pedometers appear to be appropriate for research purposes due to low reliability and average absolute errors measured at > 5%. Although the Brookstone and Accusplit had the highest accuracy, both demonstrated low accuracy when ascending and descending stairs and neither met the accuracy criteria for general use (e.g. = 10% absolute error). At the time of the investigation the Accusplit pedometer had a retail price of $20 and the Brookstone pedometer retailed for approximately $50. Given the increased number of talking pedometers in the marketplace and the turnover among models, regular review of the accuracy and usability of talking pedometer models may be helpful for consumers. The methods from the current study would be easily replicated and appropriate for reviews conducted by advocacy or consumer groups to review the accuracy of different models. Talking pedometers hold promise for increasing accessibility of these devices to those with vision impairments and there remains a need for more accurate devices.

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