Accepted Manuscript Title: Quantifying stair gait stability in young and older adults, with modifications to insole hardness Author: Patrick J. Antonio Stephen D. Perry PII: DOI: Reference:
S0966-6362(14)00528-1 http://dx.doi.org/doi:10.1016/j.gaitpost.2014.05.009 GAIPOS 4214
To appear in:
Gait & Posture
Received date: Revised date: Accepted date:
11-10-2013 12-5-2014 23-5-2014
Please cite this article as: Antonio Patrick J, Perry Stephen D.Quantifying stair gait stability in young and older adults, with modifications to insole hardness.Gait and Posture http://dx.doi.org/10.1016/j.gaitpost.2014.05.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Quantifying stair gait stability in young and older adults, with modifications to insole hardness Patrick J. Antonio, Email address: [email protected]
cr
Department of Kinesiology and Physical Education Wilfrid Laurier University 75 University Ave West Waterloo, ON, CANADA N2L 3C5
ip t
Stephen D. Perry, Email address: [email protected]
us
Highlights
M
Abstract
an
1. Age demonstrated a decreased in stability during stair gait. 2. Stair gait while barefoot was more unstable compared to shod stair gait. 3. This study suggests that wearing footwear during stair gait may improve stability.
Stair gait falls are prevalent in older adults aged 65 years and older. Extrinsic variables such as
d
changes to insole hardness are important factors that can compromise the balance control system
Ac ce pt e
and increase the incidence of falls, especially since age-related decline in the cutaneous sensation is common. Balance measurements such as the minimum center of mass/base of support (COMBOS, termed 'stability margin') and COM-BOS medial/lateral range provide information about stability during stair gait. This study was conducted to investigate stair gait stability of young and older adults, with modifications to insole hardness. Twenty healthy adults (10 young adults, 10 older adults) were recruited (mean age= 23.1, SD 2.1; mean age= 73.2, SD 5.5) and instructed to descend a 4 step staircase, for a total of 40 trials. All participants wore similar canvas shoes of varying sizes, and corresponding insole hardnesses (barefoot, soft, medium, hard). Kinematic equipment utilized 12 infrared markers anteriorly placed on the individual to record COM motion and BOS location. The findings from the study demonstrated that older adults were less
Page 1 of 20
stable during stair descent. Consequently, insole conditions revealed that the barefoot condition may increase the likelihood of falls, as opposed to the other insole hardnesses (soft, medium and hard). These results suggest that older adults while barefoot are putting themselves at a great risk
ip t
of falling during stair descent. Since age-related changes are inevitable and the preferred
us
Ac ce pt e
d
M
an
Keywords: Stair Gait, Stability, Insoles, Aging, Footwear
cr
footwear of choice inside the home is bare feet, this is a crucial issue that should be addressed.
Page 2 of 20
Introduction
In Canada, there has been a steady incline in the rates of death by approximately 6%
ip t
since 2007 [1]. Falls are the fifth ranked leading cause of death, only behind common diseases
cr
such as cancer, heart disease, stroke, and respiratory diseases [2]. A fall is defined as “an event that results in a person coming to rest inadvertently on the ground or other lower level” [3]. In
us
Canada, falls are the leading cause of injury accounting for 63% of senior cases [4]. Recent reports have identified that stair gait falls account for 26% of all self-reported falls, the second
an
most prevalent issue in adults 65 years and older [4]. Environmentally, footwear can influence
M
the likelihood of falling, specifically the density of the insole within the individual’s shoe [5][6]. This study will investigate the effects of age and insole hardness on stability during stair gait.
d
In level gait research, dynamic stability can be quantifiably measured using various
Ac ce pt e
spatial gait parameters, one measurement previously used is the relationship between the center of mass (COM) and the base of support (BOS). The ‘stability margin’ associated with the center of mass and base of support (COM-BOS), is defined as the perpendicular distance from the lateral base of support border of the single stance foot to the center of mass [7] (Figure 1). In the Perry et al. [7] study, the researchers explored the COM-BOS ‘stability margin’ of older adults with two insole types, conventional and facilitatory insoles. They found that the facilitatory insoles produced greater COM-BOS lateral stability margins as opposed to the conventional insoles. The results of 12 weeks of wearing each insole also displayed that of the 14 reported falls, 9 occurred while wearing conventional insoles (which had the smaller COM-BOS ‘stability margin’). Therefore there is an indirect correlation that suggests when the COM-BOS lateral stability margin is smaller, older adults are at a greater risk for falls. Chou et al. [8] also demonstrated that more lateral COM movement resulted in more laterally directed compensatory
Page 3 of 20
movements during obstacle crossing, which suggest that COM-BOS measurements have an association with fall risk and stability. Level gait and stair gait are quite different in their foot contact pattern, with level gait
ip t
consisting of heel-to-toe contact while stair gait comprises of toe-to-heel contact. Specifically,
cr
the metatarsal heads accept the load followed by a lowering onto the heel [9]. Previous research has highlighted specific phases inherent to stair gait, categorized as 1) transition gait phase; and,
us
2) steady state descent [10]. Transition gait phase encompass the transitions to/ from the level ground either ascending/descending the stairs. Steady state ascent/descent comprise
an
predominently at 50% of the stair gait cycle, halfway up or down the staircase during consistent stair gait motion. It is worth noting that the transition gait phase of stair descent has been
M
considered as a cause for large instabilities and a subsequent fall risk as the individual’s position
d
is travelling at a faster velocity from an elevated height [11][12]. This hazard is significantly
Ac ce pt e
detrimental to older adults as research has confirmed that falling from a height could cause injury, or worse, death [13].
Stair gait falls, like level gait, are influenced by many risk factors, which include, but are not limited to physiological or physical changes associated to aging, and environmental factors [14]. Age-related declines of the sensory system, notably the diminishing cutaneous sensation, pose a great risk to the stability of older adults during gait [15][16][17]. Furthermore, insole hardness has been found to influence gait stability. Participants wearing thick and soft insole materials have been found to cushion the individual’s cutaneous feedback information during foot impact, delaying the reaction response to perturbations [5][6]. To date, there is considerable research in level gait, and very little in stair gait. Therefore, this study will attempt to answer the following research questions: 1) Does age affect stability during stair gait?
Page 4 of 20
2) Does modification to insole hardness (soft, medium, hard, and barefoot) affect stability during stair gait? It is hypothesized that during stair descent, older adults will have compromised stability
ip t
during the single leg stance phase. Stability will be characterized by two outcome measures: 1)
cr
the lateral distance of the COM to the BOS border; and, 2) the range of the COM-BOS
measurement. Specifically, older adults (>65 years) will demonstrate reduced COM-BOS
us
‘stability margins’, forcing their COM closer to the BOS lateral limits. And they will display a larger COM-BOS range in the medial / lateral direction, indicating highly variable control of the
an
COM relative to the BOS [7].
M
Secondly, it is hypothesized that soft cushioning insoles will demonstrate the greatest instability with reduced COM-BOS ‘stability margins’ and larger COM-BOS medial/lateral
Ac ce pt e
d
range.
Methods and Materials
Participants
Twenty healthy participants volunteered to take part in the study. The participants were recruited within the Wilfrid Laurier University and surrounding Waterloo community, which were then categorized into two age groups (n=10 in each group), younger adults aged 18-30 years (mean=23.1, SD 2.1) and healthy older adults (>65 years) (mean 73.2, SD 5.5). Young adult and older adult group height and weight were of similar values (Table 1). Participants who 3
Page 5 of 20
reported having cognitive, neurological, vestibular or musculoskeletal issues that affected their balance were excluded from the research study. In addition, any other issues that affected normal gait, stability or vision were also excluded. Subjects provided written informed consent prior to
ip t
the experiment and the protocol was approved by the Institutional Ethics Review Board.
cr
Experimental Setup
us
A custom wooden staircase was built in accordance to the National Building Code of Canada. The dimensions were 2.13m x 1.3m x 0.72m (length x width x height). The staircase
an
consisted of 4 steps, with a rise of 0.18m and a run of 0.30m. For safety, handrails were built in accordance to the National Building Code of Canada (handrail height = 0.89m) (Figure 2).
M
A three-dimensional Optotrak Certus motion capture system, (Northern Digital Inc., Waterloo, Ontario) was used to record 12 frontal infrared (IRED) markers to estimate the COM
d
location, at a sampling frequency of 100 Hz. The participants were instrumented with forward-
Ac ce pt e
facing markers on the: forehead, bilateral acriomioclavicular joints, xyphoid process, bilateral anterior inferior iliac spines, bilateral tibial tuberosities, bilateral anterior distal tibias, and bilateral bases of the first metatarsals.
Three force plates (Model OR-6-2000, AMTI, Watertown, MA) were used to record kinetic data which collected the ground reaction forces at a sampling frequency of 200 Hz. The first two force plates (FP1 and FP2) were staggered on the level surface in front of the stairs, and the third force plate (FP3) was imbedded into the second step of the staircase. Lastly, varying insole hardnesses (soft, medium, and hard) were inserted inside matching canvas shoes. Structurally, the insoles were similar in shape and thickness but differed in material density. Midsole thickness was identified using the Shore classification system, a measuring scale recognized to identify material density, with scores from Shore A15 (softest),
Page 6 of 20
Shore A33 (medium), to Shore A50 (hardest). A barefoot condition was also utilized as an insole condition. The barefoot condition comprised of wearing socks without using the canvas shoes and insoles of varying hardnesses.
ip t
Protocol
cr
After obtaining informed consent, participants had anthropometric measurements taken. This included height, weight, foot length, foot width measurements. A plantar surface sensitivity
us
test was conducted using Touch-Test® Sensory Evaluator monofilaments (North Coast Medical, Inc. Gilroy, CA, USA) to certify participants had normal limits of cutaneous sensation. Once
an
instrumented with 12 IRED markers on the designated locations, participants were instructed to stand with feet shoulder width apart on one force plate with eyes open for 30 seconds. For the
M
experimental protocol, each participant was instructed to perform 5 walking trials stepping on the
d
level ground force plates with each insole condition (barefoot, soft, medium, and hard) for a total
Ac ce pt e
of 20 walking trials. Then for the stair trials, each participant was harnessed for safety and instructed to descend the stairs while wearing different insole hardnesses. In a blocked randomization grouped by insoles, participants wore each of the four insole conditions (barefoot, soft, medium, and hard) 5 consecutive times while descending down the stairs in normal office lighting. Participants had a 45-minute acclimatization period with the footwear and various insoles prior to the stair gait trials. To ensure that all steps were conducted and each study consistent, the researcher utilized this protocol for each participant study. Data Analysis The COM was calculated from the 12 IRED markers using a segmental weighted average approach (7 segments) [18], while the BOS lateral border was calculated using anthropometric distances from the toe and ankle markers of the foot, which were the IRED markers that defined 5
Page 7 of 20
the foot’s lateral borders. Once the COM was calculated, the single support phase during stair descent was identified via force plate contact. During that single support time, in the horizontal plane, the minimum, maximum, and range of the perpendicular distance between the COM
ip t
location and the lateral BOS border were calculated (in m). Gait velocity was measured using the formula: (initial foot contact location on FP3 – initial foot contact location on FP2) / (initial foot
cr
contact time on FP3 – initial foot contact time on FP2). For full procedures of the data analyses
us
and calculations refer to the study by Perry et al. [7].
an
Statistical Analysis
Post-experiment, a 2x4 analysis of variance (ANOVA) was conducted using SPSS (v.19,
M
IBM, SPSS) for data analysis. This model allowed comparison for both between (2= age) and within (4=insoles) groups. Outcome measures of stability produced were the minimum COM-
d
BOS in the medial/lateral direction termed the ‘stability margins’ and the COM-BOS
Ac ce pt e
medial/lateral range (maximum-minimum). Simple t-tests were conducted to assess age differences in: 1) cutaneous sensation, 2) gait velocity. In addition, epsilon correctional factors were implemented if Mauchly’s sphericity was violated, using Greenhouse-Geiser, or the Huhyn-Feldt. For the experiment, the activity of a single stair descent was divided into either a steady state descent phase or a transition gait phase. Data at both respective phases were analyzed using the same 2x4 ANOVAs comparing age and insoles. Results
COM-BOS Lateral Stability Margin
There was a significant main effect of age on COM-BOS ‘stability margin’ during both the transition gait phase (F(1,84) 21.7,p
S0966-6362(14)00528-1 http://dx.doi.org/doi:10.1016/j.gaitpost.2014.05.009 GAIPOS 4214
To appear in:
Gait & Posture
Received date: Revised date: Accepted date:
11-10-2013 12-5-2014 23-5-2014
Please cite this article as: Antonio Patrick J, Perry Stephen D.Quantifying stair gait stability in young and older adults, with modifications to insole hardness.Gait and Posture http://dx.doi.org/10.1016/j.gaitpost.2014.05.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Quantifying stair gait stability in young and older adults, with modifications to insole hardness Patrick J. Antonio, Email address: [email protected]
cr
Department of Kinesiology and Physical Education Wilfrid Laurier University 75 University Ave West Waterloo, ON, CANADA N2L 3C5
ip t
Stephen D. Perry, Email address: [email protected]
us
Highlights
M
Abstract
an
1. Age demonstrated a decreased in stability during stair gait. 2. Stair gait while barefoot was more unstable compared to shod stair gait. 3. This study suggests that wearing footwear during stair gait may improve stability.
Stair gait falls are prevalent in older adults aged 65 years and older. Extrinsic variables such as
d
changes to insole hardness are important factors that can compromise the balance control system
Ac ce pt e
and increase the incidence of falls, especially since age-related decline in the cutaneous sensation is common. Balance measurements such as the minimum center of mass/base of support (COMBOS, termed 'stability margin') and COM-BOS medial/lateral range provide information about stability during stair gait. This study was conducted to investigate stair gait stability of young and older adults, with modifications to insole hardness. Twenty healthy adults (10 young adults, 10 older adults) were recruited (mean age= 23.1, SD 2.1; mean age= 73.2, SD 5.5) and instructed to descend a 4 step staircase, for a total of 40 trials. All participants wore similar canvas shoes of varying sizes, and corresponding insole hardnesses (barefoot, soft, medium, hard). Kinematic equipment utilized 12 infrared markers anteriorly placed on the individual to record COM motion and BOS location. The findings from the study demonstrated that older adults were less
Page 1 of 20
stable during stair descent. Consequently, insole conditions revealed that the barefoot condition may increase the likelihood of falls, as opposed to the other insole hardnesses (soft, medium and hard). These results suggest that older adults while barefoot are putting themselves at a great risk
ip t
of falling during stair descent. Since age-related changes are inevitable and the preferred
us
Ac ce pt e
d
M
an
Keywords: Stair Gait, Stability, Insoles, Aging, Footwear
cr
footwear of choice inside the home is bare feet, this is a crucial issue that should be addressed.
Page 2 of 20
Introduction
In Canada, there has been a steady incline in the rates of death by approximately 6%
ip t
since 2007 [1]. Falls are the fifth ranked leading cause of death, only behind common diseases
cr
such as cancer, heart disease, stroke, and respiratory diseases [2]. A fall is defined as “an event that results in a person coming to rest inadvertently on the ground or other lower level” [3]. In
us
Canada, falls are the leading cause of injury accounting for 63% of senior cases [4]. Recent reports have identified that stair gait falls account for 26% of all self-reported falls, the second
an
most prevalent issue in adults 65 years and older [4]. Environmentally, footwear can influence
M
the likelihood of falling, specifically the density of the insole within the individual’s shoe [5][6]. This study will investigate the effects of age and insole hardness on stability during stair gait.
d
In level gait research, dynamic stability can be quantifiably measured using various
Ac ce pt e
spatial gait parameters, one measurement previously used is the relationship between the center of mass (COM) and the base of support (BOS). The ‘stability margin’ associated with the center of mass and base of support (COM-BOS), is defined as the perpendicular distance from the lateral base of support border of the single stance foot to the center of mass [7] (Figure 1). In the Perry et al. [7] study, the researchers explored the COM-BOS ‘stability margin’ of older adults with two insole types, conventional and facilitatory insoles. They found that the facilitatory insoles produced greater COM-BOS lateral stability margins as opposed to the conventional insoles. The results of 12 weeks of wearing each insole also displayed that of the 14 reported falls, 9 occurred while wearing conventional insoles (which had the smaller COM-BOS ‘stability margin’). Therefore there is an indirect correlation that suggests when the COM-BOS lateral stability margin is smaller, older adults are at a greater risk for falls. Chou et al. [8] also demonstrated that more lateral COM movement resulted in more laterally directed compensatory
Page 3 of 20
movements during obstacle crossing, which suggest that COM-BOS measurements have an association with fall risk and stability. Level gait and stair gait are quite different in their foot contact pattern, with level gait
ip t
consisting of heel-to-toe contact while stair gait comprises of toe-to-heel contact. Specifically,
cr
the metatarsal heads accept the load followed by a lowering onto the heel [9]. Previous research has highlighted specific phases inherent to stair gait, categorized as 1) transition gait phase; and,
us
2) steady state descent [10]. Transition gait phase encompass the transitions to/ from the level ground either ascending/descending the stairs. Steady state ascent/descent comprise
an
predominently at 50% of the stair gait cycle, halfway up or down the staircase during consistent stair gait motion. It is worth noting that the transition gait phase of stair descent has been
M
considered as a cause for large instabilities and a subsequent fall risk as the individual’s position
d
is travelling at a faster velocity from an elevated height [11][12]. This hazard is significantly
Ac ce pt e
detrimental to older adults as research has confirmed that falling from a height could cause injury, or worse, death [13].
Stair gait falls, like level gait, are influenced by many risk factors, which include, but are not limited to physiological or physical changes associated to aging, and environmental factors [14]. Age-related declines of the sensory system, notably the diminishing cutaneous sensation, pose a great risk to the stability of older adults during gait [15][16][17]. Furthermore, insole hardness has been found to influence gait stability. Participants wearing thick and soft insole materials have been found to cushion the individual’s cutaneous feedback information during foot impact, delaying the reaction response to perturbations [5][6]. To date, there is considerable research in level gait, and very little in stair gait. Therefore, this study will attempt to answer the following research questions: 1) Does age affect stability during stair gait?
Page 4 of 20
2) Does modification to insole hardness (soft, medium, hard, and barefoot) affect stability during stair gait? It is hypothesized that during stair descent, older adults will have compromised stability
ip t
during the single leg stance phase. Stability will be characterized by two outcome measures: 1)
cr
the lateral distance of the COM to the BOS border; and, 2) the range of the COM-BOS
measurement. Specifically, older adults (>65 years) will demonstrate reduced COM-BOS
us
‘stability margins’, forcing their COM closer to the BOS lateral limits. And they will display a larger COM-BOS range in the medial / lateral direction, indicating highly variable control of the
an
COM relative to the BOS [7].
M
Secondly, it is hypothesized that soft cushioning insoles will demonstrate the greatest instability with reduced COM-BOS ‘stability margins’ and larger COM-BOS medial/lateral
Ac ce pt e
d
range.
Methods and Materials
Participants
Twenty healthy participants volunteered to take part in the study. The participants were recruited within the Wilfrid Laurier University and surrounding Waterloo community, which were then categorized into two age groups (n=10 in each group), younger adults aged 18-30 years (mean=23.1, SD 2.1) and healthy older adults (>65 years) (mean 73.2, SD 5.5). Young adult and older adult group height and weight were of similar values (Table 1). Participants who 3
Page 5 of 20
reported having cognitive, neurological, vestibular or musculoskeletal issues that affected their balance were excluded from the research study. In addition, any other issues that affected normal gait, stability or vision were also excluded. Subjects provided written informed consent prior to
ip t
the experiment and the protocol was approved by the Institutional Ethics Review Board.
cr
Experimental Setup
us
A custom wooden staircase was built in accordance to the National Building Code of Canada. The dimensions were 2.13m x 1.3m x 0.72m (length x width x height). The staircase
an
consisted of 4 steps, with a rise of 0.18m and a run of 0.30m. For safety, handrails were built in accordance to the National Building Code of Canada (handrail height = 0.89m) (Figure 2).
M
A three-dimensional Optotrak Certus motion capture system, (Northern Digital Inc., Waterloo, Ontario) was used to record 12 frontal infrared (IRED) markers to estimate the COM
d
location, at a sampling frequency of 100 Hz. The participants were instrumented with forward-
Ac ce pt e
facing markers on the: forehead, bilateral acriomioclavicular joints, xyphoid process, bilateral anterior inferior iliac spines, bilateral tibial tuberosities, bilateral anterior distal tibias, and bilateral bases of the first metatarsals.
Three force plates (Model OR-6-2000, AMTI, Watertown, MA) were used to record kinetic data which collected the ground reaction forces at a sampling frequency of 200 Hz. The first two force plates (FP1 and FP2) were staggered on the level surface in front of the stairs, and the third force plate (FP3) was imbedded into the second step of the staircase. Lastly, varying insole hardnesses (soft, medium, and hard) were inserted inside matching canvas shoes. Structurally, the insoles were similar in shape and thickness but differed in material density. Midsole thickness was identified using the Shore classification system, a measuring scale recognized to identify material density, with scores from Shore A15 (softest),
Page 6 of 20
Shore A33 (medium), to Shore A50 (hardest). A barefoot condition was also utilized as an insole condition. The barefoot condition comprised of wearing socks without using the canvas shoes and insoles of varying hardnesses.
ip t
Protocol
cr
After obtaining informed consent, participants had anthropometric measurements taken. This included height, weight, foot length, foot width measurements. A plantar surface sensitivity
us
test was conducted using Touch-Test® Sensory Evaluator monofilaments (North Coast Medical, Inc. Gilroy, CA, USA) to certify participants had normal limits of cutaneous sensation. Once
an
instrumented with 12 IRED markers on the designated locations, participants were instructed to stand with feet shoulder width apart on one force plate with eyes open for 30 seconds. For the
M
experimental protocol, each participant was instructed to perform 5 walking trials stepping on the
d
level ground force plates with each insole condition (barefoot, soft, medium, and hard) for a total
Ac ce pt e
of 20 walking trials. Then for the stair trials, each participant was harnessed for safety and instructed to descend the stairs while wearing different insole hardnesses. In a blocked randomization grouped by insoles, participants wore each of the four insole conditions (barefoot, soft, medium, and hard) 5 consecutive times while descending down the stairs in normal office lighting. Participants had a 45-minute acclimatization period with the footwear and various insoles prior to the stair gait trials. To ensure that all steps were conducted and each study consistent, the researcher utilized this protocol for each participant study. Data Analysis The COM was calculated from the 12 IRED markers using a segmental weighted average approach (7 segments) [18], while the BOS lateral border was calculated using anthropometric distances from the toe and ankle markers of the foot, which were the IRED markers that defined 5
Page 7 of 20
the foot’s lateral borders. Once the COM was calculated, the single support phase during stair descent was identified via force plate contact. During that single support time, in the horizontal plane, the minimum, maximum, and range of the perpendicular distance between the COM
ip t
location and the lateral BOS border were calculated (in m). Gait velocity was measured using the formula: (initial foot contact location on FP3 – initial foot contact location on FP2) / (initial foot
cr
contact time on FP3 – initial foot contact time on FP2). For full procedures of the data analyses
us
and calculations refer to the study by Perry et al. [7].
an
Statistical Analysis
Post-experiment, a 2x4 analysis of variance (ANOVA) was conducted using SPSS (v.19,
M
IBM, SPSS) for data analysis. This model allowed comparison for both between (2= age) and within (4=insoles) groups. Outcome measures of stability produced were the minimum COM-
d
BOS in the medial/lateral direction termed the ‘stability margins’ and the COM-BOS
Ac ce pt e
medial/lateral range (maximum-minimum). Simple t-tests were conducted to assess age differences in: 1) cutaneous sensation, 2) gait velocity. In addition, epsilon correctional factors were implemented if Mauchly’s sphericity was violated, using Greenhouse-Geiser, or the Huhyn-Feldt. For the experiment, the activity of a single stair descent was divided into either a steady state descent phase or a transition gait phase. Data at both respective phases were analyzed using the same 2x4 ANOVAs comparing age and insoles. Results
COM-BOS Lateral Stability Margin
There was a significant main effect of age on COM-BOS ‘stability margin’ during both the transition gait phase (F(1,84) 21.7,p
