Adrenal Hormone and Metabolic Biomarker Responses to 30 min of Intermittent Cycling Exercise in Breast Cancer Survivors.

The aim of this study was to explore the effect of one bout of aerobic exercise on epinephrine, norepinephrine, cortisol, glucose, lactate, and free fatty acid (FFA) responses in breast cancer survivors and healthy controls. 9 female breast cancer survivors and 9 women without a history of cancer completed 30 min of cycle ergometry exercise at 60% of VO2peak. Blood samples were taken pre-exercise, immediately post-exercise, and 2 h post-exercise from which plasma concentrations of study variables were measured. Immediately and 2 h post-exercise, increases were observed in epinephrine (control group only) norepinephrine (both groups), lactate (both groups), and FFA (both groups immediately post-exercise; breast cancer survivor group only at 2 h post-exercise) (p<0.05). Cortisol decreased immediately and 2 h post-exercise in the control group while glucose decreased immediately post-exercise in the breast cancer survivor group (p<0.05). In conclusion, breast cancer survivors appeared to display attenuated epinephrine, cortisol, and lactate responses while displaying larger magnitude changes in glucose and FFA responses compared to controls. These preliminary findings may have implications for the regulation of metabolism during exercise in breast cancer survivors.

Self-reported and accelerometer-measured physical activity by body mass index in US Hispanic/Latino adults: HCHS/SOL.

The association between obesity and physical activity has not been widely examined in an ethnically diverse sample of Hispanic/Latino adults in the US. A cross-sectional analysis of 16,094 Hispanic/Latino adults 18-74 years was conducted from the multi-site Hispanic Community Health Study/Study of Latinos (HCHS/SOL). Body mass index (BMI) was measured and categorized into normal, overweight, and obese; underweight participants were excluded from analyses. Physical activity was measured using the 16-item Global Physical Activity Questionnaire and by an Actical accelerometer. Minutes/day of physical activity and prevalence of engaging in ≥ 150 moderate-vigorous physical activity (MVPA) minutes/week were estimated by BMI group and sex adjusting for covariates. No adjusted differences were observed in self-reported moderate (MPA), vigorous (VPA), or MVPA across BMI groups. Accelerometry-measured MPA, VPA, and MVPA were significantly higher for the normal weight (females: 18.9, 3.8, 22.6 min/day; males: 28.2, 6.1, 34.3 min/day, respectively) compared to the obese group (females: 15.3, 1.5, 16.8 min/day; males: 23.5, 3.6, 27.1 min/day, respectively). The prevalence of engaging in ≥ 150 MVPA minutes/week using accelerometers was lower compared to the self-reported measures. Efforts are needed to reach the Hispanic/Latino population to increase opportunities for an active lifestyle that could reduce obesity in this population at high risk for metabolic disorders.

The family partners for health study: a cluster randomized controlled trial for child and parent weight management.

OBJECTIVE: The purpose of this study was to test a two-phased nutrition and exercise education, coping skills training, and exercise intervention program for overweight or obese low-income ethnic minority 2nd to 4th grade children and their parents in rural North Carolina, USA. METHODS: A cluster randomized controlled trial was carried out with 358 children (7-10 years) and a parent for each child (n=358). General linear mixed models were used to determine the effects of the intervention on weight, adiposity, health behaviors, and eating and exercise self-efficacy by examining changes in children and parents from baseline to completion of the study (18 months). RESULTS: At 18 months, children in the experimental group did not have a significantly decreased body mass index (BMI) percentile (P=0.470); however, they showed a reduction in the growth rate of their triceps (P=0.001) and subscapular skinfolds (P<0.001) and an improvement in dietary knowledge (P=0.018) and drank less than one glass of soda per day (P=0.052) compared with the control group. Parents in the experimental group had decreased BMI (P=0.001), triceps (P<0.001) and subscapular skinfolds (P<0.001) and increased nutrition (P=0.003) and exercise (P<0.001) knowledge and more often drank water or unsweetened drinks (P=0.029). At 18 months, children in the experimental group did not show significant improvement in eating (P=0.956) or exercise self-efficacy (P=0.976). Experimental parents demonstrated improved socially acceptable eating self-efficacy (P=0.013); however, they did not show significant improvement in self-efficacy pertaining to emotional eating (P=0.155) and exercise (P=0.680). CONCLUSION: The results suggest that inclusion of children and parents in the same intervention program is an effective way to decrease adiposity and improve nutrition behaviors in both children and parents and improve weight and eating self-efficacy in parents.

Compensation or displacement of physical activity in middle-school girls: the Trial of Activity for Adolescent Girls.

OBJECTIVE: The 'activitystat' hypothesis suggests that increases in moderate-to-vigorous physical activity (MVPA) are accompanied by a compensatory reduction in light physical activity (LPA) and/or an increase in inactivity to maintain a consistent total physical activity level (TPA). The purpose of this study was to identify the evidence of compensation in middle-school girls. SUBJECTS: Participants were 6916, 8th grade girls from the Trial of Activity for Adolescent Girls (TAAG). DESIGN: Inactivity and physical activity were measured over 6- consecutive days using accelerometry (MTI Actigraph). A within-girl, repeated measures design was used to assess associations between physical activity and inactivity using general linear mixed models. RESULTS: Within a given day, for every one MET-minute more of inactivity, there was 3.18 MET-minutes (95% confidence interval (CI): -3.19, -3.17) less of TPA (activity >2 METS) on the same day. Daily inactivity was also negatively associated with TPA on the following day. Each additional minute of MVPA was associated with 1.85 min less of inactivity on the same day (95% CI: -1.89, -1.82). Daily MVPA was also negatively associated with inactivity the following day. CONCLUSION: Our results, based on 6 days of observational data, were not consistent with the 'activitystat' hypothesis, and instead indicated that physical activity displaced inactivity, at least in the short term. Longer intervention trials are needed, nevertheless our findings support the use of interventions to increase physical activity over discrete periods of time in middle-school girls.

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 > or =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.

Vigorous physical activity and cytokines in adolescents.

Habitual physical activity and chronic exercise may positively influence circulating cytokines in youth as in adults. The purpose of this study was to determine if adolescents reporting higher amounts of physical activity had a better cytokine profile independent of weight status. We compared the concentrations of cytokines in highly active (n = 60) and less active adolescents (n = 60) of different weight status [normal weight (BMI < 75th percentile), and overweight (BMI > 95th percentile)]. Vigorous physical activity (VPA) was obtained through a questionnaire and included activities with a MET level of > or =6. Adiponectin, resistin, TNF-alpha and IL-6 were measured in fasting plasma samples. Anovas indicated that girls with high VPA had higher adiponectin than girls with low VPA (P < 0.05), but similar resistin, TNF-alpha and IL-6 concentrations (P > 0.05). Boys with high VPA had only a trend to lower resistin than those with low VPA (P = 0.052). Differences between VPA groups were independent of weight status. In adolescents, higher amounts of accumulated habitual VPA may improve some cytokines, reducing the risk of inflammation associated with increased adiposity and insulin resistance. The effect of physical activity appears to be independent of weight status.

Body fat and circulating leukocytes in children.

OBJECTIVE: To determine the effects of obesity on baseline levels of circulating granulocytes, monocytes, and lymphocyte subtypes in otherwise healthy children. DESIGN: Two group comparison of leukocytes in normal weight control and overweight children. SUBJECTS: In total, 38 boys and girls, ages 6-18 years, divided in two groups: normal weight, (NW, BMI<85th %tile, n=15) and overweight (OW, body mass index (BMI)>85th %tile, n=23). MEASUREMENTS: BMI obtained from direct measures of height and body mass. Body fat was assessed by DEXA. Complete blood counts (CBC) were obtained by standard clinical hematology methods and surface antigen staining by flow cytometry. RESULTS: The OW group compared to the NW group had increased total leukocytes counts (P=0.011), neutrophils (P=0.006), monocytes (P=0.008), total T (CD3) lymphocytes (P=0.022), and Helper T (CD4(+)) cells (P=0.003). Significant correlations were evident between leukocytes, and BMI percentile, BMI, or percent body fat. Neither lean body mass nor VO(2peak) per unit lean body mass were significantly related to any of the leukocytes. Percent body fat and BMI percentile were positively correlated (P<0.05) to total T cells (CD3) and/or helper T cells (CD4(+)). CONCLUSION: A group of 23 overweight children displayed elevated counts in most types of circulating immune cells, suggesting the presence of low-grade systemic inflammation, a known pathogenetic mechanism underlying most long-term complications of obesity. Our data provide an additional rationale for the importance of avoiding or correcting pediatric obesity.

Relationship between caloric intake, body composition, and physical activity to leptin, thyroid hormones, and cortisol in adolescents.

This study examined the interrelationships between (1) the hormones leptin, TSH, free T3, and cortisol, and (2) caloric intake, body composition, and physical activity to these select hormones in adolescent boys and girls (n = 125, age = 13.4 +/- 0.9 years). The data indicate that adolescent boys and girls have some common hormonal interrelationships. However, certain hormonal relationships are not in agreement with reports for adults, suggesting that researchers should not assume that all endocrine findings in adults are automatically applicable to adolescents.

Changes in common activities of 3rd through 10th graders: the CHIC study.

PURPOSE: This study was a longitudinal examination of the change in both the activities done and the intensity of those activities from childhood to adolescence. METHODS: Common activities were assessed by questionnaire initially on 656 subjects from 21 elementary schools; 50.5% were female, 83.4% were Caucasian, 20.6% African-American, and 6.0% were other races. RESULTS: Girls more often reported sedentary activities overall. Weighted least squares analyses showed boys consistently reported more vigorous activities than girls (P < 0.0008). African-American girls reported fewer vigorous activities than Caucasian or other race girls (P = 0.027). Sedentary activities were more frequently reported with increasing age (X2 P < 0.001). The youngest African-American and Caucasian boys reported similar activity patterns. However, boys from other races reported more intense activities until sixth and seventh grades when African-American boys began reporting more sedentary activities than Caucasians or other races (P = 0.004). During sixth-eighth grades, Generalized Estimating Equations (GEE) models show that girls with more advanced pubertal status reported more sedentary activities than girls who were less developed (P < 0.0001). For high school girls, race was a marginally significant predictor (P = 0.05) of activity status. Neither race nor pubertal status were significant factors in activities chosen by middle school boys. However, for male high school students, Caucasians were more likely than African-Americans to report vigorous activities (P = 0.005). CONCLUSIONS: Variation in activities by race within gender suggests that establishing activity patterns in youth may be race-specific as well as gender-specific and must be accounted for in designing physical activity interventions. Also, pubertal maturation is a factor in activity choices in middle school girls.

Determinants of adolescent physical activity and inactivity patterns.

OBJECTIVES: Despite recognition of the important influence of environmental determinants on physical activity patterns, minimal empirical research has been done to assess the impact of environmental/contextual determinants of physical activity. This article aims to investigate environmental and sociodemographic determinants of physical activity and inactivity patterns among subpopulations of US adolescents. We define environmental determinants as modifiable factors in the physical environment that impose a direct influence on the opportunity to engage in physical activity. The present research examines environmental and sociodemographic determinants of physical activity and inactivity with the implication that these findings can point toward societal-level intervention strategies for increasing physical activity and decreasing inactivity among adolescents. STUDY DESIGN AND METHODOLOGY: The study population consists of nationally representative data from the 1996 National Longitudinal Study of Adolescent Health on 17 766 US adolescents enrolled in US middle and high schools (including 3933 non-Hispanic blacks, 3148 Hispanics, and 1337 Asians). Hours/week of inactivity (TV/video viewing and video/computer games) and times/week of moderate to vigorous physical activity were collected by questionnaire. Outcome variables were moderate to vigorous physical activity and inactivity, which were broken into categories (physical activity: 0-2 times/week, 3-4 times/week, and >/=5 times/week; inactivity: 0-10 hours/week, 11-24 hours/week, and >/=25 hours/week). Sociodemographic and environmental correlates of physical activity and inactivity were used as exposure and control variables and included sex, age, urban residence, participation in school physical education program, use of community recreation center, total reported incidents of serious crime in neighborhood, socioeconomic status, ethnicity, generation of residence in the United States, presence of mother/father in household, pregnancy status, work status, in-school status, region, and month of interview. Logistic regression models of high versus low and medium physical activity and inactivity were used to investigate sex and ethnic interactions in relation to environmental and sociodemographic factors to examine evidence for the potential impact of physical education and recreation programs and sociodemographic factors on physical activity and inactivity patterns. RESULTS: Moderate to vigorous physical activity was lower and inactivity higher for non-Hispanic black and Hispanic adolescents. Participation in school physical education programs was considerably low for these adolescents and decreased with age. Participation in daily school physical education (PE) program classes (adjusted odds ratio [AOR]: 2.21; confidence interval [CI]: 1.82-2.68) and use of a community recreation center (AOR: 1.75; CI: 1.56-1.96) were associated with an increased likelihood of engaging in high level moderate to vigorous physical activity. Maternal education was inversely associated with high inactivity patterns; for example, having a mother with a graduate or professional degree was associated with an AOR of.61 (CI:.48-.76) for high inactivity. High family income was associated with increased moderate to vigorous physical activity (AOR: 1.43; CI: 1.22-1.67) and decreased inactivity (AOR:.70; CI:.59-.82). High neighborhood serious crime level was associated with a decreased likelihood of falling in the highest category of moderate to vigorous physical activity (AOR:.77; CI:.66-.91). CONCLUSIONS: These results show important associations between modifiable environmental factors, such as participation in school PE and community recreation programs, with activity patterns of adolescents. Despite the marked and significant impact of participation in school PE programs on physical activity patterns of US adolescents, few adolescents participated in such school PE programs; only 21.3% of all adolescents

Towards optimizing the timing of the pre-exercise meal.

The purpose of this study was to compare the effect a 6-hr versus 3-hr prefeeding regimen on exercise performance. The subjects were 8 active women (21.4 +/- 0.9 years, 60.4 +/- 2.4 kg, 19.9 +/- 1.3% body fat, and 165.6 +/- 2.1 cm). All women completed 2 exercise trials (separated by 3-6 d) on a treadmill where they ran at moderate intensity for 30 min with 30-s sprints at 5-min intervals, followed directly by increasing incrementally the grade until volitional fatigue was achieved. The exercise trials were performed 3 hr and 6 hr after consuming 40 +/- 3 kJ/kg meal. Time to exhaustion was 0.75 min shorter (p =.0001) for the 6-H trials compared to the 3-H trials. There were no significant differences in submaximal or peak oxygen uptake, heart rate, or rating of perceived exertion (p >.05). The 6-H trials compared to the 3-H trials resulted in.05 lower RERs (p =.0002), and a 2 mmol lower blood lactate at exhaustion (p =.012). Blood glucose levels and cortisol responses to exercise were similar between trials (p >.05). However, both resting and post exercise insulin levels were lower during 6-H trials. It was concluded that performance of moderate- to high-intensity exercise lasting 35-40 min is improved by consuming a moderately-high carbohydrate, low fat, low protein meal 3-hr before exercise compared to a similar meal consumed 6 hr prior to exercise. Thus, athletes should not skip meals before competition or training sessions.

The influence of physical activity, socioeconomic status, and ethnicity on the weight status of adolescents.

OBJECTIVE: This study examined the effects of physical activity, television viewing, video game play, socioeconomic status (SES), and ethnicity on body mass index (BMI). RESEARCH METHODS AND PROCEDURES: The sample was 2389 adolescents, 10 to 16 years of age (12.7 +/- 1.0 years); 1240 (52%) females and 1149 (48%) males; 77% white and 23% African American; from rural (77%) and urban (23%) settings. BMI and skinfolds were directly assessed. All other data were obtained from questionnaires. RESULTS: Watching television on non-school days was related to being overweight (p < 0.005). However, when BMI analyses were adjusted for ethnicity and SES, there were no significant effects of television viewing on BMI (p > 0.061). Increased hours of video game play enhanced the risk of being overweight for both genders when analyses were adjusted for ethnicity and SES (p < 0.019). In males, participation in as little as one high-intensity physical activity 3 to 5 days a week decreased the ethnic- and SES-adjusted relative risk of being overweight (RR = 0.646; CI: 0.427 to 0.977). For females, the ethnic- and SES-adjusted relative risk for being overweight was not significantly altered by physical activity. The logistic analyses further indicated the influence of low SES and African American ethnicity overshadowed any direct effect of television or videos. DISCUSSION: Because weight status of male adolescents appears to be more related to exercise habits than to television or video game habits, increased participation in high-intensity exercise appears to be important. For females, neither videos nor exercise habits appear to be related to risk of being overweight. However, ethnicity and SES may be important factors that can influence body weight status, while television viewing may be of some importance. Thus, programs to reduce obesity in female adolescent should focus their efforts in lower SES communities.

Effects of training status on the metabolic responses to high carbohydrate and high fat meals.

The purpose of this study was to determine if there is a difference between the way in which aerobically trained and untrained women metabolize fats and carbohydrates at rest in response to either a high-fat or high-carbohydrate meal. Subjects, 6 per group, were fed a high CHO meal (2068 kJ, 76% CHO, 23% fat, 5% protein) and a high fat meal (2093 kJ, 21% CHO, 72% fat, 8% protein) in counterbalanced order. Resting metabolic rate (RMR) was measured every half-hour for 5 hours. RMR was similar between groups. However, after ingesting a high CHO meal, trained subjects had a peak in metabolism at minute 60, not evident in the untrained subjects. In addition, postprandial RER from minutes 120-300 were lower and fat use was greater after the high CHO meal for the trained subjects. These results suggest that aerobically trained women have an accelerated CHO uptake and overall lower CHO oxidation following the ingestion of a high CHO meal.

Effects of improvement in aerobic power on resting insulin and glucose concentrations in children.

In this study we determined the influence of improving aerobic power (VO(2max)) on basal plasma levels of insulin and glucose of 11- to 14-year-old children, while accounting for body fat, gender, pubertal status, and leisure-time physical activity (LTPA) levels. Blood samples were obtained from 349 children after an overnight fast and analyzed for plasma insulin and glucose. Height, mass, body mass index (BMI), and sum of skinfolds (Sigma triceps + subscapular sites) were measured. LTPA levels and pubertal status were estimated from questionnaires, and VO(2max) was predicted from a cycle ergometry test. Regardless of gender, insulin levels were significantly correlated (P = 0.0001) to BMI, skinfolds, pubertal stage, and predicted VO(2max), but were not related to LTPA levels. Fasting glucose levels were not correlated to measures of adiposity or exercise (LTPA score, VO(2max)) for females; however, BMI and skinfolds were correlated for males (P < 0.006). The children then took part in an 8-week aerobic exercise program. The 60 children whose VO(2max) improved (>/=3 ml x kg(-1) x min(-1)) had a greater reduction in circulating insulin than the 204 children whose VO(2max) did not increase -16 (41) vs -1 (63) pmol x l(-1); P = 0.028. The greatest change occurred in those children with the highest initial resting insulin levels. Plasma glucose levels were slightly reduced only in those children with the highest insulin levels whose VO(2max) improved (P < 0.0506). The results of this study indicate that in children, adiposity has the most significant influence on fasting insulin levels; however, increasing VO(2max) via exercise can lower insulin levels in those children with initially high levels of the hormone. In addition, LTPA does not appear to be associated with fasting insulin status, unless it is sufficient to increase VO(2max).

A public health vs a risk-based intervention to improve cardiovascular health in elementary school children: the Cardiovascular Health in Children Study.

OBJECTIVES: This study sought to determine the population effects of both classroom-based and risk-based interventions designed to reduce cardiovascular disease risk factors in children. METHODS: Elementary school children (n = 2109; age range: 7-12 years) were randomized by school to a classroom-based intervention for all third and fourth graders, a risk-based intervention only for those with 1 or more cardiovascular disease risk factors, or a control group. The 8-week interventions involved both knowledge--attitude and physical activity components. RESULTS: School-level analyses showed that physical activity in the risk-based group and posttest knowledge in the classroom-based group were significantly higher than in the control group. With regard to trends shown by individual-level analyses, cholesterol dropped more in the classroom-based than in the control group, and skinfold thickness decreased 2.9% in the classroom-based group and 3.2% in the risk-based group (as compared with a 1.1% increase in the control group). CONCLUSIONS: Both classroom-based and risk-based interventions had positive effects on physical activity and knowledge, with trends toward reduced body fat and cholesterol. However, the classroom-based approach was easier to implement and evidenced stronger results than the risk-based intervention.

Adolescent physical activity and inactivity vary by ethnicity: The National Longitudinal Study of Adolescent Health.

OBJECTIVES: To determine the extent to which physical activity and inactivity patterns vary by ethnicity among subpopulations of US adolescents. STUDY DESIGN: Nationally representative data from the 1996 National Longitudinal Study of Adolescent Health of >14,000 US adolescents (including 3135 non-Hispanic blacks, 2446 Hispanics, and 976 Asians). METHODS: Hours per week of inactivity (TV viewing, playing video or computer games) and times per week of moderate to vigorous physical activity were collected by using questionnaire data. Multinomial logistic regression models of physical activity and inactivity were used to adjust for sociodemographic factors. RESULTS: Large ethnic differences are seen for inactivity, particularly for hours of television or video viewing per week (non-Hispanic blacks, mean = 20.4; non-Hispanic whites, mean = 13.1). Physical activity (>/=5 bouts of moderate to vigorous physical activity per week, 5-8 metabolic equivalents) is lowest for female and minority adolescents. Ethnic differences are far greater for inactivity than for moderate to vigorous physical activity. CONCLUSION: Minority adolescents, with the exception of Asian females, have consistently higher levels of inactivity. Results vary by sex; males have higher inactivity and physical activity, whereas lowest physical activity is found for non-Hispanic black and Asian females, although Asian females also have low inactivity and low levels of overweight. Overall, efforts to reduce the problem of adolescent overweight should focus on increasing activity levels of adolescents, particularly female, older, and major minority subpopulations.

Cardiovascular disease risk factors and obesity of rural and urban elementary school children.

Previous studies on the influence of a rural/urban setting on the prevalence of cardiovascular disease risk factors in children have not sufficiently controlled for socioeconomic status, race, gender, and perhaps, may not have included a representative sample of rural and urban children. This study compared the cardiovascular disease risk factors and rate of obesity of children living in rural and urban settings. It also determined the magnitude of the effect of the rural/urban setting on cardiovascular disease risk factors and obesity when controlling for race, socioeconomic status, and gender. The subjects were 2,113 third- and fourth-grade children; 962 from an urban setting and 1,151 from a rural setting. Height, weight, skinfolds, resting blood pressure, and total cholesterol levels were measured. Aerobic power (pVO2max) was estimated from cycle ergometry. Physical activity and smoking history were obtained from a questionnaire. Clustering analyses using adjustment for sample error indicated that total cholesterol, blood pressure, smoking, and physical activity levels of rural and urban children were not different (P > 0.10); however, body mass index and sum of skinfolds was greater for rural youth (P < 0.004). Logistic regression indicated that rural children had a 54.7 percent increased risk of obesity (P = 0.0001). This study's results indicate that, in children, a rural setting is associated with obesity, but not with the major risk factors associated with cardiovascular disease.

Predicting aerobic power in children. A comparison of two methods.

OBJECTIVE: To compare the accuracy of two equations for predicting VO2max of children using submaximal cycle ergometry. EXPERIMENTAL DESIGN: Repeated measures comparing treadmill measured maximal aerobic power (VO2max) with two methods of predicting VO2max using cycle ergometry testing. PARTICIPANTS: Thirty-three children (15 boys and 18 girls) aged 7-13 years served as subjects. MEASURES: Each child completed a treadmill graded exercise test (GXT) to volitional fatigue to assess VO2max. Each child also completed a progressive 9-min, three-stage, submaximal cycle ergometer test. Heart rates obtained during the last minute of each stage of the ergometer test were used to predict VO2max. Predictions were based on a gender-specific modification of the PWC170 (PWCGS) and a modification of the PWC195 using a 1.17 correction factor and an age and gender-adjusted estimate of resting metabolic rate. RESULTS: The correlations between both submaximal tests and the GXT were significant (p < 0.001); however, the correlation between the GXT and the PWC195 equation (r = 0.807) was higher than the correlation between the GXT and the PWCGS equation (r = 0.658). Analysis indicated that the PWCGS equation significantly underestimated the VO2max compared to either the GXT or PWC195 (GXT = 45.0 +/- 7.1, PWC195 = 44.7 +/- 6.2, PWCGS = 42.7 +/- 5.8 ml/kg/min; p < 0.01). CONCLUSIONS: These results suggest that although the gender-specific PWCGS method is easier to compute and may be acceptable, the modified PWC195 method is a more accurate estimate of VO2max in children.

Is physical activity or aerobic power more influential on reducing cardiovascular disease risk factors?

PURPOSE: This study determined the relationship between aerobic power (VO2max), physical activity (PA), and cardiovascular disease (CVD) risk factors. The study also determined how increased VO2max and increased PA levels influence CVD risk factors of 576 low-fit adults (VO2max < 30 mL.kg-1.min-1). METHODS: PA (Baeke questionnaire) and VO2max (submaximal cycle test) of 1664 law enforcement trainees were evaluated with respect to the CVD risk factors of total cholesterol, blood pressure (BP) [BP], smoking, and obesity using separate logistic regression, adjusting for age, gender, and the other major CVD risk factors. RESULTS: Compared with the lowest tertile of VO2max, the highest tertile had a reduced relative risk (RR) for elevated cholesterol (RR, 0.56; CI, 0.36-0.43), BP (RR, 0.32; CI, 0.15-0.62) and obesity (RR, 0.09; CI, 0.06-0.12). The middle tertile of VO2max compared with the lowest had reduced RR for elevated diastolic BP (RR, 0.44; CI, 0.23-0.66) and obesity (RR: 0.38; CI 0.28-0.50). High PA tertile, compared with low PA tertile, only had lower RR for high systolic BP (RR, 0.48; CI, 0.23-0.95). Compared with the low PA tertile, moderate or high PA had no reduction in any of the RR (P > 0.05). Participation in a 9-wk exercise program by low-fit individuals resulted in a 9% increase in PA levels (P < 0.02); however, only those subjects who increased VO2max (> 3 mL.kg-1.min-1; N = 345) had a reduction in RR for high cholesterol (RR: 0.62; CI 0.42-0.92) and systolic BP (RR: 0.57; CI 0.40-0.80). No reduction in RR were noted for diastolic BP or obesity. CONCLUSIONS: Aerobic power appears to have more of an influence on CVD risk factors than PA levels. Further, in low-fit persons, it appears that PA resulting in an increased aerobic power is associated with a reduction in CVD risk factors of cholesterol and BP in as little as 9 wk.

Comparison of a computerized physical activity recall with a triaxial motion sensor in middle-school youth.

PURPOSE: To develop and test a computerized activity recall (CAR) for capturing activity and energy expenditure (EE) in youth and to further our understanding of the use of the three-dimensional accelerometer (Tritrac) for studying activity and EE. METHODS: Forty-five students (25 girls and 20 boys) in grade 6-8, completed 5 consecutive days of the CAR and were randomly assigned to wear the Tritrac during 1 day in which they also completed the CAR. Twenty-two subjects also repeated 5 d of the CAR and 1 d of Tritrac monitoring 1-2 wk later. RESULTS: The correlation between CAR and Tritrac for total EE was significant (r = 0.510, P = 0.0003). However, the total EE computed from the Tritrac was significantly greater than the CAR (1941 +/- 273 kcal vs 1576 +/- 343 kcal (8.14 +/- 1.14 vs 6.60 +/- 1.44 MJ); P < 0.001). The EE of activities was similar for the Tritrac and CAR, approximately 670 kcal (2.80 MJ), suggesting that the difference between the two methods was their estimates of resting EE. Comparison of the CAR and Tritrac for classifying active and inactive subjects indicated that both methods similarly classified 35 of the 45 subjects or 78% (P = 0.0038). Although significant, the Kappa statistic (kappa = 0.398) indicated a low-level of agreement between methods. The Tritrac indicated 50.4 +/- 29.2 min.d-1 of activities of > or = 3 METs, whereas the CAR indicated 76.7 +/- 71.9 min.d-1 (P = 0.02). The week 1 vs 2 test-retest correlation was 0.0485 (P = 0.022) for the Tritrac and 0.820 (P = 0.0001) for the CAR. CONCLUSIONS: It appears that both methods have acceptable reliability. However, the validity of each method to measure total and activity EE remains unclear, as the Tritrac appears to overestimate resting energy expenditure, whereas the CAR overestimates total minutes of activity.