Research in Developmental Disabilities 35 (2014) 3568–3573
Contents lists available at ScienceDirect
Research in Developmental Disabilities
Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy Yung-Shen Tsai a,*, Yi-Chen Yu b, Po-Chang Huang c, Hsin-Yi Kathy Cheng d a
Graduate Institute of Sports Equipment Technology, University of Taipei, Taipei, Taiwan New Taipei Municipal Bali Junior High School, New Taipei, Taiwan c Department of Physical Medicine and Rehabilitation, National Yang-Ming University Hospital, I-Lan, Taiwan d Graduate Institute of Early Intervention, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 July 2014 Received in revised form 27 August 2014 Accepted 28 August 2014 Available online 19 September 2014
The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 158 anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Rehabilitation Motor activity Control
1. Introduction Cerebral palsy (CP) is a non-progressive disorder that affects muscle tone, strength, coordination, and motor skills during human development (Woollacott et al., 2005). To improve or maintain their movement function, children with CP typically require substantial daily rehabilitation exercises or activities (Willis, Morello, Davie, Rice, & Bennett, 2002). These rehabilitation programs are often repetitive and simple, potentially reducing participant motivation. Functional rehabilitation programs involving sports and fun may facilitate treatments and provide opportunities for children with CP to interact with others; thus, the sport of Boccia was designed.
* Corresponding author at: Graduate Institute of Sports Equipment Technology, University of Taipei, No. 101, Sec. 2, Jhongcheng Rd., Shinlin District, Taipei City 11153, Taiwan. Tel.: +886 2 28718288x7241; fax: +886 2 28751551. E-mail addresses: [email protected], [email protected] (Y.-S. Tsai). http://dx.doi.org/10.1016/j.ridd.2014.08.033 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
Y.-S. Tsai et al. / Research in Developmental Disabilities 35 (2014) 3568–3573
3569
Boccia is played indoors on a hard surface court similar in size to a badminton court. The aim of the game is to get game balls closer to a white target ball (the jack) than opponent. The game requires coordination, accuracy, concentration, the ability to strategize, emotional control, and interaction with others. The development of these abilities may contribute to both physical and mental development among children with CP. Boccia must be played from a seated position. Releasing the ball without having at least one buttock in contact with the throwing chair warrants penalty balls and the retraction of the thrown ball. In certain classifications, if players are unable to propel the ball onto the court using their hands, they are allowed to use an assistive device. In addition to the assistive device (if required), the chair plays a crucial role, providing stable support when throwing. Studies have produced various findings regarding how seat surface inclination affects postural control during reaching among children with CP (Cherng, Lin, Ju, & Ho, 2009; Hadders-Algra et al., 2007; McClenaghan, Thombs, & Milner, 1992; Myhr & von Wendt, 1991, 1993; Nwaobi, 1986, 1987; Nwaobi, Brubaker, Cusick, & Sussman, 1983; Seeger, Caudrey, & O’Mara, 1984; van der Heide, Otten, van Eykern, & Hadders-Algra, 2003). These studies reached contradicting conclusions based on various factors, namely, the angles of seat surface inclination, study groups, and research tasks. Although various studies have addressed forward reaching efficiency and movement stability, no researchers have discussed how seat surface inclination affects postural stability and throwing performance among children with CP while playing Boccia. Investigating this topic and determining the optimal sitting posture for playing Boccia may improve the throwing ability among children with CP; this could increase their self-confidence and willingness to participate in the sport. Therefore, this study explored how anterior-inclined, horizontal, and posterior-inclined seat surfaces affect Boccia ball throwing movements (of the head, trunk, shoulder, and elbow) and postural stability. Throwing performance, including movement time and throwing accuracy, were evaluated. 2. Materials and methods 2.1. Participants This is a descriptive study examining the effects of seat surface inclination on Boccia ball throwing movement and postural stability among children with CP. Twelve children (5 boys and 7 girls) with bilateral spastic CP from hospitals and institutions were invited to participate in this study. Their age, body height, and body mass were 10.4 (2.1) years, 139.5 (11.7) cm, and 32.7 (12.6) kg. Among the participants, three were classified as Level I according to the gross motor function classification system, five were classified as Level II, and four were classified as Level III. The participants were able to follow oral instructions to complete the experimental tasks, could maintain an independent sitting posture during throwing, and were able to throw a Boccia ball farther than 1.5 m (the minimal requirement) during competitions. None of the participants had experience playing Boccia before the study or received botulin injections within 6 months of the study. 2.2. Instruments In this study, a three-dimensional electromagnetic motion tracking system (Liberty, Polhemus, Colchester, VT) and MotionMonitor software (Innovative Sports Training, Inc., Chicago, IL) was used to collect and analyze motion data at a sampling rate of 240 Hz. A force plate (4060-NC-2000, Bertec Corporation, Columbus, OH) was placed under the feet of the participants and synchronized with the motion tracking system to record the COP trajectory and GRF during throwing at a sampling rate of 1200 Hz. A set of wooden chairs, of which the height and seat surface inclination (158 anterior-inclined, horizontal, and 158 posterior-inclined) could be adjusted, were used to satisfy the height requirements of the participants. The chair height was adjusted to be the same as the lower leg length of each participant. Standard Boccia balls, as specified by the Cerebral Palsy International Sports and Recreation Association, were used. To assess the throwing accuracy, the distance between the thrown Boccia ball and the target jack was measured using a standard ruler employed in Boccia competitions. 2.3. Procedures The demographic information for all participants and a written consent form signed by their parents were collected before the tests. The study was approved by the Institutional Review Board at the National Yang-Ming University Hospital. The collected data comprised sex, age, height, weight, dominant hand, and gross motor function classification. Pediatric reach tests (Bartlett & Birmingham, 2003) were conducted using each seat surface inclination to examine the balance abilities of the participants in various sitting conditions. Regarding the motion analysis, 7 sensors were fixed to the following positions on each participant: the back of the head, the first thoracic vertebra, the first sacral vertebra, and the lateral and posterior angles of the acromion, upper arm, forearm, and back of the throwing hand. Bony landmarks and the coordinates of each body part were specified according to the recommendations of the International Society of Biomechanics (ISB) (Wu et al., 2005). The times when the hand grasped and released the Boccia ball were determined using a prefabricated finger switch worn by each participant. The switch produced electronic signals that synchronized with the motion analysis system and the force plate when the hand touched a Boccia ball. The signal deactivated when the ball was released. These procedures were similar to the methods used in a previous study investigating the differences between children with CP and normally developed children regarding throwing patterns of Boccia balls (Huang, Pan, Ou, Yu, & Tsai, 2014).
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Y.-S. Tsai et al. / Research in Developmental Disabilities 35 (2014) 3568–3573
Before the data on each sitting condition was collected, each participant was instructed to practice three times, using an overhand throw, to familiarize themselves with the test method. Each participant placed both hands on the edge of a table adjusted to be the same height of their elbow as a starting position. They then grasped a Boccia ball placed on the lateral side of their throwing hand and threw the ball as close to the jack as possible. The jack was placed 5 m directly in front of the participants on the ground. Six trials were recorded for each sitting condition. The testing sequence of each sitting condition was randomly assigned. 2.4. Data analysis The maximal moving distances that each participant could reach in the forward, leftward, and rightward directions during the pediatric reach tests were summed to represent their balance abilities during each sitting condition (Gan, Tung, Tang, & Wang, 2008). The changes of various joint angles were calculated based on the Euler angle sequence of rotations recommended by the ISB (Wu et al., 2005). The amplitudes of the head and trunk flexion and extension, rotation, and lateral bending; the amplitudes of shoulder abduction and flexion; and the amplitude of elbow flexion during movement time were selected for motion analysis. The movement time was defined as the duration between ball contact and ball release. To assess postural stability, the peak vertical ground reaction force (PVGRF), movement range of the center of pressure (COP) in the anterior–posterior (AP) and medial–lateral (ML) direction, and COP sway ratio during throwing were derived based on the force plate data (Cherng et al., 2009; Liao, Yang, Hsu, Chan, & Wei, 2003). The PVGRF was standardized as a percentage of body weight for each participant. The sway ratio was calculated as the total displacement of the COP in the AP direction divided by the total displacement of the COP in the ML direction (Liao et al., 2003). The three throwing trials in which the closest distance between the thrown ball and the jack was attained were selected for data analysis. 2.5. Statistical analysis A one-way ANOVA with repeated measures followed by a Fisher’s least significant difference comparison was used to examine the differences among the variables of the three seat surface inclinations. The level of statistical significance was set at p < 0.05. 3. Results Table 1 shows the results of the pediatric reach test, kinematic and kinetic variables of throwing movement, movement duration, and the average distance between the thrown Boccia balls and jack in each sitting condition. The seat surface inclination significantly affected the results of the pediatric reach test (F = 4.316, p = 0.026), the amplitude of elbow flexion Table 1 The results (mean SD) of pediatric reach test, kinematic and kinetic variables of throwing movement, movement duration, and the average distance between thrown Boccia balls and the jack in each seat surface. Anterior-inclined
Horizontal
Posterior-inclined
F
P
47.27 24.15 1.72 0.56 43.63 26.54
50.18 20.00 1.66 0.68 46.84 28.91
40.13 27.04 2.05 0.91 49.88 29.64
4.316 2.290 0.206
0.026* 0.127 0.815
Kinematics Head flexion and extension (8) Head rotation (8) Head lateral bending (8) Trunk flexion and extension (8) Trunk rotation (8) Trunk lateral bending (8) Shoulder abduction (8) Shoulder flexion (8) Elbow flexion (8)
20.34 13.97 14.42 5.75 10.15 4.49 15.32 8.26 11.66 5.24 8.33 4.88 59.57 20.61 72.64 17.89 46.16 10.40a
16.79 12.45 14.62 7.16 9.67 4.38 19.35 10.96 11.05 6.00 7.63 5.46 54.82 19.72 68.30 19.78 38.21 8.64
21.99 12.77 14.14 7.33 8.77 3.61 17.82 6.53 11.23 3.26 8.76 6.16 54.41 15.89 67.70 17.75 38.97 12.40
3.057 0.027 1.072 1.510 0.103 0.379 1.420 0.768 3.930
0.069 0.973 0.363 0.243 0.903 0.690 0.265 0.479 0.036*
Kinetics PVGRF (%BW) COP range in AP direction (cm) COP range in ML direction (cm) Sway ratio
126.18 53.29a,b 2.38 1.49a,b 3.15 1.72b 0.72 0.11
80.71 26.13c 3.47 2.35 4.42 1.93 0.64 0.20
58.47 28.80 4.37 3.43 6.11 3.66 0.71 0.15
17.648 4.821 6.969 1.155
Contents lists available at ScienceDirect
Research in Developmental Disabilities
Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy Yung-Shen Tsai a,*, Yi-Chen Yu b, Po-Chang Huang c, Hsin-Yi Kathy Cheng d a
Graduate Institute of Sports Equipment Technology, University of Taipei, Taipei, Taiwan New Taipei Municipal Bali Junior High School, New Taipei, Taiwan c Department of Physical Medicine and Rehabilitation, National Yang-Ming University Hospital, I-Lan, Taiwan d Graduate Institute of Early Intervention, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 July 2014 Received in revised form 27 August 2014 Accepted 28 August 2014 Available online 19 September 2014
The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 158 anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Rehabilitation Motor activity Control
1. Introduction Cerebral palsy (CP) is a non-progressive disorder that affects muscle tone, strength, coordination, and motor skills during human development (Woollacott et al., 2005). To improve or maintain their movement function, children with CP typically require substantial daily rehabilitation exercises or activities (Willis, Morello, Davie, Rice, & Bennett, 2002). These rehabilitation programs are often repetitive and simple, potentially reducing participant motivation. Functional rehabilitation programs involving sports and fun may facilitate treatments and provide opportunities for children with CP to interact with others; thus, the sport of Boccia was designed.
* Corresponding author at: Graduate Institute of Sports Equipment Technology, University of Taipei, No. 101, Sec. 2, Jhongcheng Rd., Shinlin District, Taipei City 11153, Taiwan. Tel.: +886 2 28718288x7241; fax: +886 2 28751551. E-mail addresses: [email protected], [email protected] (Y.-S. Tsai). http://dx.doi.org/10.1016/j.ridd.2014.08.033 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
Y.-S. Tsai et al. / Research in Developmental Disabilities 35 (2014) 3568–3573
3569
Boccia is played indoors on a hard surface court similar in size to a badminton court. The aim of the game is to get game balls closer to a white target ball (the jack) than opponent. The game requires coordination, accuracy, concentration, the ability to strategize, emotional control, and interaction with others. The development of these abilities may contribute to both physical and mental development among children with CP. Boccia must be played from a seated position. Releasing the ball without having at least one buttock in contact with the throwing chair warrants penalty balls and the retraction of the thrown ball. In certain classifications, if players are unable to propel the ball onto the court using their hands, they are allowed to use an assistive device. In addition to the assistive device (if required), the chair plays a crucial role, providing stable support when throwing. Studies have produced various findings regarding how seat surface inclination affects postural control during reaching among children with CP (Cherng, Lin, Ju, & Ho, 2009; Hadders-Algra et al., 2007; McClenaghan, Thombs, & Milner, 1992; Myhr & von Wendt, 1991, 1993; Nwaobi, 1986, 1987; Nwaobi, Brubaker, Cusick, & Sussman, 1983; Seeger, Caudrey, & O’Mara, 1984; van der Heide, Otten, van Eykern, & Hadders-Algra, 2003). These studies reached contradicting conclusions based on various factors, namely, the angles of seat surface inclination, study groups, and research tasks. Although various studies have addressed forward reaching efficiency and movement stability, no researchers have discussed how seat surface inclination affects postural stability and throwing performance among children with CP while playing Boccia. Investigating this topic and determining the optimal sitting posture for playing Boccia may improve the throwing ability among children with CP; this could increase their self-confidence and willingness to participate in the sport. Therefore, this study explored how anterior-inclined, horizontal, and posterior-inclined seat surfaces affect Boccia ball throwing movements (of the head, trunk, shoulder, and elbow) and postural stability. Throwing performance, including movement time and throwing accuracy, were evaluated. 2. Materials and methods 2.1. Participants This is a descriptive study examining the effects of seat surface inclination on Boccia ball throwing movement and postural stability among children with CP. Twelve children (5 boys and 7 girls) with bilateral spastic CP from hospitals and institutions were invited to participate in this study. Their age, body height, and body mass were 10.4 (2.1) years, 139.5 (11.7) cm, and 32.7 (12.6) kg. Among the participants, three were classified as Level I according to the gross motor function classification system, five were classified as Level II, and four were classified as Level III. The participants were able to follow oral instructions to complete the experimental tasks, could maintain an independent sitting posture during throwing, and were able to throw a Boccia ball farther than 1.5 m (the minimal requirement) during competitions. None of the participants had experience playing Boccia before the study or received botulin injections within 6 months of the study. 2.2. Instruments In this study, a three-dimensional electromagnetic motion tracking system (Liberty, Polhemus, Colchester, VT) and MotionMonitor software (Innovative Sports Training, Inc., Chicago, IL) was used to collect and analyze motion data at a sampling rate of 240 Hz. A force plate (4060-NC-2000, Bertec Corporation, Columbus, OH) was placed under the feet of the participants and synchronized with the motion tracking system to record the COP trajectory and GRF during throwing at a sampling rate of 1200 Hz. A set of wooden chairs, of which the height and seat surface inclination (158 anterior-inclined, horizontal, and 158 posterior-inclined) could be adjusted, were used to satisfy the height requirements of the participants. The chair height was adjusted to be the same as the lower leg length of each participant. Standard Boccia balls, as specified by the Cerebral Palsy International Sports and Recreation Association, were used. To assess the throwing accuracy, the distance between the thrown Boccia ball and the target jack was measured using a standard ruler employed in Boccia competitions. 2.3. Procedures The demographic information for all participants and a written consent form signed by their parents were collected before the tests. The study was approved by the Institutional Review Board at the National Yang-Ming University Hospital. The collected data comprised sex, age, height, weight, dominant hand, and gross motor function classification. Pediatric reach tests (Bartlett & Birmingham, 2003) were conducted using each seat surface inclination to examine the balance abilities of the participants in various sitting conditions. Regarding the motion analysis, 7 sensors were fixed to the following positions on each participant: the back of the head, the first thoracic vertebra, the first sacral vertebra, and the lateral and posterior angles of the acromion, upper arm, forearm, and back of the throwing hand. Bony landmarks and the coordinates of each body part were specified according to the recommendations of the International Society of Biomechanics (ISB) (Wu et al., 2005). The times when the hand grasped and released the Boccia ball were determined using a prefabricated finger switch worn by each participant. The switch produced electronic signals that synchronized with the motion analysis system and the force plate when the hand touched a Boccia ball. The signal deactivated when the ball was released. These procedures were similar to the methods used in a previous study investigating the differences between children with CP and normally developed children regarding throwing patterns of Boccia balls (Huang, Pan, Ou, Yu, & Tsai, 2014).
3570
Y.-S. Tsai et al. / Research in Developmental Disabilities 35 (2014) 3568–3573
Before the data on each sitting condition was collected, each participant was instructed to practice three times, using an overhand throw, to familiarize themselves with the test method. Each participant placed both hands on the edge of a table adjusted to be the same height of their elbow as a starting position. They then grasped a Boccia ball placed on the lateral side of their throwing hand and threw the ball as close to the jack as possible. The jack was placed 5 m directly in front of the participants on the ground. Six trials were recorded for each sitting condition. The testing sequence of each sitting condition was randomly assigned. 2.4. Data analysis The maximal moving distances that each participant could reach in the forward, leftward, and rightward directions during the pediatric reach tests were summed to represent their balance abilities during each sitting condition (Gan, Tung, Tang, & Wang, 2008). The changes of various joint angles were calculated based on the Euler angle sequence of rotations recommended by the ISB (Wu et al., 2005). The amplitudes of the head and trunk flexion and extension, rotation, and lateral bending; the amplitudes of shoulder abduction and flexion; and the amplitude of elbow flexion during movement time were selected for motion analysis. The movement time was defined as the duration between ball contact and ball release. To assess postural stability, the peak vertical ground reaction force (PVGRF), movement range of the center of pressure (COP) in the anterior–posterior (AP) and medial–lateral (ML) direction, and COP sway ratio during throwing were derived based on the force plate data (Cherng et al., 2009; Liao, Yang, Hsu, Chan, & Wei, 2003). The PVGRF was standardized as a percentage of body weight for each participant. The sway ratio was calculated as the total displacement of the COP in the AP direction divided by the total displacement of the COP in the ML direction (Liao et al., 2003). The three throwing trials in which the closest distance between the thrown ball and the jack was attained were selected for data analysis. 2.5. Statistical analysis A one-way ANOVA with repeated measures followed by a Fisher’s least significant difference comparison was used to examine the differences among the variables of the three seat surface inclinations. The level of statistical significance was set at p < 0.05. 3. Results Table 1 shows the results of the pediatric reach test, kinematic and kinetic variables of throwing movement, movement duration, and the average distance between the thrown Boccia balls and jack in each sitting condition. The seat surface inclination significantly affected the results of the pediatric reach test (F = 4.316, p = 0.026), the amplitude of elbow flexion Table 1 The results (mean SD) of pediatric reach test, kinematic and kinetic variables of throwing movement, movement duration, and the average distance between thrown Boccia balls and the jack in each seat surface. Anterior-inclined
Horizontal
Posterior-inclined
F
P
47.27 24.15 1.72 0.56 43.63 26.54
50.18 20.00 1.66 0.68 46.84 28.91
40.13 27.04 2.05 0.91 49.88 29.64
4.316 2.290 0.206
0.026* 0.127 0.815
Kinematics Head flexion and extension (8) Head rotation (8) Head lateral bending (8) Trunk flexion and extension (8) Trunk rotation (8) Trunk lateral bending (8) Shoulder abduction (8) Shoulder flexion (8) Elbow flexion (8)
20.34 13.97 14.42 5.75 10.15 4.49 15.32 8.26 11.66 5.24 8.33 4.88 59.57 20.61 72.64 17.89 46.16 10.40a
16.79 12.45 14.62 7.16 9.67 4.38 19.35 10.96 11.05 6.00 7.63 5.46 54.82 19.72 68.30 19.78 38.21 8.64
21.99 12.77 14.14 7.33 8.77 3.61 17.82 6.53 11.23 3.26 8.76 6.16 54.41 15.89 67.70 17.75 38.97 12.40
3.057 0.027 1.072 1.510 0.103 0.379 1.420 0.768 3.930
0.069 0.973 0.363 0.243 0.903 0.690 0.265 0.479 0.036*
Kinetics PVGRF (%BW) COP range in AP direction (cm) COP range in ML direction (cm) Sway ratio
126.18 53.29a,b 2.38 1.49a,b 3.15 1.72b 0.72 0.11
80.71 26.13c 3.47 2.35 4.42 1.93 0.64 0.20
58.47 28.80 4.37 3.43 6.11 3.66 0.71 0.15
17.648 4.821 6.969 1.155
