Motivation and emotion/Book/2018/Walking and emotion

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Walking and emotion:
How does walking affect emotion?

Overview[edit | edit source]

[Provide more detail]

Focus questions
  • What effect does walking have on our emotions?
  • What factors should we consider when examining the relationship between walking and emotion?

Walking and depression[edit | edit source]

[Provide more detail]

Walking and the Beck Depression Inventory[edit | edit source]

Figure 1: Walking has a positive impact on not only depression but on schizophrenia, anxiety disorders, post-traumatic disorders and substance abuse (Rosenbaum and colleagues 2015)

Depression is defined by Bröer and Besseling in 2017 as the emotion sadness with the durability of a mood.[1] Cooney and colleagues in 2014 ran a meta-analysis on walking and depression from a very extensive data set comprising of 39 trails and totaling in 2,326 participants.[2] Their study found that exercise could significantly predict a reduction in depression scores. The team found a Beck Depression Inventory (BDI) of -0.62 and confidence intervals being between -.81 and -.42. This was considered to be a moderate effect size (with .20 being small, .50 being moderate and .80 being a large effect). These statistics mean that those who exercised more experienced less depression because the BDI is in the negative direction. By reducing depression we are therefore reducing the chance that one will feel the emotion associated with sadness.

Mobility and depression[edit | edit source]

The benefits of walking extend to coping, self-esteem and health status. This was Bergland and colleague's hypothesis for their journal article in 2010.[3] Although their study had a mean age for participants being 65.6 only 0.7 percent were not able to walk and 80.8 percent could walk at least one kilo-meter without pause. The results for their study are discussed and they found that participants who report higher self-report health had higher outdoor walking ability. While those participants who had a poor self-reported mobility had higher levels of depression.

The relationship between walking and emotion in Parkinson's disease[edit | edit source]

What is the relationship between walking ability, emotion and cognitive impairment in people with Parkinson's disease. This was the research question posed by Avanzino and colleagues in a recent 2018 article.[4] The team found growing evidence that emotional disturbances related to affect disorders such as anxiety and depression contributed to walking disorders among people with Parkinson's disease. The team also found that cognitive impairment could predict whether participants had a walking disorder. In consequence the team proposed that we need to consider emotional and cognitive factors when examining the performance of walking among people with Parkinson's disease.

Yearlong walking improves depression in older adults[edit | edit source]

Aoki and colleagues in 2017 conducted a year long experiment to see if they could increase walking in participants and whether that improved their mental health.[5] 180 participants were divided between two groups, one being an exercise group and the second being a non exercise group with a mean age of 72.2. The results showed that participants in the exercise group had a significant improvement in CES-D (The Center for Epidemiological Studies Depression Scale) scores p < .001 when compared to the baseline values. The average steps counted per day of walking for the exercise group significantly increased, compared to the baseline values. So in conclusion Aoki and colleagues in 2017 suggest that walking can be used in order to treat depression and that exercise can be increased with the right interventions. In the exercise and mood book chapter for 2014, it was reported by Berger and Motl in 2000 that exercise could also regulate short-term mood by reducing feelings of anger, stress and depression.[6] Anger is also described as an emotion, so sadness is not the only emotion that improves with exercise.

Walking to treat other disorders: an Australian study[edit | edit source]

In 2015 Rosenbaum and colleagues reflect on how physical activity has been used increasingly to treat mental disorders.[7] The team found that physical activity doesn't just treat depression but can also be used to treat disorders like schizophrenia, anxiety disorders, post-traumatic stress disorders and substance abuse. Rosenbaum and colleagues concluded that physical activity is effective to usual care while acknowledging the need for psychiatrists, psychologists, physiologists, physiotherapists and other requirements that the patient may need. Overall however the team agreed that there must be investments in aiming to increase physical activity for mental health patients, ensuring that not only mental benefits are reaching the patient but the physical too. In the exercise and emotion book chapter for 2013, it was also reported by Fox and colleagues in 2006 that exercise can prevent dementia and Alzheimer's disease.[8]

Quiz[edit | edit source]

1 Which disorder was correlated with poor self-reported mobility in Bergland and colleagues study?

walking disorder.
anxiety disorder.
cognitive disorder.
depressive disorder.
eating disorder.

2 Cooney and colleagues in 2014 found a negative correlation -0.62 between walking and the Beck Depression Inventory (BDI), what does this mean?

BDI scores were higher for participants who walked.
Participants who walked in the study experienced less depression.
Participants who walked in the study experience more depression.
Walking behavior could not predict BDI scores for participants.

3 What was the three variables investigated for participants with Parkinson's disease in Avanzino and colleagues study?

walking ability, emotion and cognitive impairment.
walking ability, stress, social support.
emotion, social support, stress.
stress, cognitive impairment, social support.

4 What was the probability of the scores from the participants who were in exercise group of Aoki and colleagues study was coming from chance?


5 What mental disorder was not reported as treatable with physical activity?

Anxiety disorders.
Post-traumatic disorders.
Obsessive-compulsive disorder.

Walking, emotion and environment[edit | edit source]

[Provide more detail]

Walking in the prospect heights of Brooklyn[edit | edit source]

Figure 2: A walk through the prospect heights of Brooklyn. Gabrielle Bendiner-Viani in 2005 reported positive emotion even though it was considered as no utopia.

There is empirical evidence to support walking in relieving depression. What about the environment in which people walk, does that have an impact on the psyche? There is a study that suggests it does. Gabrielle Bendiner-Viani in 2005 looked at walking, emotion and dwelling in the prospect heights of Brooklyn. [9] The researcher discovered that when locals walk among their local environments there are deep emotional connections that foster positive relationships between not only the environment where they walk but among themselves too. Even to an outsider visiting the prospect heights, the researcher described the walk through the local playground and supermarket as having a warm positive energy even though this place was considered as no utopia. In the green exercise and emotion book chapter for 2013 it included walking in an urban park as green exercise because you are exposed to nature.

Emotions of young, walking adults[edit | edit source]

In another study Seto and colleagues in 2016 looked at the influence of routine, physical activity, emotion and food environment.[10] The study included 12 participants and each one required a smartphone for recording. The team reported that all participants regardless of being underweight (17%), overweight (17%) or normal weight (66%) believed that exercise is important in their lives. Furthermore the team found that the participants reported moderate levels of happiness which is defined as positive emotions ranging from contentment to extreme joy. While the participants had on average low levels of stress, tiredness and sadness. These higher levels of happiness and lower levels of sadness could be due to the amount of walking each participant did in the 2 week program. Seto and colleagues in 2016 found that on average each participant had 33 stay points with 6 being the minimum. While on average each participant came in proximity with 1158 food establishments over the 2 weeks of tracking. This is a substantial statistic and its important because it reflects the participants young age group's (mean age 24.6) walking patterns and offers reasons for the low levels of negative emotion.

Environment plays a role in walking patterns[edit | edit source]

Patterson and colleagues in 2014 investigated the relationship between the environment and its effect on walking.[11] Barriers that prevent people from experiencing positive emotion when they walk may come from abnormal walking patterns. The conditions presented to participants included a normal path, busy hallway, rough ground, blind folded and on a hill. The technology used to monitor walking patterns was quite advanced with sensors on the chest and shins, with a camera on the chest too. All five conditions proved to be significant in predicting walking patterns. The conclusion therefore being that the environment in which we walk effects the way we walk and thereby how pleasant the walk will be. This has important implications as abnormal walking may be the result of the environment rather than internal changes. Bergland and colleagues in 2010 investigated the relationship between mobility and depression. One consideration to make for their study in particular would therefore be to also assess the environment in which a participant is walking, to see if it's having an impact on mobility.

Quiz[edit | edit source]

1 What finding was most important for Gabrielle Bendiner-Viana in 2005 when exploring the prospect heights of Brooklyn?

That environments considered to be no utopia can foster positive emotion.
That walking anywhere produces positive effects.
That the environment in which you walk is irrelevant to emotion.
Emotions can be triggered by environmental cues.

2 Which number comes closest to the average amount of food establishments that participants came in proximity with in Seto and colleagues study?


3 What was the main conclusion in Patterson and colleagues study?

That environment's can be a hard place to walk on.
That abnormal walking may be the result of the environment rather than internal causes.
That normal paths, busy hallways, rough grounds, being blind folded and hills produce different effects.
That technology is improving quite rapidly.

Walking and music effect on emotion[edit | edit source]

[Provide more detail]

The joy of walking faster with music[edit | edit source]

Figure 3: From the classic: The Sound of Music starring Mary Martin. This particular scene includes music and running.

An interesting piece of literature to study is how music affects our performance in walking. Leow and colleauges in 2015 investigated the relationship between music and walking performance, with a particular interest in the familiarity of music and if it brought the participants joy.[12] Two key findings to highlight from this study are firstly that being familiar with the beat structure of the music predicts a more synchronized and faster walk (or gait). The second finding is that being familiar with the music also predicts enjoyment which if combined with the first finding means that you walk faster with music that you enjoy. Leow and colleagues also have evidence for this in their explanation of how familiar music can release the neurotransmitter dopamine into the system which in turn makes one move faster.

Less physical exertion with music[edit | edit source]

A similar finding was also discussed by Silva and colleagues in the same year of 2015.[13] They found that the 12 obese participants taking part in the study to walk for 30 minutes experienced less perceived exertion and more positive affect when walking with music as apposed to no music. In this study the results showed a peculiar finding however, the %HRmax-VT (percent of maximum heart rate and ventricular tachycardia) was the same for those who listened to music and those who did not. So even though the participants listening to music were under the same physical pressure as the participants not listening to music, the one's listening to music experienced less perceived pressure. It was noted by Silva and colleagues in 2015 that the participants listening to music also had more positive affect. This is similar to Leow and colleagues 2015 study because they suggest that music and physical activity produces joy.

Music can change velocity and motivation[edit | edit source]

Participants in Buhmann and colleagues 2016 study were first instructed to walk on an indoor track in silence and then with tempo-matched music.[14] The results were able to find music that has an activating effect, increasing velocity and motivation and music that has a relaxing effect, decreasing velocity and motivation. The team also discuss how there is emerging evidence that self-paced walking produces more positive affect over prescribed intensity training. The team conclude with these findings that applying this knowledge can improve emotion, prevent injuries, guide walking rehabilitation and improving performance in sports activities.

Quiz[edit | edit source]

1 What were the two key findings for Leow and colleagues study in 2015?

People walk more with music and enjoyment comes after walking.
That a familiar beat structure correlates with a faster and more enjoyable walk.
Music has little relationship with walking because evidence shows that people either listen to music on the computer or in the car.
People who walk with music experience emotions that are mild and stable.

2 What psychological and physical effects did Silva and colleagues find from participants who listened to music while walking?

Psychologically participants felt joy, physically they felt less pain
Psychologically participants felt tired, physically they felt energized
Psychologically participants felt calm, physically they felt strong
Psychologically participants felt less exertion, physically they felt the same
Psychologically participants felt more exertions, physically they felt strong

3 What two variables changed when music changed in Buhmann and colleagues study?

Emotion and motivation.
Motivation and synchronicity.
Velocity and motivation.
Synchronicity and velocity.

The relationship between walking and emotion[edit | edit source]

[Provide more detail]

A hint to the positive affect of walking[edit | edit source]

Figure 4: This is the average walking speed for a person. Approximately one and a half meters per second. Ekkekakis and colleagues in 2008 suggest walking speed as a factor to determine how much positive affect you will feel from walking.

What effect does walking have on emotion and in particular is the effect positive or just neutral. Ekkekakis and colleagues in 2008 explored the relationship between these variables.[grammar?][15] The team hypothesized that the effect would be neutral mainly because the evidence at this time was scarce in favour for a positive affect. Ekkekakis and colleagues main point was that walking isn't intense and long enough to produce a positive affect. Although this was the hypothesis, the results painted a different picture. The team found that even short, self-paced walking left participants feeling more energized.

Experiment finds a positive affect on emotion[edit | edit source]

Could this mean feelings of happiness from the participants or just a revitalized feeling in the body. A recent study by Miller and Krizan in 2016 investigated the relationship between walking and positive affect with an emphasis on emotion.[16] The team first defined a high positive affect as experiencing feelings of positive engagement with the environment accompanied with emotions like excitement, joy and enthusiasm. Miller and Krizan in 2016 included 232 undergraduate students in their study on walking and positive affect. Participants were randomly assigned to either a sitting condition or a walking condition. The team had to use some mild deception to make participants think that they were responding to how particular environments made them feel. One group was assigned to walk a tour around the campus while the other group was assigned to sit in a computer lab to go on a virtual tour (showing pictures of the campus). Both experiments lasted 12 minutes and participants were required to remain silent throughout the experiment. Finally students were asked questions about their tour experience and a PANAS (positive and negative affect schedule) was conducted. The results showed that the positive affect associated with the positive emotions, excitement, joy and enthusiasm were significantly higher for those in the walking condition p < .0001.

Positive emotion can predict walking frequency among participants with knee osteoarthritis[edit | edit source]

White and colleagues conducted an interesting study in 2012 that analyzed the relationship between a positive attitude and walking with knee osteoarthritis.[17] The results showed that participants with positive emotions walked a similar number of steps per day while those with depressive symptoms walked less. Therefore those participants high in positive affect were associated with more daily walking among adults with knee osteoarthritis. The team concluded therefore that positive emotions represent a crucial psychological factor to consider for promoting walking among those with painful knee osteoarthritis.

Quiz[edit | edit source]

1 In summary what was Ekkekakis and colleagues hypothesis and results?

That walking would have a neutral affect; even short self-paced walking produced benefits.
That walking would have a positive affect; only long self-paced walking produced benefits.
That walking would have a neutral affect; only long self-paced walking produced benefits.
That walking would have a positive affect; even short self-paced walking produced benefits.

2 What three emotions were associated with positive affect in Miller Krizan 2016 experiment on walking?

Joy, satisfaction, pride
Excitement, satisfaction, pride
Joy, excitement, enthusiasm
Enthusiasm, excitement, satisfaction
Excitement, enthusiasm, pride

3 Why was White and colleagues study on knee osteoarthritis different from Bergland and colleagues study on mobility?

Because knee osteoarthritis is more severe than most mobility issues.
Because White and colleagues study improved participants walking ability while Bergland didn't.
Because 80% of participants could walk in Bergland study.
Because in White and colleagues study, emotion predicted walking ability, while in Bergland and colleagues study, walking ability predicted emotion.
Because in Bergland and colleagues study participants were younger than White and colleagues study.

Walking with social support[edit | edit source]

[Provide more detail]

Contact with neighbors reinforces walking[edit | edit source]

Figure 5: This is an unusual case of walking. People here are involved in 'proper walking' because they have a goal, as well as 'dispersed walking' because their attention is split between walking and socializing.

Van Cauwenberg and colleagues in 2014 introduce the idea of neighborhood social environment and walking for the transportation of older adults.[18] They first acknowledge the physical, social and mental health benefits of regular exercise and state that this knowledge is well-established. The team found a positive relationship between participants contact with neighbours and daily walking. Furthermore the statistic representing this was that participants were 98% more likely to walk if the frequency of contact with neighbours was high rather then if it was not. The team concluded that there are three dimensions to consider when investigating the relationship between social environment and walking. They are, the effect of interpersonal relationships, place attachment and formal community engagement.

Proper walks and dispersed walking[edit | edit source]

Harries and Rettie in a 2016 article thought it was important to distinguish between the different ways to measure walking and types of walking in general.[19] The team warn people of the limitations of digital feedback and the exercise value of walking as these measurements for walking only provide a partial view. The team argues that in order to understand why people walk and therefore implement strategies to increase and maintain walking, one needs to view walking as a social practice. Consequently we must understand and distinguish between 'proper walks' and 'dispersed walking'. Harries and Rettie defined 'proper walks' as walks that have a specific goal (hikes). While 'dispersed walking' is far more complex because it refers to the type of walking you do in the house, at the supermarket, with friends and family etc. The team argue that this is the reason why walking is less salient as running for example, because people often do it without realizing they are. Harries and Rettie reported one participant Perter, who said that when walking with friends, the focus is on having a laugh The Fun Theory 1 - Piano Staircase Initiative: Volkswagen and you often forget that you are walking.

Walking and social activity to improve sleep in nursing home[edit | edit source]

One can fall into a deep sleep after feeling the emotion of contentment resulting from a satisfying days work. Richards and colleagues in 2011 knew this and so they devised a study that aimed to increase participants sleep in a nursing home.[20] There influence included the implementation of strength training, walking and social activity. The team labeled strength training and walking as E and social activity as SA. The results proved to be significant with the ESA group being higher in sleep time than the control group (adjusted means 364.2 minutes vs 328.9 minutes).

Quiz[edit | edit source]

1 What percentage represents the likelihood of participants walking if they come in regular contact with neighbours for Van Cauwenberg and colleagues study?


2 Why was Figure 5 unusual?

Because a lot of people were hiking together
Because they were all happy
Because these people were taking part in both 'proper' walking and 'dispersed' walking
Because everyone was involved in 'proper' walking even though they were together
Because they were doing intense 'dispersed' walking

3 Approximately, how many minutes of extra sleep did the ESA group get when compared to the control group in Richards and colleagues study?

10 minutes
20 minutes
30 minutes
40 minutes
50 minutes

Conclusion[edit | edit source]

When evaluating the effect that walking has on our emotions, there are a few key findings that need to be highlighted. Firstly, that depression is defined as the emotion sadness with the durability of a mood. With the right interventions Aoki and colleagues found that walking can significantly improve depression. In Seto and colleagues’ study, the youthful participants (mean age 24.6) who believed that exercise was important part of their lives reported higher levels of happiness (emotions ranging from contentment to extreme joy) and lower levels of stress, tiredness and sadness. Music was also found to not only predict walking performance but joy too. In Leow and colleagues’ study the team found that participants listening to familiar music improved walking speed and enjoyment. Miller and Krizan inventory for a positive affect in walking included the emotions excitement, joy and enthusiasm. These emotions were found in their study to increase when compared to the control group. Finally Harries and Rettie theorized that people can engage in ‘dispersed’ walking where people don’t even realize they are because the social support, making walking more enjoyable and less physically exerting. In conclusion this evidence suggests that not only can walking reduce negative emotions like anger and sadness and it can also facilitate positive emotions like excitement and joy.

See also[edit | edit source]

References[edit | edit source]

External links[edit | edit source]

  1. Bröer, Christian; Besseling, Broos (2017-06). "Sadness or depression: Making sense of low mood and the medicalization of everyday life". Social Science & Medicine 183: 28–36. doi:10.1016/j.socscimed.2017.04.025. ISSN 0277-9536. 
  2. Cooney, Gary; Dwan, Kerry; Mead, Gillian (2014-06-18). "Exercise for Depression". JAMA 311 (23): 2432. doi:10.1001/jama.2014.4930. ISSN 0098-7484. 
  3. Bergland, Astrid; Thorsen, Kirsten; Loland, Nina Waaler (2010/08). "The relationship between coping, self-esteem and health on outdoor walking ability among older adults in Norway". Ageing & Society 30 (6): 949–963. doi:10.1017/S0144686X1000022X. ISSN 1469-1779. 
  4. Avanzino, Laura; Lagravinese, Giovanna; Abbruzzese, Giovanni; Pelosin, Elisa (2018-09). "Relationships between gait and emotion in Parkinson’s disease: A narrative review". Gait & Posture 65: 57–64. doi:10.1016/j.gaitpost.2018.06.171. ISSN 0966-6362. 
  5. Aoki, Takumi; Sakuma, Haruo; Ishii, Kojiro (2017-05). "Yearlong Walking Exercise Improves Depression and Health-related Quality of Life in Older Adults". Medicine & Science in Sports & Exercise 49: 3. doi:10.1249/01.mss.0000516813.91395.5c. ISSN 0195-9131. 
  6. Berger, Bonnie G.; Motl, Robert W. (2000-03). "Exercise and mood: A selective review and synthesis of research employing the profile of mood states". Journal of Applied Sport Psychology 12 (1): 69–92. doi:10.1080/10413200008404214. ISSN 1041-3200. 
  7. Rosenbaum, Simon; Tiedemann, Anne; Stanton, Robert; Parker, Alexandra; Waterreus, Anna; Curtis, Jackie; Ward, Philip B (2015-07-02). "Implementing evidence-based physical activity interventions for people with mental illness: an Australian perspective". Australasian Psychiatry 24 (1): 49–54. doi:10.1177/1039856215590252. ISSN 1039-8562. 
  8. Fox, Kenneth R.; Stathi, Afroditi; McKenna, Jim; Davis, Mark G. (2007-02-07). "Physical activity and mental well-being in older people participating in the Better Ageing Project". European Journal of Applied Physiology 100 (5): 591–602. doi:10.1007/s00421-007-0392-0. ISSN 1439-6319. 
  9. Bendiner-Viani, Gabrielle (2005-11). "Walking, Emotion, and Dwelling". Space and Culture 8 (4): 459–471. doi:10.1177/1206331205280144. ISSN 1206-3312. 
  10. Seto, Edmund; Hua, Jenna; Wu, Lemuel; Shia, Victor; Eom, Sue; Wang, May; Li, Yan (2016-04-06). "Models of Individual Dietary Behavior Based on Smartphone Data: The Influence of Routine, Physical Activity, Emotion, and Food Environment". PLOS ONE 11 (4): e0153085. doi:10.1371/journal.pone.0153085. ISSN 1932-6203. PMID 27049852. PMC PMC4822823. 
  11. Patterson, Matthew R.; Whelan, Darragh; Reginatto, Brenda; Caprani, Niamh; Walsh, Lorcan; Smeaton, Alan F.; Inomata, Akihiro; Caulfield, Brian (2014-08). "Does external walking environment affect gait patterns?". 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE). doi:10.1109/embc.2014.6944249. ISBN 9781424479290. 
  12. Leow, Li-Ann; Rinchon, Cricia; Grahn, Jessica (2015-03). "Familiarity with music increases walking speed in rhythmic auditory cuing". Annals of the New York Academy of Sciences 1337 (1): 53–61. doi:10.1111/nyas.12658. ISSN 0077-8923. 
  13. Silva, Aldo C.; Alves, Ragami C.; Ferreira, Sandro S.; Follador, Lucio; Baldari, Carlo; da Silva, Sergio G. (2015-05). "Influence of Music During Walking at a Self-paced Intensity on Ratings of Perceived Exertion and Affective Responses in Obese Women". Medicine & Science in Sports & Exercise 47: 785. doi:10.1249/ ISSN 0195-9131. 
  14. Buhmann, Jeska; Desmet, Frank; Moens, Bart; Van Dyck, Edith; Leman, Marc (2016-05-11). "Spontaneous Velocity Effect of Musical Expression on Self-Paced Walking". PLOS ONE 11 (5): e0154414. doi:10.1371/journal.pone.0154414. ISSN 1932-6203. PMID 27167064. PMC PMC4864300. 
  15. Ekkekakis, Panteleimon; Backhouse, Susan H.; Gray, Catherine; Lind, Erik (2008-05). "Walking is popular among adults but is it pleasant? A framework for clarifying the link between walking and affect as illustrated in two studies". Psychology of Sport and Exercise 9 (3): 246–264. doi:10.1016/j.psychsport.2007.04.004. ISSN 1469-0292. 
  16. Miller, Jeffrey Conrath; Krizan, Zlatan (2016). "Walking facilitates positive affect (even when expecting the opposite).". Emotion 16 (5): 775–785. doi:10.1037/a0040270. ISSN 1931-1516. 
  17. White, Daniel K.; Keysor, Julie J.; Neogi, Tuhina; Felson, David T.; LaValley, Michael; Gross, K. Doug; Niu, Jingbo; Nevitt, Michael et al. (2012-08-27). "When it hurts, a positive attitude may help: association of positive affect with daily walking in knee osteoarthritis. Results from a multicenter longitudinal cohort study". Arthritis Care & Research 64 (9): 1312–1319. doi:10.1002/acr.21694. ISSN 2151-464X. PMID 22504854. PMC PMC3410957. 
  18. Van Cauwenberg, Jelle; De Donder, Liesbeth; Clarys, Peter; De Bourdeaudhuij, Ilse; Buffel, Tine; De Witte, Nico; Dury, Sarah; Verté, Dominique et al. (2014-03). "Relationships between the perceived neighborhood social environment and walking for transportation among older adults". Social Science & Medicine 104: 23–30. doi:10.1016/j.socscimed.2013.12.016. ISSN 0277-9536. 
  19. Harries, Tim; Rettie, Ruth (2016-02-07). "Walking as a social practice: dispersed walking and the organisation of everyday practices". Sociology of Health & Illness 38 (6): 874–883. doi:10.1111/1467-9566.12406. ISSN 0141-9889. 
  20. Richards, Kathy C.; Lambert, Corinne; Beck, Cornelia K.; Bliwise, Donald L.; Evans, William J.; Kalra, Gurpreet K.; Kleban, Morton H.; Lorenz, Rebecca et al. (2011-02). "Strength Training, Walking, and Social Activity Improve Sleep in Nursing Home and Assisted Living Residents: Randomized Controlled Trial". Journal of the American Geriatrics Society 59 (2): 214–223. doi:10.1111/j.1532-5415.2010.03246.x. ISSN 0002-8614. PMID 21314643. PMC PMC3124380.