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Use of Accelerometers to Examine Sedentary Time on an Acute Stroke Unit

Mattlage, Anna E. BS; Redlin, Sara A. DPT; Rippee, Michael A. MD; Abraham, Michael G. MD; Rymer, Marilyn M. MD; Billinger, Sandra A. PT, PhD

Journal of Neurologic Physical Therapy: July 2015 - Volume 39 - Issue 3 - p 166–171
doi: 10.1097/NPT.0000000000000092
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Background and Purpose: Observational studies demonstrate low levels of physical activity during inpatient stroke rehabilitation. There are no prior studies that have objectively measured sedentary time on the acute stroke unit and whether sedentary time is related to functional outcomes. The purpose of this study was to characterize sedentary time after acute stroke and determine whether there is a relationship to functional performance at discharge.

Methods: Thirty-two individuals (18 men; 56.5 ± 12.7 years) with acute stroke were enrolled within 48 hours of hospital admission. An accelerometer was placed on the stroke-affected ankle to measure 24-hour activity and was worn for 4 days or until discharge from the hospital. Performance of activities of daily living, walking endurance, and functional mobility were assessed using the Physical Performance Test, Six-Minute Walk Test, and Timed Up and Go, respectively.

Results: Mean percent time spent sedentary was 93.9 ± 4.1% and percent time in light activity was 5.1 ± 2.4%. When controlling for baseline performance, the mean time spent sedentary per day was significantly related to Physical Performance Test performance at discharge (r = −0.37; P = .05), but not the Six-Minute Walk Test or Timed Up and Go.

Discussion and Conclusions: Patients with acute stroke were sedentary most of their hospital stay. To minimize the potential negative effects of inactivity, our data suggest that there should be greater emphasis on increasing physical activity during the hospital stay.

Video Abstract Available for more insights from the authors (Supplemental Digital Content 1, http://links.lww.com/JNPT/A101).

Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City (A.E.M., S.A.R., and S.A.B.); Department of Neurology, University of Kansas Medical Center, Kansas City (M.A.R. and M.G.A.); and University of Kansas Hospital, Kansas City (M.M.R.).

Correspondence: Sandra A. Billinger, PT, PhD, Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, 3901 Rainbow Blvd, Mail Stop 2002, Kansas City, KS 66160 (sbillinger@kumc.edu).

Preliminary aspects of this work were previously presented at the 2014 International Stroke Conference, February 13, 2014 in San Diego, California.

S.A.B. was supported in part by K01HD067318 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. S.A.R. and A.E.M. were supported in part by T32HD057850 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. A.E.M. was also supported in part by Award Number 14PRE20040026 from the American Heart Association. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The REACH laboratory space was supported by the Georgia Holland Endowment Fund. The authors also thank the participants for giving their time and effort to this study. In addition, the authors thank Dr Lee Rosterman for providing data regarding lesion size, Lindsay Lloyd for assisting in gathering data from the electronic health record for therapy minutes, and Michael Bagwell, Cara Stingley, and Courtney Rooney for their assistance with the data collection.

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's Web site (www.jnpt.org).

The authors declare no conflicts of interest.

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INTRODUCTION

Older adults recovering from an acute illness in the hospital spend approximately 83% of their day lying in bed and this high level of inactivity has been termed an “underrecognized epidemic.”1 What do we know about inactivity after acute stroke? In trying to understand activity patterns during stroke recovery, observational studies in Australia and Norway have also examined activity during inpatient stroke rehabilitation and have reported high levels of sedentary time.2,3 When activity was observed in 10-minute intervals from 8:00 AM to 5:00 PM, patients during inpatient stroke rehabilitation were seen in bed or sitting 76% of the day and standing or walking 23% of the day.2 Furthermore, greater time spent in bed has been associated with a poorer outcome on the modified Rankin Scale at 3 months poststroke.3 This evidence suggests that during an inpatient rehabilitation stay, individuals after stroke are spending a large majority of their time engaging in sedentary behavior, which could have a negative impact on functional recovery. Because the acute stroke hospital length of stay in the United States is considerably shorter than lengths of stay in the countries participating in the early mobilization trials (∼14 days),4,5 it is imperative that we better understand activity patterns during the acute stroke hospital stay in the United States so that we can consider strategies for decreasing sedentary time.

Direct observation of people hospitalized with acute stroke is an acceptable method for describing activities performed during the day. However, this method has the potential to miss capturing physical activity that occurs outside of the observed time. For example, the observation studies in people with stroke have typically been conducted during the weekday and during usual work hours (ie, 8:00 AM to 5:00 PM).2,3,5 This limits documentation of activity in the evening hours, nighttime, or on weekends. However, using an objective measure such as accelerometry would allow for continuous 24-hour monitoring (including sleep hours) without additional personnel burden for observation of activity. The accelerometers would provide information on intensity of activity such as light or vigorous activity, steps, and characterization of physical activity patterns in people who were inpatients in an acute stroke unit. To our knowledge, no objective quantification of physical activity using accelerometers has been conducted during the acute stroke hospital stay in the United States.

Therefore, the purpose of this study was to objectively assess sedentary time using triaxial accelerometers during the acute US hospital stay of individuals with stroke. We examined whether the amount of time sedentary was related to functional performance at discharge. On the basis of previous research,1 we hypothesized that individuals with acute stroke would spend more than 80% of their hospital stay sedentary. Furthermore, we hypothesized that greater mean time spent sedentary over a course of a day would be moderately and significantly related to poorer functional performance on the Physical Performance Test (PPT), 6-Minute Walk Test (6MWT), and Timed Up and Go (TUG) at discharge from the hospital.

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METHODS

Study Design

This study used a prospective design with a sample of convenience. Approval of the project was obtained from the Human Subjects Committee at University of Kansas Medical Center. Institutionally approved written informed consent was obtained prior to the study participation.

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Participants

Participants with a diagnosis of acute stroke who were between 20 and 80 years of age were enrolled into the study within 24 to 48 hours of their admission to the certified Comprehensive Stroke Unit at the University of Kansas Hospital. Participants were admitted into either the neurological progressive care or neurological intensive care units of the hospital. Patients who are suspected of, or diagnosed with, stroke are commonly admitted to these floors. The neurological progressive care unit is staffed with 1 nurse for every 4 patients and several nursing aids across the floor. The intensive care unit is staffed with 1 nurse for every 2 patients as well as several nursing aids. Rehabilitation services are available 7 days per week. Therapy services on the weekends were identical in duration and intensity to those provided during the week day. A comprehensive list of participant demographics can be found in Table 1. Individuals were excluded if they were on physician-ordered bed rest.

Table 1

Table 1

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Overview

After consent, a tri-axial accelerometer (ActiGraph GT3X+, ActiGraph LLC, Pensacola, Florida) was placed on the stroke-affected limb at the ankle. When the Fugl-Meyer score was 34/34 on both legs (n = 6), we collected data from the right ankle. The accelerometer is more reliable when placed on the ankle versus the hip or spine to measure step count in older adults with and without an assistive device.6 The water-resistant accelerometers were worn for 24 hours per day until the day of discharge from the hospital, but no longer than 4 days. This timeframe was selected as the maximum length a priori since the average length of stay at the University of Kansas Hospital for people with acute stroke was 4 days. Our research team would check on the participants throughout the day to make sure that the accelerometers were correctly placed and the participants were comfortable with wearing the accelerometers. Nursing staff was given our 24-hour hotline number and if any issues such as noncompliance or skin irritation occurred, they would leave a message and the team would follow up.

The accelerometers monitored 24-hour, real-time activity in all 3 planes of movement in 10-second epochs. Analysis of sedentary time (in minutes) was performed (ActiLife Version 6.6.3; ActiGraph LLC), including percent time spent in sedentary activity, and in light, moderate, and vigorous activity, steps per day, and time sedentary per day (TSPD) (in minutes). One day was defined as each 24-hour period starting immediately after consent. For example, if a person was consented at 3 PM, a day would be defined from 3 PM until 2:59 PM the next day and each day thereafter until discharge. If discharge occurred prior to a “day,” then sedentary time was calculated on the basis of the time the accelerometers were worn and not a full 24-hour period as this would bias results. Cut points for intensity of activity were based on information previously reported and validated in adults.7 These were based on the following: light activity, 1951 counts or less; moderate activity, 1952 to 5724 counts; and vigorous activity, 5725 counts or more.7 Sedentary time was defined as any activity that does not amount to more than 99 counts (per analysis software). Baseline functional assessments were performed after placement of accelerometers. Follow-up testing was conducted on the day of discharge or 4 days after baseline testing, whichever came first.

Information regarding participants' lesion size and location, previous medical history, current medications, weight, height, body mass index, and total therapy minutes for physical and occupational therapy were obtained from each participant's electronic health record. In addition, we gathered information regarding their physical and occupational therapy minutes. The Fugl-Meyer Assessment (FMA) was used to assess motor performance of the lower extremity.8 Total score on the lower extremity FMA is 34, and a higher score is indicative of lower stroke impairment. Functional assessments included PPT, 6MWT, and TUG.

The PPT, an assessment of performance of activities of daily living, has been reported as a valid and reliable test used in many populations including individuals with dementia, Parkinson disease and those who are elderly.9–13 Although data have not been published in acute stroke, the PPT has been used in individuals who have experienced transient ischemic attack and stroke.10 The PPT is a test in which the participant completes 9 tasks of activities of daily living. Each task is timed and then scored on a scale of 0 to 4, depending on their time, with 0 indicating unable to complete the task without assistance and 4 indicating completion of the task in the fastest time category. The total score on the PPT is 36, with a higher score indicative of better performance in activities of daily living. The 6MWT was performed according to previous guidelines outlined by the American Thoracic Society.14 Individuals were asked to walk as far as they could for 6 minutes and the distance walked in meters was recorded. A longer distance walked in 6 minutes is indicative of better walking endurance. Methods of the motor portion of the FMA and the TUG have been described previously.8,15 For the TUG, individuals started the test in a seated position. They were instructed to stand up, walk 3 m to and around a cone, walk back to the chair, and sit down. A faster time on the TUG suggests higher functional mobility. Participants were allowed to rest as needed between functional tasks.

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Data Analysis

Descriptive statistics were performed to obtain sample mean percent time spent in sedentary, light, moderate, and vigorous activities, sample mean steps per day (SPD), sample mean TSPD, sample mean score on PPT, sample mean distance on the 6MWT, and sample mean time on the TUG. Mean percent time spent sedentary per hour was derived from ActiLife software and then plotted using SigmaPlot (Systat Software Inc, San Jose, California). Mean percent time spent in sedentary, light, moderate, and vigorous activities was reported as an overall percent time over the duration of the hospital stay across participants. Time sedentary per day was expressed as 100 × (total minutes spent in sedentary time × 1440 minutes − 1). To assess the relationship between TSPD and functional performance of each variable (PPT, 6MWT, and TUG) at discharge, we used a Pearson correlation. To understand the strength of the relationship between TPSD and functional performance, we used criteria defined by Portney and Watkins16: Pearson coefficient (r) = 0.00 to 0.25, little to no relationship; r = 0.25 to 0.50, fair relationship; r = 0.50 to 0.75, moderate to good relationship; and r > 0.75, good to excellent relationship. Since admission (or baseline) functional scores have been reported as important predictors of discharge scores in stroke,17 we took a more conservative approach and controlled for baseline performance in our data analysis for the functional assessments. Statistical methods for the linear regressions were based off the methods previously used.18 Briefly, we used a multistep, hierarchical linear regression with TPSD as the predictor variable and the PPT score at time 2 as the response variable controlling for baseline PPT performance. Standardized residuals generated from the linear regression were then plotted. P values were considered significant at ≤.05. All statistical analyses were performed using SPSS (IBM Statistics Software Version 20, Armonk, New York).

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RESULTS

We screened 683 individuals with an acute stroke and enrolled 38 participants in our study. Of the 38 enrolled participants, 6 were not included in the analysis. The reasons for nonenrollment and exclusion from data analysis are outlined in Figure 1. Thirty-two people (18 men; mean age of 56.5 ± 12.7 years) were used for data analysis except for the Timed Up and Go (n = 23). If participants were unable to stand up from the chair using the armrests to initiate walking, they were coded as “unable” and not included in the data analysis examining the relationship between sedentary time and functional performance at discharge. These individuals were included in the primary aim, which was describing activity during the acute hospital stay.

Figure 1

Figure 1

Participants spent a mean of 2.5 ± 0.9 days enrolled in this study. Twenty-eight individuals were discharged from the hospital prior to 4 days of enrollment. Therefore, 6 individuals completed 4 full days of accelerometer monitoring. In addition, 8 individuals were enrolled the same day as their admission to the hospital and 26 were enrolled after their admission date, but within 48 hours.

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Characterization of Sedentary Time

Our results suggest that people after acute stroke spend the majority of their time sedentary and almost no time in moderate or vigorous activity (see Table 2). Participants took a mean of 1907 ± 1594 steps per day. On average, 22.6 ± 15.9 minutes per day were spent in physical therapy and 15.2 ± 12.7 minutes per day spent in occupational therapy. The total accumulated therapy minutes for physical and occupational therapy are presented in Table 2.

Table 2

Table 2

Sedentary behavior per hour was lowest during the hours of 9:00 to 11:00 AM and 2:00 to 4:00 PM. Between the hours of 9:00 and 11:00 AM, mean percent time spent sedentary per hour was at its lowest at 91% (Figure 2) while light activity accounted for 7%. During this time, participants walked a mean of 337 steps per hour.

Figure 2

Figure 2

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Sedentary Time and Functional Outcome

Baseline performance for all functional measures is presented in Table 1. A multistep hierarchical linear regression revealed a significant, weak relationship between TSPD and discharge performance on the PPT (r = −0.37; P = .05) when adjusting for baseline performance (Figure 3). However, when examining the relationship between TSPD and discharge performance on the 6MWT (r = −0.20; P = .29) and TUG (r = 0.23; P = .37), no significant relationship was observed when adjusting for baseline performance. From baseline to discharge, participants improved their PPT score, 6MWT distance, and TUG time a mean of 42%, 37%, and 12%, respectively.

Figure 3

Figure 3

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DISCUSSION

The primary finding of this study was that inpatients with stroke are sedentary for the majority of the acute hospital stay. To our knowledge, this is the first study within the US health care system to objectively quantify sedentary time using accelerometers during an acute stroke hospital stay.

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Characterization of Sedentary Time

We hypothesized that patients with stroke would spend 80% of their time sedentary as measured by accelerometers. We reported that the mean daily time spent sedentary was approximately 94% of their hospital stay. Our findings are similar to previous observational studies during inpatient rehabilitation19 in that the majority of the time is spent sedentary. Our study differs from previous studies in that we used accelerometers to continually assess activity level rather than behavioral mapping and observation.19

We report that time spent sedentary per day was high (94%) or 22.5/24 hours. Since we used 24-hour monitoring with accelerometers, this does include nighttime when patients were sleeping. The methods used in this study allowed us to capture all movement and activity during a 24-hour period in a continuous and objective manner without adding bias through observation. Typically, adults aged 60 years and older sleep for an average of 7.4 hours (30% of their day) between the hours of 10:48 PM ± 1 hour and 6:54 AM ± 1 hour.20 Sedentary time for our participants was highest within the timeframe that was reported by Klerman and Dijk.20 However, some of our participants were not completely sedentary during usual times of sleep (see Figure 2).

Our study suggests that people hospitalized with an acute stroke spend a higher percentage of time sedentary than what is reported in the literature for an acute medical illness.1 Given the negative effects of inactivity, patients with acute stroke appear to be at even greater risk for complications. Bed rest studies have demonstrated negative vascular adaptations21 and loss of muscle mass, which decreases muscle strength.22 Furthermore, people after acute stroke demonstrate poor cardiopulmonary fitness23 and previous work has suggested that activities during rehabilitation are not performed at intensities that would elicit improvements in cardiopulmonary fitness.24 Therefore, efforts to increase physical activity and minimize decline from sedentary behavior should be encouraged. Using a multidisciplinary team approach to reduce sedentary time such as early mobilization during the acute hospital stay may slow the further decline of cardiopulmonary health and allow people poststroke to engage more efficiently in rehabilitation. Because of the stroke-related impairments that often exist, such as hemiparesis and loss of muscle mass,25,26 novel strategies for decreasing the amount of time spent sedentary in the hospital are critical. Furthermore, the recent publication from the American Heart Association/American Stroke Association for Physical Activity and Exercise Recommendations for Stroke Survivors suggests that we need to better understand physical activity patterns during acute stroke and conduct research to gain a better understanding of a dose response to “slow or prevent loss of cardiopulmonary fitness.”27

While this study is the first to use accelerometers in acute stroke in the United States, others have examined physical activity during inpatient rehabilitation and community living. Prajapati and colleagues28 used accelerometers to assess self-selected walking activity in subacute stroke in one single day on the inpatient rehabilitation unit. The 8 participants ranged from 13 days to 68 days poststroke and all could ambulate with or without an assistive device independently. The authors report that while their participants were independent with their ambulation (with/without assistive device), they spent little time (about 10%) of their day in activity such as walking. This similar pattern appears to remain consistent when individuals poststroke return home. Roos and colleagues29 monitored walking activity, using activity monitors in people poststroke and otherwise healthy older adults dwelling in the community. Their findings also support that community-dwelling individuals spend less time in bouts of walking during the day after stroke when compared with healthy adults. Our data suggest that sedentary time begins during acute stroke recovery. Therefore, physical therapists and other health care providers should work with people after stroke to minimize inactivity and meet the recommended minutes for physical activity and exercise.27

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Sedentary Time and Functional Outcome

This is the first study to examine the relationship between sedentary time using accelerometry and functional performance measures. We hypothesized that we would see a moderate correlation between functional outcome measures and sedentary time. Baseline performance likely influences performance at discharge. Therefore, we chose to be conservative and control for baseline performance on all outcome measures in our analysis. We report that the PPT had a fair and significant relationship with sedentary time. This may be due to the comprehensive activities (balance, walking, feeding, dressing) that are included in the PPT. The 6MWT and TUG (n = 23) had little to no relationship with sedentary time. The 6MWT and TUG are walking activities and perhaps not sensitive to detecting change in a few days following an acute stroke. We must also consider that sedentary time may be higher early after stroke as patients are being evaluated by the therapy team regarding walking performance. Therefore, people after stroke may not be encouraged to move about during this time or wait until therapy or nursing is available to assist.

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Limitations

There are several limitations to the study that must be considered when interpreting results. The sample size for this pilot study was small but provides preliminary data to inform large-scale studies of in-hospital sedentary time and the relationship to functional outcome measures such as the 6MWT and TUG. We used the device on the ankle to provide the most accurate measure for step counts.6 However, our primary outcome was physical activity levels, not step counts. Therefore, we do not know how accurate the device is for assessing this specific parameter. We did not track the time of day that physical and occupational therapy occurred. Therefore, we do not know how much “activity” time was self-initiated or occurred during therapy time but our data do provide information regarding continuous activity during the acute hospital stay. The PPT is a measure of physical performance and consists of simulated activities of daily living but has not been validated in acute stroke. Finally, we did not gather information regarding other comorbidities or prior orthopedic injury, joint replacement, or low back pain. It is possible that comorbid conditions could have contributed to reduced mobility during the stroke hospital stay.

Future work should begin to elucidate the benefits of early physical activity and how stroke recovery may benefit from incorporating physical activity early after stroke. A recent review by Zeiler and Krakauer30 made several excellent points regarding the importance of the “sensitive period” in the early phase of stroke recovery. The authors discussed the available literature suggesting that enriched environments and engaging in activity (task-specific training) enhances recovery from stroke. The data we present suggest that early after stroke the majority of the patients with stroke are sedentary and are not spending their time engaging in activity that could be optimal for recovery. Most of the activity occurred early in the morning, which again leaves the remainder of the day inactive and patients possibly alone in their room. Considering ways to encourage more activity whether through early mobility or spending time out of their room would be advantageous.

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CONCLUSION

Patients after an acute stroke spent the vast majority of their time sedentary during the hospital stay. Furthermore, sedentary time was inversely related to performance in our outcome measures. Given the well-documented and rapid onset of the negative effects of inactivity, our data suggest that there needs to be a focus of reducing inactivity upon admission. Therapists, with their clinical understanding of movement after stroke, are key providers to initiate and guide increasing activity and mobility.

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REFERENCES

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Keywords:

accelerometer; acute stroke; functional performance; physical activity

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© 2015 Neurology Section, APTA
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