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 children's physical activity during the school year.

Altered loading patterns and femoral bone mineral density in children with unilateral Legg-Calvé-Perthes disease.

Maximization of bone accrual during the growing years is thought to be an important factor in minimizing fracture risk in old age. Mechanical loading through physical activity has been recommended as a modality for the conservation of bone mineral in adults; however, few studies have evaluated the impact of different loading regimes in growing children. The purpose of this study was to compare bone mineral density (BMD) in weight-bearing and non-weight-bearing limbs in 17 children with unilateral Legg Calvé Perthes Disease (LCPD). Children with this condition have an altered weight-bearing pattern whereby there is increased mechanical loading on the noninvolved normal hip and reduced loading on the involved painful hip. Thus, these children provide a unique opportunity to study the impact of differential mechanical loading on BMD during the growing years while controlling for genetic disposition. BMD at four regions of the proximal femur (trochanter, intertrochanter, femoral neck, total of the regions) was measured using dual energy x-ray absorptiometry (DXA), and the values were compared between the involved and noninvolved sides of the children with LCPD. The BMD of the both sides also were compared with normative values based on both chronological and skeletal age data. A significantly higher BMD was found on the noninvolved side over the involved side for all regions (P < 0.01 and percentage differences of 12-15%) except at the femoral neck (percentage difference of 3.9%). The BMD (at all regions) of the noninvolved side also was significantly greater (P < 0.01) than either the chronological or skeletal age based norms for all sites except the trochanter. The results support the concept that mechanical loading of the skeleton during the growing years is an important factor in BMD accrual.

Sudden death during exercise: how real a hazard?

The literature dealing with sudden cardiac death in relation to exercise, particularly sport, is reviewed. The exact incidence of unexpected sudden cardiac death during physical activity in persons previously presumed healthy is difficult to determine due to the wide variation in reporting methods; by all indications, it is extremely low. The most common cardiac condition underlying sudden cardiac death in persons over age 30 years is, overwhelmingly, coronary artery disease. In younger athletes it is much less common and is usually due to hypertrophic cardiomyopathy, congenital anomalies or inherent abnormalities of the conducting system. The PAR-Q (Preparation for Activity Readiness Questionnaire) appears to be an adequate pre-exercise screening tool for recreational and middle-aged athletes. A (cost) effective pre-exercise screening strategy for the younger and highly competitive athlete remains elusive. Extensive and costly screening methods (eg, ECG, echocardiography, treadmill studies) do not seem warranted for any asymptomatic, presumed healthy groups. Although the risk of sudden cardiac death is measurably higher during exercise than during sedentary activity, the overall risk is demonstrably lower in habitually active and physically fit persons. The resolution of this paradox is that even the most active persons rarely spend more than an hour or two a day at vigorous exercise, while the protective effects against sudden cardiac death operate for the remainder of the day.

Comparison of bone mineral content and bone mineral density between dominant and nondominant limbs in children 8-16 years of age.

The bone mineral content (BMC), bone mineral density (BMD), and bone free lean tissue (BFLT) of dominant limbs were compared to nondominant values in girls and boys 8-16 years of age (girls, n = 124; boys, n = 110). Results showed that BMC, BMD, and BFLT of the dominant arm was significantly greater than of the nondominant arm (P < .01). The differences were found for both boys and girls and across all age groups except for 8 to 9-year-old boys for BMC. There were no differences in BMC or BMD in the legs, but the dominant leg had significantly greater BFLT than the nondominant leg (P < .01). The greater BMC and BMD values of the dominant arm are likely a result of greater mechanical loading (resulting from normal daily activities) of the dominant arm; this speculation is supported by the greater muscularity in the dominant arm. In the legs it is likely that weight bearing and not bias muscular activity is more important in determining bone mineral status. © 1993 Wiley-Liss, Inc.

Critical evaluation of frame size determination in the 1983 Metropolitan Life weight for height tables.

According to Metropolitan Life, the criteria used in placing individuals into frame size classes on the basis of elbow breadth should result in a 25-50-25% (small-medium-large) distribution. This assumption was evaluated using a large sample of Canadians (n = 19,305). Results indicated that the hypothesized distribution was not achieved in either males or females; few subjects were classified as large frame. The small percentage of subjects classified as large frame resulted in a skewing of the weight categorizations in males, but not in females.

The effect of water fluoridation on the bone mineral density of young women.

INTRODUCTION: Osteogenic effects of therapeutic fluoride have been reported; however, the impact of exposure to low level water fluoridation on bone density is not clear. We investigated the effect of long-term exposure to fluoridated water from growth to young adulthood on bone mineral density (BMD). METHODS: BMD was measured in 24 healthy women from Regina (fluoride 0.1 mg/L) and 33 from Saskatoon (fluoride 1.0 mg/L), with no differences between groups for height, weight, lifestyle or dietary factors. RESULTS: Saskatoon women had significantly higher mean BMD at total anterior-posterior lumbar spine (APS) and estimated volumetric 1.3 (VLS), with no difference at total body (TB) or proximal femur (PF). CONCLUSION: Exposure to water fluoridation during the growing years may have a positive impact on axial spine bone density in young women.

The relationship of health-promoting behaviour to health locus of control: analysis of one baccalaureate nursing class.

This study established a health-promoting lifestyle profile in one first year baccalaureate nursing class using the Health-Promoting Lifestyle Profile (HPLP) scale (Walker, Sechrist, & Pender, 1987). Students also completed the Multidimensional Health Locus of Control Scale. Pearson correlation coefficients were run to determine the relationship between perceived health locus of control and each of the categories in the HPLP scale. The only significant, albeit low, correlations were between: stress management and internal health locus of control (r = .39, p = .01); and, interpersonal support and powerful others locus of control (r = .33, p = .03). Although low statistical power (n = 34) may have contributed to these findings, the value of health locus of control as an antecedent to health promoting behaviour is questioned. The students in the current study did engage in health-promoting behaviours as measured by the HPLP scale, with behaviours in the categories self-actualization and interpersonal support receiving the highest scores. As a group, the students displayed a high perceived internal locus of control. There was virtually no relationship between perceived health locus of control and the health-promoting lifestyle profile categories. However, the significant relationship between internal locus of control and the dimension, stress management, and the powerful others locus of control and the dimension, interpersonal support, may indicate that people with a differing locus of control have different coping strategies.

The Relationship between Falls Efficacy and Improvement in Fall Risk Factors Following an Exercise Plus Educational Intervention for Older Adults with Hip Osteoarthritis.

PURPOSE: Older adults with decreased confidence in their ability to prevent a fall may benefit from an exercise programme that includes self-efficacy-enhancing education. The objectives of this study were to explore differences in fall-risk outcomes in older adults with higher vs. lower levels of falls efficacy and to evaluate the relationship between baseline falls-efficacy status and changes in fall risk factors following two interventions. METHOD: Fifty-four older adults with hip osteoarthritis and at least one risk factor for falls received aquatic exercise twice weekly plus education once weekly (EE) or aquatic exercise only, twice weekly (EO), for 11 weeks. RESULTS: EE participants with low baseline falls efficacy demonstrated significantly (p<0.05) greater improvement in balance and falls efficacy compared to EE participants with high baseline falls efficacy. In the EE group only, baseline falls-efficacy status (low vs. high median split on the Activities-specific Balance Confidence Scale) was significantly (p<0.05) correlated with positive balance and falls-efficacy change scores (Spearman rank r=0.45 and 0.63 respectively). CONCLUSIONS: Individuals with one or more fall-risk factors and low falls efficacy may benefit from receiving an intervention that combines exercise with self-efficacy-enhancing education. Falls-efficacy screening may be important for decisions regarding referral to fall-prevention programmes.

Protective mouthguards and sports injuries.

In summary the advantages of providing custom-fitted mouthguards for athletes, especially those involved in contact sports, has been discussed along with the methodology of construction. Because of the apparent lack of negative effects on physical performance and the superior protective characteristics of custom-fitted mouthguards, it seems logical to recommend their use in the competitive sports arena.

A partial curl-up protocol for adults based on an analysis of two procedures.

The reliability and objectivity of two curl-up protocols in assessing abdominal muscle endurance were evaluated in 262 adults (18-69 + years of age). The two protocols consisted of the Canada Fitness Award procedure (Type I) and a partial curl-up described by Fitness Canada (Type II). The relationship of these protocols, body mass, trunk flexion, body mass index and waist/hip ratio to the incidence and degree of low back pain also was investigated. Based on the results, Fitness Canada recommended that a modified Type II partial curl-up be considered for adoption into the Canadian Standardized Test of Fitness (CSTF) procedure.

Prevention and management of osteoporosis: consensus statements from the Scientific Advisory Board of the Osteoporosis Society of Canada. 5. Physical activity as therapy for osteoporosis.

OBJECTIVE: To examine exercise as a therapy for people with osteoporosis. OPTIONS: Immobilization, standing low-load and high-load physical activities. OUTCOMES: Risk of injury, quality of life, risk of falls and fractures, strength and posture and pain management. EVIDENCE: Relevant epidemiologic studies, clinical trials and reviews were examined, including the large-scale FICSIT trial in the United States, a prospective 4-year study of women enrolled in an exercise program in Toronto and the large-scale Study of Osteoporotic Fractures. VALUES: Minimizing risk of injury and increasing quality of life were given a high value. BENEFITS, HARMS, AND COSTS: Moderate physical activity in people with osteoporosis can reduce the risk of falls and fractures, decrease pain and improve fitness and overall quality of life. It may also stimulate bone gain and decrease bone loss. Its positive effects are an adjunct to other interventions, such as hormonal therapy. It may give patients the confidence to resume regular activity and can provide social interaction and support. During exercise programs, proper nutrition is necessary to prevent excessive weight loss and impaired immune function resulting from inadequate protein, vitamin and mineral intake. RECOMMENDATIONS: Immobilization should be avoided if possible in anyone with osteoporosis or at increased risk for osteoporosis. Regular, moderate physical activity is recommended for those with osteoporosis. Elderly people should be assessed for risk of falling to identify those in greatest need of an exercise program. Community group exercise programs are beneficial. Younger people with osteoporosis also need exercise that will preserve or improve bone mass, muscular strength, endurance and cardiovascular fitness. Weight loss as a result of physical activity should be avoided and adequate intake of protein, vitamins and minerals assured. Because the benefits of physical activity are independent of the effect of other therapies, physical activity is an essential adjunct to appropriate nutrition and other therapies. VALIDATION: These recommendations were developed by the Scientific Advisory Board of the Osteoporosis Society of Canada at its 1995 Consensus Conference. They are in agreement with the position taken on osteoporosis and exercise by the United States Center for Disease Control and Prevention and the American College of Sports Medicine. SPONSORS: Sponsors of the 1995 conference included the Dairy Farmers of Canada, Eli Lilly Canada, Inc., Hoffmann-La Roche Canada Ltd., Merck Frosst Canada Inc. and Procter & Gamble Pharmaceuticals Canada Inc.

Regional and total body bone mineral content, bone mineral density, and total body tissue composition in children 8-16 years of age.

Normative values for total body bone mineral content (TBBM) and total body bone mineral density (TBMD) were derived from measurements on 234 children 8-16 years of age. In addition, bone mineral content (BMC) and bone mineral density (BMD) values for selected regions of interest and soft tissue (bone free lean and fat) for the total body are presented. Bone mineral and soft tissue values were determined by dual energy X-ray absorptiometry (DXA) using a Hologic QDR-2000 in the array mode. Results of a stepwise multiple regression analysis revealed a significant correlation between bone-free lean tissue (BFLT) and BMD (r2 = 0.80) in girls. Adding age to the equation accounted for an additional 2% of the variance (P < 0.05) and height accounted for another 1% of the variance (P < 0.05). Body weight and fat tissue (FT) did not account for any additional variance. In boys BFLT correlated significantly with BMD (r2 = 0.75; P < 0.05); none of the other predictor variables accounted for additional variance. No significant differences were found in TBBM or TBMD between boys and girls at any age. There was a significant overall gender effect for only three regions of interest. Boys had greater BMC in the head region and had greater BMD in the upper limbs, but post hoc analysis revealed no significant differences for any specific age groups. Girls had greater overall BMD in the pelvis, but this difference was only significant at the 15-16-year age group. The changes in BFLT and FT over the age ranges were consistent with the growth literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone densitometry in Canadian children 8-17 years of Age.

Normative bone mineral density (BMD) and bone mineral content (BMC) values for the total body (TB), proximal femur (PF), and antero-posterior lumbar spine (LS) were obtained from a large cross-sectional sample of children and adolescents who were 8-17 years of age. There were 977 scans for the TB, 892 for the PF, and 666 for the LS; bone mineral values were obtained using a HOLOGIC QDR 2000 in array mode. Data are presented for the subregions of the PF (femoral neck, trochanter, intertrochanter, and the total region) and for the LS (L1-L4 and L3). Female and male values for the FN, LS (L1-L4), and the TB were compared across age groups using a two-way ANOVA. In addition, we compared the 17-year-old female values to a separate sample of young adult women (age 21). At all these sites, BMC and BMD increased significantly with age. There was no gender difference in TB BMC until age 14 or in TB BMD until age 16, when male values were significantly greater. Females had significantly greater LS BMC at ages 12 and 13, but by age 17 the male values were significantly greater. Females had significantly greater LS BMD across all age groups, however. Males had significantly greater FN BMC and BMD across all age groups. There were no significant differences in BMC or BMD at any sites between the 17- and 21-year-old women.

Body composition in nutritionally adequate ambulatory and non-ambulatory children with cerebral palsy and a healthy reference group.

Bone-mineral content (BMC; g) and density (BMD; g/cm2) were measured by dual energy X-ray absorptiometry in the proximal femur, femoral neck, and total body of nutritionally adequate children (n=17; 11 girls, six boys; aged 7.6 to 13.8 years) with spastic cerebral palsy (CP). Bone-mineral-free lean tissue (BMFL; g) and fat mass (FM; g) were obtained from total body scans. Chronological and developmental age-based z scores for the children with CP were derived from a pediatric database (n=894). Children with CP had BMC z scores from -1.8 (total body) to -3.2 (femoral neck) SDs below the normative sample. Non-independent ambulators had lower z scores for total body BMD, femoral neck BMD, and BMC than independent ambulators. The BMFL z score of individuals with CP was 2 SDs below that of the reference group and higher in the independent ambulators than in the non-independent ambulators, whereas FM deviated little. These findings suggest that non-nutritional factors, such as ambulation, account for the low BMC, BMD, and BMFL tissue observed in this population.

Peak bone mineral accrual and age at menarche in adolescent girls: a 6-year longitudinal study.

BACKGROUND AND OBJECTIVES: The greatest increase in bone mineral content occurs during adolescence. The amount of bone accrued may significantly affect bone mineral status in later life. We carried out a longitudinal investigation of the magnitude and timing of peak bone mineral content velocity (PBMCV) in relation to peak height velocity (PHV) and the age at menarche in a group of adolescent girls over a 6-year period. METHODS: The 53 girls in this study are a subset of the 115 girls (initially 8 to 16 years) in a 6-year longitudinal study of bone mineral accretion. The ages at PBMCV and PHV were determined by using a cubic spline curve fitting procedure. Determinations were based on height (n = 12) and bone (n = 6) measurements over 6 years. RESULTS: The timing of PBMCV and menarche were coincident, preceded approximately 1 year earlier by PHV. Correlation showed a negative relationship between age at menarche and both peak bone mineral accrual (r = -0.42, P < .002) and PHV (r = -0.45, P < .001). CONCLUSIONS: This longitudinal study demonstrated the close association between age at PBMCV and age at menarche and confirmed the relationship between greater PBMCV and PHV in earlier, as compared with later, maturing girls.