The purpose of this study is to support the notion of the motor area as indicator of integrated child development in children from 3 to 24 months old, for its use in population studies. Knowledge of the objective differences in child development will help identify some of the causes that explain these differences and is relevant to the social programming necessary to prevent or mitigate its consequences in the population. / El propósito de este trabajo es fundamentar la selección del área motora en niños/as de 3 a 24 meses de edad como indicador del desarrollo integral infantil para su aplicación en estudios poblacionales. El conocimiento de las diferencias objetivas en el desarrollo infantil entre regiones, departamentos, altura sobre el nivel del mar, etc., ayudará a la identificación de algunas de las causas que explican esas diferencias, lo que se convierte en información relevante para la programación social necesaria para la prevención de esas diferencias o la atenuación de sus consecuencias a nivel poblacional.

Children with cerebral palsy and powerful whole body extensor spasms find sitting in a rigid seat uncomfortable and sometimes painful due to the large forces they apply to their constraints. They are usually unable to speak and communication is difficult. The spasms affect every aspect of their lives. This thesis describes the genesis of a new functional dynamic seat for children with severe whole body extensor spasms, and the novel method used to design it. This novel seat technology is known as ‘Whole Body Dynamic Seating’. The thesis describes the clinical need this seat addresses, and the design and technology context in which this research takes place. The user evaluation, observation, measurement, analysis and reasoning that led to a successful seat design are described in detail. Children with cerebral palsy sometimes have whole body spasms that mean they cannot be seated in conventional static seating that positions a child in a fixed posture. For this research the children were classified as functioning at Chailey Sitting Ability Level 1 and Gross Motor Functional Classification System Level V. Such children spend much of their time being held by a person, or lying on a mat, bed or pad. This results in difficulty with social engagement and physical functioning, particularly in school. This research created a seat that such children could sit in, providing a comfortable and functional seat for use in a home or school classroom environment. This seat was designed with the direct and essential involvement of disabled children, their parents, therapists, teachers and carers. The work is part of a larger programme of research into seating and support technology that will enhance a child’s ability to gain functional movement and communication skills that can be employed to enable the child’s free self expression and social participation. The research investigated means of supporting children with whole body extensor spasms through a progressive iterative method utilizing direct user evaluation of a series of prototypes incrementing in complexity and fidelity towards a fully functional physical seat. An iterative method was used to design, build and evaluate three dynamic seats. This method incorporated two new approaches to prototyping developed for the research programme in response to difficulties encountered in designing dynamic systems for children with highly complex neuromotor disability. Soft and Semi-soft prototyping and evaluation methods provided essential feedback on dynamic seating concepts that guided proposed solutions, without requiring costly and time-consuming manufacture. Video was used to create a record of the children’s movements and responses for subsequent analysis. Instrumentation was built into the seats to enable direct objective measurement of the reaction forces and seat movement caused by extensor spasms. This thesis presents several unique features created through this research programme: 1. Independent and virtually hinged anatomical dynamic thigh supports; 2. Independent anatomical dynamic foot supports; 3. A virtually hinged dynamic back support; 4. An anatomical dynamic head support concept. The final Whole Body Dynamic Seat was child-centred in its functionality and aesthetic design, and was favourably commented upon by parents, children and school staff. Use of the new dynamic seating by three children (including one from a previous work programme) showed that children with severe whole body extensor spasms can be seated comfortably. The children also demonstrated gains in physical and social function as a result of using the dynamic seats. The two fully independent dynamic seats made advances in comfort over static seating for children with whole body extensor spasms. One of the children especially liked the seat and resisted being put back into his usual seating. An adult with severe cerebral palsy and extensor spasms evaluated a dynamic foot support concept and reported very significant reductions in spasticity and pain, and gains in physical function. The Whole Body Dynamic Seats showed gains in postural symmetry and in hand and head function over the usual static seats when used by the children with spasms. These gains were reported by staff during long term evaluations and measured specifically during the final evaluation. Two children learned to control the movement of seats in which they were sat, and were able to control their posture and use that control to carry out functions such as switch pressing. Such learning through the use of dynamic seating by children with severe dystonic cerebral palsy and whole body extensor spasms has not previously been documented. The seats did not just affect the children - school staff were affected too. School staff working around the children in the dynamic seats were observed to be more inclusive towards the children, and to expect more interaction from them. The ability of the children to move altered staff expectations of their ability to participate and communicate. This new seating has improved the quality of life of the children that use it. Future implementation of this technology in commercially produced seating offers the possibility of similar gains to many more severely disabled children who are currently less comfortable and less functional than they need to be.

Longer breastfeeding durations may enhance cognition and accelerate motor development; motor development, and in particular, crawling, may lead to dramatic changes in cognition. Based on these empirical relations, the hypothesis that crawling mediates breastfeeding duration and cognitive outcome was tested. Specifically, it was hypothesized that longer breastfeeding durations would significantly predict both earlier crawling and higher cognitive scores at 2 years of age, that earlier crawling would also predict higher cognitive scores, and that earlier crawling would account for part of the relationship between longer breastfeeding durations and higher cognitive scores. A sample of 44 full term infants from Winnipeg, Manitoba was followed longitudinally between birth and 2 years of age. Data on breastfeeding duration and crawling were collected through daily parent checklists, with supplemental breastfeeding information obtained via questionnaires. Near the toddlers’ 2nd birthdays, cognitive abilities were assessed with the MacArthur Communicative Development Inventory: Words and Sentences (Fenson et al., 1993) and the Parent Report of Children’s Abilities (Saudino et al., 1998). All 3 key variables were measured on continuous scales, and a mediational analysis based on Baron and Kenny’s (1986) classic approach of 3 regressions was used. Several covariates were considered for inclusion in the regressions, but none reached significance in preliminary tests and thus, were not included. In the first 2 regression analyses, exclusive and partial breastfeeding durations significantly predicted neither cognitive scores (p = .59) nor age of crawling attainment (p = .41). The 3rd regression analysis showed a significant, small-to-medium effect size for earlier crawling attainment predicting higher cognitive scores (p < .05, adjusted R2 = .09). However, crawling onset had no effect on the breastfeeding-cognition link. The overall test of the mediation was inconclusive, due to low power. The significant finding between age of crawling onset and cognitive outcomes at 2 years of age may be due to earlier crawling altering the course of development, to reverse causation whereby more cognitively advanced infants are motivated to crawl sooner, or to a 3rd variable affecting both crawling and cognition. Future research should continue to explore motor and cognitive connections in infant development. / May 2005

Moment arms are important in many contexts. Various methods have been used to estimate moment arms. It has been shown that a moment arm changes as a function of joint angle and contraction state. However, besides the influence of these anatomical factors, results from recent studies suggest that the estimation of moment arm is also dependent on the methods employed. The overall goal of this thesis was to explore the interaction between the methodological and anatomical influences on moment arm and their effect on estimates of muscle-tendon forces during biomechanical modelling. The first experiment was a direct comparison between two different moment arm methods that have been previously used for the estimation of Achilles tendon moment arm. The results of this experiment revealed a significant difference in Achilles tendon moment arm length dependent on the moment arm method employed. However, besides the differences found, results from both methods were well correlated. Based on these results, methodological differences between these two methods were compared across different joint angles and contraction states in study two. Results of experiment two revealed that Achilles tendon moment arms obtained using both methods change in a similar way as a function of joint angle and contraction state. In the third experiment, results from the first two experiments were used to determine how methodological and anatomical influences on Achilles tendon moment arm would change muscle-tendon forces during the task of submaximal cycling. Results of the third experiment showed the importance of taking the method, ankle angle and contraction state dependence of Achilles tendon moment arm into account when using biomechanical modelling techniques. Together, these findings emphasis the importance of carefully considering methodological and anatomical modifiers when estimating Achilles tendon moment arm.

Research indicates that children with Human Immunodeficiency Virus (HIV) / Acquired Immune Deficiency Syndrome (AIDS) display a variety of neuro-developmental, cognitive, motor and nutritional deficiencies (Epstein el al., 1986:678; Davis-McFarland, 2000:20; Blanchette et al., 2001:50). Research also substantiates a need for additional intervention strategies such as improved nutrition and exercise programmes to improve the quality of life for HIV-infected children (Brady, 1994: 18; Stein et al., 1995:3 1 ; Parks & Danoff, 1999:527). The maintenance of motor skills in above-mentioned children is an important objective for intervention programmes, especially gross motor skills (Parks & Danoff, 1999:525). Literature indicates that growth retardation, exhaustion of fat storage and neuro-developmental deficiencies are related to HIV/AIDS (Aylward et al., 1992:218; Miller & Garg, 1998:368; Davis-McFarland, 2000:20; Miller et al., 200 1 : 1287). The monitoring of growth status is of outmost importance as children with serious stunting and wasting run the risk of early death. Growth retardation can also be an indication of infection or fast disease progression (Bobat et al, 200! :209). The aim of this study was firstly to determine the state of the motor development of 2, to 6-year old children infected with HIV and to compare it with that of affected (in that they are not infected with HIV, but have lost one or both parents to AIDS-related diseases) and non-affected children. Secondly the study aimed to determine the effect of a motor intervention programme for 2 to 6-year old children infected with and affected by HIV. A third aim was to determine the growth status of 2 to 6-year old children infected with HIV and to compare it with that of affected and non-affected children; and the last aim was to monitor the developmental tendencies of body composition and growth of 2 to 6-year old children infected with HIV in the course of nine months and to compare it with that of affected and non-affected children. The Peabody Developmental Motor Scales-:! (PDMS-2) (Folio & Fewell, 2000), which consist of six subtests, was used to determine the motor development of the children. Regarding the growth status the children were subjected to a series of anthropometric measurements of height, weight, circumference (upper arm - both tonic and relaxed), as well as skin folds (triceps, sub-scapular, calf), in accordance with standard procedures as prescribed by the International Society of Advanced Kinanthropometry (ISAK). The data was analysed using Statistica for Windows (Statsoft-, Inc S.A., 2001) and SAS (2000- 2003). Descriptive statistics were used to determine means (M), standard deviations (SD) and maximum and minimum values. One-way variance of analysis, forward stepwise discriminant analysis, independent T-testing, dependant T-testing and an ANCOVA, repeated measures ANOVA, and Bonferroni post hoc analysis were used to analyse the data in accordance with the above-mentioned aims. The level of statistic significance was set at p<0,05. Practical significance of differences (ES) between the testing sessions was calculated by dividing the mean difference (M) between the two testing sessions by the largest standard deviation (SD), as recommended by Cohen (1988) and Steyn (1999). Cohen (1988) set the following guidelines for interpreting practical significance, namely ES = 0,2 (small effect); ES = 0,5 (medium effect) and ES = 0,8 (large effect). Due to the small number of subjects it was considered practically significant if this effect size indicated a medium and larger effect. From the results of the study it seemed that the HIV-infected children performed the poorest of the groups regarding gross motor, fine motor and total motor skills. This group's gross motor skills showed larger deficits than their fine motor skills, while loco-motor skills contributed the most to the discrimination between the groups. The motor intervention programme led to a statistically significant improvement in loco-motor, fine motor, as well as total motor skills. The infected children showed better improvement compared to the affected children. The infected group displayed the poorest growth status of the three groups compared to the Centre for Disease Control (CDC) growth profiles, although they did not differ significantly from the affected children. The infected children differed significantly regarding height percentile, fat percentage and height-for-age 2-score (HAZ) from non-affected children. The infected group also displayed the least significant effects in the form of growth increases over the nine months monitoring period. It can be concluded from the results that motor deficiencies and growth impediments are part OF the life of HIV infected children. To address these problems, intervention strategies, such as motor intervention and nutrition programmes are needed. / Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2008.

In the holistic development of the young child, optimal gross motor development has an important influence on optimal physical, perceptual, cognitive, language, affective-social and normative (behavioural) development (Kapp, 1991; Gallahue & Ozmun, 1998), and is therefore considered to be essential in the preschool years. The goal of this dissertation was to present the results of much-needed recent research on gross motor development of a group of children living in an urban area in South Africa, by 1) determining the current levels of gross motor development, 2) assessing the prevalence of and the influence of overweight and obesity on gross motor development, 3) establishing the relationship between overweight and obesity, gross motor development and gender, 4) determining the relationship between quantitative and qualitative assessment results of the one leg balance, and 5) investigating the occurrence of gender differences in gross motor development, in a group of 3-6 year old children living in Potchefstroom. These aims were addressed by structuring the dissertation in eight chapters, Chapter 1 constituting the introduction and statement of the problem, Chapter 2 a review of relevant literature, Chapters 3 to 7 constituting 5 research articles addressing the specific aims of the study, and Chapter 8 including the summary, conclusions and recommendations. For each of the 5 research articles, the participants were 3-6 year old children (N = 514) who lived in Potchefstroom and had been enrolled in the movement development program (MDP) presented by movement developmentalists of the Potchefstroom University for Christian Higher Education (P.U. for C.H.E.). Descriptive statistics (Chapter 3-7), practical significance based on effect sizes (Chapter 4 and 5), 2 way frequency tables and Pearson Chi-square as well as the Phi for two-way tables (Chapter 6), and t-values, degrees of difference and p-values (Chapter 7) were used. The current levels of gross motor development of preschool children in Potchefstroom (Chapter 3) were determined by testing a total of 462 3-6 year old children (215 males and 247 females) on 8 gross motor tasks, and comparing the results to norms and criteria as found in the literature. The 3, 4 and 5 year olds compared favourably to their counterparts in all the tests except for balance walk and catching, standing long jump in the 4 year olds and throwing in the 5 year old group. The 6 year old group scored lower than the norms and criteria in all the tests except for standing long jump, indicating alarming implications for school readiness. Chapter 4 and Chapter 5 examined the prevalence of and the differences in the quantitative and qualitative execution of four gross motor tasks (standing long jump, hopping, one leg balance and catching) between groups of overweight and obese (0) and nonobese (NO) boys, and girls, respectively. In the male study, 17 0-participants and 49 NO-participants were compared, while 13 0-participants and 54 NO-participants were used in the female study. Differences of practical significance (medium or large effects) in favour of nonobese groups were found in all the quantitative and qualitative tests among the male participants, while similar differences were found in only the quantitative tests for the one leg balance and all the qualitative tests among the female participants. A prevalence of overweight and obesity of 16.35% was found among the boys and 11.81% among the girls. The results indicated that 0-children of the ages 3-6 years generally compare poorly to NO-children in relation to gross motor proficiency. In Chapter 6, the one leg balance ability of 514 subjects was quantitatively and qualitatively assessed using valid norms and criteria found in literature. A positive relationship of statistical significance (p :S 0.05) was established between the quantitative and qualitative scores of the one leg balance in every age group. A relatively large percentage (44.10%) of 3 year olds scored well above the average level for their age in both types of assessment, indicating that the norms and criteria used might not be appropriate for 3 year olds. Relatively large percentages (25.27% - 27.47%) of the 6 year olds scored below the average level for 5 year olds in the qualitative assessment, suggesting developmental balance delays or disorders. These findings indicate that a quantitative and qualitative assessment should be combined to assure a more accurate assessment. The results of Chapter 7, involving 221 male and 243 female participants, showed significant gender differences in hopping and balancing on the right leg in favour of the females in the 3 year old group, and in the standing long jump and throwing for distance in favour of the males in the 5 and 6 year old groups, indicating that separate norms should be used for the different genders when assessing standing long jump and throwing for distance in 5 and 6 year olds. In the light of the findings of these studies, recommendations presented in Chapter 8 for the assessment and structuring of a programme for the optimal development of gross motor skills in preschool children, living in urban areas in South Africa, include that: 1) special attention should be given to the optimal development of gross motor skills of 6 year olds in a structured gross motor development programme, 2) obesity should be addressed even in the preschool years, and activities for the specific skills shown to be related to overweight and obesity (balance skills and catching in boys and girls and standing long jump in boys) should also be specifically emphasized in these children, 3) both a quantitative and a qualitative assessment should be used specifically in the one leg balance assessment and is recommended for other fundamental motor assessments, and 4) separate norms should be used for the assessment of the standing long jump and throwing for distance in 5 and 6 year olds, and more emphasis should be placed on ball skills in girls, and co-ordination skills of boys in the structuring of a movement development programme. / Thesis (Ph.D. (Human Movement Science))--Potchefstroom University for Christian Higher Education, 2002

In the holistic development of the young child, optimal gross motor development has an important influence on optimal physical, perceptual, cognitive, language, affective-social and normative (behavioural) development (Kapp, 1991; Gallahue & Ozmun, 1998), and is therefore considered to be essential in the preschool years. The goal of this dissertation was to present the results of much-needed recent research on gross motor development of a group of children living in an urban area in South Africa, by 1) determining the current levels of gross motor development, 2) assessing the prevalence of and the influence of overweight and obesity on gross motor development, 3) establishing the relationship between overweight and obesity, gross motor development and gender, 4) determining the relationship between quantitative and qualitative assessment results of the one leg balance, and 5) investigating the occurrence of gender differences in gross motor development, in a group of 3-6 year old children living in Potchefstroom. These aims were addressed by structuring the dissertation in eight chapters, Chapter 1 constituting the introduction and statement of the problem, Chapter 2 a review of relevant literature, Chapters 3 to 7 constituting 5 research articles addressing the specific aims of the study, and Chapter 8 including the summary, conclusions and recommendations. For each of the 5 research articles, the participants were 3-6 year old children (N = 514) who lived in Potchefstroom and had been enrolled in the movement development program (MDP) presented by movement developmentalists of the Potchefstroom University for Christian Higher Education (P.U. for C.H.E.). Descriptive statistics (Chapter 3-7), practical significance based on effect sizes (Chapter 4 and 5), 2 way frequency tables and Pearson Chi-square as well as the Phi for two-way tables (Chapter 6), and t-values, degrees of difference and p-values (Chapter 7) were used. The current levels of gross motor development of preschool children in Potchefstroom (Chapter 3) were determined by testing a total of 462 3-6 year old children (215 males and 247 females) on 8 gross motor tasks, and comparing the results to norms and criteria as found in the literature. The 3, 4 and 5 year olds compared favourably to their counterparts in all the tests except for balance walk and catching, standing long jump in the 4 year olds and throwing in the 5 year old group. The 6 year old group scored lower than the norms and criteria in all the tests except for standing long jump, indicating alarming implications for school readiness. Chapter 4 and Chapter 5 examined the prevalence of and the differences in the quantitative and qualitative execution of four gross motor tasks (standing long jump, hopping, one leg balance and catching) between groups of overweight and obese (0) and nonobese (NO) boys, and girls, respectively. In the male study, 17 0-participants and 49 NO-participants were compared, while 13 0-participants and 54 NO-participants were used in the female study. Differences of practical significance (medium or large effects) in favour of nonobese groups were found in all the quantitative and qualitative tests among the male participants, while similar differences were found in only the quantitative tests for the one leg balance and all the qualitative tests among the female participants. A prevalence of overweight and obesity of 16.35% was found among the boys and 11.81% among the girls. The results indicated that 0-children of the ages 3-6 years generally compare poorly to NO-children in relation to gross motor proficiency. In Chapter 6, the one leg balance ability of 514 subjects was quantitatively and qualitatively assessed using valid norms and criteria found in literature. A positive relationship of statistical significance (p :S 0.05) was established between the quantitative and qualitative scores of the one leg balance in every age group. A relatively large percentage (44.10%) of 3 year olds scored well above the average level for their age in both types of assessment, indicating that the norms and criteria used might not be appropriate for 3 year olds. Relatively large percentages (25.27% - 27.47%) of the 6 year olds scored below the average level for 5 year olds in the qualitative assessment, suggesting developmental balance delays or disorders. These findings indicate that a quantitative and qualitative assessment should be combined to assure a more accurate assessment. The results of Chapter 7, involving 221 male and 243 female participants, showed significant gender differences in hopping and balancing on the right leg in favour of the females in the 3 year old group, and in the standing long jump and throwing for distance in favour of the males in the 5 and 6 year old groups, indicating that separate norms should be used for the different genders when assessing standing long jump and throwing for distance in 5 and 6 year olds. In the light of the findings of these studies, recommendations presented in Chapter 8 for the assessment and structuring of a programme for the optimal development of gross motor skills in preschool children, living in urban areas in South Africa, include that: 1) special attention should be given to the optimal development of gross motor skills of 6 year olds in a structured gross motor development programme, 2) obesity should be addressed even in the preschool years, and activities for the specific skills shown to be related to overweight and obesity (balance skills and catching in boys and girls and standing long jump in boys) should also be specifically emphasized in these children, 3) both a quantitative and a qualitative assessment should be used specifically in the one leg balance assessment and is recommended for other fundamental motor assessments, and 4) separate norms should be used for the assessment of the standing long jump and throwing for distance in 5 and 6 year olds, and more emphasis should be placed on ball skills in girls, and co-ordination skills of boys in the structuring of a movement development programme. / Thesis (Ph.D. (Human Movement Science))--Potchefstroom University for Christian Higher Education, 2002

Research indicates that children with Human Immunodeficiency Virus (HIV) / Acquired Immune Deficiency Syndrome (AIDS) display a variety of neuro-developmental, cognitive, motor and nutritional deficiencies (Epstein el al., 1986:678; Davis-McFarland, 2000:20; Blanchette et al., 2001:50). Research also substantiates a need for additional intervention strategies such as improved nutrition and exercise programmes to improve the quality of life for HIV-infected children (Brady, 1994: 18; Stein et al., 1995:3 1 ; Parks & Danoff, 1999:527). The maintenance of motor skills in above-mentioned children is an important objective for intervention programmes, especially gross motor skills (Parks & Danoff, 1999:525). Literature indicates that growth retardation, exhaustion of fat storage and neuro-developmental deficiencies are related to HIV/AIDS (Aylward et al., 1992:218; Miller & Garg, 1998:368; Davis-McFarland, 2000:20; Miller et al., 200 1 : 1287). The monitoring of growth status is of outmost importance as children with serious stunting and wasting run the risk of early death. Growth retardation can also be an indication of infection or fast disease progression (Bobat et al, 200! :209). The aim of this study was firstly to determine the state of the motor development of 2, to 6-year old children infected with HIV and to compare it with that of affected (in that they are not infected with HIV, but have lost one or both parents to AIDS-related diseases) and non-affected children. Secondly the study aimed to determine the effect of a motor intervention programme for 2 to 6-year old children infected with and affected by HIV. A third aim was to determine the growth status of 2 to 6-year old children infected with HIV and to compare it with that of affected and non-affected children; and the last aim was to monitor the developmental tendencies of body composition and growth of 2 to 6-year old children infected with HIV in the course of nine months and to compare it with that of affected and non-affected children. The Peabody Developmental Motor Scales-:! (PDMS-2) (Folio & Fewell, 2000), which consist of six subtests, was used to determine the motor development of the children. Regarding the growth status the children were subjected to a series of anthropometric measurements of height, weight, circumference (upper arm - both tonic and relaxed), as well as skin folds (triceps, sub-scapular, calf), in accordance with standard procedures as prescribed by the International Society of Advanced Kinanthropometry (ISAK). The data was analysed using Statistica for Windows (Statsoft-, Inc S.A., 2001) and SAS (2000- 2003). Descriptive statistics were used to determine means (M), standard deviations (SD) and maximum and minimum values. One-way variance of analysis, forward stepwise discriminant analysis, independent T-testing, dependant T-testing and an ANCOVA, repeated measures ANOVA, and Bonferroni post hoc analysis were used to analyse the data in accordance with the above-mentioned aims. The level of statistic significance was set at p<0,05. Practical significance of differences (ES) between the testing sessions was calculated by dividing the mean difference (M) between the two testing sessions by the largest standard deviation (SD), as recommended by Cohen (1988) and Steyn (1999). Cohen (1988) set the following guidelines for interpreting practical significance, namely ES = 0,2 (small effect); ES = 0,5 (medium effect) and ES = 0,8 (large effect). Due to the small number of subjects it was considered practically significant if this effect size indicated a medium and larger effect. From the results of the study it seemed that the HIV-infected children performed the poorest of the groups regarding gross motor, fine motor and total motor skills. This group's gross motor skills showed larger deficits than their fine motor skills, while loco-motor skills contributed the most to the discrimination between the groups. The motor intervention programme led to a statistically significant improvement in loco-motor, fine motor, as well as total motor skills. The infected children showed better improvement compared to the affected children. The infected group displayed the poorest growth status of the three groups compared to the Centre for Disease Control (CDC) growth profiles, although they did not differ significantly from the affected children. The infected children differed significantly regarding height percentile, fat percentage and height-for-age 2-score (HAZ) from non-affected children. The infected group also displayed the least significant effects in the form of growth increases over the nine months monitoring period. It can be concluded from the results that motor deficiencies and growth impediments are part OF the life of HIV infected children. To address these problems, intervention strategies, such as motor intervention and nutrition programmes are needed. / Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2008.

Longer breastfeeding durations may enhance cognition and accelerate motor development; motor development, and in particular, crawling, may lead to dramatic changes in cognition. Based on these empirical relations, the hypothesis that crawling mediates breastfeeding duration and cognitive outcome was tested. Specifically, it was hypothesized that longer breastfeeding durations would significantly predict both earlier crawling and higher cognitive scores at 2 years of age, that earlier crawling would also predict higher cognitive scores, and that earlier crawling would account for part of the relationship between longer breastfeeding durations and higher cognitive scores. A sample of 44 full term infants from Winnipeg, Manitoba was followed longitudinally between birth and 2 years of age. Data on breastfeeding duration and crawling were collected through daily parent checklists, with supplemental breastfeeding information obtained via questionnaires. Near the toddlers’ 2nd birthdays, cognitive abilities were assessed with the MacArthur Communicative Development Inventory: Words and Sentences (Fenson et al., 1993) and the Parent Report of Children’s Abilities (Saudino et al., 1998). All 3 key variables were measured on continuous scales, and a mediational analysis based on Baron and Kenny’s (1986) classic approach of 3 regressions was used. Several covariates were considered for inclusion in the regressions, but none reached significance in preliminary tests and thus, were not included. In the first 2 regression analyses, exclusive and partial breastfeeding durations significantly predicted neither cognitive scores (p = .59) nor age of crawling attainment (p = .41). The 3rd regression analysis showed a significant, small-to-medium effect size for earlier crawling attainment predicting higher cognitive scores (p < .05, adjusted R2 = .09). However, crawling onset had no effect on the breastfeeding-cognition link. The overall test of the mediation was inconclusive, due to low power. The significant finding between age of crawling onset and cognitive outcomes at 2 years of age may be due to earlier crawling altering the course of development, to reverse causation whereby more cognitively advanced infants are motivated to crawl sooner, or to a 3rd variable affecting both crawling and cognition. Future research should continue to explore motor and cognitive connections in infant development.

Longer breastfeeding durations may enhance cognition and accelerate motor development; motor development, and in particular, crawling, may lead to dramatic changes in cognition. Based on these empirical relations, the hypothesis that crawling mediates breastfeeding duration and cognitive outcome was tested. Specifically, it was hypothesized that longer breastfeeding durations would significantly predict both earlier crawling and higher cognitive scores at 2 years of age, that earlier crawling would also predict higher cognitive scores, and that earlier crawling would account for part of the relationship between longer breastfeeding durations and higher cognitive scores. A sample of 44 full term infants from Winnipeg, Manitoba was followed longitudinally between birth and 2 years of age. Data on breastfeeding duration and crawling were collected through daily parent checklists, with supplemental breastfeeding information obtained via questionnaires. Near the toddlers’ 2nd birthdays, cognitive abilities were assessed with the MacArthur Communicative Development Inventory: Words and Sentences (Fenson et al., 1993) and the Parent Report of Children’s Abilities (Saudino et al., 1998). All 3 key variables were measured on continuous scales, and a mediational analysis based on Baron and Kenny’s (1986) classic approach of 3 regressions was used. Several covariates were considered for inclusion in the regressions, but none reached significance in preliminary tests and thus, were not included. In the first 2 regression analyses, exclusive and partial breastfeeding durations significantly predicted neither cognitive scores (p = .59) nor age of crawling attainment (p = .41). The 3rd regression analysis showed a significant, small-to-medium effect size for earlier crawling attainment predicting higher cognitive scores (p < .05, adjusted R2 = .09). However, crawling onset had no effect on the breastfeeding-cognition link. The overall test of the mediation was inconclusive, due to low power. The significant finding between age of crawling onset and cognitive outcomes at 2 years of age may be due to earlier crawling altering the course of development, to reverse causation whereby more cognitively advanced infants are motivated to crawl sooner, or to a 3rd variable affecting both crawling and cognition. Future research should continue to explore motor and cognitive connections in infant development.