Robert W. Schutz

Augmented trochanteric bone mineral density after modified physical education classes: A randomized school-based exercise intervention study in prepubescent and early pubescent children ☆ ☆☆

BACKGROUND Of the few exercise intervention studies focusing on pediatric populations, none have confined the intervention to the scheduled physical education curriculum. OBJECTIVE To examine the effect of an 8-month school-based jumping program on the change in areal bone mineral density (aBMD), in grams per square centimeter, of healthy third- and fourth-grade children. STUDY DESIGN Ten elementary schools were randomized to exercise (n = 63) and control groups (n = 81). Exercise groups did 10 tuck jumps 3 times weekly and incorporated jumping, hopping, and skipping into twice weekly physical education classes. Control groups did regular physical education classes. At baseline and after 8 months of intervention, we measured aBMD and lean and fat mass by dual-energy x-ray absorptiometry (Hologic QDR-4500). Calcium intake, physical activity, and maturity were estimated by questionnaire. RESULTS The exercise group showed significantly greater change in femoral trochanteric aBMD (4.4% vs 3.2%; P <.05). There were no group differences at other sites. Results were similar after controlling for covariates (baseline aBMD change in height, change in lean, calcium, physical activity, sex, and ethnicity) in hierarchical regression. CONCLUSIONS An easily implemented school-based jumping intervention augments aBMD at the trochanteric region in the prepubertal and early pubertal skeleton.

The Analysis of Repeated Measures Designs Involving Multiple Dependent Variables

Abstract Experimental designs involving repeated measures may be analyzed using traditional ANOVA methods (if all assumptions are met), or, given sufficient sample size, with a MANOVA-type procedure (if only some assumptions are met). Recent statistical advances have made possible the extension of these procedures to repeated measures experimental designs involving multiple dependent variables. This tutorial presents the concepts, complete examples (including computer control commands), and interpretations for four methods of testing differences among means in a mixed model repeated measures design. The four methods of analysis are: The traditional ANOVA and the MANOVA method for the single dependent variable case, and a Multivariate Mixed Model analysis and a Doubly Multivariate analysis for the multiple dependent variable case.

Causal model of stress and coping: Women in management.

A model of managerial womens stress was tested (N = 249) with structural equation modeling. The model was developed from Lazaruss (1966) theoretical framework of stress/coping and incorporated 3 causal antecedent constructs (Demographics, Sex Role Attitudes, Agentic Traits), 4 mediating constructs (Environment, Appraisals, Engagement Coping, Disengagement Coping), and 3 outcomes (Work Performance, Distress, Satisfaction). The final model, found to be most plausible in the sample population, accounted for 56% of the total variance among the constructs. Lazaruss theory of psychological stress, which postulates a central role for cognitive appraisals and coping, was supported. In addition, agentic traits and sex role attitudes had both direct and indirect effects on outcome variables. Implications for career development theory and counseling, as well as limitations of the study, are discussed.

Statistical Analyses of Volleyball Team Performance

The purpose of this study was to investigate the playing characteristics of team performance in international mens volleyball. The specific purposes were (a) to examine differences in playing characteristics (in particular, the set and spike) between the Attack Process and the Counterattack Process; (b) to examine changes in playing characteristics as a function of team success (as indicated by single-game outcomes and by final tournament standings); and (c) to determine the best predictor, or a set of predictors, of team success among the selected skill components. Seventy-two sample games from the Third Federation of International Volleyball Cup mens competition were recorded using a computerized recording system. Results showed that the significant differences between Team Standing and Game Outcome were due to better performances on those skills used in the Counterattack Process. Among the eight selected skills, the block and spike were the most important in determining team success. The methodology used in this study and the subsequent results provide valuable aids for the coach in the evaluation of team performance and ultimately in the preparation of training sessions in volleyball.

Examination of the Factorial Validity of the Group Environment Questionnaire

The purpose of this study was to test the hypothesized factor structure of the Group Environment Questionnaire (GEQ) with confirmatory factor analysis and to ascertain the degree of factorial invariance across gender and across type of sport (team, individual). Additionally, the underlying theoretical structure on which the GEQ was developed was examined by fitting the data to alternative hierarchical factor structures. These models were tested with GEQ data collected on 740 high school varsity athletes (426 males, 314 females). It was shown that the males and females had different factor structures and that neither group exhibited the hypothesized structure. Attempts to fit the data to a two-factor and a second-order hierarchical factor model were unsuccessful. Finally, exploratory factor analysis did not produce a satisfactory four-factor solution. It was concluded that the data from this sample do not support the hypothesized four-factor structure of the GEQ and that further examination of the factor structure of this instrument is required.

Lifestyle Determinants of Bone Mineral: A Comparison Between Prepubertal Asian- and Caucasian-Canadian Boys and Girls

Abstract The purpose of this study was to examine the difference in lifestyle and morphometric factors that affect bone mineral and the attainment of peak bone mass in 168 healthy Asian (n = 58) and Caucasian (n = 110) Canadian, prepubertal girls and boys (mean age 8.9 ± 0.7) living in close geographical proximity. DXA (Hologic 4500) scans of the proximal femur (with regions), lumbar spine, and total body (TB) were acquired. We report areal bone mineral densities (aBMD g/cm2) at all sites and estimated volumetric density (νBMD, g/cm3) at the femoral neck. Dietary calcium, physical activity, and maturity were estimated by questionnaire. Of these prepubertal children, all of the boys and 89% of the girls were Tanner stage 1. A 2 × 2 ANOVA demonstrated no difference between ethnicities for height, weight, body fat, or bone mineral free lean mass. Asian children consumed significantly less dietary calcium (35%) on average and were significantly less active (15%) than their Caucasian counterparts (P < 0.001). There were significant ethnicity main effects for femoral neck bone mineral content (BMC) and αBMD (both P < 0.001) and significant sex by ethnicity interactions (P < 0.01). The Asian boys had significantly lower femoral neck BMC (11%), aBMD (8%), and νBMD (4.4%). At the femoral neck, BMFL mass, sex, and physical activity explained 37% of the total variance in aBMD (P < 0.05). In summary, this study demonstrated differences in modifiable lifestyle factors and femoral neck bone mineral between Asian and Caucasian boys.

Statistical power for the two-factor repeated measures ANOVA

Determining a priori power for univariate repeated measures (RM) ANOVA designs with two or more within-subjects factors that have different correlational patterns between the factors is currently difficult due to the unavailability of accurate methods to estimate the error variances used in power calculations. The main objective of this study was to determine the effect of the correlation between the levels in one RM factor on the power of the other RM factor. Monte Carlo simulation procedures were used to estimate power for the A, B, and AB tests of a 2×3, a 2×6, a 2×9, a 3×3, a 3×6, and a 3×9 design under varying experimental conditions of effect size (small, medium, and large), average correlation (.4 and .8), alpha (.01 and .05), and sample size (n = 5, 10 ,15, 20, 25, and 30). Results indicated that the greater the magnitude of the differences between the average correlation among the levels of Factor A and the average correlation in the AB matrix, the lower the power for Factor B (and vice versa). Equations for estimating the error variance of each test of the two-way model were constructed by examining power and mean square error trends across different correlation matrices. Support for the accuracy of these formulae is given, thus allowing for direct analytic power calculations in future studies.

Analysis of Proximal Femur DXA Scans in Growing Children: Comparisons of Different Protocols for Cross- Sectional 8-Month and 7-Year Longitudinal Data

Dual‐energy X‐ray absorptiometry (DXA) is a widely used method for measuring bone mineral in the growing skeleton. Because scan analysis in children offers a number of challenges, we compared DXA results using six analysis methods at the total proximal femur (PF) and five methods at the femoral neck (FN). In total we assessed 50 scans (25 boys, 25 girls) from two separate studies for cross‐sectional differences in bone area, bone mineral content (BMC), and areal bone mineral density (aBMD) and for percentage change over the short term (8 months) and long term (7 years). At the proximal femur for the short‐term longitudinal analysis, there was an approximate 3.5% greater change in bone area and BMC when the global region of interest (ROI) was allowed to increase in size between years as compared with when the global ROI was held constant. Trend analysis showed a significant (p < 0.05) difference between scan analysis methods for bone area and BMC across 7 years. At the femoral neck, cross‐sectional analysis using a narrower (from default) ROI, without change in location, resulted in a 12.9 and 12.6% smaller bone area and BMC, respectively (both p < 0.001). Changes in FN area and BMC over 8 months were significantly greater (2.3%, p < 0.05) using a narrower FN rather than the default ROI. Similarly, the 7‐year longitudinal data revealed that differences between scan analysis methods were greatest when the narrower FN ROI was maintained across all years (p < 0.001). For aBMD there were no significant differences in group means between analysis methods at either the PF or FN. Our findings show the need to standardize the analysis of proximal femur DXA scans in growing children.

Transition play in team performance of volleyball: a log-linear analysis.

The purpose of this study was to develop and test a method to analyze and evaluate sequential skill performances in a team sport. An on-line computerized system was developed to record and summarize the sequential skill performances in volleyball. Seventy-two sample games from the third Federation of International Volleyball Cup mens competition were videotaped and grouped into two categories according to the final team standing and game outcome. Log-linear procedures were used to investigate the nature and degree of the relationship in the first-order (pass-to-set, set-to-spike) and second-order (pass-to-spike) transition plays. Results showed that there was a significant dependency in both the first-order and second-order transition plays, indicating that the outcome of a skill performance is highly influenced by the quality of a preceding skill performance. In addition, the pattern of the transition plays was stable and consistent, regardless of the classification status: Game Outcome, Team Standing, or Transition Process. The methodology and subsequent results provide valuable aids for a thorough understanding of the characteristics of transition plays in volleyball. In addition, the concept of sequential performance analysis may serve as an example for sport scientists in investigating probabilistic patterns of motor performance.

Inventories and Norms for Children's Attitudes Toward Physical Activity.

Abstract This paper summarizes the development of an inventory for the assessment of childrens attitudes toward physical activity (CATPA), including an overview of its psychometric properties. Through a series of studies, an original and frequently used attitude inventory was restructured, resulting in a revised inventory which is both shorter and psychometrically superior to the original. This instrument, which assesses attitudinal dispositions toward each of seven physical activity subdomains, is shown to possess high internal consistency and strong factor validity. In addition, a new CATPA inventory suitable for grade 3 children is introduced. The two inventories are presented, along with instructions for their administration and scoring. Norms, based on samples of approximately 500 children of each grade and sex, are provided for boys and girls in grades 3, 7, and 11. Throughout the paper consideration is given to research applications, as well as cautions relative to the use and interpretation of th...