Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: David A. Barlow, Dept. of Health, Nutrition, & Exercise Sciences. Includes bibliographical references.

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published_or_final_version / Education / Master / Master of Philosophy

High impact loading activities such as jumping, performed during childhood is advocated as one preventive method for increasing peak bone mass. Thus, we conducted a randomized intervention to examine the effect of high impact loading on bone mass in 34 pre-pubescent boys and girl over a seven month period. Participants meeting all inclusion criteria were randomized into either a jumping (n=18) or stretching group (n=16), both of which exercised three times per week for 15 minutes. The jumping group completed 100 jumps off 24-inch boxes each session, while the stretching group performed low impact flexibility exercises. Attrition was 85% (6 drop outs), with an overall attendance rate of 95%. Bone area and bone mineral content (BMC) was assessed using dual energy x-ray absorptiometery (Ho logic QDR 1000/W) for the left hip (femoral neck, greater trochanter, total hip), and lumbar spine (L[subscript 2-4]). Other measures were body composition (Lang skinfold calipers); physical activity (self-report questionnaire); and calcium intake (food survey). All measurements were assessed at baseline and 7 months. Significance is denoted as p<.05. Analysis of variance (ANOVA) revealed no baseline difference between groups for age, height, weight, body fat, physical activity, or calcium intake (p>.05); however, gender differences were found for FN BMC at baseline (p<.05). Repeated measures ANOVA identified significant group differences for FN BMC (p=.015), with a trend for significance for FN area (p=.055). No significant differences in BMC or bone area were found at all other skeletal sites (p>.05). No group by gender interactions were found at baseline or at the completion of the seven month intervention. No significant differences between groups were identified for body composition, physical activity, or calcium intake in repeated measures ANOVA analyses (p>.05). In conclusion, 100 jumps performed 3 times per week at approximately 8x body weight were sufficient to stimulate an osteogenic response at the femoral neck in pre-pubescent boys and girls. Implementing jumping exercises into regular physical activity programs during pre-pubescent growing years may increase peak bone mass and potentially reduce the onset of osteoporosis. / Graduation date: 1999

Thesis (Ph.D.)--Kent State University, 2008. / Title from PDF t.p. (viewed Jan. 5, 2010). Advisor: Jacob Barkley. Keywords: Peer Influence; children; physical activity; overweight. Includes bibliographical references (p. 96-108).

This thesis reports research which set out to examine whether exercise interventions embedded within school curricula could confer immediate benefits on students’ attentive functions; an aspect of cognition which is important for academic performance. A novel visuo-motor task was first developed to provide a more direct measure of participants’ attentive functioning than previously possible. Participants tracked moving targets on a tablet computer with a stylus, under single- (following one target) and dual-task conditions (intermittently switching between targets in response to a secondary cue-detection task). Manipulations of attentional load during this task affected adult (19-50 years) and children’s (8-12 years) mean accuracy and intra-individual variability. Age differences between these groups also existed, even after adjusting for motor-control differences. In children, outcomes on the task were validated against the Gordon Diagnostic System (a standardised test of sustained attention) and parental reports of children’s attentiveness (measured using standardised questionnaires). Differences in strategic behaviours whilst dual-tasking were also found that were dependent on task difficulty and whether or not a participant had a developmental disorder. Finally, a repeated-measures crossover-design trial (3 sessions one week apart at the same time of day) was conducted in two schools. Children’s (n = 39) visuo-motor task performance after a 15 min aerobic, moderate-to-vigorous intensity, bench-stepping Exercise Intervention was compared against their Baseline performance (assessment on week 1) and their Control performance (i.e. after a 15 min non-physically active Card-Sorting task). Exercise and Control were separate sessions, weeks 2 and 3, counterbalanced for order. Results indicated no differences between visuo-motor attention post-Exercise, post-Control or at Baseline. Two possible interpretations of this finding are: (1) Exercise does not affect attention acutely to a degree likely to be of subsequent benefit to children’s academic performance. (2) Immediate, short-term, benefits from exercise are conferred on other cognitive processes but not sustained or divided attention.

Exercise is known to have a long-term benefit on bone mass in children, but little is known about the underlying mechanisms. The purpose of this investigation was to determine the acute effect of exercise on bone metabolism in pre-pubertal children. Biochemical markers of bone formation were measured in 4 male and 4 female children, 8 to 11 years of age. Each subject performed 50 vertical jumps. Serum osteocalcin and C-telopeptide of type I collagen (CTx), were determined prior to exercise and at 24 and 72 hours post exercise as indicators of bone formation and bone resorption. Osteocalcin concentration was 8.20 ± 3.65 ng•mL"' before exercise, and was 7.1 ± 3.7 ng•mL-' and7.4 ± 3.7 ng•mL-' at 24 hours and 72 hours post exercise, respectively (P > 0.05). CTx concentrations were 11632 ± 4093 pmol•L-' before exercise, and was 9831 ± 3159 pmol•L-' at 24 hours and 9722 ± 2426 pmol•L7' at 72 hours post exercise (P > 0.05). In conclusion an acute bout of ballistic exercise appears to have no effect on bone metabolism in pre-pubertal children. / School of Physical Education

Physiological and thermoregulatory responses to exercise in a cold environment have been well documented in adults. However, limited information is available regarding the physiological and perceptual responses in children exercising in a cold environment. The purpose of this study was to compare the metabolic, cardiorespiratory, and perceptual responses of children performing submaximal exercise in a cold and neutral temperature. Sixteen children (8 male, 8 female), with a mean ± SD age, height, and weight of 11.4 ± 0.9 yrs, 149.4 ± 8.8 cm, and 40.0 ± 7.2 kg, respectively, participated as subjects in this study. Laboratory assessments occurred on three different days. On the first day of testing, a graded exercise test on a cycle ergometer was administered to determine ventilatory threshold (VT) and VO2max (1.21 + 0.18 I-min-1, 1.74 + 0.21 1-min-1, respectively). On seperate days, subjects cycled in 5°C or 22°C for 30 minutes at an intensity corresponding to VT (103 ± 11 W). The order of testing was counterbalanced. V02, HR, and RPE were assessed every 5 minutes; blood samples from an indwelling catheter were taken every 10 minutes for blood lactate (LA) determination. Data were analyzed using arepeated measure ANOVA. V02, VE, HR, and LA responses were significantly (p < 0.05) higher in the cold (1.36 ± 0.18 vs 1.14 ± 0.18 1-min-1, 35.6 ± 5.3 vs 29.2 ± 5.8 1-min-1, 165.7 ± 12.3 vs 155.9 ± 12.9 bpm, and 2.18 ± 1.18 vs 1.53 ± 0.84 mmol-l-1, respectively) (Mean ± SE). RPE values tended to be higher in the cold (13.6 + 3.4 vs 12.6 + 2.9); however, the difference was not statistically significant (p > 0.05). More research is needed to determine the factors responsible for cold-induced alterations in the exercise response. / School of Physical Education

The purpose of this study was to examine the effects of warm-up intensity on anaerobic performance and recovery in children. Six male children (11.0 ± 0.6 yr) performed an IAT following a mild (85% of VAT), intense (115% of VAT), or no warm-up protocol. VAT was determined during a previously performed GXT. A catheter allowed for multiple blood samples drawn thoughout each trial. Performance indices, PP, MP, TW, and FI%, were not significantly different across trials. Blood analysis revealed significant interactions for recovery [LA] and [HC03-], although no significant interaction for pH values. There was also a significant interaction for V02 recovery pattern. The ALA (5.2 vs. 7.1 mmol•1-1, respectively) and AHC03- (6.1 vs. 8.4 mmol-l-1, respectively) were significantly lower for the AVAT trial compared to NWU trial. These data indicate that the AVAT warm-up resulted in less acid-base balance disturbance suggesting greater dependence on aerobic metabolism during the IAT. / School of Physical Education