PubMed Health⌕ Search

Biomedical subjects

T L McKenzie

Publications and source records attributed to T L McKenzie.

At least 19 recordsLinked to original sources
PubMed2000

Leisure-time physical activity in school environments: an observational study using SOPLAY.

BACKGROUND: Schools provide settings for physical activity (PA), but objective tools for measuring PA are lacking. We assessed an instrument to directly observe group PA and measured the leisure-time PA of adolescents throughout the school day. METHODS: Leisure-time PA was studied by direct observation in 24 middle schools in Southern California using SOPLAY (System for Observing Play and Leisure Activity in Youth). SOPLAY uses momentary time sampling to record the activity of each individual as sedentary, walking, or very active. RESULTS: The largest proportion of students visited activity areas at lunch time (19.5%), followed by before (4. 1%) and after school (2.1%). More boys than girls visited activity areas before school (33.4 vs 7.7) and at lunch time (148.8 vs 36.7). Boys in areas engaged in more moderate to vigorous PA than girls before school (59.6 vs 40%) and at lunch time (67.7 vs 51.7%). CONCLUSIONS: Few students use opportunities to be physically active during lesiure time at school. Policies and environmental manipulations (e.g., supervision, equipment, structured programs) are needed to attract more adolescents, especially girls, to existing activity areas. The feasibility of SOPLAY for measuring group PA was established.

Adolescent↗
PubMed2000

Physical activity behavior change: issues in adoption and maintenance.

The many benefits of participation in regular moderate- or vigorous-intensity physical activity are well established, yet more than 60% of the population is sedentary or insufficiently active. Published studies have revealed that behavior modification and cognitive-behavior modification can be successfully used to assist patients, healthy adults, and youth in the adoption of physically active lifestyles. However, few studies with adults and youth have examined the maintenance of physical activity behavior beyond 6 months of adoption of this behavior. Maintenance of physical activity is critically important because ongoing participation in the behavior is necessary to sustain health benefits. Knowledge of effective intervention strategies for long-term maintenance of physical activity is at an early stage. The authors provide a summary of what is known about the maintenance of physical activity behavior in adults and youth and how physical activity behavior relates to other health behaviors such as smoking, as well as recommendations for research on physical activity behavior change and maintenance.

Adolescent↗
PubMed1999

Predictors of change in children's physical activity over 20 months. Variations by gender and level of adiposity.

BACKGROUND: Physical activity declines during childhood and determinants of this decline are poorly understood. The purpose of this prospective study was to examine modifiable psychological and social correlates of physical activity change over 20 months. SUBJECTS: 370 girls and 362 boys in public schools, studied through the 4th and 5th grades. MEASURES: A physical activity index was computed from child reports, parent reports, and objective activity monitoring. Predictor variables were assessed by child and parent surveys. RESULTS: In multiple regressions, after adjustments for demographic variables, psychological variables explained 4% of the variance in boys' physical activity change, parent variables explained 8%, and interactions with skinfolds explained 3%, for a total of 15% (unadjusted). Regarding change in girls' physical activity, psychological variables explained 3%, parent variables explained 1.5%, and interactions with skinfold explained 1.5%, for a total of 6% explained variance (unadjusted). There were differences in predictors among children with high and low levels of body fat. CONCLUSIONS: Children's preferences for physical activity and frequency of parents transporting children to activity locations explained significant proportions of variance for girls and boys. The results support a dynamic model of the determinants of children's physical activity, but most of the variance was left unexplained.

California↗
PubMed1999

Effects of health-related physical education on academic achievement: project SPARK.

The effects of a 2-year health-related school physical education program on standardized academic achievement scores was assessed in 759 children who completed Metropolitan Achievement Tests before and after the program. Schools were randomly assigned to condition: (a) Specialists taught the Sports, Play, and Active Recreation for Kids curriculum; (b) classroom teachers were trained to implement the curriculum; and (c) controls continued their usual programs. The Trained Teacher condition was superior to Control on Language, Reading, and Basic Battery. The Specialist condition was superior to Control on Reading, but inferior on Language. Despite devoting twice as many minutes per week to physical education as Controls, the health-related physical education program did not interfere with academic achievement. Health-related physical education may have favorable effects on students' academic achievement.

California↗
PubMed1999

Correlations among physical activity and eating behaviors in 4- to 7-year-old Anglo- and Mexican-American children.

Physical activity and dietary behaviors are often correlated in adults and adolescents. This association was examined in 351 Anglo- and Mexican-American children between the ages of 4 and 7 years. Behaviors were assessed by structured observations and interviews at home and school. Observed physical activity was significantly correlated with energy intake (r = .43), but was unrelated to the percentage of calories from total fat or saturated fat. Thus, interventions with young children to improve dietary behavior or physical activity should not be expected to automatically lead to changes in the other.

Child↗
PubMed1998

Determinants of dietary intake in a sample of white and Mexican-American children.

OBJECTIVE: To assess the influence of several potential psychosocial determinants on children's eating behavior. PARTICIPANTS: Three hundred fifty-one Mexican-American and non-Hispanic white children (mean age = 4.4 years old at baseline) participated in the San Diego Study of Children's Activity and Nutrition for up to 2.5 years. METHODS: Child's eating behavior was described by 3 dependent variables: total energy, percentage energy from fat, and sodium intake per 1,000 kcal. Dietary information was collected 4 days a year using a 24-hour food intake record, which was a combination of direct observation and interviews with food preparers. The 35 predictor variables from child, parental, demographic, and environmental domains were collected by behavioral observation, interviewer-administered questionnaires, and physical measurements. STATISTICAL ANALYSES: Bivariate and regression analyses via mixed linear models were performed. RESULTS: Variables from the children's domain (such as skinfold thickness and weight) had the strongest associations with energy intake; parental variables (such as fat avoidance behavior and prompts to increase children's food intake) were associated with child's percentage energy from fat and sodium intake. In regression analyses, parsimonious subsets of variables accounted for 46% of variance in energy intake (3 variables), 40% of the variance in percentage of energy from fat (4 variables), and 44% of variance in sodium intake per 1,000 kcal energy (1 variable) in between-subject variance components. CONCLUSIONS: Fat and sodium intake of children may be improved by improving parents' nutrition habits and by having parents encourage children to eat a healthful diet. Few modifiable correlates of children's energy intake were identified.

California↗
PubMed1998

Effects of physical activity interventions in youth. Review and synthesis.

INTRODUCTION: Physical inactivity has been identified as an important public health concern for youth. School and community settings can be important infrastructures for promoting physical activity (PA). This paper reviews studies of physical activity in school and community settings among preschool through college-aged persons to determine characteristics and effects of interventions. Studies in progress are included. METHODS: Studies from 1980 to 1997 testing physical activity interventions in schools and community settings were identified by computerized search methods and reference lists of published reviews. Studies needed to have used a quantitative assessment of PA, used a comparison or control group, included participants who were preschool through college age, and be conducted in the United States or foreign school or community settings. Significance of effects was examined overall and for various types of interventions. RESULTS: Twenty-two school-based studies were reviewed, 14 completed and 8 in progress. Three studies were in countries other than the United States. The 8 studies in progress were all in the United States. Only 7 community studies were reviewed, all in the United States. Four studies were in progress. Several community studies involved a high percentage of African-American or Hispanic youth and their families. Studies showing the best results used randomized designs, valid and reliable measurements, and more extensive interventions. Some follow-up results showed PA was sustained after interventions ended. CONCLUSIONS: The collection of school and community studies is limited for several age groups with none below third grade and only three at college age. There are few community studies. The most is known about upper-elementary-age-students, including the first multicenter randomized trial to report significant results for increasing moderate to vigorous physical activity (MVPA) in physical education (PE) and increase vigorous PA outside of school. A number of older study designs were weak and assessments less than optimal, but studies in progress are stronger. Special attention is needed for girls, middle schools, and community settings for all youth. More objective assessments are needed for measuring PA outside of school and in younger children, since they cannot provide reliable self-report.

Adolescent↗
PubMed1998

Direct home observations of the prompting of physical activity in sedentary and active Mexican- and Anglo-American children.

Social interactions are important correlates of physical activity in children. Previous studies used global measures; the present study examined the influence of specific social interactions on immediate physical activity in children with data obtained from the Behaviors of Eating and Activity for Child Health: Evaluation System (BEACHES). The study examined parental and peer prompting of physical activity at home among 178 Mexican-American and 113 Anglo-American children at age 4 years and again at age 6.5 years. Most activity prompts came from adults interacting with children when they were sedentary. A reduction in the frequency of prompts from baseline to follow-up occurred in the prompter group (adult or child peer), gender, ethnicity, and preprompted activity level categories. Children's responses to these prompts showed that as they aged, they seemed to rely less on the interpersonal (especially adult) aspects of their environment for cues to be more active.

Adult↗
PubMed1998

Tracking of health-related fitness components in youth ages 9 to 12.

PURPOSE: The purpose of this study was to examine the tracking of multiple health-related fitness components in children from fourth to sixth grade. METHODS: A battery of fitness tests was used to measure 414 children (213 boys, 201 girls, mean = 9.48 yr, +/- 0.41) from three elementary schools in Southern California. Children were assessed during the fall and spring of each grade. Baseline scores were correlated (Spearman) with each subsequent time point. RESULTS: For boys 3-yr correlations of body mass index (BMI) (0.89), skinfold thickness (0.80), sit-and-reach test (0.67), and the pull-up test (0.66) indicated high levels of tracking. Mile run (0.56), sit-up test (0.46), and waist-to-hip ratio (0.30) tracked moderately. For girls BMI (0.83), sum of skinfolds (0.75), sit-and-reach test (0.72), and the pull-up test (0.63) tracked highly, while mile run (0.42), sit-up test (0.47), and waist-to-hip ratio (0.42) tracked moderately. CONCLUSIONS: Results suggest that relative rankings of BMI, skinfold thickness, and sit-and-reach test performance are more likely to track during early adolescence. Measures of cardiovascular fitness, muscular strength, and endurance and fat distribution may be less likely to track into adolescence, possibly because they are more influenced by changes in physical activity or because tracking may be reduced by measurement error.

Body Composition↗
PubMed1997

Factors parents use in selecting play spaces for young children.

BACKGROUND: The amount of time children spend in play spaces (ie, physical locations that are appropriate for children's physical activity) near their homes is correlated with their level of physical activity. OBJECTIVE: To examine factors used in parents' decisions about the selection of play spaces for their children. SUBJECTS: Parents (primarily mothers) of 178 Mexican American and 122 white children who were a mean age of 4.9 years old at the first measurement. MEASURES: In individual interviews, parents rated 24 factors on their importance in selecting for their children a play space that is away from their home or yard. Decision factors were rated from 1 (ie, not important at all) to 5 (ie, very important). RESULTS: The most important factors, with ratings ranging from 4.8 to 4.2, were safety and availability of toilets, drinking water, lighting, and shade. Mexican American parents rated 8 of 24 items significantly higher than did white parents, including lighted at night, organized activities, play supplies, and drinking water. White parents rated 5 of 24 items significantly higher than did Mexican American parents, including distance from home, cost of admission, and child's friends go there. The rated importance of 7 of 24 items increased during 1 year, including play supplies, drinking water, distance from home, and parents' friends or relatives go there. CONCLUSIONS: These results indicate that parents can identify factors they use in selecting places for their young children to play, and selection factors differ somewhat by ethnicity or socioeconomic status. Further studies are needed to determine whether improvements on the most important selection factors might be effective in increasing the use of play spaces by children and their parents. Clinicians may be able to use the most highly rated decision factors to help parents assess the acceptability of play spaces in their areas.

Adult↗
PubMed1997

Physical activity levels and prompts in young children at recess: a two-year study of a bi-ethnic sample.

We investigated physical activity and encouragement for activity in a bi-ethnic cohort during recess. Activity and associated interactions of 287 children were recorded at preschool and again 2.2 years later. Children expended nearly twice as much energy at preschool recess than at elementary recess. Activity levels declined as recess time elapsed. At preschool, European-American children engaged in more moderate to vigorous activity than Mexican-Americans. As participants moved to elementary school, teachers' prompts to be active decreased and prompts from peers increased. Boys and girls received similar amounts of activity prompts at preschool, but prompts to boys increased over time. The findings suggest that school environments could be altered to promote healthful physical activity among young children.

Age Factors↗
PubMed1997

Long-term effects of a physical education curriculum and staff development program: SPARK.

This 4-year study, conducted in seven elementary schools assigned to three conditions--Physical Education Specialists (PES), Trained Classroom Teachers (TT), and Controls (CO)--had two parts. The first investigated effects of a health-related physical education program on quantity and quality of lessons. Specialists produced the best outcomes, and TT were significantly better than nontrained peers. Part Two assessed maintenance effects approximately 1.5 years after intervention termination. Withdrawal of specialists significantly reduced the quantity and quality of physical education. TT maintained PES frequency but with a loss in lesson quality and a decline in student activity to 88% of intervention levels. Results support employing specialists and demonstrate the need for extensive professional development for classroom teachers responsible for physical education.

Child↗
PubMed1997

The effects of a 2-year physical education program (SPARK) on physical activity and fitness in elementary school students. Sports, Play and Active Recreation for Kids.

OBJECTIVES: This study evaluated a health-related physical education program for fourth- and fifth-grade students designed to increase physical activity during physical education classes and outside of school. METHODS: Seven schools were assigned to three conditions in a quasi-experimental design. Health-related physical education was taught by physical education specialists or trained classroom teachers. Students from these classes were compared with those in control classes. Analyses were conducted on 955 students with complete data. RESULTS: Students spent more minutes per week being physically active in specialist-led (40 min) and teacher-led (33 min) physical education classes than in control classes (18 min; P < .001). After 2 years, girls in the specialist-led condition were superior to girls in the control condition on abdominal strength and endurance (P < .001) and cardiorespiratory endurance (P < .001). There were no effects on physical activity outside of school. CONCLUSIONS: A health-related physical education curriculum can provide students with substantially more physical activity during physical education classes. Improved physical education classes can potentially benefit 97% of elementary school students.

California↗
PubMed1995

Improved accumulation and activity of ribozymes expressed from a tRNA-based RNA polymerase III promoter.

RNA polymerase III (pol III) transcripts are abundant in all cells. Therefore, pol III promoters may be ideal for expressing high levels of exogenous RNAs, such as antisense RNAs, decoy RNAs and ribozymes, in many different cell types. We have improved accumulation of recombinant RNAs expressed from a human meti tRNA-derived pol III promoter > 100-fold by modifying the 3' terminus of the transcripts to hybridize to the 5' terminus. This terminal duplex includes the 8 nt leader sequence present in the primary wild-type meti tRNA transcript that is normally removed during processing to the mature tRNA. Expression of an anti-HIV ribozyme was analyzed in cells stably transduced with retroviral vectors encoding pol III transcription units containing this modification. High accumulation of recombinant pol III ribozyme transcripts was observed in all cell lines tested. Due to the enhanced transcript accumulation, ribozyme cleavage activity was readily detectable in total RNA extracted from stably transduced human T cell lines. One pol III transcription unit, termed 'TRZ', was optimized further for ribozyme cleavage activity. The improved pol III transcription units reported here may be useful for expressing a variety of functional and therapeutic RNAs.

Base Sequence↗
PubMed1995

Children's activity levels and lesson context during third-grade physical education.

Little is known about children's activity levels during physical education classes and how they relate to the national health objectives for the year 2000 (U.S. Public Health Service, 1991). We systematically observed students' physical activity and associated variables in 293 third-grade physical education lessons in 95 schools in 4 Child and Adolescent Trial for Cardiovascular Health (CATCH) centers in California, Louisiana, Minnesota, and Texas. The influence of independent variables was assessed simultaneously by analysis of variance. Significant differences among study centers were evidenced for both physical activity and lesson context variables. Additionally, there were differences among variables for lesson location and teacher specialty, but not for teacher gender. Boys were more active than girls, but only during free play opportunities. The findings have widespread implications for educators responsible for developing and implementing health-related physical education programs, as well as for designing and conducting staff development.

Analysis of Variance↗
PubMed1995

Variability and tracking of physical activity over 2 yr in young children.

The purpose of this study was to examine tracking of physical activity at home and recess in young children. Three hundred fifty-one Mexican-American and Anglo-American children entered the study (mean age = 4.4 yr), and 83% completed 2 yr of measurement. Physical activity was directly observed on 10 d over 2 yr. Measurement waves occurred every 6 months, and each wave consisted of 2 d of observation within 1 wk. Children were observed for 60 min at home on a weekday evening and up to 30 min during recess at preschool or school. Maximum likelihood procedures using a linear mixed-effects model indicated that most of the variance in home and recess physical activity was accounted for by short-term/weekly factors. Tracking of physical activity accounted for 15% of the total variance at home and 8% at recess. Pearson correlations for physical activity over time were higher at home than at recess. Tracking of home physical activity was r = 0.15 when single days were correlated and r = 0.36 when the means of 4 d were correlated. There was a small, but detectable, stable component of physical activity in young children, at least at home.

Child Behavior↗
PubMed1994

Localization of the squalene synthase gene (FDFT1) to human chromosome 8p22-p23.1.

Recently, we reported the isolation of a cDNA encoding the human enzyme squalene synthase, the first step of sterol biosynthesis uniquely committed to synthesis of cholesterol (6). As such, it is likely that this enzyme occupies a critical regulatory position in the synthesis of cholesterol. As part of continuing studies of the role of this gene in cellular metabolism, we undertook the mapping of this gene on the human chromosomes. To localize the gene, we have first isolated a yeast artificial chromosome (YAC) containing the squalene synthase gene. We then used fluorescence in situ hybridization (FISH) with yeast DNA containing the YAC to localize the gene to chromosome 8. Assignment to human chromosome 8 was confirmed by polymerase chain reaction analysis of a somatic cell hybrid containing human chromosome 8. Use of a somatic cell hybrid regional mapping panel dividing chromosome 8 into several fragments localized the gene to 8p21-pter. Fractional length analysis of the FISH mapping placed the signal generated with this YAC at 8p22-p23.1.

Base Sequence↗