Exploring Body-Related Experiences among Individuals with Spinal Cord Injury

Using modified constructivist grounded theory, the purpose of the present study was to explore body-related experiences, specifically body image, in people with spinal cord injury. A total of nine participants (five women, four men) who had a broad range of body image experiences (from very negative to very positive) were interviewed. Most participants explained experiencing a fluctuating body image that varied from day-to-day. Negative body image experiences were represented by appearance, weight concerns, and function with all body image experiences encompassed by self-presentational concerns and tactics (an unanticipated finding). Positive body image was represented by acceptance, appreciation and gratitude of the body. Interestingly, negative body image experiences were not found to be represented by the opposite of positive body image experiences as they were each distinct. These findings have direct implications for medical professionals in hospital and rehabilitation settings to understand the importance of body image after spinal cord injury.

The Association of Energy Intake with Body Mass in Children With and Without Probable Developmental Coordination Disorder

Objective To determine if there is an association between energy intake (EI) and overweight or obesity status (OWOB) in children with and without probable developmental coordination disorder (p-DCD). Methods 1905 children were included. The Bruininks-Oseretsky Test of Motor Proficiency was used to assess p-DCD, body mass index for OWOB, and the Harvard Food Frequency Questionnaire for EI. Comparative tests and logistic regressions were performed. Results Reported EI was similar between p-DCD and non-DCD children among boys (2291 vs. 2281 kcal/day, p=0.917), but much lower in p-DCD compared to non-DCD girls (1745 vs.. 2068 kcal/day, p=0.007). EI was negatively associated with OWOB in girls only (OR: 0.82 (0.68, 0.98)). Conclusions Girls with p-DCD have a lower reported EI compared to their non-DCD peers. EI is negatively associated with OWOB in girls with p-DCD. Future research is needed to assess longitudinally the potential impact of EI on OWOB in this population.

Genetic and Electrophysiological Correlates of Self-Regulation in Adolescence

Self-regulation is considered a powerful predictor of behavioral and mental health outcomes during adolescence and emerging adulthood. In this dissertation I address some electrophysiological and genetic correlates of this important skill set in a series of four studies. Across all studies event-related potentials (ERPs) were recorded as participants responded to tones presented in attended and unattended channels in an auditory selective attention task. In Study 1, examining these ERPs in relation to parental reports on the Behavior Rating Inventory of Executive Function (BRIEF) revealed that an early frontal positivity (EFP) elicited by to-be-ignored/unattended tones was larger in those with poorer self-regulation. As is traditionally found, N1 amplitudes were more negative for the to-be-attended rather than unattended tones. Additionally, N1 latencies to unattended tones correlated with parent-ratings on the BRIEF, where shorter latencies predicted better self-regulation. In Study 2 I tested a model of the associations between selfregulation scores and allelic variations in monoamine neurotransmitter genes, and their concurrent links to ERP markers of attentional control. Allelic variations in dopaminerelated genes predicted both my ERP markers and self-regulatory variables, and played a moderating role in the association between the two. In Study 3 I examined whether training in Integra Mindfulness Martial Arts, an intervention program which trains elements of self-regulation, would lead to improvement in ERP markers of attentional control and parent-report BRIEF scores in a group of adolescents with self-regulatory difficulties. I found that those in the treatment group amplified their processing of attended relative to unattended stimuli over time, and reduced their levels of problematic behaviour whereas those in the waitlist control group showed little to no change on both of these metrics. In Study 4 I examined potential associations between self-regulation and attentional control in a group of emerging adults. Both event-related spectral perturbations (ERSPs) and intertrial coherence (ITC) in the alpha and theta range predicted individual differences in self-regulation. Across the four studies I was able to conclude that real-world self-regulation is indeed associated with the neural markers of attentional control. Targeted interventions focusing on attentional control may improve self-regulation in those experiencing difficulties in this regard.

Risk-taking behaviours in adolescent boys and girls : sexuality and dietary health

This study examined adolescents' reported sexual and dietary health-risk behaviours and perceptions. Specifically, this study analyzed the data of 600 students (300 male~ 300 female) in grades 9, I 1, and OAC (mean, standard deviation). The mean age of the students in the sample is 16 with a standard deviation of 1.6. The study was a secondary analysis ofthe first-year data of a 3-year longitudinal study conducted by Youth Lifestyle Choices-Community University Research Alliance (YLC-CURA) on adolescents. To explore sexuality and dietary health, this study purposefully selected sections of the survey that represented sex and dieting behaviours of adolescents. Separate gender and age data analyses revealed different patterns among the variables. Specifically., findings revealed that adolescents who engaged in recent sexual activities were more likely to have a relatively more positive body image perception and were relatively more likely to engage in disordered eating. Across both genders and 3 age levels, adolescents reported that despite their unhealthy dietary habits they felt that dieting was not a high-risk behaviour. Results were discussed in terms of educational implication for sexual health programs.

Bullying in physical education : its prevalence & impact on the intention to continue secondary school physical education

The purpose of this study was to determine the prevalence of bullying in physical education and its influence on students' intention to participate in the class in the future. Additionally, the study researched the relationship between bullying and body image as well as bullying and physical competency in physical education. A survey was utilized that collected both quantitative and qualitative data about students' experiences in physical education. Two-hundred and thirty-four grade 10 students (144 female and 90 male) from 8 different secondary schools participated in the study. Data analyses were completed using the Statistical Package for the Social Sciences (SPSS) version 16.0. Results showed thaLapproximately 18.3% of respondents had .experienced physical bullying in physical education; 23.7% had experienced verbal bullying; and 20.4% experienced social bullying. Furthermore, those who experienced frequent bullying in physical education did not intend on taking the class in the future. The relationship between body image and bullying was not found to be significant. However, physical competence was found to significantly predict bullying in physical education. These results show how prevalent bullying is in physical education classes and how it negatively impacts future participation in the class.

Relative importance of body composition, osteoporosis- related behaviours and socioeconomic status on bone SOS in adolescent females

The purpose of this study was to examine the associations between bone speed of sound (SOS) and body composition, osteoporosis-related health behaviours, and socioeconomic status (SES) in adolescent females. A total of 442 adolescent females in grades 9-11 participated. Anthropometric measures of height, body mass, and percent body fat were taken, and osteo-protective behaviours such as oral contraceptive use (OC), physical activity and daily calcium intake were evaluated using self-report questionnaires. Bone SOS was measured by transaxial quantitative ultrasound (QUS) at the distal radius and mid-tibia. The results suggest that fat mass is a significant negative predictor of tibial SOS, while lean mass is positively associated with radial SOS scores and calcium intake was positively associated with tibial SOS scores (pin adolescents with an increased fat mass, and influenced positively by OC use, calcium intake and lean mass.

The role of self-presentation in adolescent health risk behaviours

Self-presentation has been identified as playing a key role in the perfonnance of various potentially hazardous health behaviours such as substance abuse, eating disorders and reckless behaviours (Leary, Tchividjian, & Kraxberger, 1994; Martin & Leary, 2001; Martin, Leary, & O'Brien, 2001). The present study investigated the role of selfpresentation on adolescent health-risk behaviours. Specifically, this study examined the prevalence of adolescent identified health-risk behaviours rooted in self-presentational motives in youths aged 13-18 years. The current study also identified the specific images associated with these behaviours desired by youth, and the targets of these behaviours. Also, the relationship between these behaviours, and several trait measures (social physique anxiety, public-self consciousness, fear of negative evaluations, selfpresentational efficacy) of self-presentation were examined. Finally, the gender differences in health risk behaviours and self-presentational concerns were examined. Participants in the present study were 96 adolescent students, 34 male and 62 female, recruited from various private schools across Southern Ontario. Students ranged in age from 13 to 18 years for both males (M age = 15.81 years, SD = 1.49) and females (M age = 14.89 years, SD = 1.17) and ranged from grades 8 through 13. Results of the current study suggested that Canadian adolescents between the ages of 13 and 18 years participated in health risk behaviours for self-presentational purposes. Drinking alcohol, skipping school, and performing stunts and dares were identified as the most common health risk behaviours performed for self-presentational purposes by both males and females. Appearing fun and cool were the most commonly reported desired images while appearing brave and mature were the least reported. The most desired target group cited was same sex friends, followed by other sex friends. Trait measures of self-presentational concerns identified females as being higher in public self-consciousness, and social physique anxiety than males. Males were found to be higher in self-presentational efficacy than females. The total number of health risk behaviours was predicted by selfpresentational efficacy and social physique anxiety for males, and social physique anxiety for females. Findings of the current study suggest that Canadian adolescents' health risk behaviours are rooted, in part, in self-presentational motives. Thus far, an educational approach to health interventions has been favoured and/or adopted by teachers, health promoters, and educators (Jessor, 1992). Implications of the current study suggest that although educational interventions are beneficial in presenting the associated risks with certain activities and/or behaviours, one reason this type of approach may be ineffective in changing adolescent behaviour over the long run is that it does not address the strong and prominent influences of interpersonal motives on health damaging behaviour. It is evident that social acceptance and public image are of importance to adolescents, and the desire to make the "right" impression and to achieve peer approval and acceptance often override health and safety concerns (Jessor, 1992). Thus, a self-presentational approach focusing on changing the images associated with the behaviours may be more successful at deterring adolescent health risk behaviours.

Electrophysiological correlates of performance monitoring in middle and late adolescence

The ability to monitor and evaluate the consequences of ongoing behaviors and coordinate behavioral adjustments seems to rely on networks including the anterior cingulate cortex (ACC) and phasic changes in dopamine activity. Activity (and presumably functional maturation) of the ACC may be indirectly measured using the error-related negativity (ERN), an event-related potential (ERP) component that is hypothesized to reflect activity of the automatic response monitoring system. To date, no studies have examined the measurement reliability of the ERN as a trait-like measure of response monitoring, its development in mid- and late- adolescence as well as its relation to risk-taking and empathic ability, two traits linked to dopaminergic and ACC activity. Utilizing a large sample of 15- and 18-year-old males, the present study examined the test-retest reliability of the ERN, age-related changes in the ERN and other components of the ERP associated with error monitoring (the Pe and CRN), and the relations of the error-related ERP components to personality traits of risk propensity and empathy. Results indicated good test-retest reliability of the ERN providing important validation of the ERN as a stable and possibly trait-like electrophysiological correlate of performance monitoring. Ofthe three components, only the ERN was of greater amplitude for the older adolescents suggesting that its ACC network is functionally late to mature, due to either structural or neurochemical changes with age. Finally, the ERN was smaller for those with high risk propensity and low empathy, while other components associated with error monitoring were not, which suggests that poor ACe function may be associated with the desire to engage in risky behaviors and the ERN may be influenced by the extent of individuals' concern with the outcome of events.

Determinants of left ventricular mass as measured by Doppler echocardiography in pre-adolescents

This study examined factors contributing to the differences in left ventricular mass as measured by Doppler echocardiography in children. Fourteen boys (10.3 ± 0.3 years of age) and 1 1 girls (10.5 ± 0.4 years of age) participated in the study. Height and weight were measured, and relative body fat was determined from the measurement of skinfold thickness according to Slaughter et al. (1988). Lean Body Mass was then calculated by subtracting the fat mass from the total body mass. Sexual maturation was self-assessed using the stages of sexual maturation by Tanner (1962). Both pubic hair development and genital (penis or breast for boys and girls respectively) development were used to determine sexual maturation. Carotid Pulse pressure was assessed by applanation tomometry in the left carotid artery. Cardiac mass was measured by Doppler Echocardiography. Images of cardiac structures were taken using B-Mode and were then translated to M- Mode. The dimensions at the end diastole were obtained at the onset of the QRS complex of the electrocardiogram in a plane through a standard position. Measurements included: (a) the diameter of the left ventricle at the end diastole was measured from the septum edge to the endocardium mean border, (b) the posterior wall was measured as the distance from to anterior wall to the epicardium surface, and (c) the interventricular septum was quantified as the distance from the surface of the left ventricle border to the right ventricle septum surface. Systolic time measurements were taken at the peak of the T-wave of the electrocardiogram. Each measurement was taken three to five times before averaging. Average values were used to calculate cardiac mass using the following equation (Deveraux et al. 1986). Weekly physical activity metabolic equivalent was calculated using a standardize activity questionnaire (Godin and Shepard, 1985) and peakV02 was measured on a cycloergometer. There were no significant differences in cardiovascular mesurements between boys and girls. Left ventricular mass was correlated (p<0.05) with size, maturation, peakV02 and physical activity metabolic equivalent. In boys, lean body mass alone explained 36% of the variance in left ventricular mass while weight was the single strongest predictor of left ventricular mass (R =0.80) in girls. Lean body mass, genital developemnt and physical activity metabolic equivalent together explained 46% and 81% in boys and girls, respectively. However, the combination of lean body mass, genital development and peakV02 (ml kgLBM^ min"') explained up to 84% of the variance in left ventricular mass in girls, but added nothing in boys. It is concluded that left ventricular mass was not statistically different between pre-adolescent boys and girls suggesting that hormonal, and therefore, body size changes in adolescence have a main effect on cardiac development and its final outcome. Although body size parameters were the strongest correlates of left ventricular mass in this pre-adolescent group of children, to our knowledge, this is the first study to report that sexual maturation, as well as physical activity and fitness, are also strong associated with left ventricular mass in pre-adolescents, especially young females. Arterial variables, such as systolic blood pressure and carotid pulse pressure, are not strong determinants of left ventricular mass in this pre-adolescent group. In general, these data suggest that although there is no gender differences in the absolute values of left ventricular mass, as children grow, the factors that determine cardiac mass differ between the genders, even in the same pre-adolescent age.

Secretory immunity in overweight and obese versus normal-weight early-and late-pubertal females

Obesity is a condition associated with a wide variety of health problems including hypertension, dyslipidemia, diabetes mellitus, certain forms of cancer, cardiovascular disease, and gallstones (157). TTiere is growing evidence that obesity may also be related to compromised immune function due to altered metabolic, psychological, and physical attributes (93). The aim of this study was to compare: a) immunity-related variables such as frequency of upper respiratory tract infections (URTI) and salivary secretory immunoglobulin A (sIgA) levels between overweight/obese (OB) and normal weight (NW) early-pubertal and late-pubertal girls, and b) stress-related variables such as Cortisol, melatonin, the melatonin/cortisol ratio, testosterone and the testosterone/cortisol ratio. Physical activity levels, stress indicators, and fatigue were used to explain potential differences in the dependent variables. It was hypothesized that the OB females would have lower melatonin (M) and higher Cortisol (C) and testosterone (T) levels compared with NW girls, regardless of maturity status. The altered levels of melatonin, Cortisol, and testosterone, would result in decreased M/C and T/C ratios, despite the increase in testosterone in OB females. It was hypothesized that this altered hormonal status results in a compromised immunity marked by higher frequency of upper respiratory tract infections (URTI) and decreased levels of secretory immunoglobulin A (sIgA). It was also hypothesized that OB girls would participate in less hours of physical activity than their NW counterparts and that this would relate to their stress and immunity levels. Forty (16 early- and 24 late-pubertal) overweight and obese females were compared to fifty-three (27 eariy- and 26 late-pubertal) age-matched normal-weight control subjects. Participants were categorized as early-pubertal (EP) or late-pubertal (LP) using Tanner self-staging of secondary sex characteristics. Subjects were classified into the two adiposity groups according to relative body fat (%BF), where normal weight (NW) subjects had a %BF less than 25%, and overweight and obese (OB) subjects had a %BF greater than 27.5%. Participants completed a number of questionnaires and information was collected on menstrual history, smoking history, alcohol and caffeine consumption, and medical history. Following the determination of maturity status, a complete anthropometric assessment was made including height, body mass, and body composition. All questionnaires and measurements were completed during a one-hour visit between 1 500 and 1900 hours Relative body fat was assessed using bioelectrical impedance analysis. Resting saliva samples were obtained and assayed (ELISA) for testosterone, Cortisol, melatonin and secretory immunoglobulin A. Physical activity was self-reported using the Godin- Shephard Leisure time questionnaire, and quantified using Actigraph GTIM accelerometers, which participants wore for seven consecutive days from the time they woke up in the morning, until the time they went to bed. Late-pubertal girls also completed questionnaires on their perceived stress and fatigue. Finally, all participants also filled out a one-month health log to record frequency of symptoms of upper respiratory tract infections (URTI). Significant age effects were found for testosterone, Cortisol, incidence of sickness, and sIgA when controlling for physical activity, however there were no significant effects of adiposity on any of the variables. There was a trend which neared-significance for an effect of adiposity on sIgA (p=0.01). There were no significant differences between the groups on the total selfreported leisure-time physical activity in METs per week, however EP girls recorded significantly greater levels of moderate, hard, and very hard physical activity from accelerometers. Results of the perceived stress and fatigue questionnaires in late-pubertal girls demonstrated that contrary to what was hypothesized, NW girls reported more stress and more fatigue than OB girls. Results of the present study suggest that excess adiposity in early- and latepubescent girls may not have a negative impact on immunity as hypothesized.

Lifespan, body size and oxygen : aerobic metabolism and oxidative stress in cultured fibroblasts /

The allometric scaling relationship observed between metabolic rate (MR) and species body mass can be partially explained by differences in cellular MR (Porter & Brand, 1995). Here, I studied cultured cell lines derived from ten mammalian species to determine whether cells propagated in an identical environment exhibited MR scaling. Oxidative and anaerobic metabolic parameters did not scale significantly with donor body mass in cultured cells, indicating the absence of an intrinsic MR setpoint. The rate of oxygen delivery has been proposed to limit cellular metabolic rates in larger organisms (West et al., 2002). As such cells were cultured under a variety of physiologically relevant oxygen tensions to investigate the effect of oxygen on cellular metabolic rates. Exposure to higher medium oxygen tensions resulted in increased metabolic rates in all cells. Higher MRs have the potential to produce more reactive oxygen species (ROS) which could cause genomic instability and thus reduced lifespan. Longer-lived species are more resistant to oxidative stress (Kapahi et al, 1999), which may be due to greater antioxidant and/or DNA repair capacities. This hypothesis was addressed by culturing primary dermal fibroblasts from eight mammalian species ranging in maximum lifespan from 5 to 120 years. Only the antioxidant manganese superoxide dismutases (MnSOD) positively scaled with species lifespan (p<0.01). Oxidative damage to DNA is primarily repaired by the base excision repair (BER) pathway. BER enzyme activities showed either no correlation or as in the case of polymerase p correlated, negatively with donor species (p<0.01 ). Typically, mammalian cells are cultured in a 20% O2 (atmospheric) environment, which is several-fold higher than cells experience in vivo. Therefore, the secondary aim of this study was to determine the effect of culturing mammalian cells at a more physiological oxygen tension (3%) on BER, and antioxidant, enzyme activities. Consistently, standard culture conditions induce higher antioxidant and DNA ba.se excision repair activities than are present under a more physiological oxygen concentration. Therefore, standard culture conditions are inappropriate for studies of oxidative stress-induced activities and species differences in fibroblast DNA BER repair capacities may represent differences in ability to respond to oxidative stress. An interesting outcome firom this study was that some inherent cellular properties are maintained in culture (i.e. stress responses) while others are not (i.e. MR).

Identifying the psychosexual implications of radical radiation treatment in prostate cancer

The purpose of this study was to determine whether there was any evidence of psychosexual morbidity among men who experienced radical radiation treatment for prostate cancer. With relatively little known or available retrospective data on the psychosexual implications of radical radiation treatment in men with prostate cancer, this study posited eight research questions which provided the basis for the research. Fifty men from Southern Ontario, between the ages of 52 to 78 years, were included in the study. They had been previously randomized to a clinical trial comparing radical radiation therapy by external beam radiation, or radical radiation using a combination of a temporary iridium implant plus external beam radiation, for localized or locally advanced prostate cancer. Assessment of sexual functioning, drive, attitudes, body image, and sexual satisfaction was drawn from a multidimensional approach, since psychosexuality was viewed as having an impact on biological, psychological, and sociological domains of functioning. Medical chart reviews, semi-structured interviews, demographical profiles of each participant, and the Derogatis Sexual Functioning Inventory (DSFI) were the methods used to collect data over a four-month period. Both quantitative and qualitative research methods were incorporated in the design and evaluation of the study. Frequencies, contingency analysis, Pearson's coefficient of correlation, t-tests, and ANOVA comprised the quantitative analysis. Data obtained from audio-taped interviews were analyzed qualitatively, and used for offering further insight and for facilitating the quantitative aspect of the analysis. Overall, there was sufficient evidence to suggest psychosexual morbidity among men who were treated with radiation therapy for prostate cancer. As well,there were a number of significant findings available to answer all of the posited research questions. The most significant findings were noted in post-treatment erectile ability and sexual activity. A post-treatment change in erectile ability was reported by eighty percent of men. Sixty percent of men noted a decrease in their ability to achieve an erection by reporting some morning stiffness only, penile rigidity insufficient for penetration, decreased control of erection, and loss of spontaneous erection. Other contributing factors associated with change in erectile status were: pain or altering sensation of orgasm, blood in ejaculate, pain and decreased amount of ejaculate, and penile numbness or pain. Eighty-two percent of men experienced a post-treatment change in sexual function, primarily due to the impact of decreasing erectile status. Only seven men reported that they experienced a decrease in desire mentally, whereas the vast majority did not experience any change in desire. Changes in foreplay, stress with optimal sexual positioning, and reduced spontaneity of sex, were other factors reported with the changes in sexual activity. The findings in this study broaden our understanding of what middle- to later-aged men feel and experience as they venture onward following treatment. This was the first study that evaluated available prospective data on pre-treatment erectile status and sexual activity. As well, this study was the first (with participant compliance rates of 100 percent) to have included an interview format to capture the views of such a large number of men. This study concluded with recommendations and implications for future research and practice as we move in the direction of understanding what is necessary for preserving psychosexual well being and enhancing quality of life in men treated with radiation therapy for prostate cancer.

Weight-preoccupation, personality and depression in university students : an interactionist perspective

The present research was designed to examine Beck's (1983; 1987) cognitive diathesis-stress model of depression in a new context. Specifically, this cross-sectional study investigated whether Beck's cognitive-personality traits of sociotropy and autonomy interacted with a specific daily hassle/stressor, weightpreoccupation, in the prediction of depressed mood in women and men. Weightpreoccupation was chosen as the particular daily stressor, because, according to Kanner, Coyne, Schaeffer, and Lazarus (1981). concern about weight and physical appearance were two of the most troublesome daily hassles among university students. ContraIy to current stereotypes, men also express concerns with weight and appearance (Cash, Winstead, &, landi, 1986), in both the direction of weight loss and weight/muscle gain (Drewnowski &, Yee, 1987). Thus, unique to this study was the examination of weight-preoccupation in men, not only in the direction of weight loss, but also in the direction of weight and muscle gain. Two hundred and fifty-one undergraduates were administered the revised SociotropyAutonomy Scale (SAS), the Beck Depression Inventory (BDij, the Hassles and Uplifts Scale, the Eating Disorders Inventory (EDI), and the Restraint Scale (RS). Through a process of model building, a final model was devised in which depression (ie., BDI total scores) was regressed on personality (Le., SAS Sociotropy) and weight-preoccupation (i.e., Drive for Thinness, Body Dissatisfaction, and the Restraint Scale). Separate hierarchical multiple regression analyses, with BDI as the dependent variable, were carried out for each of the 2 3 weight-preoccupation variables. Results revealed a specific congruent interaction between weight,..preoccupation and personality. Specifically, drive for thinness and body dissatisfaction interacted with sociotropy to predict depressed mood in both women and men, but the interaction between sociotropy and the Restraint Scale was marginal. Findings suggested that weight-preoccupied women and men experienced depressed mood to the extent that they were characterized as more highly sociotropic. As predicted, personality (i.e., sociotropy), moderated the relationship between daily stress (i.e., weight-preoccupation) and depression. Thus, results revealed that the proposed diathesis-stress model seemed to operate in the same manner for women and men. Moreover, the examination of weightpreoccupation among men (i.e., in the direction of both weight loss and weight/muscle gain) further revealed that, when curvilinearity was taken into account, highly sociotropic men, who had a low desire to gain weight and muscle mass (i.e., most likely those who desired to lose weight), experienced higher levels of depressed mood than those who had a "medium" desire for weight and muscle gain. However, the highest levels of depressed mood was experienced by highly sociotropic men who were highly weight-preoccupied in the direction of wanting to gain weight and muscle mass. In addition, possible reasons for the present fmdings, as wen as iimitations and impiicalions for future research are discussed.

Bone speed of sound in overweight and normal-weight girls and adolescents

Over the last two decades, the prevalence of obesity in the general population has been steadily increasing. Obesity is a major issue in scientific research because it is associated with many health problems, one of which is bone quality. In adult females, adiposity is associated with increased bone mineral density, suggesting that there is a protective effect of fat on bone. However, the association between adiposity and bone strength during childhood is not clear. Thus, the purpose of this study was to compare bone strength, as reflected by speed of sound (SOS), of overweight and obese girls and adolescents with normal-weight age-matched controls. Data from 75 females included normal-weight girls (G-NW; body fat:::; 25%; n = 21), overweight and obese girls (GOW; body fat ~ 28%; n = 19), normal-weight adolescents (A-NW, body fat:::; 25%; n = 13) and overweight and obese adolescents (A-OW; body fat ~ 28%; n = 22). Nutrition was assessed with a 24-hour recall questionnaire and habitual physical activity was measured for one week using accelerometry. Using quantitative ultrasound (QUS; Sunlight Omnisense™), bone SOS was measured at the distal radius and mid-tibia. No differences were found between groups in daily total energy, calcium or vitamin D intake. However, all groups were below the recommended daily calcium intake of 1300 mg (Osteoporosis Canada, 2008). Adolescents were significantly less active than girls (14.7 ± 0.6 vs. 6.3 ± 0.6% active for G and A, respectively). OW accumulated significantly less minutes of moderate-to-very vigorous physical activity per day (MVPA) than NW in both age groups (114 ± 6 vs. 57 ± 5 min/day for NW and OW, i respectively). Girls had significantly lower radial SOS (3794 ± 87 vs. 3964 ± 64 mls for G-NW and A-NW, respectively), and tibial SOS (3678 ± 86 vs. 3878 ± 52 mls for G-NW and A-NW, respectively) than adolescents. Radial SOS was similar in the two adiposity groups within each age group. However, tibial SOS was lower in the two overweight groups (3601 ± 75 mls vs. 3739 ± 134 mls for G-OW and A-OW, respectively) compared with the age-matched normal-weight controls. Body fat percentage negatively correlated with tibial SOS in the study sample as a whole (r = -0.30). However, when split into groups, percent bo~y fat correlated with tibial SOS only in the A-OW group (r = -0.53). MVPA correlated with tibial SOS (r = 0.40), once age was partialed out. In conclusion, in contrast withthe higher bone strength characteristic of obese adult women, overweight and obese girls and adolescents are characterized by low tibial bone strength, as assessed with QUS. The differences between adiposity groups in tibial SOS may be at least partially due to the reduced weight-bearing physical activity levels in the overweight girls and adolescents. However, other factors, such as hormonal influences associated with high body fat may also playa role in reducing bone strength in overweight girls. Further research is required to reveal the mechanisms causing low bone strength in overweight and obese children and adolescents.