Is achieving 7,000 steps/day associated with older adults’ lower-extremity performance? Cross-sectional and prospective ndings from Taiwan

Background: Evidence regarding the association between daily steps recommendation and older adults’ lower limb strength is lacking; thus, this study investigated whether taking at least 7,000 steps/day is cross-sectionally and prospectively related to lower-extremity performance in older Taiwanese adults. 89 community-dwelling adults aged over 60 years (mean age: 69.5 years) who attended both baseline and follow-up surveys. Methods: This study used adjusted logistic regression analysis to explore cross-sectional and prospective relationships between their accelerometer-assessed daily steps and lower-extremity performance (ve-times-sit-to-stand test). Results: This study found the older adults who took 7,000 steps/day were more likely to have better lower-extremity performance cross-sectionally (odds ratio [OR] = 3.82; 95% condence interval [CI]: 1.04, 13.95; p = 0.04), as well as to maintain or increase their lower-extremity performance prospectively (OR=3.53; 95% CI: 1.05, 11.84; p = 0.04). Conclusions: Our ndings support a minimum recommended level of step-based physical activity for older adults, namely, 7,000 steps/day, as benecial for maintaining or increasing older adults’ lower-extremity performance.


Background
According to a United Nations report [1], more than 40% of the population of Taiwan is expected to be aged 60 years or older by 2050, which would make Taiwan one of the top ten super-aged societies worldwide. As part of the aging process, older people experience a loss of muscle strength and mass [2], which makes them vulnerable to physical function decline [3]. Therefore, one of the key goals of superaged societies is maintaining or improving their aging population's physical functional abilities in order to prevent disability and increase their overall capacity for independent living [4]. Among the different components of physical function, lower-extremity strength plays a particularly critical role in preventing both impaired physical ability and disability in activities of daily living in older people [5]. As a result, it is critical to develop effective strategies for preventing older adults' physical function decline, especially with respect to their lower-extremity functional ability.
An umbrella review has highlighted the nding that engaging in regular physical activity effectively supports older adults in improving or delaying the loss of physical function [6]. It is well-documented that older adults should engage in at least 150 minutes of moderate-intensity aerobic physical activity and muscle-strengthening activities in a week, for the prevention of functional limitation or disability [7]. However, using type-, frequency-, duration-, and intensity-based parameters could be di cult for older adults to do with respect to self-monitoring, goal setting for, and self-managing their physical activity behavior [8].
Step-based physical activity recommendations along with assessments and interpretations of the number of steps taken per day (steps/day) could be easier for older adults to work with in terms of measuring their daily physical activity [9]. It is generally recommended that older adults take about 7,000 to 10,000 steps per day in their everyday living [10]. However, it remains unclear whether that current recommended minimum level of daily steps (that is, 7000 steps/day) is related to the maintenance or improvement of older adults' lower-extremity strength, with evidence from both cross-sectional and prospective studies in particular still lacking. Nonetheless, such information is of critical importance to healthcare professionals and physical activity professionals in designing effective strategies to prevent physical functional limitation or disability in older adults. Therefore, to strengthen the evidence base for the prevention of declines in physical function, this study investigated whether taking at least 7000 steps/day is cross-sectionally and prospectively related to lower-extremity performance in older Taiwanese adults, hypothesizing that this recommended minimum number of daily steps is both crosssectionally associated with better lower-extremity performance and prospectively related to higher odds of maintaining or increasing the lower-extremity performance community-dwelling older Taiwanese adults.

Participants and Procedures
The total of 170 community-dwelling older Taiwanese adults in this study at baseline using convenience sampling method. The all potential participants were recruited from four districts (Nangang, Wanhua, Daan, and Wenshan) of Taipei, Taiwan, from April (spring) to September (autumn) 2018. We used neighborhood broadcasts and local advertisements to recruit potential participants. Interested individuals contacted the study recruiters or neighborhood representatives. The sole inclusion criterion for the study was an age of 60 years or above. Furthermore, potential participants who were (i) unable to walk independently, (ii) not meet the minimum requirements of the accelerometer wear time (described later), or (iii) unable to understand the guidance for the questionnaires and physical function tests were excluded from the study. The 126 participants who remained after the application of these criteria were included in our study at baseline. The detailed procedure of the baseline recruitment used in this study has been previously reported [11]. At the baseline survey, each participant was administered a structured questionnaire by trained interviewers. After this interview, we gave each participant an accelerometer, which had to be worn for seven consecutive days. Every participant who completed the questionnaire, lower-extremity performance tests, and accelerometer portion of this study received a convenience store voucher worth 7 USD.
After one year, a follow-up lower-extremity performance test was conducted. A total of 98 of the older adults attended the on-site follow-up examination (follow-up rate: 77.8%). Finally, those with incomplete or missing study variable data in both the baseline and follow-up survey were subsequently excluded (n = 9). Ultimately, a total of 89 participants who provided complete data for the study variables were included in the analysis. Ethical approval was received from the Research Ethics Committee of the National Taiwan Normal University (REC number: 201711HM003). We obtained written informed consent from each participant, and the study was conducted in accordance with the ethical guidelines of the 1975 Declaration of Helsinki and all its revisions.

Accelerometer-assessed Daily Steps
Accelerometers (ActiGraph, Pensacola, FL, USA) were used to objectively assess each participants' daily step counts. The validity and reliability of such triaxial accelerometer have been widely con rmed [12][13][14][15][16][17]. For each participant, the accelerometer was used to record movement for seven continuing days. By following the standard methods [17], we used 60-second epochs for all data analyses [18]. We asked each participant to wear the accelerometer on the right side of his/her waist at all times except for waterbased activities. Non-wear time was de ned as the periods of not less than 60 consecutive minutes of zero counts per minute (cpm), with an allowance of up to 2 minutes of between 0-99 cpm [14]. Participants with at least three valid days (a valid day was de ned as at least 600 minutes of accelerometer wear time), including at least 1 weekend day, were included in this study. We utilized ActiLife software 6.0 (Pensacola, FL, USA) to analyze the accelerometer data. In accordance with the aforementioned step-based recommendation for older adults, we categorized the daily steps into "not taking at least 7,000 steps/day" and "taking at least 7,000 steps/day" [10].

Lower-extremity Performance Measures
The ve-times-sit-to-stand test is used to evaluate lower-extremity performance [19]. In taking the test, the participants were instructed to rise from a chair (which was 46 centimeters high and armless) to a full standing position and then return to a seated position as quickly as possible for ve repetitions. Each participant performed the test two times [20,21]. The best performance in terms of the total time taken for all ve repetitions (that is, the shortest time) was used for our analysis. For the cross-sectional analysis, we used a sex-speci c median for dichotomizing the baseline lower-extremity performance of the participants into "better" and "worse" categories. For the prospective analyses, we categorized the lower-extremity performance of the participants into "maintained or improved" and "declined" by calculating the differences in the lower-extremity performance between the follow-up and baseline for each participant.
Covariates Self-reported demographic characteristics, health-related behaviors, and the presence/absence of chronic diseases were assessed via interviewer-administered questionnaires. The covariates were sex, age group (60-74 or ≥ 75 years), educational level (university and higher or up to high school), marital status (married or not married), job status (with or without a full time job), living status (alone or with others), self-reported health (good or poor), current smoking status, alcohol consumption, balanced diet, hypertension status, blood lipid levels, diabetes status, depression status, and body mass index. Body mass index (BMI) was calculated using self-reported weight and height (categories: non-overweight and overweight) based on the cut-off points for the Asian population (24 kg/m 2 ) [22]. Moreover, accelerometer-measured sedentary time (< 100 counts/minute) and accelerometer wear time were included as covariates as they could confound the relationship between physical activity and health outcomes [23,24].

Statistical Analyses
Complete data for all the studied variables from 89 older adults were analyzed. Associations between taking at least 7,000 steps per day at the baseline and baseline lower-extremity performance (binary categories: "better" and "worse" based on a sex-speci c median) and the difference in lower-extremity performance between the baseline and 1-year follow-up (binary categories: "maintained or improved" and "declined") were examined using binary logistic regression models. Three different logistic regression models were conducted to investigate before and after adjusting for other covariates. The rst model showed unadjusted analyses (Model 1). In the adjusted regression models, the analyses were rst adjusted for sociodemographic characteristics (Model 2), and then further adjusted for health-related behaviors, chronic diseases, and accelerometer wear time (Model 3). Odds ratios (ORs) and their 95% con dence intervals (CIs) were estimated. Statistical analyses were conducted using SPSS 23.0 (IBM Inc., Armonk, NY, USA).

Results
In table 1, most of the overall participants who had complete data were women (70.8%), were aged 65-74 years (84.3%), had an educational level lower than university (77.5%), were without a full-time job (97.8%), were married (67.4%), lived with others (91.0%), were not overweight (53.9%), engaged in at least 9 hours per day of sedentary behavior (80.9%), took at least 7,000 daily steps (55.1%), had better lower-extremity performance at baseline (59.6%), and maintained or improved their lower-extremity performance after 1 year (52.8%). Table 1 Sociodemographic and health-related characteristics of participants  Table 2 presents the associations between taking at least 7,000 steps per day at baseline with the baseline and follow-up lower-extremity performance. In the unadjusted model (Model 1), older adults who took at least 7,000 steps per day were associated with better baseline lower-extremity performance (OR = 2.51, 95% CI = 1.05-5.97) and maintained or improved follow-up lower-extremity performance (OR = 3.14, 95% CI = 1.32-7.48) in comparison with their counterparts. In the adjusted models, similar associations were found in that those who took at least 7,000 steps per day had higher odds of better baseline lowerextremity performance (Model 2: OR = 2.54, 95% CI = 1.00-6.44; Model 3: OR = 3.82, 95% CI = 1.04-13.95) and maintained or improved follow-up lower-extremity performance (Model 2: OR = 2.89, 95% CI = 1.16-7.24; Model 3: OR = 3.53, 95% CI = 1.05-11.84) compared to those who did not take the recommended minimum of daily steps. Table 2 Achieving recommended daily steps among older adults aged 60 years or above being associated with lower-extremity performance at baseline and follow-up.

Baseline
Better lower-extremity performance

Discussion
To the best of our knowledge, this is the rst study using both a cross-sectional and prospective design to examine whether taking the recommended minimum number of steps of 7,000 steps/day was associated with lower-extremity performance in older adults. The most critical ndings of the present study were that, for older adult population, taking at least 7,000 steps per day [10] was positively related to lower-extremity performance, both in terms of the cross-sectional and prospective ndings. Therefore, with respect to initiatives for the prevention of functional decline in older adults, our ndings may be informative to health promotion practitioners and healthcare professionals in designing programs or interventions encouraging older adults to take at least 7,000 steps/day under free-living conditions. Consistent with those of previous studies [6,[25][26][27] indicating that meeting physical activity recommendation can help to improve or delay the loss of physical function in older adults, our results further extend previous ndings by demonstrating that achieving the recommended minimum level of step-based physical activity (7,000 steps/day) is also protective for older adults against lower-extremity functional decline. Our ndings can be explained by a number of previous laboratory-based trials, which demonstrated that accumulating a certain amount of physical activity in short bouts has the same health bene ts as engaging in the same overall amount of activity in a single continuous period in terms several health indicators [28][29][30][31]. Thus, the accumulation of daily steps to meet the goal of 7,000 steps/day could be as effective as goals recommended by current type-, frequency-, duration-, and intensity-based physical activity guidelines to maintain or improve physical function in older population. Our results can also add to the evidence for public health recommendations on accumulating physical activity for better health in older adults. Thus, our results indicate that in addition to type-, frequency-, duration-, and intensity-based parameters for physical activity, parameters regarding the accumulation of planned and incidental daily steps could provide an effective strategy for older adults to prevent their lower-extremity functional decline.
There were several limitations in the present study. First of all, our results need be explained with caution due to potential selection bias. For example, older adults with better physical function were more likely to attend this study than poor ones, and healthier older adults were also more likely to attend the follow-up examination. Second, the limited number of overall study participants should also be considered. As a result, our results could not be universalized to overall Taiwanese older adults. Future studies targeting larger or more representative older adult populations are warranted to further con rm our ndings. Finally, although we used only the ve-times-sit-to-stand test to evaluate lower-extremity performance, this test is one of the valid indicators for the lower limb function of older adults [32]. Nonetheless, future studies using a variety of objective measures for assessing lower-extremity strength are still needed.

Conclusions
Our ndings support the conclusion that the current recommended minimum of 7,000 steps/day for older adults is bene cial for maintaining or increasing their lower-extremity performance. Physical activity interventions focusing on the accumulation of 7,000 steps/day may thus be protective in terms of reducing the decline in physical function in older adults. These ndings provide additional evidence to support the inclusion of walking steps in the future physical activity guideline.

Declarations
Ethics approval and consent to participate Ethical approval was received from the Research Ethics Committee of the National Taiwan Normal University (REC number: 201711HM003). We obtained written informed consent from each participant, and the study was conducted in accordance with the ethical guidelines of the 1975 Declaration of Helsinki and all its revisions.

Consent for publication
Not applicable.

Availability of data and material
The dataset used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing of interest. . The Ministry of Science and Technology of Taiwan was not involved in the study design, data collection process, analysis, interpretation, or writing of this manuscript.

Authors' contributions
All authors read and approved the nal version of the manuscript. MCH, CYL, SHC and YL contributed to study conception and design, and critically reviewing and revising the manuscript. MCH, SHC conducting the study and drafting the manuscript. MCH and CYL wrote the rst draft of the manuscript. MCH, SHC and YL obtaining study funding. MCH, TFL and YCY participated the study investigation, data collection and analysis. SHC and YL were the supervisor of the whole research. All authors read and agreed the nal submitted manuscript.