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Patty S. Freedson

Precise quantification of physical activity is necessary in order to evaluate the relationship between physical activity and various types of disease and/or risk factors associated with disease. With the emergence of the study of the origins of coronary heart disease risk factors in children, it is imperative that accurate measurement of physical activity in the pediatric population be obtained. This review critically evaluates various field measures of physical activity in children including motion sensors, questionnaires, and heart rate. A new heart-rate quantification procedure is also presented that may provide an index of the quality of physical activity.

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Ann F. Maliszewski and Patty S. Freedson

In this study, running economy differences between boys and men at a common speed (ABS = 9.6 kph) and at a relative speed adjusted for body size (REL = 3.71 leg lengths per second) were examined. The caloric cost relative to mass was significantly higher for the boys for ABS (men = .17, boys = .20), but not for REL (both .19). The relative heart rate (%HRmax) and ventilatory equivalent were higher for the boys at ABS, but not at REL. Boys had significantly higher stride frequencies in both conditions. Stride length/leg length was greater for boys during ABS, and for men during REL. Respiratory exchange ratios (RERs) were not different at ABS (men = .94, boys = .96), but during REL, boys had a significantly lower RER (.93 vs. .98). Running economy differences between adults and children are reduced when speeds are adjusted relative to body size. This model may be useful for identifying developmentally based differences in the physiology and biomechanics associated with exercise.

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James R. Morrow Jr. and Patty S. Freedson

This review summarizes the research relating physical activity to aerobic fitness among adolescents. A brief description of commonly used physical activity and aerobic fitness measures is presented, followed by an interpretation of the literature that suggests a small to moderate relationship between physical activity and aerobic fitness in this population (typical correlation of .16-17). Dose-response data are lacking, which makes it difficult to offer definitive conclusions concerning the amount of physical activity necessary to elicit change in aerobic capacity. Nevertheless, recommendations about the type, amount, and quality of physical activity for adolescents are presented. Recommendations are based on a summary of the research data on daily physical activity and aerobic fitness in adolescents. Further research is needed to investigate the association between habitual physical activity and aerobic fitness in adolescents where the a priori goal is to identify a threshold of daily physical activity necessary for an aerobic benefit associated with enhanced health.

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Heidi L. Keller, Stephen E. Tolly, and Patty S. Freedson

The sport of wrestling often encourages participants to engage in extreme weight loss practices in order to compete in a weight class one to three weight categories below normal weight. This review discusses the prevalence of the problem, methods wrestlers use to accomplish weight loss, and the health and performance consequences of rapid weight loss, with particular emphasis on weight cycling and minimal safe wrestling weight assessment. Some useful and practical recommendations for minimizing extreme weight loss practices are presented. Several state wrestling associations have adjusted their rules and regulations based on recommendations by organizations such as the American College of Sports Medicine to reduce the prevalence of the problem. Nevertheless, extreme weight loss continues to be a concern among health professionals, particularly with regard to health and performance.

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Joseph Hamill, Patty S. Freedson, Priscilla M. Clarkson, and Barry Braun

This study involved an 8-day protocol to determine the effects of delayed-onset muscle soreness (DOMS) on the mechanics of the lower extremity and on oxygen consumption during level running. On Day 1 the subjects, 10 healthy female recreational runners, were administered a treadmill max V̇O2 test. They completed a 30-min downhill run on Day 3 to induce muscle soreness. On Days 2, 5, and 8 they completed a 15-min level run at a speed corresponding to 80% of V̇O2max. Subsequent to each run the subjects completed a muscle soreness questionnaire and a blood sample was taken for creatine kinase (CK) analysis. Data analysis revealed statistically significant between-day differences for perceived muscle soreness and CK activity. However, metabolic cost was not different between days. There were significant differences between days in maximum ankle support dorsiflexion and plantar flexion and maximum knee flexion during both support and swing. None of the global parameters describing the total stride produced significant differences between Days 2 and 5. Therefore DOMS appeared to have little effect on V̇O2 and a small effect on the kinematics of the lower extremity.

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David R. Bassett, Patty S. Freedson, and Dinesh John

In recent years, there has been tremendous growth in the use of wearable activity trackers in biomedical research. Activity trackers are also becoming more popular with consumers, who are able to share their data with researchers and practitioners. Steps per day is a useful variable that is estimated from most wearable activity trackers. It has intuitive meaning, is strongly associated with health variables, and has the potential to be standardized across devices. Activity trackers and other wearable medical devices could provide new information on health-related behaviors and their interaction with genetic and environmental variables. If integrated into medical practice, wearable technologies could help motivate patients to change their health behaviors and might eventually be used to diagnose medical conditions. The convergence of wearable medical devices, computer applications, smart phones, and electronic medical records could influence the practice of lifestyle medicine.

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Barry Braun, Priscilla M. Clarkson, Patty S. Freedson, and Randall L. Kohl

The effects of dietary supplementation with Coenzyme Q10 (CoQlO), a reputed performance enhancer and antioxidant, on physiological and biochemical parameters were examined. Ten male bicycle racers performed graded cycle ergometry both before and after being given 100 mg per day CoQlO or placebo for 8 weeks. Analysis of variance showed a significant difference between groups for postsupplementation serum CoQ10. Although both groups demonstrated training related improvements in all physiological parameters over the course of the study, there were no significant differences between the two groups (p>.05). Both groups showed a 21 % increase in serum MDA (an index of lipid peroxidation) after the presupplementation exercise test. After 8 weeks this increase was only 5 % , and again was identical for both groups. Supplementation with CoQlO has no measurable effect on cycling performance, VO2max, submaximal physiological parameters, or lipid peroxidation. However, chronic intense training seems to result in marked attenuation of exercise-induced lipid peroxidation.

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James F. Sallis, Wendell C. Taylor, Marsha Dowda, Patty S. Freedson, and Russell R. Pate

Correlates of physical activity were examined in young people in grades 1 through 12, and analyses were conducted separately for eight age/grade and sex subgroups. Twenty-one explanatory variables were assessed by parental report. Physical activity was assessed in 781 young people via parent report, and 200 wore an accelerometer for seven days. Between 11% and 36% of parent-reported child vigorous physical activity was explained. The most consistent correlates were peer support and use of afternoon time for active rather than sedentary recreation. Peer support was the only significant correlate of objectively monitored activity in multiple subgroups.

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Christine J. Ebbeling, Joseph Hamill, Patty S. Freedson, and Thomas W. Rowland

This study compared metabolic, kinematic, and efficiency parameters in 10 boys and 10 men while walking at speeds of similar relative intensities. Heart rate and oxygen consumption were monitored throughout the exercise and a sagittal view of the subject was filmed for biomechanical analysis. Angles of the hip, knee, and ankle changed with an increase in walking speed. There were kinematic differences between children and adults at the hip and knee. Heart rate and oxygen consumption (ml•kg−1•min−1) were greater in the children. There were no significant differences between children and adults when VO2 was normalized by body surface area rather than body mass. The work done by the body was greater in the adults, whereas the energy used was greater in the children. Therefore the children appeared less efficient. The reasons for the efficiency difference are not well documented. Scaling effects may be involved and therefore should be taken into consideration when comparing children and adults.

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Ann F. Maliszewski, Patty S. Freedson, Chris J. Ebbeling, Jill Crussemeyer, and Kari B. Kastango

The Caltrac accelerometer functions as either an activity monitor that provides activity counts based on vertical acceleration as the individual moves about, or as a calorie counter in which the acceleration units are used in conjunction with body size, age, and sex to estimate energy expenditure. This study compared VO2 based energy expenditure with Caltrac estimated energy expenditure during three speeds of treadmill walking in children and adults. It also tested the validity of the Caltrac to differentiate between high and low levels of walking activity (activity counts). Ten boys and 10 men completed three randomly assigned walks while oxygen consumption was monitored and Caltrac estimates were obtained. The results indicate that the Caltrac does not accurately predict energy expenditure for boys and men across the three speeds of walking. Although there were no significant differences between actual and predicted energy expenditure values, the standard errors of estimate were high (17-25%) and the only significant correlation was found for men at the fastest walking speed (r=.81). However, the 95% confidence intervals of the activity counts and energy expenditure estimates from the Caltrac support its use as an activity monitor during walking.