A Modest Increase in Weekly Step Counts Improved Cardiovascular Function in Healthy Elderly

1

Walking and Functional Improvement

Exercise and Health

A Modest Increase in Weekly Step Counts Improved Cardiovascular Function in Healthy Elderly Women

LLOYD LAUBACH1, KIMBER PORTER1, PETER HOVEY2, JONLINDERMAN1

1Department of Health and Sport Science, University of Dayton, Dayton, OH, U.S.A.2Department of Mathematics, University of Dayton, Dayton, OH, U.S.A.

ABSTRACT

Laubach LL, Porter KL, Hovey P, Linderman J.A Modest Increase in Weekly Step Counts ImprovedCardiovascular Function in Healthy Elderly WomenJEPonline2009;12(6): 25-32. Physical activity (PA) is often quantified with step counts using pedometers. Few studies, however, have examined the use of pedometers to quantify an increase in physical activity following an exercise intervention in older women. The purpose of the present study was to examine changes in cardiovascular function and activities of daily living (ADLs)following an intervention designed to increase daily physical activity 2,000 steps/day. Modestly active women volunteered to participate in this study and were assigned to either an intervention group (E=20) or control (C=10). Cardiovascular function was assessed using the six-minute walk test (6MWT), while ADLs were assessed with a chair stand test and the up and go test. The E group increased step count ~1,300/weekat the end of the eight-week experimental period and increased cardiovascular function (6MWT) 3.4%. While the modest intervention employed presently achieved only 93% of its target goal to improve physical activity, the increased daily step counts led to an increase in cardiovascular function. Collectively, the results indicate that the modest intervention to encourage increased PA in older women is beneficial to improving cardiovascular health.

Key Words: Aging, VO2max, Activities of Daily Living, Pedometer

INTRODUCTION

In 2005, according to the Center for Disease Control and Prevention, somewhere between 38-44% of American adults ages 55 and older do not meet the CDC/ACSM recommendations for physical activity (PA) (1). Research has clearly established a positive association between levels of PA and health (2). Walking is a simple and popular mode of low-to-moderate-intensity PAreadily available to a majority of the population. Quantification of PA through walking has been studied using pedometers (3). Although pedometers do not directly assess intensity of walking, quantifying step counts has been used to assess volume of physical activity. Further, Tudor-Locke and Bassett (3) have developed a classification of lifestyle activity based upon step volume (steps/day). Theyclassifieda volume of <5,000 steps/day as sedentary, 5,000 to 7,500 steps/dayas low active, 7,500 to 9,999 steps/day as somewhat active, 10,000 to 12,499 steps/dayas active, and ≥12, 500 steps as highly active (3).

Unfortunately, as an individual ages,average walking volume decreases (4), consistent with declining lean bodymass and increased obesity. Both of these body composition changes are associated with increased risk for cardiovascular disease. Obese individuals average ~2,000 steps/day fewer than leaner individuals (4). This volume of activity is roughly equivalent to a mile or 15 to 20 minutes of walking, and the energy expenditure associated with these 2,000 steps represents 80 to 100 kcals, depending upon the subject’s bodymass. It is also known that women are statistically more likely to be obese than men (5), suggesting that daily PA may be even more important to women than men to achieve or maintain ideal body weight (6). The purpose of the present study was to prescribe a 2,000 step/day increase in the PA for a group of women greater than 59 years of age over an eight-week period. The increase in step count was monitored using a pedometer, and changes in cardiovascular function, body composition, and activities of daily living were assessed pre- and post-intervention.We hypothesized that an increase of 2,000 steps/dayin an eight-week period would result in an improvement in cardiovascular health of modestly activeolderwomen.

METHODS

Subjects

The volunteer sample consisted of 30 modestly active women who were faculty, staff, alumni or retirees of the University of Dayton, or citizens of the Dayton, OH community enrolled in a walking program provided by the University of Dayton’s Faculty-Staff Wellness Program. The subjects chose to enroll in this program. Females 59 years of age and older were eligible to participate. Exclusion criteria included body mass index (BMI)40 kg/m², resting blood pressure 160/100 mm Hg, and orthopedic limitations to walking (2). All 30 participants were apparently healthy. They had physician consent to participate. Each one completed a health history questionnaire and a physical readiness questionnaire. All procedures were reviewed and approved by the Institutional Review Board at the University of Dayton, and all subjects signed an informed consent form prior to baseline testing. Following baseline testing,the subjects were randomly assigned to either an experimental intervention group (E=20) or a non-intervention control group (C=10).

Procedures

Subjects reported to the laboratory for baseline testing two weeks prior to the intervention. The following data were obtained: resting blood pressure, body weight, height, body mass index (BMI), body fat percentage, cardiorespiratory capacity (distance covered in a six-minute walk test), lower body strength (30-second chair stand), physical mobility (up and go test), and average baseline steps per day.

Resting systolic and diastolic blood pressure measurements were taken following a 10-minute rest period using a mercury sphygmomanometer. Body weight was obtained from each subject wearing minimal clothing (Life Measurement Instruments, Concord, CA), and height measured to the nearest mm. Height and weight werethen used to determine BMI. Body composition was determined using air displacement plethysmography(Bod Pod; Life Measurement Instruments, Concord, CA) using proceduresrecommended by the manufacturer (7). The Siri equation was used to convert density to percentage of body fat (8).

To measure the subjects’ cardiorespiratory capacity, subjects participated in a six-minute walk test (6MWT) (9). The 6MWT has been reported to be correlated to VO2maxin a number of populations,including the elderly (9) and patients with lung disease (10). Each subject wore a heart rate monitor and performed the 6MWT independently of others. The protocol required the subject to walk at herown self-selected pace for six minutes. Communicationwith each subject was done using the same verbal cue at each minute marker. Each subject walked around an unobstructed indoor course that was 50 feet in length. After completion of a lap, the subject dropped a straw in a bucket. At the end of the six minutes, the subject was asked to stop. The test administrator tallied the straws and measured the remaining distance from the starting line. The floor was marked with tape signifying the distance of the course. Testing was performed twice with at least 12 hours between the tests. The higher value was used for all subjects.

Lower body strength was determined by a 30-second chair stand test (11). Each subject was required to complete as many stands from a seated position as possible in 30 seconds. The test was started with the subject seated in the middle of the chair (16.5 inches) with back straight and feet flat on the floor. The subject was instructed to cross her arms at the wrists and hold them against her chest for the duration of the test. On the go signal, the stopwatch began, and the subject rose to a full stand, returning to a seated position for as many times as possible in 30 seconds. The chair was 16.5 inches in height and had no arms. For stability and safety purposes, the chair was placed against the wall (11).

Physical agility was measured by the up and go test (12). Each subject was instructed to stand, walk 16 feet, and sit back down in the fastest possible time. The subject began in a seated position, in a chair that was stable against a wall. On command by one of the investigators, the subject rose from the chair,walked eight feet to a cone, turned around, and returned to the chair and sat. The tester served as a spotter, ready to assist the subject in case of loss of balance. The stopwatch began when the tester said “go” and stopped when the subject was fully seated. Each subject performed the test twice. The lowest time achieved was recorded for each subject.

Two weeks prior to the walking intervention, eachsubject was required to wear a Yamax SW-200 (Yamax, Tokoyo, Japan) pedometer throughout waking hours and record step volume at the conclusion of the day. The pedometer has been shown to give reliable step volume in both clinical and field studies (13). It was placed on the belt or waistband, in the midline of the thigh. At the end of the seven days, the subject telephoned or electronically mailed her daily step count to the test administrator. The test administrator computed the baseline average daily step count of each subject.

Intervention

The subjects were randomly divided into the experimental intervention group (E) and a control group (C). The E group was given a goal of increasing daily step count by 2,000 steps/dayat the end of the eight weeks of study participation. At the beginning of each week, the subjects were notified of their individual daily step goal for that week. Their daily average step count was determined by increasing their pre-intervention baseline step count by an additional 250 steps/day, each week. By the end of eight weeks, the subjects average daily step count was to be 2,000 steps over their baseline. At the end of the eight-week intervention period, post testing took place with the same procedure as the base line assessments.

Statistical Analyses

Data were analyzed using a General Linear Model (SPSS;Statistical Package for the Social Sciences version 16.0). Significant differences in meanswere assessed using a t-test (p<0.05). The following variables were analyzed: body weight, BMI, percentage of body fat, resting systolic blood pressure, diastolic blood pressure, distance walked in six minutes (6MWT), the number of chair stand tests in 30 seconds, and the time to walk 16 feet. Increased step volume was correlated with changes in body composition, cardiorespiratory fitness, and activities of daily living (ADLs).

RESULTS

At the conclusion of the eight-week intervention, all 30 participants who completed the baseline testing remained for the post intervention testing, for a retention rate of 100%. Therefore, results are reported on all 30 subjects, with 20 subjects in the experimental group (E) and 10 subjects in the control group (C). There were no significant differences in the measurements at baseline between the control and experimental groups (Table 1).

According to the average daily baseline and ending step count, the women in this study were classified as being somewhat active (8097 vs. 8604 steps/day; E vs. C, respectively)(4). Subjects in the E group achieved 93% of the 2,000 step count increase goal (8097 vs. 9372 steps/day; pre- vs. post-intervention, respectively) (Figure 1), representing a 15.7% increase in daily physical activity. Subjects in the C group increased their daily step count ~6% (8,604 vs. 9147; pre- vs. post-intervention, respectively), but this increase was evident only in the last week (Figure 1).

The 6MWT, a measurement of cardiovascular function, revealed a significant improvement in the E group (p<0.05; Table 1). Subjects in the E group demonstrated a 3.5% increase in distance walked during the 6MWT after eight weeks (565.1 ± 46.2 vs. 584.9 ± 44.6 m; pre- vs. post-intervention, respectively). Subjects in both the experimental and control group were more cardiovascular fit than other women their age, as measured by the 6MWT (9). Women in the E group began the study at about the 65th percentile and improved to the 75thpercentile, while the C group remained around the 75th percentile pre- and post-intervention (14).

Subjects in both the E and C groups demonstrated significant improvements in ADLs (p<0.05; Table 1). The magnitude of change was similar for both groups in strength (chair stand test) and agility (sixteen feet up and go test).

DISCUSSION

The primary purpose of this study was to determine if a modest intervention, specifically a weekly goal for increased physical activity (PA) as determined from an increase in step count, would improve functional performance for elderly women. Although the subjects did not fully achieve the stated goal, an increase of ~1,300 steps over an eight-week period improved cardiovascular function, and supports findings from the Colorado on the Move Survey (4) as well as the INCHANTI study (15). Considering the improvement in cardiovascular function and the minimal investment of time by the investigators, these results should be encouraging for wellness practitioners.

Numerous previous studies indicate that pedometers are an effective tool in monitoring PA(15-17). Further, more active individuals, as determined by the use of pedometers, are leaner and have a reduced risk of cardiovascular disease (CVD) risk factors such as hypertension (16). When used as a tool in intervention studies, the use of pedometers to provide goals for increasing PA has resulted in a decrease in body mass and blood pressure (6). Hultquist and colleagues have also reported retention of higher levels of PA in a one-year follow-up study of subjects wearing pedometers following a four-week intervention to increase PA (17). Pedometersare an effective tool for monitoring PA with and without intervention,and they provide a stimulus for sustaining increased PA.

Previous studies have noted that a decline in PA with age may be a factor in the increase in weight with age (4,5,18). The increase in body mass is likely a result of the decrease in energy expenditure (EE) resulting from an age-associated decrease in PA. The YAMAX step counter has been shown to reflect EE related to PA in children (19), but reportedly underestimates EE in adult women (20). On average, the subjects in this study were classified as somewhat active based on weekly step counts and BMI (Table 1). Our results, both pre- and post-intervention, indicate thatwomen with a lower average daily step counts were more likely to have a higher BMI (r=-0.461 and -0.473, pre- vs. post-intervention, respectively). The Colorado Statewide survey found similar findings indicating that obese participants, as measured by BMI, were most likely to take the lowest number of steps per day (4). Although subjects in the present investigation did not exhibit significant reductions in body mass, BMI, or body fat (Table 1), it is likely that a longer intervention period would have led to changes in body composition.

Our measures of ADLs were improved in both the E and C groups (Table 1). The reason for this improvement is not completely clear. However, both groups received pre- and post-testing and were aware that they were involved in a study of PA and wellness. The subjects that were recruited were also enrolled in a walking program. Although the C group showed no improvement in the 6MWT, the C group did exhibit an increase in step count by the end of the intervention period of eight weeks. These observations suggest that the subjects were aware that they were being monitored, and although they received no instructions with regard to increasing PA, it is apparent that by the end of the study they had increased their activity. This conclusion is evidenced by the increase in step counts of ~6% pre- to post-intervention in the C group. However, only the E group increased step counts to the extent that it improved the 6MWT. Only those subjects given a target goal to increase PA improved cardiovascular function.

A limitation of the present study was the use of the 6MWT as an objective measure of improved cardiovascular function. It is generally accepted that VO2max is the best objective measure of cardiovascular function. Due to the age of the subjects, the investigators chose to use the 6MWT, which presented less risk and is more easily administered than a graded maximal exercise test. Previous research indicates significant correlation between the 6MWT and VO2max or VO2peak in elderly subjects (70-85 years of age; r=0.47) and subjects with lung disease (r=0.79), and this correlation is much higher (r=0.87) when factors such as weight and heart rate are included (9). It was not the aim of the present investigation to measure or predict VO2max from the 6MWT, rather to monitor change in cardiovascular function using the 6MWT.

CONCLUSIONS

Collectively, results of the present investigation indicate that the intervention (i.e., a weekly increase in step counts) increased PA and improved cardiovascular function. It is important to note thatwhile the subjects failed to fully achieve the goals for increased step counts,the intervention provided a modest training stimulus that resulted in an improvement in the subjects’ work capacity. These results are particularly encouraging given the minimal investment in time of the investigators to stimulate an increase in PA in the subjects.

ACKNOWLEDGEMENTS

The authors wish to thank Dr. Noel Hayden for his technical assistance in the collection of experimental data and Dr. Jayne Brahler for her assistance with statistics.

Address for correspondence: Jon K. Linderman, PhD. Department ofHealth and SportScienceUniversity of Dayton, Dayton, OH, USA, 45469-1210. Phone (937) 229-4207; FAX: (937)229-4244; Email.

REFERENCES

1. Haskell WL, Lee I-M, Pate RR, Powell KE, Blair SN, Franklin BA, Macera, CA, Heath, GW, Thompson PD, Bauman A. Physical activity and public health: Updated recommendations for adults from the AmericanCollege of Sports Medicine and the American Heart Association. Med Sci Sports Exer 2007; 39: 1423-1434.

2. Nelson ME, Rejeski WJ, Blair SN, Duncan PW, Judge JO, King AC, Macera CA Castaneda-Sceppa C. Physical activity and public health in older adults: Recommendation from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 2007; 39:1435-1445.

3.Tudor-Locke C, Bassett Jr. DR. How many steps/day are enough? Preliminary indices for public health. Sports Med 2004; 34:1-8.

4. Wyatt HR, Peters JC, Reed GW, Barry M, Hill JO. A Colorado statewide survey of walking and its relation to excessive weight. Med Sci Sports Exerc 2005;37:724-730.

1. Poehlman ET. Physical Activity and Obesity. C. Bouchard (Ed.) Champaign, IL: Human Kinetics, 2000:263-278.

6.Hultquist CN, Albright C, Thompson DL. Comparison of walking recommendations in previously inactive women. Med Sci Sports Exerc 2005; 37:676-683.