Journal of Aging and Physical Activity, 2015, 23, 395 -400 http://dx.doi.org/10.1123/japa.2014-0049 © 2015 Human Kinetics, Inc.
ORIGINAL RESEARCH
Steps per Day, Daily Peak Stepping Cadence, and Walking Performance in Older Adults Joaquin U. Gonzales, Jordan Shephard, and Neha Dubey We tested the hypothesis that the intensity of daily ambulation would relate with functional walking capacity in older adults. Forty-three women (n = 25) and men (n = 18) between the ages of 60–78 years wore an accelerometer for measurement of average daily steps and 30-min peak stepping cadence. A 400-m walk test was used to measure walking speed. No sex difference was found for average daily steps (p = .76), average peak cadence (p = .96), or walking speed (p = .89). Daily steps (women: r = .68, p < .01; men: r = .04) and peak cadence (women: r = .81, p < .01; men: r = –.16) were positively correlated with walking speed in women but not in men. After controlling for daily steps, peak cadence remained significantly associated with walking speed in women (partial r = .61, p < .01). Walking intensity during daily ambulation is independently related to functional walking capacity in older adults, albeit this relation may be more significant for women than men. Keywords: physical activity, accelerometer, gait speed, sex differences, ambulation, walking
Daily physical activity is advocated by public health organizations as an important strategy to maintain health and quality of life with advancing age. The U.S. government currently recommends that American adults accumulate at least 150 min of moderate intensity physical activity every week (U.S. Department of Health and Human Services, 2008). Walking is commonly prescribed to meet this physical activity recommendation as it is a simple mode of exercise. Time spent walking or greater number of steps taken per day is associated with many health benefits (Sesso, Paffenbarger, Ha, & Lee, 1999; Sesso, Paffenbarger, & Lee, 2000), and recent studies are highlighting the relative importance of walking intensity for increasing longevity in older adults (Williams & Thompson, 2013). Walking programs often use total steps (e.g., 10,000 steps per day) or minutes of walking (e.g., 150 min per week) to quantify the amount of physical activity (LIFE Study Investigators et al., 2006; Nemoto, Gen-no, Masuki, Okazaki, & Nose, 2007). This type of recommendation is easy to follow using commercially-available devices (e.g., pedometers) that provide detailed information about ambulatory activity. However, walking programs focused on total steps or accumulated time can misplace emphasis away from walking intensity. Walking at a fast pace or cadence is important for stimulating physiological adaptations that are intensity-dependent and are necessary to improve functional capacity (Nemoto et al., 2007). Indeed, older adults who spend more time walking at a moderate intensity (> 3 METs) during daily life are found to have higher preferred and fast walking speed than those who walk at a slower pace during daily activities (Aoyagi, Park, Watanabe, Park, & Shephard, 2009). In addition, time spent in daily moderate-tovigorous physical activity is found to positively correlate with fast walking speed (Gerdhem, Dencker, Ringsberg, & Åkesson, 2008) and predicts lower extremity performance in older adults (Trayers et al., 2014). It is difficult to separate the relative influence of volume versus intensity of physical activity. For example, walking at a
Gonzales, Shephard, and Dubey are with the Department of Health, Exercise and Sport Sciences, Texas Tech University, Lubbock, TX. Address author correspondence to Joaquin U. Gonzales at [email protected].
higher cadence (intensity of activity) will inadvertently increase the number of steps per day (volume of activity). Accelerometers are increasingly being used to measure daily ambulatory activity (Tudor-Locke et al., 2013). These devices allow for step count, but also the calculation of peak cadence (Tudor-Locke, Brashear, Katzmarzyk, & Johnson, 2012). Recently, a study examining these measures of daily ambulatory activity in older adults found them to hold separate associations with health markers such as body mass index (Schuna et al., 2013). Shared explained variance between these two related variables can be partitioned out using regression analysis to examine their independent associations. Using this approach, we sought to examine the independent relations of daily ambulatory volume and intensity with functional capacity in older adults. Based on the rationale that functional capacity is improved to a greater extent with intensity rather than volume of physical activity (Nemoto et al., 2007), we hypothesized that daily peak cadence would hold a stronger relationship with functional capacity than total steps per day. Moreover, we hypothesized that this relationship would remain significant even after controlling for variance explained by total steps per day. We selected the fast-pace 400-m walk test to assess functional capacity (Simonsick et al., 2001). From this test we can assess fast walking speed, which declines with advancing age (Ko, Hausdorff, & Ferrucci, 2010). Moreover, time to complete the 400-m walk test correlates with peak aerobic capacity (Simonsick, Fan, & Fleg, 2006), discriminates physical performance among well-functioning adults (Sayers, Guralnik, Newman, Brach, & Fielding, 2006), and strongly predicts future disability in older adults (Newman et al., 2006).
Methods Participants Data collected for a previous study (Gonzales, Defferari, Fisher, Shephard, & Proctor, 2014) examining the influence of vascular function on walking fatigue was used for the present investigation. Participants were recruited by posting advertisements in the local city newspaper and via weekly e-mail announcements sent to the university community. Advertisements called for people with no 395
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personal history of cardiovascular disease, diabetes, and pulmonary disease. Other exclusion criteria included taking medication for high blood pressure, cholesterol, or hormone replacement therapy, along with obesity (body mass index ≥ 30 kg/m2), hypertension (blood pressure > 149/99 mmHg), abnormal fasting blood glucose level > 115 mg/dL, or orthopedic limitations (e.g., knee pain) that impaired walking. Body weight was measured using a standard scale, blood pressure was measured by auscultation, and blood glucose was measured by finger prick after a 12-hr fast (Accu-Chek Active, Roche Diagnostics, Indianapolis, IN). Participants provided written informed consent before data collection. Fifty-seven older (≥ 60 years) adults consented and were screened. One adult was excluded for taking cholesterol medication, one adult was excluded for being classified as obese, two adults were excluded due to hypertension, and eight were excluded due to high fasting blood glucose levels. Forty-five community-dwelling older adults (25 women and 20 men, range 60–78 years) were included in this study. The Human Research Protection Program at Texas Tech University provided ethics approval for this study.
Daily Ambulatory Activity Daily ambulatory activity was objectively measured using a triaxial accelerometer (ActiGraph model GT3X+, Pensacola, FL) worn over the right hip with an elastic belt for seven consecutive days. Participants were asked to take it off during bathing, swimming, and sleeping. Accelerometers were programmed to collect data at a sampling rate of 30 Hz. Raw acceleration data were integrated to 60-s epochs without low-frequency extension to avoid exaggerated estimates of steps per day (Wanner, Martin, Meier, ProbstHensch, & Kriembler, 2013). The integrated file underwent wear time validation using automated software (ActiLife v6, Pensacola, FL). Nonwear time was defined using a 90-min time window for consecutive zero or nonzero activity counts, a 30-min consecutive zero activity count window for detection of artificial movements, and a 2-min spike tolerance (Choi, Liu, Matthews, & Buchowski, 2011). We also added a criterion that a day must have ≥ 10 hr of wear time to be considered valid (Troiano et al., 2008). All nonwear time was excluded from further analysis. As a result, two men had no valid days for analysis and were not included in this study. On average, adults wore the accelerometer for 6.3 ± 1.0 days after wear time validation. There was no sex difference in the number
of valid days analyzed for women (6.2 ± 1.2 days) and men (6.5 ± 0.8 days, p = .24). Steps per day were averaged across all valid days for each adult, and 30-min peak stepping cadence was calculated as the average steps per min for the 30 highest minutes in a day (but not necessarily consecutive minutes) for each adult as previously described (Tudor-Locke et al., 2012).
Walk Performance Test Participants were asked to refrain from caffeine for ≥ 12 hr and to avoid food and vitamins or supplements for 4 hr before completing the 400-m walk test to ensure testing procedures were consistent between individuals (American College of Sports Medicine, 2014). Two traffic cones were placed 20 m apart in a long flat-surfaced hallway. Participants were instructed to “Select a pace that you can comfortably maintain for 10 laps but you feel that you can complete in your best time.” No participants needed a break period during the test. The fastest lap (40 m) time was used to calculate fast walking speed. This was done to avoid the deleterious effect of performance fatigue on walking speed that can occur with endurance-based walking tests (Gonzales et al., 2014). Time to complete the entire 400 m was also recorded. Two 400-m walk tests were performed on separate days, the first for familiarization purposes and the second test was used for data analysis.
Statistics All data were normally distributed as assessed by a Kolmogorov– Smirnov test. Independent samples t tests were used to test for differences in descriptive characteristics between women and men. Pearson product–moment correlation coefficients were used to examine for bivariate relationships between variables. Partial correlation analysis was used to assess relationships between variables after adjusting for covariates. Data are presented as mean ± SD. Statistical significance was defined as p ≤ .05.
Results Table 1 presents the sample characteristics for all participants, separated by sex. Women were shorter, weighed less, and had a smaller body mass index than men (p < .05). No sex differences were found for age, resting blood pressure, daily ambulatory activity, or walking
Table 1 Characteristics of Participants Variable
All (N = 43)
Women (n = 25)
Men (n = 18)
p-value
Age (years)
67.3 ± 5.3
67.2 ± 5.6
67.5 ± 4.9
.89
Height (cm)
168.2 ± 9.4
162.5 ± 7.0
176.1 ± 6.1
< .01
Weight (kg)
66.2 ± 11.5
59.4 ± 8.0
75.6 ± 8.9
< .01
Body mass index (kg/m2)
23.2 ± 2.4
22.4 ± 2.4
24.3 ± 2.2
.01
Resting mean blood pressure (mmHg)
85.5 ± 9.8
84.2 ± 9.4
87.2 ± 10.6
.33
Fasting blood glucose (mg/dL)
94.5 ± 6.8
95.3 ± 6.8
93.5 ± 6.9
.39
7,083 ± 2,728
7,185 ± 3,148
6,941 ± 2,087
.76
77.0 ± 27.3
77.2 ± 29.5
76.8 ± 25.0
.96
Fast walking speed (m/s)
1.52 ± 0.17
1.52 ± 0.16
1.52 ± 0.19
.89
400 m walk time (s)
279.1 ± 32.4
279.6 ± 30.4
278.6 ± 36.0
.92
Ambulatory activity variables Steps per day Peak stepping cadence (steps/min) Walking performance variables
Note. Values are mean ± SD. JAPA Vol. 23, No. 3, 2015
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performance variables. Age was inversely correlated with steps per day (women: r = –.49, p = .01; men: r = –.58, p = .01) and peak cadence (women: r = –.49, p = .01; men: r = –.63, p = .005). Body mass index was unrelated to steps per day (women: r = –.28, p = .17; men: r = –.16, p = .52), but inversely correlated with peak cadence in women (r = –.46, p = .02) but not in men (r = –.07, p = .76). Fasting blood glucose and resting blood pressure were not associated with ambulatory activity in either sex (p > .05). The relationship between daily ambulatory activity and walking performance variables are shown in Table 2. Fast walking speed and 400-m walk time were correlated with steps per day and peak cadence (p < .05). These associations were present in women (p < .01), but not in men. After adjusting for steps per day, peak cadence remained significantly associated with walking performance variables in all participants and in women (p < .05), but not in men. Controlling for peak cadence attenuated the relationship between steps per day and walking performance variables to nonsignificant levels in all groups (p > .05). To further examine the strength of the association between daily peak cadence and walking performance, we adjusted for age, body mass index, and steps per day. Peak cadence remained significantly associated with fast walking speed and 400-m walk time in women, but not in men (Figure 1).
Discussion Walking is a common mode of exercise during daily physical activity in older adults (Bryan & Katzmarzyk, 2009) and, as such, is important for maintaining independence in activities of daily living (Brach & VanSwearingen, 2002). Few studies have examined the relationship between daily ambulatory activity and walking performance (Zalewski, Smith, Malzahn, VanHart, & O’Connell, 2009; Aoyagi et al., 2009), but this information is important in the design of walking programs and the promotion of walking to increase functional capacity and improve quality of life in older adults. To better gauge the relative influence of daily ambulatory
volume and intensity on walking performance, the current study examined the relationship between 30-min peak stepping cadence and walking speed after statistically controlling for the variance explained by average steps per day. Our novel finding is that peak cadence is independently related to fast walking speed and time to complete 400 m. Moreover, the relationship between average steps per day and walking performance was no longer present after controlling for daily peak cadence. Together, these results highlight the importance of walking intensity during daily physical activity with regard to lower extremity functional performance in older adults. The association between daily ambulatory activity and walking performance was found in women but not in men. This was unexpected considering that both sexes had similar average values for steps per day, peak cadence, fast walking speed, and 400-m walk time (Table 1). In addition, a previous study in older adults found steps per day and duration of activity at > 3 METs averaged over one year to associate with preferred and maximal walking speed in older women and men (Aoyagi et al., 2009). The authors noted a possible ceiling effect such that increased walking speed was marginal in adults that walked more than 10,000 steps per day or spent more than 30 min/day active in > 3 METs activity. In the current study, we did not observe a threshold for increased walking performance for daily steps or peak cadence in either sex (Figure 1). Furthermore, more women had taken > 10,000 steps per day (n = 5 vs. 1) or had a stepping cadence above the often-cited moderate intensity pace of 100 steps per min (n = 5 vs. 3) as compared with men (Marshall et al., 2009). Thus, it is unlikely that our results for men were due to a ceiling effect; however, it should be stressed that our sample size was small and may have limited our ability to observe a ceiling effect if present. Support for a possible sex difference in the relation between daily ambulatory activity and lower extremity performance does exist in the literature. In the same study mentioned above (Aoyagi et al., 2009), yearly averaged daily ambulatory activity was significantly associated with peak knee extension torque in
Table 2 Correlation Coefficients for the Relationship Between Daily Ambulatory Activity and Walking Performance Pearson Correlations Variable
Steps per Day
Peak Cadence
Partial Correlations Steps per Day†
Peak Cadence‡
All Steps per day
.80a
Fast walking speed
.36a
.48a
–.04
.34b
400 m walk time
–.35b
–.45a
.02
–.30b
Women Steps per day
.83a
Fast walking speed
.68a
.81a
–.01
.61a
400 m walk time
–.64a
–.74a
–.05
–.49a
Men Steps per day
.74a
Fast walking speed
–.16
.04
–.28
.21
400 m walk time
.14
–.05
.27
–.24
p < .01. p ≤ .05. † Adjusted for peak stepping cadence. ‡ Adjusted for steps per day. a
b
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Figure 1 — Partial regression plots showing the relationship between daily 30-min peak stepping cadence and walking performance in older women (A, C) and men (B, D). Variables in each plot were adjusted for age, body mass index, and steps per day.
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women but not in men. Other studies also report no association between average daily steps and leg muscle quality in older men despite a significant relationship in women (Scott, Blizzard, Fell, & Jones, 2009). Moreover, results from the Life-P study show that a year-long physical activity intervention focused primarily on walking increased 400-m walking speed in older women and men, but the change in walking speed was much more variable in men than women (LIFE Study Investigators et al., 2006). Given that sex differences have been identified for predictors of walking speed in older adults (Fragala et al., 2012), it is possible that daily ambulatory activity provides a potent stimulus to change factors that contribute to improved walking speed in women (Simonsick, Guralnik, Volpato, Balfour, & Fried, 2005) but provide an insufficient stimulus to change factors important for walking speed in men. More research with a larger and more diverse population is needed to address this postulation. Consistent with previous studies (Tudor-Locke et al., 2012; Schuna et al., 2013; Trayers et al., 2014; Tudor-Locke et al., 2013), we found that age is inversely associated with steps per day and peak cadence in older women and men. In addition, we found body mass index was inversely associated with peak cadence in women but not in men, supporting recent findings (Schuna et al., 2013). However, we extended current knowledge by demonstrating peak cadence is significantly associated with walking performance even after controlling for age, body mass index, and total daily steps (Figure 1). This makes sense when one considers that 30-min peak cadence is a measure of highest daily effort (Tudor-Locke et al., 2012), and it would be expected that older adults who perform regular brisk walking would be better suited to walk faster during a performance-based test. Thus, the current study finds 30-min peak cadence to provide unique information beyond age, body mass, and the volume of daily ambulatory activity relative to functional walking capacity in older adults. Future research in a larger sample is needed to confirm our results and test its usefulness in intervention studies aimed at improving walking capacity in older adults using daily ambulation as the primary mode of physical activity. Based on normative data (Tudor-Locke et al., 2013; TudorLocke et al., 2012), participants in this study had steps per day and peak cadence values above average for their age. For example, on average, women were between the 80–85th percentile and men between the 65–70th percentile for steps per day (Tudor-Locke et al., 2013). This suggests that our participants may have been more active than a general population of U.S. older adults. Thus, the present results should be interpreted with caution and may be more relevant to healthy free-living older adults. Indeed, other studies have reported a lack of association between daily ambulatory activity and walking speed in older adults with multiple comorbidities residing in health care retirement communities (Zalewski et al., 2009). Compared with the current study, steps per day were similar but peak cadence was much lower in the retirement community (20 vs. 70+ steps per min). Although the current study does not show causation, our results do suggest that higher daily 30-min peak cadence relates to increased walking performance. Thus, higher peak stepping cadences may be essential to observe a relationship between daily ambulatory activity and walking speed in older adults. The present study found steps per day (volume) were no longer associated with functional walking capacity after controlling for 30-min peak stepping cadence (intensity). This result supports the belief that more emphasis should be placed on intensity rather than volume when advocating walking as a means to improve health and fitness in older adults. Increasing stepping cadence in a walking
program could easily be achieved by using heart rate to inform of an intensity-based target cadence, audio feedback to either set the pace of walking or simply alert the individual to start walking faster, and/or incorporating intermittent fast pace walking (e.g., every other minute). The wide range of 30-min peak stepping cadence values in this study (all participants, 29–136 steps per min), and the fact that 81% of our participants had cadence values below what is thought to be a moderate intensity walking pace for adults (100 steps per min) (Marshall et al., 2009), prevents us from advocating a specific walking cadence from our data. Rather, our results suggest that simply walking at a faster cadence during daily physical activity may lead to greater functional capacity for older adults. There are some limitations in the present investigation. First, the sample size is small and comprised of healthy older adults that may not represent the general population. In addition, our exclusion criteria imposed a bias in recruitment toward older adults with a low cardiovascular risk profile, thus our data may not be generalizable to older adults with vascular disease. Second, we implemented a cross-sectional study design that prevents examination of cause and effect between daily ambulatory activity and walking performance variables. It is possible that people with higher 400-m walking speed had the functional (and mental) capacity to walk at a faster cadence during the top 30 min of daily physical activity. However, considering that regular exercise is a requisite to maintain functional capacity (Chodzko-Zajko et al., 2009), it is more likely that our peak cadence during daily ambulation served a stimulatory role for enhanced walking speed. Lastly, we assessed daily ambulatory activity using an accelerometer for only one week with some of these days removed from analysis after wear time validation. However, on average, we were able to analyze 6.3 ± 1.0 days (range 4–7 days) for daily ambulatory activity, which is above the recommended 4 days needed to achieve for 80% reliability in measuring walking behavior in older adults from a randomly-selected sample (Togo et al., 2008).
Conclusion Our results support the hypothesis that walking intensity during daily ambulation is more strongly related to functional walking capacity in older adults than the volume of daily ambulation, albeit this relation may be more significant for women than men. Practical implications of these results lie within promotion of daily physical activity with an emphasis of daily peak stepping cadence as a means of possibly improving walking ability in older adults.
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ORIGINAL RESEARCH
Steps per Day, Daily Peak Stepping Cadence, and Walking Performance in Older Adults Joaquin U. Gonzales, Jordan Shephard, and Neha Dubey We tested the hypothesis that the intensity of daily ambulation would relate with functional walking capacity in older adults. Forty-three women (n = 25) and men (n = 18) between the ages of 60–78 years wore an accelerometer for measurement of average daily steps and 30-min peak stepping cadence. A 400-m walk test was used to measure walking speed. No sex difference was found for average daily steps (p = .76), average peak cadence (p = .96), or walking speed (p = .89). Daily steps (women: r = .68, p < .01; men: r = .04) and peak cadence (women: r = .81, p < .01; men: r = –.16) were positively correlated with walking speed in women but not in men. After controlling for daily steps, peak cadence remained significantly associated with walking speed in women (partial r = .61, p < .01). Walking intensity during daily ambulation is independently related to functional walking capacity in older adults, albeit this relation may be more significant for women than men. Keywords: physical activity, accelerometer, gait speed, sex differences, ambulation, walking
Daily physical activity is advocated by public health organizations as an important strategy to maintain health and quality of life with advancing age. The U.S. government currently recommends that American adults accumulate at least 150 min of moderate intensity physical activity every week (U.S. Department of Health and Human Services, 2008). Walking is commonly prescribed to meet this physical activity recommendation as it is a simple mode of exercise. Time spent walking or greater number of steps taken per day is associated with many health benefits (Sesso, Paffenbarger, Ha, & Lee, 1999; Sesso, Paffenbarger, & Lee, 2000), and recent studies are highlighting the relative importance of walking intensity for increasing longevity in older adults (Williams & Thompson, 2013). Walking programs often use total steps (e.g., 10,000 steps per day) or minutes of walking (e.g., 150 min per week) to quantify the amount of physical activity (LIFE Study Investigators et al., 2006; Nemoto, Gen-no, Masuki, Okazaki, & Nose, 2007). This type of recommendation is easy to follow using commercially-available devices (e.g., pedometers) that provide detailed information about ambulatory activity. However, walking programs focused on total steps or accumulated time can misplace emphasis away from walking intensity. Walking at a fast pace or cadence is important for stimulating physiological adaptations that are intensity-dependent and are necessary to improve functional capacity (Nemoto et al., 2007). Indeed, older adults who spend more time walking at a moderate intensity (> 3 METs) during daily life are found to have higher preferred and fast walking speed than those who walk at a slower pace during daily activities (Aoyagi, Park, Watanabe, Park, & Shephard, 2009). In addition, time spent in daily moderate-tovigorous physical activity is found to positively correlate with fast walking speed (Gerdhem, Dencker, Ringsberg, & Åkesson, 2008) and predicts lower extremity performance in older adults (Trayers et al., 2014). It is difficult to separate the relative influence of volume versus intensity of physical activity. For example, walking at a
Gonzales, Shephard, and Dubey are with the Department of Health, Exercise and Sport Sciences, Texas Tech University, Lubbock, TX. Address author correspondence to Joaquin U. Gonzales at [email protected].
higher cadence (intensity of activity) will inadvertently increase the number of steps per day (volume of activity). Accelerometers are increasingly being used to measure daily ambulatory activity (Tudor-Locke et al., 2013). These devices allow for step count, but also the calculation of peak cadence (Tudor-Locke, Brashear, Katzmarzyk, & Johnson, 2012). Recently, a study examining these measures of daily ambulatory activity in older adults found them to hold separate associations with health markers such as body mass index (Schuna et al., 2013). Shared explained variance between these two related variables can be partitioned out using regression analysis to examine their independent associations. Using this approach, we sought to examine the independent relations of daily ambulatory volume and intensity with functional capacity in older adults. Based on the rationale that functional capacity is improved to a greater extent with intensity rather than volume of physical activity (Nemoto et al., 2007), we hypothesized that daily peak cadence would hold a stronger relationship with functional capacity than total steps per day. Moreover, we hypothesized that this relationship would remain significant even after controlling for variance explained by total steps per day. We selected the fast-pace 400-m walk test to assess functional capacity (Simonsick et al., 2001). From this test we can assess fast walking speed, which declines with advancing age (Ko, Hausdorff, & Ferrucci, 2010). Moreover, time to complete the 400-m walk test correlates with peak aerobic capacity (Simonsick, Fan, & Fleg, 2006), discriminates physical performance among well-functioning adults (Sayers, Guralnik, Newman, Brach, & Fielding, 2006), and strongly predicts future disability in older adults (Newman et al., 2006).
Methods Participants Data collected for a previous study (Gonzales, Defferari, Fisher, Shephard, & Proctor, 2014) examining the influence of vascular function on walking fatigue was used for the present investigation. Participants were recruited by posting advertisements in the local city newspaper and via weekly e-mail announcements sent to the university community. Advertisements called for people with no 395
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personal history of cardiovascular disease, diabetes, and pulmonary disease. Other exclusion criteria included taking medication for high blood pressure, cholesterol, or hormone replacement therapy, along with obesity (body mass index ≥ 30 kg/m2), hypertension (blood pressure > 149/99 mmHg), abnormal fasting blood glucose level > 115 mg/dL, or orthopedic limitations (e.g., knee pain) that impaired walking. Body weight was measured using a standard scale, blood pressure was measured by auscultation, and blood glucose was measured by finger prick after a 12-hr fast (Accu-Chek Active, Roche Diagnostics, Indianapolis, IN). Participants provided written informed consent before data collection. Fifty-seven older (≥ 60 years) adults consented and were screened. One adult was excluded for taking cholesterol medication, one adult was excluded for being classified as obese, two adults were excluded due to hypertension, and eight were excluded due to high fasting blood glucose levels. Forty-five community-dwelling older adults (25 women and 20 men, range 60–78 years) were included in this study. The Human Research Protection Program at Texas Tech University provided ethics approval for this study.
Daily Ambulatory Activity Daily ambulatory activity was objectively measured using a triaxial accelerometer (ActiGraph model GT3X+, Pensacola, FL) worn over the right hip with an elastic belt for seven consecutive days. Participants were asked to take it off during bathing, swimming, and sleeping. Accelerometers were programmed to collect data at a sampling rate of 30 Hz. Raw acceleration data were integrated to 60-s epochs without low-frequency extension to avoid exaggerated estimates of steps per day (Wanner, Martin, Meier, ProbstHensch, & Kriembler, 2013). The integrated file underwent wear time validation using automated software (ActiLife v6, Pensacola, FL). Nonwear time was defined using a 90-min time window for consecutive zero or nonzero activity counts, a 30-min consecutive zero activity count window for detection of artificial movements, and a 2-min spike tolerance (Choi, Liu, Matthews, & Buchowski, 2011). We also added a criterion that a day must have ≥ 10 hr of wear time to be considered valid (Troiano et al., 2008). All nonwear time was excluded from further analysis. As a result, two men had no valid days for analysis and were not included in this study. On average, adults wore the accelerometer for 6.3 ± 1.0 days after wear time validation. There was no sex difference in the number
of valid days analyzed for women (6.2 ± 1.2 days) and men (6.5 ± 0.8 days, p = .24). Steps per day were averaged across all valid days for each adult, and 30-min peak stepping cadence was calculated as the average steps per min for the 30 highest minutes in a day (but not necessarily consecutive minutes) for each adult as previously described (Tudor-Locke et al., 2012).
Walk Performance Test Participants were asked to refrain from caffeine for ≥ 12 hr and to avoid food and vitamins or supplements for 4 hr before completing the 400-m walk test to ensure testing procedures were consistent between individuals (American College of Sports Medicine, 2014). Two traffic cones were placed 20 m apart in a long flat-surfaced hallway. Participants were instructed to “Select a pace that you can comfortably maintain for 10 laps but you feel that you can complete in your best time.” No participants needed a break period during the test. The fastest lap (40 m) time was used to calculate fast walking speed. This was done to avoid the deleterious effect of performance fatigue on walking speed that can occur with endurance-based walking tests (Gonzales et al., 2014). Time to complete the entire 400 m was also recorded. Two 400-m walk tests were performed on separate days, the first for familiarization purposes and the second test was used for data analysis.
Statistics All data were normally distributed as assessed by a Kolmogorov– Smirnov test. Independent samples t tests were used to test for differences in descriptive characteristics between women and men. Pearson product–moment correlation coefficients were used to examine for bivariate relationships between variables. Partial correlation analysis was used to assess relationships between variables after adjusting for covariates. Data are presented as mean ± SD. Statistical significance was defined as p ≤ .05.
Results Table 1 presents the sample characteristics for all participants, separated by sex. Women were shorter, weighed less, and had a smaller body mass index than men (p < .05). No sex differences were found for age, resting blood pressure, daily ambulatory activity, or walking
Table 1 Characteristics of Participants Variable
All (N = 43)
Women (n = 25)
Men (n = 18)
p-value
Age (years)
67.3 ± 5.3
67.2 ± 5.6
67.5 ± 4.9
.89
Height (cm)
168.2 ± 9.4
162.5 ± 7.0
176.1 ± 6.1
< .01
Weight (kg)
66.2 ± 11.5
59.4 ± 8.0
75.6 ± 8.9
< .01
Body mass index (kg/m2)
23.2 ± 2.4
22.4 ± 2.4
24.3 ± 2.2
.01
Resting mean blood pressure (mmHg)
85.5 ± 9.8
84.2 ± 9.4
87.2 ± 10.6
.33
Fasting blood glucose (mg/dL)
94.5 ± 6.8
95.3 ± 6.8
93.5 ± 6.9
.39
7,083 ± 2,728
7,185 ± 3,148
6,941 ± 2,087
.76
77.0 ± 27.3
77.2 ± 29.5
76.8 ± 25.0
.96
Fast walking speed (m/s)
1.52 ± 0.17
1.52 ± 0.16
1.52 ± 0.19
.89
400 m walk time (s)
279.1 ± 32.4
279.6 ± 30.4
278.6 ± 36.0
.92
Ambulatory activity variables Steps per day Peak stepping cadence (steps/min) Walking performance variables
Note. Values are mean ± SD. JAPA Vol. 23, No. 3, 2015
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performance variables. Age was inversely correlated with steps per day (women: r = –.49, p = .01; men: r = –.58, p = .01) and peak cadence (women: r = –.49, p = .01; men: r = –.63, p = .005). Body mass index was unrelated to steps per day (women: r = –.28, p = .17; men: r = –.16, p = .52), but inversely correlated with peak cadence in women (r = –.46, p = .02) but not in men (r = –.07, p = .76). Fasting blood glucose and resting blood pressure were not associated with ambulatory activity in either sex (p > .05). The relationship between daily ambulatory activity and walking performance variables are shown in Table 2. Fast walking speed and 400-m walk time were correlated with steps per day and peak cadence (p < .05). These associations were present in women (p < .01), but not in men. After adjusting for steps per day, peak cadence remained significantly associated with walking performance variables in all participants and in women (p < .05), but not in men. Controlling for peak cadence attenuated the relationship between steps per day and walking performance variables to nonsignificant levels in all groups (p > .05). To further examine the strength of the association between daily peak cadence and walking performance, we adjusted for age, body mass index, and steps per day. Peak cadence remained significantly associated with fast walking speed and 400-m walk time in women, but not in men (Figure 1).
Discussion Walking is a common mode of exercise during daily physical activity in older adults (Bryan & Katzmarzyk, 2009) and, as such, is important for maintaining independence in activities of daily living (Brach & VanSwearingen, 2002). Few studies have examined the relationship between daily ambulatory activity and walking performance (Zalewski, Smith, Malzahn, VanHart, & O’Connell, 2009; Aoyagi et al., 2009), but this information is important in the design of walking programs and the promotion of walking to increase functional capacity and improve quality of life in older adults. To better gauge the relative influence of daily ambulatory
volume and intensity on walking performance, the current study examined the relationship between 30-min peak stepping cadence and walking speed after statistically controlling for the variance explained by average steps per day. Our novel finding is that peak cadence is independently related to fast walking speed and time to complete 400 m. Moreover, the relationship between average steps per day and walking performance was no longer present after controlling for daily peak cadence. Together, these results highlight the importance of walking intensity during daily physical activity with regard to lower extremity functional performance in older adults. The association between daily ambulatory activity and walking performance was found in women but not in men. This was unexpected considering that both sexes had similar average values for steps per day, peak cadence, fast walking speed, and 400-m walk time (Table 1). In addition, a previous study in older adults found steps per day and duration of activity at > 3 METs averaged over one year to associate with preferred and maximal walking speed in older women and men (Aoyagi et al., 2009). The authors noted a possible ceiling effect such that increased walking speed was marginal in adults that walked more than 10,000 steps per day or spent more than 30 min/day active in > 3 METs activity. In the current study, we did not observe a threshold for increased walking performance for daily steps or peak cadence in either sex (Figure 1). Furthermore, more women had taken > 10,000 steps per day (n = 5 vs. 1) or had a stepping cadence above the often-cited moderate intensity pace of 100 steps per min (n = 5 vs. 3) as compared with men (Marshall et al., 2009). Thus, it is unlikely that our results for men were due to a ceiling effect; however, it should be stressed that our sample size was small and may have limited our ability to observe a ceiling effect if present. Support for a possible sex difference in the relation between daily ambulatory activity and lower extremity performance does exist in the literature. In the same study mentioned above (Aoyagi et al., 2009), yearly averaged daily ambulatory activity was significantly associated with peak knee extension torque in
Table 2 Correlation Coefficients for the Relationship Between Daily Ambulatory Activity and Walking Performance Pearson Correlations Variable
Steps per Day
Peak Cadence
Partial Correlations Steps per Day†
Peak Cadence‡
All Steps per day
.80a
Fast walking speed
.36a
.48a
–.04
.34b
400 m walk time
–.35b
–.45a
.02
–.30b
Women Steps per day
.83a
Fast walking speed
.68a
.81a
–.01
.61a
400 m walk time
–.64a
–.74a
–.05
–.49a
Men Steps per day
.74a
Fast walking speed
–.16
.04
–.28
.21
400 m walk time
.14
–.05
.27
–.24
p < .01. p ≤ .05. † Adjusted for peak stepping cadence. ‡ Adjusted for steps per day. a
b
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Figure 1 — Partial regression plots showing the relationship between daily 30-min peak stepping cadence and walking performance in older women (A, C) and men (B, D). Variables in each plot were adjusted for age, body mass index, and steps per day.
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women but not in men. Other studies also report no association between average daily steps and leg muscle quality in older men despite a significant relationship in women (Scott, Blizzard, Fell, & Jones, 2009). Moreover, results from the Life-P study show that a year-long physical activity intervention focused primarily on walking increased 400-m walking speed in older women and men, but the change in walking speed was much more variable in men than women (LIFE Study Investigators et al., 2006). Given that sex differences have been identified for predictors of walking speed in older adults (Fragala et al., 2012), it is possible that daily ambulatory activity provides a potent stimulus to change factors that contribute to improved walking speed in women (Simonsick, Guralnik, Volpato, Balfour, & Fried, 2005) but provide an insufficient stimulus to change factors important for walking speed in men. More research with a larger and more diverse population is needed to address this postulation. Consistent with previous studies (Tudor-Locke et al., 2012; Schuna et al., 2013; Trayers et al., 2014; Tudor-Locke et al., 2013), we found that age is inversely associated with steps per day and peak cadence in older women and men. In addition, we found body mass index was inversely associated with peak cadence in women but not in men, supporting recent findings (Schuna et al., 2013). However, we extended current knowledge by demonstrating peak cadence is significantly associated with walking performance even after controlling for age, body mass index, and total daily steps (Figure 1). This makes sense when one considers that 30-min peak cadence is a measure of highest daily effort (Tudor-Locke et al., 2012), and it would be expected that older adults who perform regular brisk walking would be better suited to walk faster during a performance-based test. Thus, the current study finds 30-min peak cadence to provide unique information beyond age, body mass, and the volume of daily ambulatory activity relative to functional walking capacity in older adults. Future research in a larger sample is needed to confirm our results and test its usefulness in intervention studies aimed at improving walking capacity in older adults using daily ambulation as the primary mode of physical activity. Based on normative data (Tudor-Locke et al., 2013; TudorLocke et al., 2012), participants in this study had steps per day and peak cadence values above average for their age. For example, on average, women were between the 80–85th percentile and men between the 65–70th percentile for steps per day (Tudor-Locke et al., 2013). This suggests that our participants may have been more active than a general population of U.S. older adults. Thus, the present results should be interpreted with caution and may be more relevant to healthy free-living older adults. Indeed, other studies have reported a lack of association between daily ambulatory activity and walking speed in older adults with multiple comorbidities residing in health care retirement communities (Zalewski et al., 2009). Compared with the current study, steps per day were similar but peak cadence was much lower in the retirement community (20 vs. 70+ steps per min). Although the current study does not show causation, our results do suggest that higher daily 30-min peak cadence relates to increased walking performance. Thus, higher peak stepping cadences may be essential to observe a relationship between daily ambulatory activity and walking speed in older adults. The present study found steps per day (volume) were no longer associated with functional walking capacity after controlling for 30-min peak stepping cadence (intensity). This result supports the belief that more emphasis should be placed on intensity rather than volume when advocating walking as a means to improve health and fitness in older adults. Increasing stepping cadence in a walking
program could easily be achieved by using heart rate to inform of an intensity-based target cadence, audio feedback to either set the pace of walking or simply alert the individual to start walking faster, and/or incorporating intermittent fast pace walking (e.g., every other minute). The wide range of 30-min peak stepping cadence values in this study (all participants, 29–136 steps per min), and the fact that 81% of our participants had cadence values below what is thought to be a moderate intensity walking pace for adults (100 steps per min) (Marshall et al., 2009), prevents us from advocating a specific walking cadence from our data. Rather, our results suggest that simply walking at a faster cadence during daily physical activity may lead to greater functional capacity for older adults. There are some limitations in the present investigation. First, the sample size is small and comprised of healthy older adults that may not represent the general population. In addition, our exclusion criteria imposed a bias in recruitment toward older adults with a low cardiovascular risk profile, thus our data may not be generalizable to older adults with vascular disease. Second, we implemented a cross-sectional study design that prevents examination of cause and effect between daily ambulatory activity and walking performance variables. It is possible that people with higher 400-m walking speed had the functional (and mental) capacity to walk at a faster cadence during the top 30 min of daily physical activity. However, considering that regular exercise is a requisite to maintain functional capacity (Chodzko-Zajko et al., 2009), it is more likely that our peak cadence during daily ambulation served a stimulatory role for enhanced walking speed. Lastly, we assessed daily ambulatory activity using an accelerometer for only one week with some of these days removed from analysis after wear time validation. However, on average, we were able to analyze 6.3 ± 1.0 days (range 4–7 days) for daily ambulatory activity, which is above the recommended 4 days needed to achieve for 80% reliability in measuring walking behavior in older adults from a randomly-selected sample (Togo et al., 2008).
Conclusion Our results support the hypothesis that walking intensity during daily ambulation is more strongly related to functional walking capacity in older adults than the volume of daily ambulation, albeit this relation may be more significant for women than men. Practical implications of these results lie within promotion of daily physical activity with an emphasis of daily peak stepping cadence as a means of possibly improving walking ability in older adults.
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