Gait & Posture 40 (2014) 658–663
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Effects of manual task complexity on gait parameters in school-aged children and adults Laurel D. Abbruzzese a,*, Ashwini K. Rao a,b, Rachel Bellows c, Kristina Figueroa d, Jennifer Levy e, Esther Lim f, Lauren Puccio g a Program in Physical Therapy, Department of Rehabilitation and Regenerative Medicine Columbia University College of Physicians and Surgeons, New York, USA b G.H. Sergievsky Center, Columbia University College of Physicians and Surgeons, New York, USA c Spear Physical Therapy, New York, USA d YAI/NYL Gramercy School, New York, USA e Swedish Medical Center, Seattle, USA f Memorial Sloan-Kettering Cancer Center, New York, USA g St. Mary’s Hospital for Children, Bayside, New York, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 January 2014 Received in revised form 26 June 2014 Accepted 21 July 2014
This study examined the dual-task interference effects of complexity (simple vs. complex), type of task (carrying a pitcher vs. tray), and age (young adults vs. 7–10 year old children) on temporal-spatial and variability measures of gait. All participants first walked on the GAITRite1 walkway without any concurrent task, followed by four dual-task gait conditions. The group of children had a more variable step length and step time than adults across all walking conditions. They also slowed down, took fewer, smaller steps and spent more time in double limb support than adults in the complex dual task conditions. Gait in healthy young adults and school aged children was relatively unaffected by concurrent performance of simple versions of the manual tasks. Our overall analysis suggests that dualtask gait in school aged children is still developing and has not yet reached adult capacity. This study also highlights the critical role of task demand and complexity in dual-task interference. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Gait Dual-task Children Cognitive-motor development
1. Introduction The ability to walk while carrying objects is an essential daily function and a common activity for individuals of all ages. In some situations, the addition of a concurrent task results in a slower gait velocity, which is often accompanied by related changes in stride length, cadence and stance time [1–4]. However, in some dual-task situations, concurrent tasks may be performed while walking without any apparent interference effects on preferred gait speed [5–7]. The dominant theory explaining dual-task interference effects assumes that attention resources are limited [8]. Researchers have proposed that interference effects occur when the demands of the concurrent tasks exceed the available processing capacity of the performer [9]. It has also been suggested that the task that will be prioritized will be the task that is perceived to
* Corresponding author at: Program in Physical Therapy, 710 West, 168th Street, 8th Floor, New York, NY 10032, USA. Tel.: +1 212 305 3916; fax: +1 212 305 4569. E-mail address: [email protected] (L.D. Abbruzzese). http://dx.doi.org/10.1016/j.gaitpost.2014.07.017 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
have a higher perceptual difficulty versus cognitive difficulty [10] or the task perceived as the higher threat [11]. Although numerous dual-task paradigms have been explored in the elderly [12–14] and neurological populations [3,4,7,15–18], relatively fewer researchers have investigated dual-task gait effects in children. By age 7, school-aged children should be capable of performing complex locomotor tasks such as walking and carrying a lunch tray or carrying a cup of water without spilling [19,20]. Investigations of dual-task gait performance in young children have demonstrated that the ‘‘cost’’ of performing a secondary task while walking is lower gait velocity, decreased cadence, lower stride length, increased base of support and increased time spent in double limb support [1]. Cherng and colleagues (2007) demonstrated that preschool children (aged 4–6) had a greater dual-task cost when performing a difficult task of carrying a tray with marbles versus carrying an empty tray [1]. Young children (ages 3–6) can carry a tray with a cup of water without spilling, but need to slow down [20]. Studies examining simple manual tasks [22] or cognitive secondary tasks [23] in older children (over age 6) suggest that the ability to perform secondary tasks while walking improves with
L.D. Abbruzzese et al. / Gait & Posture 40 (2014) 658–663
age as bimanual coordination and attention resources improve. However, the interference effects of complex manual tasks on gait have not been explored in school-aged children (aged 7–10). As children grow and gain experience walking, arm swing emerges and joint kinematic measures begin to approximate those of adults [24]. Up until age 4, gait maturation is attributed to central nervous system maturation. Subsequent changes in spatial-temporal parameters may be attributed to skeletal growth [25]. In addition to increased velocity, decreased cadence and increased step length, the relative base of support narrows and single limb stance time increases, reflecting greater stability by age 7 [25]. By age 7, children also demonstrate a more mature headtrunk coordination strategy under difficult balance conditions that is not seen in children aged 3–6 [26]. Cognitive development and the ability to adapt locomotor strategies to environmental constraints also progresses with age. As the attention resources required for locomotion decrease, the ability to allocate attention to secondary tasks increases [27]. Given that dual task interference is greater when performing more complex tasks [1,28] and in young children (age 3–6) when performing concurrent manual tasks [1,22], it is reasonable to expect that school aged children would demonstrate increased variability and decrements in gait parameters under complex dual task conditions. However, previous research has not focused on the influence of task difficulty on gait with concurrent manual tasks in this older age group. Therefore, the purpose of this study was to examine the effects of complexity, type of task, and age on the ability to walk while performing concurrent manual tasks by comparing typically developing school-aged children aged 7–10 years with healthy young adults aged 21–37 years. We hypothesized that (1) dual-task costs (changes in temporal-spatial gait parameters) while walking and performing concurrent manual tasks would be greater under more complex, attention demanding versions of carrying a tray or pitcher for both children and adults, (2) dual-task costs would be greater for children compared with adults on the complex but not simple versions of the tasks, and (3) variability in stride parameters under complex dual-task conditions would be greater in children than adults. 2. Methods 2.1. Participants The participant sample included ten typically developing school-aged children aged 7–10 years (8.1 1.2 years) and ten healthy young adults aged 21–37 years (26.8 4.9 years). Adult subjects were recruited from the Columbia University community. Children were recruited from the family and friends of Columbia University faculty members. All participants were free of any known neuromuscular diseases or attention deficit disorders. Informed consent approved by the Institutional Review Board of Columbia University’s Medical Center was obtained from the children and parents/guardians as well as all adult participants prior to participation in this study.
659
2.2. Apparatus Data was collected using the GAITRite1 instrumented walkway (CIR Industries, Clifton, NJ, USA), a 4.6-m-long instrumented carpet with sensors embedded within its surface. The GAITRite apparatus contains six sensor pads within a roll up carpet with a 0.61 m wide and 3.66 m long active area. As subjects walked across the carpet walkway, the sensors embedded within the walkway captured and recorded the relative position and pressure applied at each footfall as a function in time. For data collection, the walkway was connected to a laptop computer via a serial port. The application’s software (version 3.7) processed the raw data into spatial and temporal parameters. The following gait parameters were collected for data analysis in this study: gait velocity (centimeters per second), cadence (steps per minute), step length (centimeters), base of support (the perpendicular distance from heel point of one footfall to the line of progression of the opposite foot in centimeters), and percent time in double limb support. Variability of step length and step time parameters was also included. 2.3. Single-task and dual-task gait data collection procedures Gender, date of birth, and leg length of each subject was entered into the GAITRite1 application software prior to data collection on the walkway. Leg length was measured as the distance from the greater trochanter to where the heel of the subject’s footwear made contact with the floor. All trials began with subjects being asked to walk the length of the GAITRite1 walkway at a preferred, comfortable speed, arms free with the instruction to avoid stepping on the sensor pads. Subjects began walking 2 m before the edge of the walkway and ended the walk 2 m beyond the end of the carpet (start and end positions designated by markings on the floor), and were given verbal cues when to ‘‘begin’’ walking and when to ‘‘stop’’. The extra 2 m at the beginning and end of the walkway were added to eliminate the acceleration and deceleration during each trial. In order to determine dual-task cost, the single-task walking trials were used as a baseline for comparison with four dual task conditions: (1) dual task-simple pitcher (SP), (2) dual task-simple tray (ST), (3) dual task-complex pitcher (CP), and (4) dual taskcomplex tray (CT). In the simple dual tasks, subjects were instructed to walk while holding an empty pitcher with one hand (SP) or to walk while holding an empty tray with both hands (ST). In the complex dual tasks, subjects were instructed to walk without spilling water from a cup secured inside the pitcher (CP) or without tipping over a cup balanced on the tray (CT). They were also instructed to walk at their preferred, comfortable speed, just as they had when their arms were free. Subjects performed three trials under each of the walking conditions. Following the single task condition, the order of the SP, ST, CP and CT tasks was randomized across subjects to minimize an order effect. Characteristics of the four dual-task conditions are presented in Table 1.
Table 1 Characteristics of the four dual-task walking conditions (simple tray, simple pitcher, complex tray, complex pitcher). Simple dual task
Task details Added instructions Weight
Complex dual task
Tray
Pitcher
Tray
Pitcher
Empty tray Held with two hands
Pitcher with empty cup secured inside Held with one hand by the handle
Tray with unsecured empty cup on top Held with two hands Do not let the cup tip, fall or slide
Pitcher with cup of water secured inside Held with one hand by the handle Do not let water spill into the pitcher
145 g
190 g
250 g
380 g
L.D. Abbruzzese et al. / Gait & Posture 40 (2014) 658–663
660
2.4. Statistical analysis Baseline measures of gait velocity were normalized using leg length and used for between group comparisons. Dual-task cost was determined by calculating the difference between the single task and each dual-task condition data for each of the five gait variables measured using the GAITRite1 (gait velocity, cadence, stride length, base of support and percent time in double limb support.) The average dual-task cost was analyzed using two-way repeated measures ANOVA to determine main effects for complexity (simple vs. complex), type of manual task (pitcher vs. tray) and group (adult vs. child). Coefficient of variation (CoV) was calculated for stride time and stride length by dividing the standard deviation by the mean for each individual subject. The mean step length and step time CoV under single task conditions for children was compared to the CoV for adults using a t-test for two independent means. The effect of task and complexity on variability was further analyzed using a repeated measures ANOVA. Statistical Package for the Social Sciences (SPSS) V 20 for Mac was used for data analysis and a p value of .05 was used to determine significance for all of the statistical tests.
Table 4. The normalized gait velocities were comparable for adults and children and are included in Table 2. However, since gait velocity normalization did not change the main effects or interaction effects on dual task costs only the cost results using the original gait measures are presented. 3.1. Manual task performance All twenty subjects were able to successfully perform both versions of the tray and pitcher tasks while standing still and while walking at preferred, comfortable speed. In the complex versions of the tray task, subjects were able to keep the empty cup on the tray without letting it tip over or slide off. In the complex version of the pitcher task, water spillage was checked after each trial. All subjects were able to transport the pitcher without water spilling out of the cup into the pitcher. 3.2. Effect of complexity of task The main effects of task complexity were significant for velocity, step length, cadence, and double limb support, but not for base of support (Table 4). Specifically, the complex versions of both manual tasks resulted in a shorter average step length, fewer steps taken per minute, slower walking velocity and increased time in double limb support as compared to the simple versions of the tasks (Table 2). Main effect of task complexity was observed for both healthy young adults and school aged children. The difference in cost due to task complexity was greater for children compared with adults. A significant interaction between age and task complexity is depicted in Fig. 1. The dual task cost was negligible for both adults and children for the simple task conditions.
3. Results Mean and standard deviation for the five temporal-spatial gait parameters with and without simple and complex manual tasks are presented in Table 2. Coefficient of variation means and standard deviations for step length and time are presented in Table 3. The interference effects (dual-task costs) of age group (adults versus school age children), task complexity (simple and complex) and type of task (pitcher and tray) are depicted in Fig. 1 for the gait variables with significant effects. The main effects of complexity, task type, age group and group by task and complexity interactions on the dual-task costs for all measures are presented in
3.3. Effect of type of task Our analysis revealed a significant main effect for type of task for step length and gait velocity (Table 4). On average, the mean dual-task cost effects on step length and velocity were greater in the tray versus pitcher conditions. Both adults and school-aged children reduced step length and gait velocity more in the tray conditions (Fig. 1A and B). There was a significant interaction effect for step length only (Table 4; Fig. 1A). The difference between adults and children was greater in the tray conditions compared to the pitcher conditions.
Table 2 The means and standard deviations of the gait parameters when participants walked without a concurrent task (single task), with a concurrent simple manual task (simple dual task) and with a concurrent complex manual task (complex dual task). Single task
Simple dual task Tray
Normalized velocity (leg lengths/s) Adults 1.71 (.19) Children 1.73 (.31) Velocity (cm/s) Adults 150.46 (15.79) Children 120.49 (24.57) Step length (cm) Adults 80.79 (7.69) Children 63.44 (8.72) Cadence (steps/min) Adults 111.76 (6.79) Children 112.95 (11.18) Double limb support (% of gait cycle) Adults 25.46 (3.74) Children 24.58 (2.82) Base of support (cm) Adults 9.05 (2.05) Children 8.70 (1.49)
Complex dual task Pitcher
Tray
Pitcher
1.72 (.17) 1.84 (.35)
1.73 (.16) 1.76 (.41)
1.64 (.10) 1.42 (.47)
1.66 (.14) 1.48 (.50)
152.94 (16.01) 122.03 (26.26)
152.11 (15.26) 127.42 (20.98)
142.27 (13.11) 97.59 (31.04)
146.69 (12.97) 102.18 (31.04)
80.88 (7.24) 62.33 (9.5)
80.49 (7.21) 64.15 (8.4)
76.62 (7.06) 54.63 (9.62)
113.68 (9.52) 116.46 (11.34)
113.48 (8.09) 118.82 (9.17)
78.24 (6.71) 58.85 (11.75)
111.8 (9.37) 105.03 (17.15)
112.64 (7.83) 107.58 (14.44)
25.44 (4.17) 24.51 (2.31)
25.06 (3.9) 24.18 (2.58)
26.28 (3.18) 28.06 (3.92)
26.31 (5.33) 28.46 (3.35)
9.05 (3.52) 8.47 (2.08)
9.22 (1.79) 8.01 (2.55)
8.99 (1.61) 7.85 (1.06)
9.05 (2.17) 8.39 (1.72)
Table 3 The mean coefficient of variation (CoV) and standard deviation for CoV for step length and step time when participants walked without a concurrent task (single task), with a concurrent simple manual task (simple dual task) and with a concurrent complex manual task (complex dual task). Single task
Step length (CoV) Adults Children Step time (CoV) Adults Children
Simple dual task
Complex dual task
Tray
Pitcher
Tray
Pitcher
2.85 (2.15) 4.92 (2.89)
1.89 (0.89) 3.44 (2.29)
1.89 (1.05) 3.83 (3.20)
2.89 (2.23) 4.62 (2.47)
1.71 (1.12) 1.71 (1.12)
2.41 (1.08) 4.60 (2.66)
5.63 (5.46) 4.16 (1.57)
2.29 (1.95) 3.72 (2.83)
3.44 (2.92) 5.4 (2.62)
4.10 (7.15) 4.10 (7.15)
[(Fig._1)TD$IG]
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661
Fig. 1. Average dual-task cost for step length (A), velocity (B), cadence (C) and percent time in double limb support (% Time in DLS) (D). A positive value for velocity, step length, and cadence indicates that the value for the measure decreased under the concurrent manual task condition. A dual task cost for percent time in DLS is represented by a negative number (more time spent in DLS). The error bars in the graph represent standard errors of the mean. Table 4 Statistical results and main effects from the two-way repeated measures ANOVA of the dual-task costs for each gait parameter and repeated measures ANOVA for the variability measures. Complexity
Average Velocity Average Step length Average Cadence Average Double limb support Average Base of support Step length Variability Step time variability
Type of task
Age group
Group by complexity interaction
Group by task interaction
F1,18
p
F1,18
p
F1,18
p
F1,18
p
F1,18
p
42.942 81.22 12.441 64.808 0.85 0.050 1.014
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Effects of manual task complexity on gait parameters in school-aged children and adults Laurel D. Abbruzzese a,*, Ashwini K. Rao a,b, Rachel Bellows c, Kristina Figueroa d, Jennifer Levy e, Esther Lim f, Lauren Puccio g a Program in Physical Therapy, Department of Rehabilitation and Regenerative Medicine Columbia University College of Physicians and Surgeons, New York, USA b G.H. Sergievsky Center, Columbia University College of Physicians and Surgeons, New York, USA c Spear Physical Therapy, New York, USA d YAI/NYL Gramercy School, New York, USA e Swedish Medical Center, Seattle, USA f Memorial Sloan-Kettering Cancer Center, New York, USA g St. Mary’s Hospital for Children, Bayside, New York, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 January 2014 Received in revised form 26 June 2014 Accepted 21 July 2014
This study examined the dual-task interference effects of complexity (simple vs. complex), type of task (carrying a pitcher vs. tray), and age (young adults vs. 7–10 year old children) on temporal-spatial and variability measures of gait. All participants first walked on the GAITRite1 walkway without any concurrent task, followed by four dual-task gait conditions. The group of children had a more variable step length and step time than adults across all walking conditions. They also slowed down, took fewer, smaller steps and spent more time in double limb support than adults in the complex dual task conditions. Gait in healthy young adults and school aged children was relatively unaffected by concurrent performance of simple versions of the manual tasks. Our overall analysis suggests that dualtask gait in school aged children is still developing and has not yet reached adult capacity. This study also highlights the critical role of task demand and complexity in dual-task interference. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Gait Dual-task Children Cognitive-motor development
1. Introduction The ability to walk while carrying objects is an essential daily function and a common activity for individuals of all ages. In some situations, the addition of a concurrent task results in a slower gait velocity, which is often accompanied by related changes in stride length, cadence and stance time [1–4]. However, in some dual-task situations, concurrent tasks may be performed while walking without any apparent interference effects on preferred gait speed [5–7]. The dominant theory explaining dual-task interference effects assumes that attention resources are limited [8]. Researchers have proposed that interference effects occur when the demands of the concurrent tasks exceed the available processing capacity of the performer [9]. It has also been suggested that the task that will be prioritized will be the task that is perceived to
* Corresponding author at: Program in Physical Therapy, 710 West, 168th Street, 8th Floor, New York, NY 10032, USA. Tel.: +1 212 305 3916; fax: +1 212 305 4569. E-mail address: [email protected] (L.D. Abbruzzese). http://dx.doi.org/10.1016/j.gaitpost.2014.07.017 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
have a higher perceptual difficulty versus cognitive difficulty [10] or the task perceived as the higher threat [11]. Although numerous dual-task paradigms have been explored in the elderly [12–14] and neurological populations [3,4,7,15–18], relatively fewer researchers have investigated dual-task gait effects in children. By age 7, school-aged children should be capable of performing complex locomotor tasks such as walking and carrying a lunch tray or carrying a cup of water without spilling [19,20]. Investigations of dual-task gait performance in young children have demonstrated that the ‘‘cost’’ of performing a secondary task while walking is lower gait velocity, decreased cadence, lower stride length, increased base of support and increased time spent in double limb support [1]. Cherng and colleagues (2007) demonstrated that preschool children (aged 4–6) had a greater dual-task cost when performing a difficult task of carrying a tray with marbles versus carrying an empty tray [1]. Young children (ages 3–6) can carry a tray with a cup of water without spilling, but need to slow down [20]. Studies examining simple manual tasks [22] or cognitive secondary tasks [23] in older children (over age 6) suggest that the ability to perform secondary tasks while walking improves with
L.D. Abbruzzese et al. / Gait & Posture 40 (2014) 658–663
age as bimanual coordination and attention resources improve. However, the interference effects of complex manual tasks on gait have not been explored in school-aged children (aged 7–10). As children grow and gain experience walking, arm swing emerges and joint kinematic measures begin to approximate those of adults [24]. Up until age 4, gait maturation is attributed to central nervous system maturation. Subsequent changes in spatial-temporal parameters may be attributed to skeletal growth [25]. In addition to increased velocity, decreased cadence and increased step length, the relative base of support narrows and single limb stance time increases, reflecting greater stability by age 7 [25]. By age 7, children also demonstrate a more mature headtrunk coordination strategy under difficult balance conditions that is not seen in children aged 3–6 [26]. Cognitive development and the ability to adapt locomotor strategies to environmental constraints also progresses with age. As the attention resources required for locomotion decrease, the ability to allocate attention to secondary tasks increases [27]. Given that dual task interference is greater when performing more complex tasks [1,28] and in young children (age 3–6) when performing concurrent manual tasks [1,22], it is reasonable to expect that school aged children would demonstrate increased variability and decrements in gait parameters under complex dual task conditions. However, previous research has not focused on the influence of task difficulty on gait with concurrent manual tasks in this older age group. Therefore, the purpose of this study was to examine the effects of complexity, type of task, and age on the ability to walk while performing concurrent manual tasks by comparing typically developing school-aged children aged 7–10 years with healthy young adults aged 21–37 years. We hypothesized that (1) dual-task costs (changes in temporal-spatial gait parameters) while walking and performing concurrent manual tasks would be greater under more complex, attention demanding versions of carrying a tray or pitcher for both children and adults, (2) dual-task costs would be greater for children compared with adults on the complex but not simple versions of the tasks, and (3) variability in stride parameters under complex dual-task conditions would be greater in children than adults. 2. Methods 2.1. Participants The participant sample included ten typically developing school-aged children aged 7–10 years (8.1 1.2 years) and ten healthy young adults aged 21–37 years (26.8 4.9 years). Adult subjects were recruited from the Columbia University community. Children were recruited from the family and friends of Columbia University faculty members. All participants were free of any known neuromuscular diseases or attention deficit disorders. Informed consent approved by the Institutional Review Board of Columbia University’s Medical Center was obtained from the children and parents/guardians as well as all adult participants prior to participation in this study.
659
2.2. Apparatus Data was collected using the GAITRite1 instrumented walkway (CIR Industries, Clifton, NJ, USA), a 4.6-m-long instrumented carpet with sensors embedded within its surface. The GAITRite apparatus contains six sensor pads within a roll up carpet with a 0.61 m wide and 3.66 m long active area. As subjects walked across the carpet walkway, the sensors embedded within the walkway captured and recorded the relative position and pressure applied at each footfall as a function in time. For data collection, the walkway was connected to a laptop computer via a serial port. The application’s software (version 3.7) processed the raw data into spatial and temporal parameters. The following gait parameters were collected for data analysis in this study: gait velocity (centimeters per second), cadence (steps per minute), step length (centimeters), base of support (the perpendicular distance from heel point of one footfall to the line of progression of the opposite foot in centimeters), and percent time in double limb support. Variability of step length and step time parameters was also included. 2.3. Single-task and dual-task gait data collection procedures Gender, date of birth, and leg length of each subject was entered into the GAITRite1 application software prior to data collection on the walkway. Leg length was measured as the distance from the greater trochanter to where the heel of the subject’s footwear made contact with the floor. All trials began with subjects being asked to walk the length of the GAITRite1 walkway at a preferred, comfortable speed, arms free with the instruction to avoid stepping on the sensor pads. Subjects began walking 2 m before the edge of the walkway and ended the walk 2 m beyond the end of the carpet (start and end positions designated by markings on the floor), and were given verbal cues when to ‘‘begin’’ walking and when to ‘‘stop’’. The extra 2 m at the beginning and end of the walkway were added to eliminate the acceleration and deceleration during each trial. In order to determine dual-task cost, the single-task walking trials were used as a baseline for comparison with four dual task conditions: (1) dual task-simple pitcher (SP), (2) dual task-simple tray (ST), (3) dual task-complex pitcher (CP), and (4) dual taskcomplex tray (CT). In the simple dual tasks, subjects were instructed to walk while holding an empty pitcher with one hand (SP) or to walk while holding an empty tray with both hands (ST). In the complex dual tasks, subjects were instructed to walk without spilling water from a cup secured inside the pitcher (CP) or without tipping over a cup balanced on the tray (CT). They were also instructed to walk at their preferred, comfortable speed, just as they had when their arms were free. Subjects performed three trials under each of the walking conditions. Following the single task condition, the order of the SP, ST, CP and CT tasks was randomized across subjects to minimize an order effect. Characteristics of the four dual-task conditions are presented in Table 1.
Table 1 Characteristics of the four dual-task walking conditions (simple tray, simple pitcher, complex tray, complex pitcher). Simple dual task
Task details Added instructions Weight
Complex dual task
Tray
Pitcher
Tray
Pitcher
Empty tray Held with two hands
Pitcher with empty cup secured inside Held with one hand by the handle
Tray with unsecured empty cup on top Held with two hands Do not let the cup tip, fall or slide
Pitcher with cup of water secured inside Held with one hand by the handle Do not let water spill into the pitcher
145 g
190 g
250 g
380 g
L.D. Abbruzzese et al. / Gait & Posture 40 (2014) 658–663
660
2.4. Statistical analysis Baseline measures of gait velocity were normalized using leg length and used for between group comparisons. Dual-task cost was determined by calculating the difference between the single task and each dual-task condition data for each of the five gait variables measured using the GAITRite1 (gait velocity, cadence, stride length, base of support and percent time in double limb support.) The average dual-task cost was analyzed using two-way repeated measures ANOVA to determine main effects for complexity (simple vs. complex), type of manual task (pitcher vs. tray) and group (adult vs. child). Coefficient of variation (CoV) was calculated for stride time and stride length by dividing the standard deviation by the mean for each individual subject. The mean step length and step time CoV under single task conditions for children was compared to the CoV for adults using a t-test for two independent means. The effect of task and complexity on variability was further analyzed using a repeated measures ANOVA. Statistical Package for the Social Sciences (SPSS) V 20 for Mac was used for data analysis and a p value of .05 was used to determine significance for all of the statistical tests.
Table 4. The normalized gait velocities were comparable for adults and children and are included in Table 2. However, since gait velocity normalization did not change the main effects or interaction effects on dual task costs only the cost results using the original gait measures are presented. 3.1. Manual task performance All twenty subjects were able to successfully perform both versions of the tray and pitcher tasks while standing still and while walking at preferred, comfortable speed. In the complex versions of the tray task, subjects were able to keep the empty cup on the tray without letting it tip over or slide off. In the complex version of the pitcher task, water spillage was checked after each trial. All subjects were able to transport the pitcher without water spilling out of the cup into the pitcher. 3.2. Effect of complexity of task The main effects of task complexity were significant for velocity, step length, cadence, and double limb support, but not for base of support (Table 4). Specifically, the complex versions of both manual tasks resulted in a shorter average step length, fewer steps taken per minute, slower walking velocity and increased time in double limb support as compared to the simple versions of the tasks (Table 2). Main effect of task complexity was observed for both healthy young adults and school aged children. The difference in cost due to task complexity was greater for children compared with adults. A significant interaction between age and task complexity is depicted in Fig. 1. The dual task cost was negligible for both adults and children for the simple task conditions.
3. Results Mean and standard deviation for the five temporal-spatial gait parameters with and without simple and complex manual tasks are presented in Table 2. Coefficient of variation means and standard deviations for step length and time are presented in Table 3. The interference effects (dual-task costs) of age group (adults versus school age children), task complexity (simple and complex) and type of task (pitcher and tray) are depicted in Fig. 1 for the gait variables with significant effects. The main effects of complexity, task type, age group and group by task and complexity interactions on the dual-task costs for all measures are presented in
3.3. Effect of type of task Our analysis revealed a significant main effect for type of task for step length and gait velocity (Table 4). On average, the mean dual-task cost effects on step length and velocity were greater in the tray versus pitcher conditions. Both adults and school-aged children reduced step length and gait velocity more in the tray conditions (Fig. 1A and B). There was a significant interaction effect for step length only (Table 4; Fig. 1A). The difference between adults and children was greater in the tray conditions compared to the pitcher conditions.
Table 2 The means and standard deviations of the gait parameters when participants walked without a concurrent task (single task), with a concurrent simple manual task (simple dual task) and with a concurrent complex manual task (complex dual task). Single task
Simple dual task Tray
Normalized velocity (leg lengths/s) Adults 1.71 (.19) Children 1.73 (.31) Velocity (cm/s) Adults 150.46 (15.79) Children 120.49 (24.57) Step length (cm) Adults 80.79 (7.69) Children 63.44 (8.72) Cadence (steps/min) Adults 111.76 (6.79) Children 112.95 (11.18) Double limb support (% of gait cycle) Adults 25.46 (3.74) Children 24.58 (2.82) Base of support (cm) Adults 9.05 (2.05) Children 8.70 (1.49)
Complex dual task Pitcher
Tray
Pitcher
1.72 (.17) 1.84 (.35)
1.73 (.16) 1.76 (.41)
1.64 (.10) 1.42 (.47)
1.66 (.14) 1.48 (.50)
152.94 (16.01) 122.03 (26.26)
152.11 (15.26) 127.42 (20.98)
142.27 (13.11) 97.59 (31.04)
146.69 (12.97) 102.18 (31.04)
80.88 (7.24) 62.33 (9.5)
80.49 (7.21) 64.15 (8.4)
76.62 (7.06) 54.63 (9.62)
113.68 (9.52) 116.46 (11.34)
113.48 (8.09) 118.82 (9.17)
78.24 (6.71) 58.85 (11.75)
111.8 (9.37) 105.03 (17.15)
112.64 (7.83) 107.58 (14.44)
25.44 (4.17) 24.51 (2.31)
25.06 (3.9) 24.18 (2.58)
26.28 (3.18) 28.06 (3.92)
26.31 (5.33) 28.46 (3.35)
9.05 (3.52) 8.47 (2.08)
9.22 (1.79) 8.01 (2.55)
8.99 (1.61) 7.85 (1.06)
9.05 (2.17) 8.39 (1.72)
Table 3 The mean coefficient of variation (CoV) and standard deviation for CoV for step length and step time when participants walked without a concurrent task (single task), with a concurrent simple manual task (simple dual task) and with a concurrent complex manual task (complex dual task). Single task
Step length (CoV) Adults Children Step time (CoV) Adults Children
Simple dual task
Complex dual task
Tray
Pitcher
Tray
Pitcher
2.85 (2.15) 4.92 (2.89)
1.89 (0.89) 3.44 (2.29)
1.89 (1.05) 3.83 (3.20)
2.89 (2.23) 4.62 (2.47)
1.71 (1.12) 1.71 (1.12)
2.41 (1.08) 4.60 (2.66)
5.63 (5.46) 4.16 (1.57)
2.29 (1.95) 3.72 (2.83)
3.44 (2.92) 5.4 (2.62)
4.10 (7.15) 4.10 (7.15)
[(Fig._1)TD$IG]
L.D. Abbruzzese et al. / Gait & Posture 40 (2014) 658–663
661
Fig. 1. Average dual-task cost for step length (A), velocity (B), cadence (C) and percent time in double limb support (% Time in DLS) (D). A positive value for velocity, step length, and cadence indicates that the value for the measure decreased under the concurrent manual task condition. A dual task cost for percent time in DLS is represented by a negative number (more time spent in DLS). The error bars in the graph represent standard errors of the mean. Table 4 Statistical results and main effects from the two-way repeated measures ANOVA of the dual-task costs for each gait parameter and repeated measures ANOVA for the variability measures. Complexity
Average Velocity Average Step length Average Cadence Average Double limb support Average Base of support Step length Variability Step time variability
Type of task
Age group
Group by complexity interaction
Group by task interaction
F1,18
p
F1,18
p
F1,18
p
F1,18
p
F1,18
p
42.942 81.22 12.441 64.808 0.85 0.050 1.014
