Tinker D. Murray

Rationale, design and methods of the HEALTHY study physical education intervention component

The HEALTHY primary prevention trial was designed to reduce risk factors for type 2 diabetes in middle school students. Middle schools at seven centers across the United States participated in the 3-year study. Half of them were randomized to receive a multi-component intervention. The intervention integrated nutrition, physical education (PE) and behavior changes with a communications strategy of promotional and educational materials and activities. The PE intervention component was developed over a series of pilot studies to maximize student participation and the time (in minutes) spent in moderate-to-vigorous physical activity (MVPA), while meeting state-mandated PE guidelines. The goal of the PE intervention component was to achieve ⩾150 min of MVPA in PE classes every 10 school days with the expectation that it would provide a direct effect on adiposity and insulin resistance, subsequently reducing the risk of type 2 diabetes in youth. The PE intervention component curriculum used standard lesson plans to provide a comprehensive approach to middle school PE. Equipment and PE teacher assistants were provided for each school. An expert in PE at each center trained the PE teachers and assistants, monitored delivery of the intervention and provided ongoing feedback and guidance.

The energy cost of horizontal walking and running in adolescents

PURPOSE This study developed and cross-validated generalized equations for predicting VO2 (mL x kg(-1) x min(-1)) and caloric expenditure (kcal x kg(-1) x min(-1)) during horizontal walking and running in adolescents. METHODS Subjects were 47 male and 35 female adolescent volunteers, ages 12-18. Each subject underwent a submaximal treadmill exercise test to determine VO2 at randomly selected walking and jogging speeds (67-215 m x min(-1)). Caloric expenditure was estimated from VO2 and RER. Multiple regression was used to develop prediction equations for estimating VO2 and caloric expenditure from a derivation sample of 77 random observations, both walking and running. RESULTS The group relationship between running speed and energy cost in the derivation sample was linear, whereas the relationship between walking speed and energy cost was quadratic. Gender, age, and height each failed to account for significant additional variation in energy cost after speed and mode were considered. Skinfolds accounted for a small yet significant amount of additional variation in energy cost. The derived equations were cross-validated on a sample of 76 separate random observations. The cross-validation statistics are: for VO2, R = 0.95, error = 3.58 mL x kg(-1) x min(-1), and for caloric expenditure, R = 0.94, error = 0.019 kcal x kg(-1) x min(-1). Most selected adult equations consistently underestimated both VO2 and caloric expenditure in the cross-validation sample. CONCLUSIONS These results suggest that in adolescents, within the range of speeds tested, the relationship between speed of movement and energy cost for running is linear, but for walking is curvilinear. Also, adult models for estimating VO2 or caloric expenditure do not account for the higher relative energy cost of walking and running in adolescents.

HEALTHY Intervention: Fitness, Physical Activity, and Metabolic Syndrome Results

PURPOSE This study aimed to assess the effect of the HEALTHY intervention on the metabolic syndrome (Met-S), fitness, and physical activity levels of US middle-school students. METHODS Cluster randomized controlled trial conducted in 42 (21 intervention) US middle schools. Participants were recruited at the start of sixth grade (2006) when baseline assessments were made, with post-assessments made 2.5 yr later at the end of eighth grade (2009). The HEALTHY intervention had four components: 1) improved school food environment, 2) physical activity and eating educational sessions, 3) social marketing, and 4) revised physical education curriculum. Met-S risk factors, 20-m shuttle run (fitness), and self-reported moderate to vigorous physical activity (MVPA) were assessed at each time point. Ethnicity and gender were self-reported. Obesity status (normal weight, overweight, or obese) was also assessed. RESULTS At baseline, 5% of the participants were classified with Met-S, with two-thirds of the males and one-third of the females recording below average baseline fitness levels. Control group participants reported 96 min of MVPA at baseline with 103 min reported by the intervention group. There were no statistically significant (P < 0.05) differences in Met-S, fitness, or MVPA levels at the end of the study after adjustment for baseline values and confounders. There were no differences in any ethnic, obesity, or ethnic × obesity subgroups for either gender. CONCLUSIONS The HEALTHY intervention had no effect on the Met-S, fitness, or physical activity levels. Approaches that focus on how to change physical activity, fitness, and Met-S using nonschool or perhaps in addition to school based components need to be developed.

Validation of a 20-Minute Steady-State Jog as an Estimate of Peak Oxygen Uptake in Adolescents

Distance run tests are often used to estimate peak oxygen uptake (peak VO2) in children. This study examined the concurrent validity of a 20-min steady-state jog (20MSSJ). The sample consisted of 43 boys and 32 girls who performed a 20MSSJ and completed a maximal treadmill test 1 week later. Peak VO2 was measured by indirect calorimetry. Subject characteristics were as follows: boys, mean age = 15.1 +/- 1.0 years, mean peak VO2 = 46.4 +/- 7.7 ml.kg-1 x min-1, mean 20MSSJ = 2.3 +/- 0.5 miles; girls, mean age = 15.3 +/- 1.1 years, mean peak VO2 = 40.4 +/- 5.1 ml.kg-1 x min-1, mean 20MSSJ = 2.1 +/- 0.5 miles. The correlation between 20MSSJ and peak VO2 was .68 across boys and girls. The regression slopes of the boys and girls were common, but the intercepts differed, F (1, 72) = 10.9, p < .05. The influence of weight and skinfold fat was examined. Separate models were developed, and the R for each was increased to .79 (SEE = 4.45 ml.kg-1 x min-1) for the model using weight and .80 (SEE = 4.36 ml.kg-1 x min-1) for the model using sum of skinfolds. The regression equations are as follows: peak VO2 = 35.10 + 6.19 (Run) + 2.96 (Gender) -0.26 (Skinfold fat) peak VO2 = 33.94 + 7.64 (Run) + 5.84 (Gender) -0.18 (Weight) (Run = 20MSSJ performance in miles; Gender; females = 0, males = 1; Skinfold fat = sum of two-site skinfolds in mm; Weight = body weight in kg).(ABSTRACT TRUNCATED AT 250 WORDS)

The Association Between Waist Circumference and FITNESSGRAM® Aerobic Capacity Classification in Sixth-Grade Children.

Cardiorespiratory fitness is often assessed through measures of maximal oxygen uptake, sometimes referred to as aerobic capacity (26). The importance of adequate aerobic capacity for optimal health has been observed in numerous studies examining both adults (1,2,20) and children (17,24). An increased risk of overweight and metabolic syndrome in adults can result from a reduction in aerobic capacity from childhood to adolescence (4,11).

High-Activity Skills Progression A Method for Increasing MVPA

JOPERD • Volume 78 No. 7 • September 2007 T he “method wars” (teaching method A versus teaching method B) has a long and mixed history in educational research (Brophy & Good, 1986). One year, physical educators are trained that method A is a better way to teach game skills compared to method B, only to discover the next year that little-known method C is really best. It is certainly healthy, but confusing, for the profession to explore the merits of various teaching methodologies. Michael Metzler (2005), in his text Instructional Models for Physical Education, summarizes this phenomenon simply, “...there can be no one best way to teach physical education” (p. 14). We agree with Metzler and do not contend that the approach outlined in this article is the “best way.” We submit the high-activity skills progression (HASP) to readers to enhance their teaching repertoire and believe that it is a positive method by which to balance student engagement and ever-increasing class sizes. Academic achievement, or motor skill acquisition in the fi eld of physical education, has been the most frequent variable under study when exploring student engagement. However, Sallis and McKenzie’s 1991 landmark article, “Physical Education’s Role in Public Health,” made many health experts question this view. In their article, Sallis and McKenzie provided a strong rationale for physical educators to consider using their fi eld as an avenue for the promotion of physical activity, and specifi cally moderate-to-vigorous physical activity (MVPA). Although target heart-rate values representing MVPA in adolescents are not consistently reported in the research literature, many exercise physiologists consider heart rate responses from 130 to 140 beats per minute to represent an MVPA threshold for adolescents (Fairclough & Stratton, 2005; Fairclough & Stratton, 2006). Sallis and McKenzie (1991) stated that physical education in schools is the only public institution currently responsible for promoting physical activity for all children and believed that physical education is an investment in society’s economic and health care future. Wallhead & Buckworth (2004) agreed and reported that participation in physical education is an effective method by which physical activity levels are positively affected in youths. Their literature review of physical education theory and research revealed that enjoyment of physical activity often results from successful mastery experiences, which lead to increased self-perceived skill competence and enjoyment. Several studies reviewed by Wallhead and Buckworth (2004) revealed that there is a High-Activity Skills Progression A Method for Increasing MVPA

METABOLIC COST OF AEROBIC DANCE BENCH STEPPING AT VARYING CADENCES AND BENCH HEIGHTS

To determine the metabolic and cardiovascular responses of aerobic dance bench stepping (ADBS) at commonly used cadences and bench heights, 30 women (19–47 years of age) performed a graded maximal treadmill test and four 8-minute submaximal ADBS routines. Subjects followed identical videotape sequences of basic ADBS movements at cadences of 125 and 130 beats·min-1 at bench heights of 6 and 8 in. Physiological measurements were taken during each minute of each test. Mean values calculated from the last 3 minutes were used for data analysis. Although there were no physiological differences between ADBS at the 2 cadences, there were significant physiological differences between ADBS at the 2 bench heights. On average, a 2-in. increase in bench height, increased heart rate, Vo2, and rating of perceived exertion by 10 beats·min-1, 3.09 ml·kg-1 min-1, and 1.53, respectively. In conclusion, it appears that bench height is more of a factor than cadence in increasing metabolic cost of ADBS. Results from this study provide information about the energy cost of ADBS at the common bench heights and cadences used in this study and, therefore, may be used to help aerobic participants select the proper bench height and cadence combination to control body weight and develop cardiorespiratory fitness safely and effectively.