Peter R.E. Crocker

Bio: Peter R.E. Crocker is an academic researcher from University of British Columbia. The author has contributed to research in topics: Coping (psychology) & Athletes. The author has an hindex of 44, co-authored 136 publications receiving 8357 citations. Previous affiliations of Peter R.E. Crocker include University of Saskatchewan.

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.

Abstract: 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.

Abstract: 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 children's physical activity during the school year.

Validation of the Physical Activity Questionnaire for Older Children

Abstract: Two studies assessed the validity of the Physical Activity Questionnaire for Older Children (PAQ-C), a 7-day recall that assesses general moderate to vigorous physical activity levels during the school year. The first study, involving 89 elementary school students in Grades 4–8, investigated convergent, divergent, and construct validity. The PAQ-C was moderately related to an activity rating (r = .63), week summation of 24-hr moderate to vigorous activity recalls (r = .53), a teacher’s rating of physical activity (r = .45), and perceptions of athletic competence (r = .48). As expected, the PAQ-C was not related to perceptions of behavioral conduct. The second study, involving 97 elementary school students, investigated convergent and construct validity. The PAQ-C was moderately related to an activity rating (r = .57), the Leisure Time Exercise Questionnaire (r = .41), a Caltrac motion sensor (r = .39), a 7-day physical activity recall interview (r = .46) and a step test of fitness (r = .28). The PAQ-C val...

Convergent Validity of the Physical Activity Questionnaire for Adolescents

Abstract: This study assessed the convergent validity of the Physical Activity Questionnaire for Adolescents (PAQ-A). The PAQ-A is a modified version for high school students of the Physical Activity Questionnaire for Older Children (PAQC). The PAQ-A is a 7-day recall used to assess general physical activity levels during the school year. Eighty-five high school students in Grades 8 through 12 filled out the PAQ-A and other physical activity measures. The PAQ-A was moderately related to an activity rating (r = .73), the Leisure Time Exercise Questionnaire (r = .57), a Caltrac motion sensor (r = .33), and the 7-day physical activity recall interview (r = .59). The results of this study support the convergent validity of the PAQ-A as a measure of general physical activity level for high school students.

Using Multivariate Statistics

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A review of correlates of physical activity of children and adolescents.

Abstract: SALLIS, J. F., J. J. PROCHASKA, and W. C. TAYLOR. A review of correlates of physical activity of children and adolescents. Med. Sci. Sports Exerc., Vol. 32, No. 5, pp. 963‐975, 2000. Background: Understanding the factors that influence physical activity can aid the design of more effective interventions. Previous reviews of correlates of youth physical activity have produced conflicting results. Methods: A comprehensive review of correlates of physical activity was conducted, and semiquantitative results were summarized separately for children (ages 3‐12) and adolescents (ages 13‐18). The 108 studies evaluated 40 variables for children and 48 variables for adolescents. Results: About 60% of all reported associations with physical activity were statistically significant. Variables that were consistently associated with children’s physical activity were sex (male), parental overweight status, physical activity preferences, intention to be active, perceived barriers (inverse), previous physical activity, healthy diet, program/facility access, and time spent outdoors. Variables that were consistently associated with adolescents’ physical activity were sex (male), ethnicity (white), age (inverse), perceived activity competence, intentions, depression (inverse), previous physical activity, community sports, sensation seeking, sedentary after school and on weekends (inverse), parent support, support from others, sibling physical activity, direct help from parents, and opportunities to exercise. Conclusion: These consistently related variables should be confirmed in prospective

Standards for educational and psychological testing

Abstract: Pedagosko i psiholosko testiranje i procjenjivanje spadaju među najvažnije doprinose znanosti o ponasanju nasem drustvu i pružaju temeljna i znacajna poboljsanja u odnosu na ranije postupke. Iako se ne može ustvrditi da su svi testovi dovoljno usavrseni niti da su sva testiranja razborita i korisna, postoji velika kolicina informacija koje ukazuju na ucinkovitost kvalitetnih instrumenata u onim situacijama u kojima je njihovo koristenje potkrijepljeno validacijskim podacima. Pravilna upotreba testova može dovesti do boljih odluka o pojedincima i programima nego sto bi to bio slucaj bez njihovog koristenja, a također i ukazati na put za siri i pravedniji pristup obrazovanju i zaposljavanju. Međutim, losa upotreba testova može dovesti do zamjetne stete nanesene ispitanicima i drugim sudionicima u procesu donosenja odluka na temelju testovnih podataka. Cilj Standarda je promoviranje kvalitetne i eticne upotrebe testova te uspostavljanje osnovice za ocjenu kvalitete postupaka testiranja. Svrha objavljivanja Standarda je uspostavljanje kriterija za evaluaciju testova, provedbe testiranja i posljedica upotrebe testova. Iako bi evaluacija prikladnosti testa ili njegove primjene trebala ovisiti prvenstveno o strucnim misljenjima, Standardi pružaju okvir koji osigurava obuhvacanje svih relevantnih pitanja. Bilo bi poželjno da svi autori, sponzori, nakladnici i korisnici profesionalnih testova usvoje Standarde te da poticu druge da ih također prihvate.

Systematic review of the health benefits of physical activity and fitness in school-aged children and youth

Abstract: The purpose was to: 1) perform a systematic review of studies examining the relation between physical activity, fitness, and health in school-aged children and youth, and 2) make recommendations based on the findings. The systematic review was limited to 7 health indicators: high blood cholesterol, high blood pressure, the metabolic syndrome, obesity, low bone density, depression, and injuries. Literature searches were conducted using predefined keywords in 6 key databases. A total of 11,088 potential papers were identified. The abstracts and full-text articles of potentially relevant papers were screened to determine eligibility. Data was abstracted for 113 outcomes from the 86 eligible papers. The evidence was graded for each health outcome using established criteria based on the quantity and quality of studies and strength of effect. The volume, intensity, and type of physical activity were considered. Physical activity was associated with numerous health benefits. The dose-response relations observed in observational studies indicate that the more physical activity, the greater the health benefit. Results from experimental studies indicate that even modest amounts of physical activity can have health benefits in high-risk youngsters (e.g., obese). To achieve substantive health benefits, the physical activity should be of at least a moderate intensity. Vigorous intensity activities may provide even greater benefit. Aerobic-based activities had the greatest health benefit, other than for bone health, in which case high-impact weight bearing activities were required. The following recommendations were made: 1) Children and youth 5-17 years of age should accumulate an average of at least 60 minutes per day and up to several hours of at least moderate intensity physical activity. Some of the health benefits can be achieved through an average of 30 minutes per day. [Level 2, Grade A]. 2) More vigorous intensity activities should be incorporated or added when possible, including activities that strengthen muscle and bone [Level 3, Grade B]. 3) Aerobic activities should make up the majority of the physical activity. Muscle and bone strengthening activities should be incorporated on at least 3 days of the week [Level 2, Grade A].