Fear of falling: Difference between revisions
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===The Elderly=== |
===The Elderly=== |
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{{see also|Falls in older adults}} |
{{see also|Falls in older adults}} |
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For a long time, the fear of falling was merely believed to be a result of the psychological trauma of a fall, also called ‘post-fall syndrome’.<ref>{{cite journal|last=Legsters|first=K.|title=Fear of falling|journal=Phys Ther|year=2002|volume=82|pages=264–272|accessdate=29 Sep 2011}}</ref> This syndrome was first mentioned in 1982 by Murphy and Isaacs,<ref>{{cite journal|last=Murphy|first=J.|author2=B. Isaacs|title=The post-fall syndrome: a study of 36 elderly patients|journal=Gerontology|year=1982|volume=28|pages=265–270|accessdate=29 Sep 2011}}</ref> who noticed that after a fall, ambulatory persons developed intense fear and walking disorders. FOF has been identified as one of the key symptoms of this syndrome. Since that time, FOF has gained recognition as a specific health problem among older adults. However, FOF was also commonly found among elderly persons who had not yet experienced a fall.<ref>{{cite journal|last=Suzuki|first=M.|author2=Ohyama N. |author3=Yamada K. |author4=et al. |title=The relationship between fear of falling, activities of daily living and quality of life among elderly individuals|journal=Nurs Health Sci|year=2002|volume=4|pages=155–161|accessdate=29 Sep 2011}}</ref> |
For a long time, the fear of falling was merely believed to be a result of the psychological trauma of a fall, also called ‘post-fall syndrome’.<ref>{{cite journal|last=Legsters|first=K.|title=Fear of falling|journal=Phys Ther|year=2002|volume=82|pages=264–272|accessdate=29 Sep 2011}}</ref> This syndrome was first mentioned in 1982 by Murphy and Isaacs,<ref>{{cite journal|last=Murphy|first=J.|author2=B. Isaacs|title=The post-fall syndrome: a study of 36 elderly patients|journal=Gerontology|year=1982|volume=28|pages=265–270|accessdate=29 Sep 2011|doi=10.1159/000212543}}</ref> who noticed that after a fall, ambulatory persons developed intense fear and walking disorders. FOF has been identified as one of the key symptoms of this syndrome. Since that time, FOF has gained recognition as a specific health problem among older adults. However, FOF was also commonly found among elderly persons who had not yet experienced a fall.<ref>{{cite journal|last=Suzuki|first=M.|author2=Ohyama N. |author3=Yamada K. |author4=et al. |title=The relationship between fear of falling, activities of daily living and quality of life among elderly individuals|journal=Nurs Health Sci|year=2002|volume=4|pages=155–161|accessdate=29 Sep 2011 |doi=10.1046/j.1442-2018.2002.00123.x}}</ref> |
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Prevalence of FOF appeared to increase with age and to be higher in women. Age remains significant in multiple logistic regression analyses.<ref>{{cite journal|last=Friedman|first=SM|author2=Munoz B |author3=West SK |author4=et al. |title=Falls and fear of falling: which comes first? A longitudinal prediction model suggest strategies for primary and secondary prevention|journal=Am Geriatr Soc|year=2002|volume=50|pages=329–335|accessdate=29 Sep 2011}}</ref> The results of different studies have reported gender as a somewhat significant risk factor for fear of falling.<ref>{{cite journal|last=Lachman|first=ME|author2=Howland J. |author3=Tennstedt S. |author4=et al. |title=Fear of falling and activity restriction: the survey of activities and fear of falling in the elderly (SAFE)|journal=J Gerontol B Psychol Sci Soc Sci|year=1998|volume=53|pages=43–50|accessdate=29 Sep 2011}}</ref><ref>{{cite journal|last=Howland|first=J.|author2=Peterson EW |author3=Levin WC |title=Fear of falling among the community-dwelling elderly|journal=J Aging Health|year=1993|volume=5|pages=229–243|accessdate=29 Sep 2011}}</ref> Other risk factors of fear of falling in the elderly include dizziness, self-rated health status, depression, and problems with gait and balance.<ref>{{cite journal|last=Arfken|first=Cl|author2=Lach HW |author3=Birge SJ |author4=et al. |title=The prevalence and correlates of fear of falling in elderly persons living in the community|journal=Am J Public Health|year=1994|volume=84|pages=565–570|accessdate=29 Sep 2011|doi=10.2105/AJPH.84.4.565|pmc=1614787|pmid=8154557}}</ref><ref>{{cite journal|last=Tinetti|first=ME|author2=Richman D |author3=Powell L |title=Falls efficacy as a measure of fear of falling|journal=J Gerontol|year=1990|volume=45|pages=239–243|accessdate=29 Sep 2011}}</ref> |
Prevalence of FOF appeared to increase with age and to be higher in women. Age remains significant in multiple logistic regression analyses.<ref>{{cite journal|last=Friedman|first=SM|author2=Munoz B |author3=West SK |author4=et al. |title=Falls and fear of falling: which comes first? A longitudinal prediction model suggest strategies for primary and secondary prevention|journal=Am Geriatr Soc|year=2002|volume=50|pages=329–335|accessdate=29 Sep 2011}}</ref> The results of different studies have reported gender as a somewhat significant risk factor for fear of falling.<ref>{{cite journal|last=Lachman|first=ME|author2=Howland J. |author3=Tennstedt S. |author4=et al. |title=Fear of falling and activity restriction: the survey of activities and fear of falling in the elderly (SAFE)|journal=J Gerontol B Psychol Sci Soc Sci|year=1998|volume=53|pages=43–50|accessdate=29 Sep 2011}}</ref><ref>{{cite journal|last=Howland|first=J.|author2=Peterson EW |author3=Levin WC |title=Fear of falling among the community-dwelling elderly|journal=J Aging Health|year=1993|volume=5|pages=229–243|accessdate=29 Sep 2011|doi=10.1177/089826439300500205}}</ref> Other risk factors of fear of falling in the elderly include dizziness, self-rated health status, depression, and problems with gait and balance.<ref>{{cite journal|last=Arfken|first=Cl|author2=Lach HW |author3=Birge SJ |author4=et al. |title=The prevalence and correlates of fear of falling in elderly persons living in the community|journal=Am J Public Health|year=1994|volume=84|pages=565–570|accessdate=29 Sep 2011|doi=10.2105/AJPH.84.4.565|pmc=1614787|pmid=8154557}}</ref><ref>{{cite journal|last=Tinetti|first=ME|author2=Richman D |author3=Powell L |title=Falls efficacy as a measure of fear of falling|journal=J Gerontol|year=1990|volume=45|pages=239–243|accessdate=29 Sep 2011}}</ref> |
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==Fear of falling in animals== |
==Fear of falling in animals== |
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===Postural control=== |
===Postural control=== |
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The postural control system has two functions: 1) to ensure that balance is maintained by bracing the body against gravity, and 2) to fix the orientation and position of the features that serve as a frame of reference for perception and action with respect to the external world.<ref>{{cite journal|last=Massion|first=J.|title=Postural control system|journal=Current Opinion in Neurobiology|year=1994|volume=4|issue=6|pages=877–887|accessdate=27 Sep 2011}}</ref> Postural control relies on multisensory processing and [[motor system|motor responses]] that seem to be automatic and occur without conscious awareness. Studies have shown that people afraid of heights or falling have poor postural control, especially in the absence of strong visual cues. These individuals rely heavily on vision to regulate their posture and balance.<ref name="Postural control">{{cite journal|last=Strang|first=Adam J.|coauthors=Joshua Haworth, Hieronymus Mathias, et al.|title=Structural changes in postural sway lend insight into effects of balance training, vision, and support surface on postural control in a healthy population|journal=European Journal of Applied Physiology|date=Jul 2011|volume=111|issue=7|pages=1485–1495|accessdate=28 Nov 2011}}</ref> When faced with high or unstable ground, the [[vestibular system]] in these individuals senses the instability and attempts to correct it by increasing postural sway to reactivate visual balance feedback (postural sway refers to the phenomenon of constant displacement and correction of the position of the center of gravity within the base of support).<ref>{{cite web|title=Physical Therapy Dictionary|url=http://www.physicaltherapydictionary.com/P.aspx?Term=postural%20sway|accessdate=29 Sep 2011}}</ref> This often fails, however, resulting in a feeling of increased instability and anxiety, which is often interpreted as fear. |
The postural control system has two functions: 1) to ensure that balance is maintained by bracing the body against gravity, and 2) to fix the orientation and position of the features that serve as a frame of reference for perception and action with respect to the external world.<ref>{{cite journal|last=Massion|first=J.|title=Postural control system|journal=Current Opinion in Neurobiology|year=1994|volume=4|issue=6|pages=877–887|accessdate=27 Sep 2011|doi=10.1016/0959-4388(94)90137-6}}</ref> Postural control relies on multisensory processing and [[motor system|motor responses]] that seem to be automatic and occur without conscious awareness. Studies have shown that people afraid of heights or falling have poor postural control, especially in the absence of strong visual cues. These individuals rely heavily on vision to regulate their posture and balance.<ref name="Postural control">{{cite journal|last=Strang|first=Adam J.|coauthors=Joshua Haworth, Hieronymus Mathias, et al.|title=Structural changes in postural sway lend insight into effects of balance training, vision, and support surface on postural control in a healthy population|journal=European Journal of Applied Physiology|date=Jul 2011|volume=111|issue=7|pages=1485–1495|accessdate=28 Nov 2011|doi=10.1007/s00421-010-1770-6}}</ref> When faced with high or unstable ground, the [[vestibular system]] in these individuals senses the instability and attempts to correct it by increasing postural sway to reactivate visual balance feedback (postural sway refers to the phenomenon of constant displacement and correction of the position of the center of gravity within the base of support).<ref>{{cite web|title=Physical Therapy Dictionary|url=http://www.physicaltherapydictionary.com/P.aspx?Term=postural%20sway|accessdate=29 Sep 2011}}</ref> This often fails, however, resulting in a feeling of increased instability and anxiety, which is often interpreted as fear. |
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===Height vertigo=== |
===Height vertigo=== |
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==Falling in dreams== |
==Falling in dreams== |
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<!-- Deleted image removed: [[File:Child balancing.png|thumb|Falling is a common occurrence in dreams.]] --><ref>{{cite web|title=Wikimedia Commons|url=http://en.wikipedia.org/wiki/Sleeping|work=Child sleeping|accessdate=28 Nov 2011}}</ref> |
<!-- Deleted image removed: [[File:Child balancing.png|thumb|Falling is a common occurrence in dreams.]] --><ref>{{cite web|title=Wikimedia Commons|url=http://en.wikipedia.org/wiki/Sleeping|work=Child sleeping|accessdate=28 Nov 2011}}</ref> |
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According to [[Sigmund Freud]]'s ''[[The Interpretation of Dreams]]'', falling dreams fall under the category of “typical dreams,” meaning the “dreams which almost everyone has dreamt alike and which we are accustomed to assume must have the same meaning for everyone."<ref>{{cite book|last=Freud|first=Sigmund|title=The Interpretation of Dreams|year=1999|publisher=Oxford UP|location=Oxford}}</ref> In the fairly recent study, The Typical Dreams of Canadian University Students, common dreams were investigated by administering a Typical Dreams Questionnaire (TDQ).<ref>{{cite journal|last=Nielsen|first=A. T.|author2=Zadra A. L. |author3=Simard V. |author4=Saucier S. |author5=Stenstro P. |author6=Smith C. |author7=et al. |title=The typical dreams of Canadian University students|journal=Dreaming|year=2003|volume=13|issue=4|pages=211–235|accessdate=Sep 27, 2011}}</ref> The results confirmed that typical dreams are consistent over time, region, and gender, and a few themes can be considered almost universal: falling (73.8% prevalence), flying or soaring in the air (48.3%), and swimming (34.3%). In 1967, Saul and Curtis published a paper entitled, 'Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent.’<ref name="Dream Form">{{cite journal|last=Saul|first=Leon J.|author2=George C. Curtis|title=Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent|journal=The International Journal of Psychoanalysis|year=1967|volume=48|pages=281–287|accessdate=28 Nov 2011}}</ref> According to Saul and Curtis, dreams of falling can have various meanings, such as the sensation of falling asleep, the symbolization of a real risk of falling from bed, the repetition of traumatic experiences of falling or sensations of falling from parents’ arms in childhood, birth/delivery, ambition or the renouncement of responsibility, or life experiences such as flying in an airplane. They quote another author, Gutheil (1951), who suggests a range of possible meanings subsumed under the general idea of loss of (mental) equilibrium. These include loss of temper, loss of self-control, yielding, decline of the accepted moral standard or loss of consciousness.<ref name="Visual Cliff">{{cite journal}}</ref> Studies performed in recent years on the dream patterns of a group of 685 students attending secondary schools in Milan have concluded that, in dreams, fear is more frequently associated with falling, while happiness is connected with flying, and surprise with suspension and vertical content. |
According to [[Sigmund Freud]]'s ''[[The Interpretation of Dreams]]'', falling dreams fall under the category of “typical dreams,” meaning the “dreams which almost everyone has dreamt alike and which we are accustomed to assume must have the same meaning for everyone."<ref>{{cite book|last=Freud|first=Sigmund|title=The Interpretation of Dreams|year=1999|publisher=Oxford UP|location=Oxford}}</ref> In the fairly recent study, The Typical Dreams of Canadian University Students, common dreams were investigated by administering a Typical Dreams Questionnaire (TDQ).<ref>{{cite journal|last=Nielsen|first=A. T.|author2=Zadra A. L. |author3=Simard V. |author4=Saucier S. |author5=Stenstro P. |author6=Smith C. |author7=et al. |title=The typical dreams of Canadian University students|journal=Dreaming|year=2003|volume=13|issue=4|pages=211–235|accessdate=Sep 27, 2011 |doi=10.1023/b:drem.0000003144.40929.0b}}</ref> The results confirmed that typical dreams are consistent over time, region, and gender, and a few themes can be considered almost universal: falling (73.8% prevalence), flying or soaring in the air (48.3%), and swimming (34.3%). In 1967, Saul and Curtis published a paper entitled, 'Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent.’<ref name="Dream Form">{{cite journal|last=Saul|first=Leon J.|author2=George C. Curtis|title=Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent|journal=The International Journal of Psychoanalysis|year=1967|volume=48|pages=281–287|accessdate=28 Nov 2011}}</ref> According to Saul and Curtis, dreams of falling can have various meanings, such as the sensation of falling asleep, the symbolization of a real risk of falling from bed, the repetition of traumatic experiences of falling or sensations of falling from parents’ arms in childhood, birth/delivery, ambition or the renouncement of responsibility, or life experiences such as flying in an airplane. They quote another author, Gutheil (1951), who suggests a range of possible meanings subsumed under the general idea of loss of (mental) equilibrium. These include loss of temper, loss of self-control, yielding, decline of the accepted moral standard or loss of consciousness.<ref name="Visual Cliff">{{cite journal}}</ref> Studies performed in recent years on the dream patterns of a group of 685 students attending secondary schools in Milan have concluded that, in dreams, fear is more frequently associated with falling, while happiness is connected with flying, and surprise with suspension and vertical content. |
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==References== |
==References== |
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Revision as of 11:15, 8 May 2014
The fear of falling (FOF) is a natural fear and is typical of most humans and mammals, in varying degrees of extremity. It differs from acrophobia (the fear of heights), although the two fears are closely related and sometimes indistinguishable. The fear of falling encompasses the anxieties accompanying the sensation and the possibly dangerous effects of falling, opposed to the heights themselves.[1] Individuals suffering from barophobia may fear falling solely because of the gravity pull associated with it.[2]
Fear of falling in humans
Infants
Studies done by psychologists Eleanor J. Gibson and Richard D. Walk have further explained the nature of this fear. One of their more famous studies is the “Visual cliff.” Below is their description of the cliff:[3]
…a board laid across a large sheet of heavy glass which is supported a foot or more above the floor. On one side of the board a sheet of patterned material is placed flush against the undersurface of the glass, giving the glass the appearance as well as the substance of solidity. On the other side a sheet of the same material is laid upon the floor; this side of the board thus becomes the visual cliff.
Thirty-six infants were tested in their experiments, ranging from six to fourteen months. Gibson and Walk found that when placed on the board, 27 of the infants would crawl on the shallow side when called by their mothers; only three ventured off the “edge” of the cliff. Many infants would crawl away from their mothers who were calling from the deep end, and some would cry because they couldn’t reach their mothers without crossing an apparent chasm. Some would pat the glass on the deep end, but even with this assurance would not crawl on the glass. These results, although unable to prove that this fear is innate, indicate that most human infants have well developed depth perception and are able to make the connection between depth and the danger that accompanies falling.
The Elderly
For a long time, the fear of falling was merely believed to be a result of the psychological trauma of a fall, also called ‘post-fall syndrome’.[4] This syndrome was first mentioned in 1982 by Murphy and Isaacs,[5] who noticed that after a fall, ambulatory persons developed intense fear and walking disorders. FOF has been identified as one of the key symptoms of this syndrome. Since that time, FOF has gained recognition as a specific health problem among older adults. However, FOF was also commonly found among elderly persons who had not yet experienced a fall.[6]
Prevalence of FOF appeared to increase with age and to be higher in women. Age remains significant in multiple logistic regression analyses.[7] The results of different studies have reported gender as a somewhat significant risk factor for fear of falling.[8][9] Other risk factors of fear of falling in the elderly include dizziness, self-rated health status, depression, and problems with gait and balance.[10][11]
Fear of falling in animals
Studies on nonhuman subjects more support the theory of falling as an inborn fear. Gibson and Walk performed identical experiments with chicks, turtles, rats, kids, lambs, kittens, and puppies.[3] The results were similar to those of the human infants, although each animal behaved a little differently according to the characteristics of its species.
The chicks were tested less than 24 hours after birth. It appeared that depth perception develops rather quickly in chickens, as the chicks never made the “mistake” of walking off the “deep” side of the cliff. The kids and lambs were also tested young-as soon as they could stand on their own. During the experiment, no goat or lamb ever stepped onto the glass of the deep side. When placed there, the animals displayed typical behavior by going into a posture of defense, with their front legs rigid and their back legs limp. In this state of immobility, the animals were pushed forward across the glass until their head and field of vision crossed the solid edge on the opposite side of the cliff; the goats and lambs would then relax and proceed to spring forward upon its surface. Based on the results of the animals tested, the danger of falling is instilled in animals at a very young age.
Factors that influence the fear of falling
Postural control
The postural control system has two functions: 1) to ensure that balance is maintained by bracing the body against gravity, and 2) to fix the orientation and position of the features that serve as a frame of reference for perception and action with respect to the external world.[12] Postural control relies on multisensory processing and motor responses that seem to be automatic and occur without conscious awareness. Studies have shown that people afraid of heights or falling have poor postural control, especially in the absence of strong visual cues. These individuals rely heavily on vision to regulate their posture and balance.[13] When faced with high or unstable ground, the vestibular system in these individuals senses the instability and attempts to correct it by increasing postural sway to reactivate visual balance feedback (postural sway refers to the phenomenon of constant displacement and correction of the position of the center of gravity within the base of support).[14] This often fails, however, resulting in a feeling of increased instability and anxiety, which is often interpreted as fear.
Height vertigo
Closely related to postural control is the sensation of vertigo: a warning signal created by loss of postural control when the distance between the observer and visible stationary objects becomes too large, and caused by a dysfunction of the vestibular system in the inner ear. In short, it is the feeling of motion when one is actually stationary. Symptoms of vertigo include dizziness, nausea, vomiting, shortness of breath, and/or the inability to walk or stand. Some individuals are more reliant on visual cues to control posture than others. Vestibular sensations can arise when unsound information is detected along the sensory channels (this happens even to those with normal vestibular function), and feelings of vertigo can result in people with postural control issues.
Space and motion discomfort
Studies have shown that people with acrophobia and/or an extreme fear of falling have higher scores of SMD, or space and motion discomfort- referring to physical symptoms elicited by visual or kinesthetic information that is inadequate for normal spatial orientation. SMD arises when conflicting information is detected among visual, kinesthetic, and vestibular sensory channels. Evidence has supported the claim that patients with anxiety and SMD rely more heavily on visual cues for postural control.
Falling in dreams
[15] According to Sigmund Freud's The Interpretation of Dreams, falling dreams fall under the category of “typical dreams,” meaning the “dreams which almost everyone has dreamt alike and which we are accustomed to assume must have the same meaning for everyone."[16] In the fairly recent study, The Typical Dreams of Canadian University Students, common dreams were investigated by administering a Typical Dreams Questionnaire (TDQ).[17] The results confirmed that typical dreams are consistent over time, region, and gender, and a few themes can be considered almost universal: falling (73.8% prevalence), flying or soaring in the air (48.3%), and swimming (34.3%). In 1967, Saul and Curtis published a paper entitled, 'Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent.’[18] According to Saul and Curtis, dreams of falling can have various meanings, such as the sensation of falling asleep, the symbolization of a real risk of falling from bed, the repetition of traumatic experiences of falling or sensations of falling from parents’ arms in childhood, birth/delivery, ambition or the renouncement of responsibility, or life experiences such as flying in an airplane. They quote another author, Gutheil (1951), who suggests a range of possible meanings subsumed under the general idea of loss of (mental) equilibrium. These include loss of temper, loss of self-control, yielding, decline of the accepted moral standard or loss of consciousness.[3] Studies performed in recent years on the dream patterns of a group of 685 students attending secondary schools in Milan have concluded that, in dreams, fear is more frequently associated with falling, while happiness is connected with flying, and surprise with suspension and vertical content.
References
- ^ "Wikimedia Commons". Child balancing. Wikipedia.org. Retrieved 28 Nov 2011.
- ^ http://voices.yahoo.com/barophobia-fear-gravity-2365501.html
- ^ a b c Gibson, E.J.; Walk, R. D. "The "visual cliff"". Scientific American. 202: 67–71.
{{cite journal}}:|access-date=requires|url=(help) Cite error: The named reference "Visual Cliff" was defined multiple times with different content (see the help page). - ^ Legsters, K. (2002). "Fear of falling". Phys Ther. 82: 264–272.
{{cite journal}}:|access-date=requires|url=(help) - ^ Murphy, J.; B. Isaacs (1982). "The post-fall syndrome: a study of 36 elderly patients". Gerontology. 28: 265–270. doi:10.1159/000212543.
{{cite journal}}:|access-date=requires|url=(help) - ^ Suzuki, M.; Ohyama N.; Yamada K.; et al. (2002). "The relationship between fear of falling, activities of daily living and quality of life among elderly individuals". Nurs Health Sci. 4: 155–161. doi:10.1046/j.1442-2018.2002.00123.x.
{{cite journal}}:|access-date=requires|url=(help); Explicit use of et al. in:|author4=(help) - ^ Friedman, SM; Munoz B; West SK; et al. (2002). "Falls and fear of falling: which comes first? A longitudinal prediction model suggest strategies for primary and secondary prevention". Am Geriatr Soc. 50: 329–335.
{{cite journal}}:|access-date=requires|url=(help); Explicit use of et al. in:|author4=(help) - ^ Lachman, ME; Howland J.; Tennstedt S.; et al. (1998). "Fear of falling and activity restriction: the survey of activities and fear of falling in the elderly (SAFE)". J Gerontol B Psychol Sci Soc Sci. 53: 43–50.
{{cite journal}}:|access-date=requires|url=(help); Explicit use of et al. in:|author4=(help) - ^ Howland, J.; Peterson EW; Levin WC (1993). "Fear of falling among the community-dwelling elderly". J Aging Health. 5: 229–243. doi:10.1177/089826439300500205.
{{cite journal}}:|access-date=requires|url=(help) - ^ Arfken, Cl; Lach HW; Birge SJ; et al. (1994). "The prevalence and correlates of fear of falling in elderly persons living in the community". Am J Public Health. 84: 565–570. doi:10.2105/AJPH.84.4.565. PMC 1614787. PMID 8154557.
{{cite journal}}:|access-date=requires|url=(help); Explicit use of et al. in:|author4=(help) - ^ Tinetti, ME; Richman D; Powell L (1990). "Falls efficacy as a measure of fear of falling". J Gerontol. 45: 239–243.
{{cite journal}}:|access-date=requires|url=(help) - ^ Massion, J. (1994). "Postural control system". Current Opinion in Neurobiology. 4 (6): 877–887. doi:10.1016/0959-4388(94)90137-6.
{{cite journal}}:|access-date=requires|url=(help) - ^ Strang, Adam J. (Jul 2011). "Structural changes in postural sway lend insight into effects of balance training, vision, and support surface on postural control in a healthy population". European Journal of Applied Physiology. 111 (7): 1485–1495. doi:10.1007/s00421-010-1770-6.
{{cite journal}}:|access-date=requires|url=(help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Physical Therapy Dictionary". Retrieved 29 Sep 2011.
- ^ "Wikimedia Commons". Child sleeping. Retrieved 28 Nov 2011.
- ^ Freud, Sigmund (1999). The Interpretation of Dreams. Oxford: Oxford UP.
- ^ Nielsen, A. T.; Zadra A. L.; Simard V.; Saucier S.; Stenstro P.; Smith C.; et al. (2003). "The typical dreams of Canadian University students". Dreaming. 13 (4): 211–235. doi:10.1023/b:drem.0000003144.40929.0b.
{{cite journal}}:|access-date=requires|url=(help); Explicit use of et al. in:|author7=(help) - ^ Saul, Leon J.; George C. Curtis (1967). "Dream Form and Strength of Impulse in Dreams of Falling and Other Dreams of Descent". The International Journal of Psychoanalysis. 48: 281–287.
{{cite journal}}:|access-date=requires|url=(help)
