Physical fitness measures among children and adolescents: are they all necessary?

AIM: The aim of this paper was to investigate the relationship among health and skill-related physical fitness variables, and with anthropometric measures in a sample of children and adolescents. METHODS: A cross-sectional study was conducted with 526 Brazilian students aged 7-15 years. Physical fitness abilities/skills were assessed through a battery of eight tests: sit-and-reach, standing long jump, 1-minute curl-up, modified pull-up, medicine-ball throw, 9-minute run, 20-meter run and 4 meter shuttle-run. Anthropometric measures considered were weight, height, body mass index (BMI) and wingspan. Analyses included descriptive statistics, Pearson correlations, multiple linear regression and principal component analysis. RESULTS: Anthropometric measures were directly associated between each other. Weight and BMI were negatively associated with the performance in all physical tests requiring propulsion or lifting of the body mass. Direct associations between tests persisted after adjustments for sex, age, type of school and geographic region of school. CONCLUSION: Results from the principal component analysis evidenced that all physical abilities/motor skills, except flexibility, are strongly associated with each other, suggesting that one test can reflect the overall fitness among youth. Although it is unclear from these analyses which test would be the single choice indicator, previous work on the health impact of cardiorespiratory fitness would suggest that.

Cardiorespiratory fitness, glycemic status, and mortality risk in men.

OBJECTIVE: To determine the association of baseline cardiorespiratory fitness to all-cause mortality across the range of blood glucose levels. RESEARCH DESIGN AND METHODS: Data from a prospective study of 8715 men (average age 42 yr), followed for an average of 8.2 yr (range 1-15 yr), were analyzed. Cardiorespiratory fitness was assessed by maximal-exercise treadmill testing. Men with evidence of clinical vascular disease or who did not achieve 85% of their age-predicted maximum heart rate during exercise testing were excluded from analyses. RESULTS: Age-adjusted death rates increased with higher levels, of fasting blood glucose. Regardless of glycemic status, fit men had lower age-adjusted all-cause death rates than their less fit counterparts. For men with fasting blood glucose greater than or equal to 7.8 mM or physician-diagnosed non-insulin-dependent diabetes mellitus (NIDDM), the age-adjusted death rates per 10,000 person-yr of follow-up in unfit and fit subjects were 82.5 and 45.9, respectively. The age-adjusted relative risk of death due to all causes was significantly elevated in the lower-fitness group within each of three glycemic status levels: fasting blood glucose less than 6.4 mM; relative risk (RR) = 1.93 (95% confidence interval [95% CI] 1.15-3.26); fasting blood glucose 6.4-7.8 mM; RR = 3.42 (95% CI 2.27-5.15); and fasting blood glucose greater than or equal to 7.8 mM or with NIDDM, RR = 1.80 (95% CI = 1.25-2.58). Multivariate analyses, controlling for risk factors of mortality (age, resting systolic blood pressure, serum cholesterol, body mass index, family history of heart disease, follow-up interval, and smoking habit) showed a higher risk of death due to all causes for unfit compared with fit men. Multivariate risks of death associated with low fitness, compared with higher fitness (RR), in the three glycemic status groups were: fasting blood glucose less than 6.4 mM, RR = 1.38 (95% CI 1.09-1.74); fasting blood glucose 6.4-7.8 mM, RR = 1.61 (95% CI 0.91-2.86); and fasting blood glucose greater than or equal to 7.8 mM or with NIDDM, RR = 1.92 (95% CI 0.75-4.90).

High-resolution STEM imaging with a quadrant detector--conditions for differential phase contrast microscopy in the weak phase object approximation.

Differential phase contrast is a contrast mechanism that can be utilized in the scanning transmission electron microscope (STEM) to determine the distribution of magnetic or electric fields. In practice, several different detector geometries can be used to obtain differential phase contrast. As recent high resolution differential phase contrast experiments with the STEM are focused on ring quadrant detectors, we evaluate the contrast transfer characteristics of different quadrant detector geometries, namely two ring quadrant detectors with different inner detector angles and a conventional quadrant detector, by calculating the corresponding phase gradient transfer functions. For an ideal microscope and a weak phase object, this can be done analytically. The calculated phase gradient transfer functions indicate that the barely illuminated ring quadrant detector setup used for imaging magnetic fields in the specimen reduces the resolution limit to about 2.5Å for an aberration corrected STEM. Our results show that the resolution can be drastically improved by using a conventional quadrant detector instead.

Exercise tolerance and alcohol intake. Blood pressure relation.

The relations of systolic and diastolic blood pressures to alcohol intake and exercise tolerance levels in 15,612 men and 3,855 women were investigated. Alcohol intake was assessed by questionnaire and stratified into seven levels for men and six for women according to the ounces of ethanol consumed per week. Exercise tolerance was determined by maximal treadmill exercise testing and was categorized into six age-specific by sex-specific levels. Both systolic and diastolic blood pressure were significantly related to both alcohol intake and exercise tolerance levels in both men and women. These relations, which were positive for alcohol and negative for exercise tolerance, remained after covariance adjustment for age, body mass index, and cigarette smoking. Alcohol intake was not significantly correlated with exercise tolerance. The relation of blood pressure to alcohol was not linear because the blood pressure of moderate consumers of alcohol tended to be slightly lower than that of nondrinkers. Higher blood pressure was found only in drinkers whose ethanol intake exceeded 9.5 ounces (approximately 285 ml or 19 drinks) per week. However, heavy drinkers in high exercise tolerance categories had no higher blood pressure than nondrinkers in low exercise tolerance groups. Exercise tolerance or physiological fitness appears to be important in quantifying the relation between alcohol intake and blood pressure and should be considered in describing this relation.

Effects of diflunisal on platelet function and fecal blood loss.

The effects of diflunisal, a nonacetylated difluorinated salicylate, on platelet function were compared with those of aspirin and placebo. In a randomized, double-blind trial, normal subjects were given diflunisal, 250, 500, or 1,000 mg twice daily; aspirin, 650 or 1,300 mg twice daily; or placebo for 8-day periods. Difunisal, 250 mg, had no effect on platelet function, whereas 500 mg induced minimal inhibition of colagen-induced release of platelet serotonin, and 1,000 mg inhibited platelet malondialdehyde production, moderately prolonged template bleeding times (P = NS), and increased fecal blood loss (P less than 0.05). In contrast, aspirin, 650 mg, markedly inhibited collagen-induced platelet aggregation and serotonin release, and 1,300 mg prolonged bleeding time (P less than 0.01) and increased fecal blood loss (P less than 0.01). The effects of aspirin lasted for up to 5 days, whereas changes induced by diflunisal had returned to baseline 24 hr after the drug was discontinued. We conclude that in doses in the same range as those of aspirin diflunisal inhibits platelet function less.

Development of physical activity behaviors among children and adolescents.

Physical activity is a key component of energy balance and is promoted in children and adolescents as a lifelong positive health behavior. Understanding the potential behavioral determinants necessitates understanding influences from three fundamental areas: 1) physiologic and developmental factors, 2) environmental factors, and 3) psychological, social, and demographic factors. The literature to date has generally investigated potential predictors of physical activity in children and adolescents in each of these three general areas, although existing data rely largely on cross-sectional studies in which it is difficult to distinguish a determinant from a correlate. In all likelihood, aspects of each of these three areas interact in a multidimensional way to influence physical activity in youth. This article reviews evidence of potential determinants of physical activity in children and adolescents and provides recommendations for future work.

Intake and food sources of dietary fat among schoolchildren in The Woodlands, Texas.

To investigate the nutrient intake and food use patterns among schoolchildren, diet was assessed among 138 children and adolescents in grades 5 through 12 using three random, nonconsecutive, 1-day food records. Mean intake of total fat, saturated fat, and polyunsaturated fat as percent of calories was 35.6%, 13.4%, and 6.6%, respectively. Among all subjects, 17% consumed diets containing less than 30% of calories from fat, 34% consumed greater than or equal to 38% of calories from fat, 7% consumed less than 10% of calories from saturated fatty acids, and greater than 97% ate less than 300 mg of cholesterol per day. While intake of calories, sodium, and beta-carotene per 1000 kcal was higher in subjects consuming higher fat diets, intake of other micronutrients was either higher among those eating low-fat diets or did not differ by level of fat intake. Differences were seen in the amount of saturated fat and cholesterol that individual food sources contributed to the diets of subjects eating high and low fat diets. These cross-sectional data show that a substantial proportion of children and adolescents in this population are consuming diets low in fat and cholesterol without systematic differences in intake of other nutrients, suggesting that current dietary guidelines regarding fat intake are attainable within the current food use pattern of healthy, school-aged children and adolescents.

Physical activity, physical fitness, and all-cause and cancer mortality: a prospective study of men and women.

We studied physical fitness and physical activity in relation to all-cause and cancer mortality in a cohort of 7080 women and 25,341 men examined at the Cooper Clinic in Dallas, Texas, during 1970 to 1989. Physical fitness was assessed at baseline by a maximal treadmill exercise test, while physical activity was self-reported on the attendant health habits questionnaire. Both men and women averaged about 43 years of age at baseline (range, 20 to 88 years), and they were followed for approximately 8 years on average. Through the end of 1989, the women contributed 52,982 person-years of observation and incurred 89 deaths, including 44 deaths due to cancer. The men contributed 211,996 person-years and incurred 601 deaths, with 179 due to cancer. After adjustment for baseline differences in age, examination year, cigarette habit, chronic illnesses, and electrocardiogram abnormalities, we found a strong inverse association between risk of all-cause mortality and level of physical fitness in both men and women (P for trend < 0.001). Physically active men also were at lower risk of all-cause mortality than were sedentary ones (P for trend = 0.01). Among women, however, self-reported physical activity was not significantly related to risk of death from all causes. The risk of mortality from cancer declined sharply across increasing levels of fitness among men (P for trend < 0.001), whereas among women the gradient was suggestive but not significant (P for trend = 0.07). Physically active men also were at lower risk of death from cancer than were sedentary men (P for trend = 0.002), but among women physical activity was unrelated to cancer mortality.

Food-frequency questionnaire validation among Mexican-Americans: Starr County, Texas.

A food-frequency questionnaire (FFQ) for low-income Mexican-Americans in Starr County, Texas, was developed as part of an epidemiologic study of gallbladder disease during 1985 and 1986. The FFQ was developed from 7-day food records collected from the first sample. In the validity study, using the second sample, correlations between nutrients calculated from 3-day food records and the FFQ were 0.77, 0.76, and 0.61 for energy, total fat, and saturated fat, respectively. In the reliability study, using the third sample, for the 1-month interval between baseline and a repeat FFQ measurement correlations ranged from 0.90 for energy to 0.85 for total fat and for the 2-month interval they were 0.84 for energy and 0.70 for total fat. The high correlations are largely explained by the lack of diversity in the diets of Starr County individuals which facilitated the high agreement between the FFQ and the food records for estimates of energy, fats, and cholesterol.

Exaggerated blood pressure response to dynamic exercise and risk of future hypertension.

This study examined the association between an exaggerated blood pressure response to treadmill exercise and the risk of developing hypertension. Subjects were healthy normotensive men (n = 5386) who had a baseline graded maximal exercise test between 1971 and 1982, and completed a mailed follow-up questionnaire. At follow-up in 1986, cases (n = 151) reported physician diagnosed hypertension and controls (n = 201) reported normotension. Those who had developed hypertension at follow-up were more likely to have had an exaggerated blood pressure response to exercise (OR = 2.4, 1.4-4.3). In multiple logistic regression analysis an exaggerated response was significantly associated (OR = 3.0, 1.5-6.1) with future hypertension after controlling for sitting systolic and diastolic blood pressure, weight change from age 21 to follow-up, entry age, family history of hypertension, body mass index, treadmill time, alcohol consumption, and years of follow-up. These results suggest that an exaggerated blood pressure response to exercise is independently associated with increased risk of future hypertension, and therefore, may be an important factor in determining hypertension risk.

Effect of intrinsic sympathomimetic activity on the ability of hypertensive patients to derive a cardiorespiratory training effect during chronic beta-blockade.

The effect of intrinsic sympathomimetic activity (ISA) on the ability of patients with high blood pressure (BP) to derive a cardiorespiratory training effect during long-term beta-blocker therapy was studied. Fifty sedentary hypertensive subjects were randomly assigned to propranolol (n = 23) or pindolol (n = 27) therapy for a 22 week double-blind parallel study. Over the first 2 weeks, during which subjects remained sedentary, drug doses were titrated to produce equipotent, clinically significant BP reductions. Subjects subsequently continued drug therapy and completed 20 weeks of exercise training. Although pindolol tended to preserve submaximal exercise heart rates to a greater degree than propranolol, the initial 2 weeks of drug therapy resulted in equivalent reductions in maximal oxygen uptake with propranolol (6% reduction) and pindolol (8% reduction). Likewise, 20 weeks of training induced similar, statistically significant (P = .0001) increases in maximal oxygen uptake during propranolol (10% increase) and pindolol (11% increase) treatment. We therefore conclude that ISA does not confer any advantage to patients with high BP who receive chronic beta-blocker therapy and wish to improve their cardiorespiratory fitness by participating in exercise training.

Rubella screening and vaccination follow-up by a hospital employee health office.

The data in the present study indicate two major points. One is that the facility under question has an unusually low rate of rubella susceptibility. The other is that the referral of seronegative employees to an outside agency for vaccination (in this case the local CHD) is not nearly as effective, with respect to employee compliance, as an in-house program. Despite the added immediate cost to the hospital for administering the vaccine, the possibility of employee-to-patient transmission of the rubella virus poses the threat of a much higher future cost. It is suggested that facilities that do not currently have an in-house rubella vaccination program should reevaluate the effectiveness of their programs.

Intrinsic PEEP monitored in the ventilated ARDS patient with a mathematical method.

Under mechanical volume-controlled ventilation, the intensive care patient can develop intrinsic positive end-expiratory pressure (iPEEP); that is, the passive expiration is terminated by the following inspiration before the alveolar pressure comes to its physical equilibrium value. We present a mathematical method to estimate this alveolar dynamic iPEEP breath by breath, without the need of a maneuver. We tested it in paralyzed patients ventilated for adult respiratory distress syndrome after multiple trauma and/or sepsis, and we compared the results obtained with the new mathematical method with those from the occlusion method introduced by Pepe and Marini. The results agreed well (median difference of 0.8 mbar in 201 investigations in 12 patients). However, the mathematically determined values, representing dynamic iPEEP, are systematically slightly smaller than those measured by the occlusion maneuver. A variation of expiratory time suggests that this difference might be due to mechanical time-constant inhomogeneity, viscoelastic processes, or other mechanisms showing time dependence.

Relativistic calculations of intensity distributions in elemental maps using contrast transfer functions.

The interpretation of highly resolved elemental maps is not straightforward: one has to consider the quantum mechanical nature of the scattering process as well as the influence of the microscope. Existing calculations of the contrast in elemental maps are based on a non-relativistic approach, while in most of the currently installed electron microscopes, the electrons penetrate the specimen with relativistic energies >/= 200 keV. Therefore, we have recalculated the intensity distribution in elemental maps based on a fully relativistic theory. Using the concept of contrast transfer functions, the simulations account for lens aberrations as well as the defocus. Surprisingly, the results exhibit considerable deviations between the relativistic and non-relativistic calculations even in the region of low acceleration voltages such as 100 kV. These differences increase with increasing acceleration voltage and are strongly dependent on aperture and energy loss. Quantitative simulations and evaluations of highly resolved elemental maps should therefore make use of a fully relativistic theory.

In vitro studies of a new synthetic thrombin inhibitor.

(2R, 4R)4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetrahydro-8-quinoline- sulfonyl)-L-arginyl]-2-piperidine carboxylic acid monohydrate (MCI-9038) was found to be a potent synthetic inhibitor of thrombin. In concentrations as low as 1 microM, the thrombin time, prothrombin time, and partial thromboplastin time were more than doubled. The venom (Bothrops atrox) time was similarly prolonged. The drug also inhibited the thrombin-induced activation of factors VIII and XIII. While MCI-9038 in concentrations of 10(-4) M had no effect on platelet aggregation induced by collagen, ADP, epinephrine, and arachidonate, nanomolar concentrations inhibited thrombin-induced platelet aggregation and the release of platelet ADP. The drug also significantly inhibited the adhesion of thrombin-treated platelets to cultured bovine aortic endothelial cells. We conclude that MCI-9038 is an extremely potent inhibitor of the effects of thrombin on platelets and clotting factors.

Effects of diflunisal on platelet function and fecal blood loss.

The effects of diflunisal, a nonacetylated difluorinated salicylate, on platelet function were compared with those of aspirin and placebo. In a randomized, double-blind trial, normal subjects were given diflunisal, 250, 500, or 1,000 mg twice daily; aspirin, 650 or 1,300 mg twice daily; or placebo for 8-day periods. Diflunisal, 250 mg, had no effect on platelet function, whereas 500 mg induced minimal inhibition of collagen-induced release of platelet serotonin, and 1,000 mg inhibited platelet malondialdehyde-production, moderately prolonged template bleeding times (p = NS), and increased fecal blood loss (p less than 0.05). In contrast, aspirin, 650 mg, markedly inhibited collagen-induced platelet aggregation and serotonin release, and 1,300 mg prolonged bleeding time (p less than 0.01) and increased focal blood loss (p less than 0.01). The effects of aspirin lasted for up to 5 days, whereas changes induced by diflunisal had returned to baseline 24 hours after the drug was discontinued. We conclude that in doses in the same range as those of aspirin diflunisal inhibits platelet function less.

Physical activity and cancer. An epidemiological perspective.

This article reviews the existing epidemiological evidence on the association between physical activity and cancer. Relatively little is known about the role that increased physical activity may have in protecting humans from malignancy. Herein, studies are reviewed on the basis of the type of physical activity exposure studied: occupational or leisure time. Results suggest that if any consistencies emerge, there may be a protective effect of increased physical activity exposure upon cancer of the colon, and no effect on cancer of the rectum, in men. Increased physical activity in women during college years may protect against certain reproductive system cancers. Methodological deficiencies in assessment of physical activity (total exposure over lifetime) and in lack of control for other potential explanations block further, more solid conclusions. The fact that an association has been demonstrated in spite of these drawbacks, however, indicates the importance of further study. Suggested directions for future work are presented.

Synthesis of 3 beta-hydroxy-5 alpha-cholest-8-en-7-one and 3 beta-hydroxy-5 alpha-cholest-8-en-11-one: evaluation as potential hypocholesterolemic agents.

An efficient procedure for the chemical synthesis of 3 beta-hydroxy-5 alpha-cholest-8-en-7-one and 3 beta-hydroxy-5 alpha-cholest-8-en-11-one is described. These ketosterols have been shown to have possible significant hypocholesterolemic effects when fed to normal rats at a level of 0.15% in a laboratory chow diet. The diets containing the steroids caused significant decreases in food consumption which were associated with decreases in the rate of gain in body weight.

The association between cardiorespiratory fitness and prostate cancer.

We conducted a prospective study to assess the association between cardiorespiratory fitness and prostate cancer. The subjects were men, aged 20-80 yr, who received a preventive medical exam at the Cooper Clinic in Dallas, TX, during 1970-1989 and provided information on cardiorespiratory fitness and prostate cancer (N = 12,975). Cardiorespiratory fitness was assessed at a baseline examination between 1971 and 1989 using a maximal exercise treadmill test. Questionnaires were mailed to the men in 1982 and 1990 to ascertain incident cases of prostate cancer. Ninety-four cases of incident prostate cancer were identified. Higher cardiorespiratory fitness levels were inversely associated with the probability of development of incident prostate cancer after controlling for age, body mass index, and smoking habits; adjusted estimates of the incidence rate ratio declined from 1.1 (95% CI 0.63-1.77) to 0.73 (95% CI 0.41-1.29) to 0.26 (95% CI 0.10-0.63) across increasing quartiles of fitness (P for trend < 0.004). This protective effect was limited to participants < 60 yr old. Also, an inverse association was observed between physical activity and prostate cancer. Compared with expending < 1000 kcal.wk-1, participants who expended 1000- < 2000, 2000- < 3000, or > or = 3000 kcal.wk-1 had adjusted incidence rate ratios of 0.37 (95% CI 0.17-0.79), 0.62 (95% CI 0.27-1.41), and 0.37 (95% CI 0.14-0.98), respectively. The results suggest that cardiorespiratory fitness and physical activity levels may protect against the development of incident prostate cancer.

A randomized trial of physical activity interventions: design and baseline data from project active.

We report here the design and baseline data from Project Active, a 2-yr randomized trial designed to compare the effectiveness of a Lifestyle physical activity intervention with the traditional Structured exercise prescription approach. Primary outcome measures are energy expenditure in physical activity (estimated by kcal per kilogram of body weight of energy expenditure) and cardiorespiratory fitness (measured by maximal oxygen uptake). The participants, 235 initially sedentary and apparently healthy adults, were randomized into either the Lifestyle or Structured intervention groups. The Lifestyle treatment consists of a personalized approach that accounts for an individual's motivational readiness and preferences for integrating physical activity into daily routines. The Structured approach is the familiar exercise prescription that is based on a frequency, intensity, and duration formula. The primary hypothesis to be tested is that there will be a difference in physical activity and cardiorespiratory fitness measures between the two conditions at the end of 24 months. The secondary hypothesis is that both groups will make significant improvements from baseline in physical activity and cardiorespiratory fitness at the end of 6 months. Six months of active intervention are followed by 18 months of a tapered follow-up maintenance intervention in both groups. Primary outcome measures are measured after 6 and 24 months.