Peter R.E. Crocker

A six-year longitudinal study of the relationship of physical activity to bone mineral accrual in growing children : The University of Saskatchewan Bone Mineral Accrual Study

To investigate the influence of physical activity on bone mineral accrual during the adolescent years, we analyzed 6 years of data from 53 girls and 60 boys. Physical activity, dietary intakes, and anthropometry were measured every 6 months and dual‐energy X‐ray absorptiometry scans of the total body (TB), lumbar spine (LS), and proximal femur (Hologic 2000, array mode) were collected annually. Distance and velocity curves for height and bone mineral content (BMC) were fitted for each child at several skeletal sites using a cubic spline procedure, from which ages at peak height velocity (PHV) and peak BMC velocity (PBMCV) were identified. A mean age‐ and gender‐specific standardized activity (Z) score was calculated for each subject based on multiple yearly activity assessments collected up until age of PHV. This score was used to identify active (top quartile), average (middle 2 quartiles), or inactive (bottom quartile) groups. Two‐way analysis of covariance, with height and weight at PHV controlled for, demonstrated significant physical activity and gender main effects (but no interaction) for PBMCV, for BMC accrued for 2 years around peak velocity, and for BMC at 1 year post‐PBMCV for the TB and femoral neck and for physical activity but not gender at the LS (all p < 0.05). Controlling for maturational and size differences between groups, we noted a 9% and 17% greater TB BMC for active boys and girls, respectively, over their inactive peers 1 year after the age of PBMCV. We also estimated that, on average, 26% of adult TB bone mineral was accrued during the 2 years around PBMCV.

Measuring general levels of physical activity: preliminary evidence for the Physical Activity Questionnaire for Older Children.

This article reports three studies that investigated psychometric properties of the Physical Activity Questionnaire for Older Children (PAQ-C). The PAQ-C is a guided self-administered 7-day recall measure designed to assess general physical activity levels during the school year for children in grades four and higher. Study one, with 215 students ranging in age from 9 to 15 yr, found the PAQ-C had acceptable item and test score characteristics such as item distribution, corrected item-total correlations, and internal consistency. Study two, involving 84 students ranging from 9 to 14 yr, indicated acceptable levels of test-retest reliability for both males (r = 0.75) and females (r = 0.82) after 1 wk. The third study used Generalizability theory to investigate the reliability for using the average of either two or three PAQ-C scores collected during fall, winter, and spring seasons. Based on the responses of 200 students ranging from 8 to 16 yr, generalizability coefficients exceeded 0.80 for either the average of two or three responses for both younger (<13 yr) and older subjects. In all three studies, the PAQ-C demonstrated acceptable internal consistency and males were significantly more active than females. These results provide preliminary support for the PAQ-C as a cost efficient method of assessing general levels of childrens physical activity during the school year.

Children's physical activity and physical self-perceptions.

The aim of this study was to determine the relationship between physical self-perceptions and physical activity in Canadian school children aged 10–14 years. The sample consisted of 220 boys and 246 girls in grades 5–8. Physical activity was assessed by 7-day recall using the Physical Activity Questionnaire for Older Children. Selfperceptions of physical conditioning, sports competence, strength, body appearance and general physical selfworth were measured by the Physical Self-Perception Profile (PSPP). We found that boys were more physically active than girls and had higher perceptions of sport competence and strength. All PSPP scales were significantly correlated with physical activity in both boys and girls. Structural equation modelling procedures found the hierarchical PSPP model provided a good fit to the observed data, with little evidence of diff erences between the sexes. Analysis of five alternative structural models of the relationship between the PSPP and physical activity found the most parsimonious model to have significant pathways from both physical conditioning and sport skills to physical activity. Models for the sample as a whole, for boys and for girls were similar, accounting for an R 2 of 0.27–0.29 for physical activity. Our results demonstrate that physical self-perceptions, especially physical conditioning and sport skills, are significant correlates of activity in this population.

Longitudinal Assessment of the Relationship Between Physical Self-Concept and Health-Related Behavior and Emotion in Adolescent Girls

This study investigated the changes in and the relationships among body mass index (BMI), global self-esteem, physical self-perceptions, social physique anxiety (SPA), physical activity, and dietary restraint in adolescent females over a 24-month period. Participants (N = 501) completed annual assessments in grade 9, 10, and 11. The results showed moderate covariance stability in all variables. There were several significant time effects (group mean change), with small increases in BMI, moderate decreases in physical activity, and very small changes over time in SPA and physical self-perceptions. Longitudinal analyses indicated that specific physical self-perceptions were important predictors of physical activity, dietary restraint and SPA; however, most of the variance was explained by previous year values. Evidence of bidirectional effects revealed that specific self-perceptions impact specific behaviors and SPA more so than the impact of behavior/emotion on self-perceptions. These results highlight the importance of understanding the physical self and its links to health-related behaviors and emotion in adolescents.

Social Physique Anxiety in Adolescence: An Exploration of Influences, Coping Strategies, and Health Behaviors.

This study explored adolescent females’ experiences of social physique anxiety (SPA) and related coping strategies. A final sample of 31 adolescent females ages 13 to 18 years discussed dealing with SPA during individual semistructured interviews. Resultant themes pertaining to the transactional experiences of SPA were coded using content analysis. There were 107 unique coping strategies reported, which were coded into 10 subthemes. The main coping categories included behavioral and cognitive avoidance, appearance management, diet, social support, physical activity, reappraisal, cognitive deflection and comparison to others, seeking sexual attention, and substance use. Informed by a stress and coping framework, it is evident that body-related thoughts and emotions are linked to various adolescent health behaviors.

The Posttraumatic Growth Inventory: an examination of the factor structure and invariance among breast cancer survivors

Objective: The present study tested the proposed five‐factor structure and invariance of the Posttraumatic Growth Inventory (PTGI; Tedeschi & Calhoun, 1996) in a sample of physically active breast cancer survivors.

Physical Self and Physical Activity Relationships in College Women: Does Social Physique Anxiety Moderate Effects?

Abstract This research assessed whether social physique anxiety moderated the relationship between physical self-perceptions and the level of physical activity involvement in young women. Participants were 354 female students who completed the Social Physique Anxiety Scale (SPAS), Physical Self-Perception Profile, Self-Administered 7-Day Physical Activity Recall (PAR), and Leisure Time Exercise Questionnaire (LTEQ). Both physical activity measures were significantly related to the SPAS and all physical self-perceptions. Multiple regressions showed that only self-perceptions of conditioning significantly predicted PAR (R2 = .24) and LTEQ (R2 = .30). SPA did not add any unique variance in predicting activity, and no moderator effects were found for either PAR or LTEQ. Findings suggest that perception of physical conditioning is the dominant predictor of physical activity levels in young women, and social physique anxiety does not moderate this relationship.

Lifestyle risk factors for osteoporosis in Asian and Caucasian girls.

PURPOSE We investigated ethnic differences in areal bone mineral density (aBMD; g x cm(-2)) and its determinants at two levels of maturity in Asian- and Caucasian-Canadian girls. METHODS Participants were 131 Asian (26 Tanner breast stage I (aTI) and 30 Tanner II (aTII)), and Caucasian (30 Tanner I (cTI) and 45 Tanner II (cTII)) girls. We measured calcium intake by a food frequency questionnaire, general physical activity, and extracurricular sports with a modified Physical Activity Questionnaire for Children and loaded physical activity by 7-d recall. Fat mass, lean mass, and aBMD for the total body (TB), and aBMD at the lumbar spine (LS), proximal femur (PF), femoral neck (FN), and trochanter (TR) were measured by DXA (Hologic QDR 4500). We used ANCOVA (controlling for size and lean and fat mass) to compare bone mineral content (BMC) and aBMD between ethnicities within Tanner stages. RESULTS Calcium intake was significantly lower for Asian girls in both TI and TII (P < 0.001) as compared with Caucasians. For physical activity measures, only the general score was greater in cTI than aTI (P < 0.05). Participation in loaded physical activities and extracurricular sports was significantly less for aTII than cTII (both, P < 0.01), whereas general physical activity did not differ. aBMD measures were similar between aTI and cTI. However, TB, PF, FN, and aBMD were significantly lower (approximately 9-14%) in aTII as compared with cTII. CONCLUSION Thus, there was greater ethnic disparity in lifestyle factors related to bone health and absolute measures of bone mineral with advanced maturity.

The contributions of goal characteristics and causal attributions to emotional experience in youth sport participants.

Abstract Objectives . To examine the role of causal attributions, goal importance, and goal discrepancy as predictors of discrete emotions in youth sport settings. More specifically, causal attributions and goal characteristics were examined in an actual performance test and a natural competitive setting. Both direct effects and moderator models were tested. Method . Two studies were conducted. In the first study, 130 adolescent soccer players completed the Leger fitness test, as well as measures of goal importance and objective goal discrepancy, and the CDSII to assess causal dimensions PANAS-X to assess emotions. In the second study, 174 adolescent swimmers and track and field athletes participated in sport-specific competitions. Participants completed the same battery of questionnaires as in the first study with the exception that a measure of subjective goal discrepancy replaced objective goal discrepancy. Results . Results showed general consistency across studies. Both causal dimensions and goal characteristics (importance and discrepancy) showed direct effects in the prediction of emotion. However, there was no support for theoretical links between causal dimensions and specific emotions. Little support was found for a moderator model examining the interactions among and between goal characteristics and causal dimensions. In addition, subjective performance discrepancy was a much stronger predictor of emotion in the second study compared with objective performance discrepancy in the first study. Conclusions . Although causal attributions and goal characteristics are important predictors of emotion, there was little support for the theoretical model proposing an interaction among these variables in the experience of emotion for youth sport participants.

Sport Participation Motivation in Young Adolescent Girls: The Role of Friendship Quality and Self-Concept

Abstract This study examined the factor structure of the Sport Friendship Quality Scale (SFQS; Weiss & Smith, 1999) and compared two models in which (a) self-worth mediated the relationship between physical self/friendship quality and sport commitment and (b) friendship quality and physical self-perceptions directly predicted self-worth and sport commitment. Female team sport participants (N= 227) between the ages of 11 and 14 years completed measures of sport commitment, enjoyment, athletic competence, physical attractiveness, self-worth, and friendship qualities. A confirmatory factor analysis found an inadequate fit for the SFQS, mainly due to problems with the loyalty and intimacy subscale. Separating the loyalty and intimacy factor into two subscales provided an adequate fit. Examination of the two structural models indicated that both models provided an adequate overall fit but that self-worth only weakly predicted sport commitment, suggesting the mediator model was impractical. Friendship quality had a weak relationship with self-worth and sport commitment. Results are discussed in light of issues in measuring sport friendship quality and future directions in this developing field.