Inflammatory factors, physical activity, and physical fitness in young people

Cardiovascular disease (CVD) remains one of the leading causes of morbidity and mortality in developed countries. Over the past decade there has been much focus on the role of inflammation in the pathogenesis of atherosclerosis; to this end, there is increasing research on inflammatory factors such as C-reactive protein (CRP), interleukin-6 (IL-6), and fibrinogen (Fg). There is compelling evidence that physical activity (PA) and physical fitness (PF) protect against chronic disease. More recently, research has shown that exercise reduces CRP, IL-6, and Fg concentration in adults, and that this is often independent of adiposity. Although there are some data to suggest that this is similarly true for young people, there is inconsistency in the literature. The following review aims to illustrate what is known about the effects of PA and PF on inflammatory factors in young people aged 5-18 years.     

Gender differences in physical activity and physical fitness in young children in Crete

BACKGROUND: To assess physical activity and physiological fitness parameters among six year old children and to determine whether there were any significant gender differences. METHODS: Design & Setting: comparative study of a representative sample of boys and girls in school and at home. Participants: 569 children (305 boys and 264 girls) selected randomly from a total of 6153 registered in the 1st grade in 1992 on the island of Crete. Measures: assessment of physical activity was based on observational methods involving teachers and parents. Cardiorespiratory fitness was estimated by performance on the 20 meter Shuttle Run Test (20mSRT). BMI, skinfold thickness, Midarm Muscle Circumference (MMC) and hemoglobin were also measured. RESULTS: Both sexes were found to spend a very small proportion of their leisure time in Moderate to Vigorous Physical Activities (MVPA). More boys engaged in MVPA than girls at school and at home, but more girls were involved in physical activity-related lessons and classes out of school. Among the physiological fitness parameters, significant gender differences were found only for MMC. No significant gender difference was found in performance on the 20mSRT. CONCLUSIONS: The results indicate that in this culture stereotypic sex preferences in physical activity begin at a very young age, and that this differentiation cannot be attributed to gender differences in cardiorespiratory fitness. The social, environmental and possibly psychological parameters involved have implications for Health Educators and Physical Education Instructors in the appropriate targeting of physical activity promotion programs among young children.     

Physical fitness does not reflect physical activity patterns in middle-aged workers

Questionnaires and a sub-maximal exercise test were used to assess occupational and leisure time physical activity as well as physical fitness in a standardized prospective study in 2,565 Belgian and Slovakian middle-aged healthy workers. Less than 5% of the subjects engaged in strenuous work requiring an energy expenditure above 31.5 kJ.min-1. One-third of the Belgians and 50% of the Slovakians reported no heavy leisure time activity during the preceding 12 months. Physical fitness, defined as the workload at heart rate 150 beats.min-1 (standardized for body weight), was significantly higher in Slovakians as compared to Belgians (1.52 +/- 0.28 W.kg-1 and 1.48 +/- 0.28 W.kg-1; P less than 0.001). Occupational physical activity in Belgians and heavy leisure time activity in Slovakians were independently related to fitness levels. However, each activity score explained less than 1% of the variance of physical fitness. We conclude that in these mainly sedentary, middle-aged subjects, fitness levels are independent from the usual physical activity patterns.     

Smoking history is related to free-living daily physical activity in claudicants.

PURPOSE: To determine whether smoking history was related to free-living daily physical activity in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication, and whether the effect of smoking history on physical activity level persisted after controlling for group differences in ambulatory function, peripheral circulation, and body composition. METHODS: Patients were separated into three groups: those who never smoked (N = 35), those who had a lower pack-year history of smoking (< or =40 pack-yr; N = 33), and those who had a higher pack-year history (>40 pack-yr; N = 30). Free-living daily physical activity was assessed by activity monitors (an accelerometer and a pedometer) worn on each hip over 2 consecutive weekdays. Patients also were characterized on ambulatory function, peripheral circulation, and body composition because of their relationship with physical activity. RESULTS: A progressive decline (P < 0.001) in free-living daily physical activity with increasing smoking exposure was obtained from the accelerometer in the nonsmokers (482 +/- 36 kcal x d(-1); mean +/- SE), smokers with a lower pack-year history (361 +/- 37 kcal x d(-1)), and smokers with a higher pack-year history (227 +/- 23 kcal x d(-1)). A similar decline was found with the pedometer data (P < 0.001). After controlling for group differences in 6-min walk distance and in calf transcutaneous heating power, group differences in free-living daily physical activity were no longer significant. CONCLUSION: Progressive decrements in free-living daily physical activity with greater levels of smoking exposure in PAOD patients are primarily due to smoking-related impairments in ambulatory function and peripheral circulation.     

Objectively measured daily physical activity related to cardiac size in young children

Training studies in children have suggested that endurance training can give enlargement of cardiac dimensions. This relationship has not been studied on a population-based level in young children with objective methods. A cross-sectional study was made of 248 children (140 boys and 108 girls), aged 8–11 years, from a population-based cohort. Left ventricular end-diastolic diameter (LVDD) and left atrial end-systolic diameter (LA) were measured with echocardiography and indexed for body surface area (BSA). Physical activity was assessed by accelerometry, and the duration of vigorous physical activity per day (VPA) was calculated. Acceptable accelerometer and echocardiography measurements were obtained in 228 children (boys=127, girls=101). Univariate correlations between VPA and LVDD were indexed for BSA in boys ( r =0.27, P <0.05) and in girls ( r =0.10, NS). Multiple regression analysis showed that independent factors for LVDD, indexed for BSA for boys, were age and VPA. LA indexed for BSA was not related to physical activity variables in either gender. No clear relationship exists between cardiac size and daily physical activity in children aged 8–11 years. This suggests that significant cardiac remodelling due to volume exposure secondary to a high amount of physical activity begins later in life.     

Daily physical activity related to aerobic fitness and body fat in an urban sample of children

This study evaluates associations between objectively measured daily physical activity vs aerobic fitness and body fat in children aged 8-11 years. A cross-sectional study of 225 children aged 7.9-11.1 years was performed. Abdominal fat mass (AFM) and total body fat (TBF) were quantified by dual-energy x-ray absorptiometry. TBF was calculated as percentage of total body mass (BF%). Body fat distribution was calculated as AFM/TBF. Aerobic fitness was measured by indirect calorimetry during a maximal cycle ergometer exercise test. Daily physical activity was assessed by accelerometers for 4 days and daily accumulation of moderate-to-vigorous and vigorous activity was calculated. Significant relationships (P<0.05) existed for vigorous activity vs ln BF% (r=-0.40), ln AFM (r=-0.35), TBF/AFM (r=-0.22) and aerobic fitness (r=0.38), whereas moderate-to-vigorous activity displayed weaker relationships (-0.22, -0.18, -0.12 NS, and 0.25). Multiple regression analyses with inclusion of possible confounders concluded that vigorous activity was independently related to aerobic fitness and ln BF% or ln AFM. Moderate-to-vigorous activity was only independently related to aerobic fitness. In this population, low daily accumulation of vigorous activity was, already in children aged 8-11 years, associated with more body fat and lower aerobic fitness. A similar relation was not found for daily accumulation of moderate-to-vigorous activity.     

Objectively-measured physical activity in New Zealand workers.

To date, no objective measurements of New Zealanders' physical activity have been reported. The relative contribution of work time activity to total daily physical activity by gender and occupational category has also not been measured objectively in any population. The present study reports such data using pedometer steps counts to quantify both work and non-work physical activity in a sample of New Zealand adult workers in six different occupational categories over a three-day period. Females (9943+/-3855 steps) had slightly higher, but not significantly different (F=0.084(1,179)1, p=0.772) daily step counts than males (9766+/-3965 steps). Using the 10 000 steps a day criterion, 57% of the sample were considered at least low-active. Analysis of variance was used to identify between group (occupational) differences in workplace physical activity (F=11.189(5,175), p<0.001), non-work physical activity (F=2.596(5.175), p=0.027), and total physical activity (F=6.265(5,175), p<0.001). Tukey post hoc comparisons showed significant differences with retail and blue collar workers achieving higher activity levels in comparison to the other occupational categories in work and total physical activity. Odds ratios were calculated to find the odds of being in the top half of activity classification for work and non-work physical activity by tertile splits of work time, active transportation use, sport and exercise participation, television and computer viewing, and passive recreation. Active transportation and passive recreation were related to increased odds of higher work pedometer steps. For non-work pedometer values, television and computer use increased the likelihood of being in the lowest activity group, while sport and exercise participation were associated with increased activity levels.     

Tracking of physical fitness and physical activity from youth to adulthood in females

PURPOSE: To evaluate stability of physical fitness and physical activity from adolescence into middle adulthood in Flemish females. METHODS: Within the scope of the Leuven Longitudinal Study on Lifestyle, Fitness and Health, 138 females (mean age=16.6+/-1.1 yr) from the Leuven Growth Study of Flemish Girls were seen in adulthood (mean age=40.5+/-1.1 yr). Several body dimensions and motor fitness tests were taken. Physical activity was assessed by means of a sports participation inventory. Inter-age correlations were calculated between adolescent and adult values. Cross-tabulation was used to identify the percentage of subjects remaining in the same BMI and physical activity group or shifting from one group to another from adolescence to adulthood. Odds ratios for less activity and overweight in adulthood according to adolescent activity or weight status were calculated. RESULTS: Except for flamingo balance, plate tapping, leg lifts, and arm pull, all anthropometric and physical fitness characteristics were stable from adolescence to adulthood (r ranging from 0.49 to 0.96). Sports participation was not a stable characteristic (r=0.13). From adolescence to adulthood, 84.5 and 63.6%, respectively, remained in the normal-weight and overweight group, whereas 62.5 and 54.4%, respectively, remained in the less active and active group. The odds of being overweight in adulthood was 9.53 (95% CI: 3.1-29.8) times greater in overweight compared with normal-weight adolescent girls. CONCLUSION: In Flemish females, anthropometric and fitness characteristics demonstrate higher levels of stability from adolescence to middle adulthood than physical activity. Weight status during adolescence is indicative of adult weight status, and a pattern of less activity rather than activity tends to continue from youth to adulthood.     

Occupational relevance and body mass bias in military physical fitness tests

Recent evidence makes a compelling case that US Army, Navy, and Air Force health-related physical fitness tests penalize larger, not just fatter, service members. As a result, they tend to receive lower scores than their lighter counterparts, the magnitude of which can be explained by biologic scaling laws. Larger personnel, on the other hand, tend to be better performers of work-related fitness tasks such as load carriage, heavy lifting, and materiel handling. This has been explained by empirical evidence that lean body mass and lean body mass to dead mass ratio (dead mass = fat mass and external load to be carried/lifted) are more potent determinants of performance of these military tasks than the fitness test events such as push-ups, sit-ups, or 2-mile-distance run time. Because promotions are based, in part, on fitness test performance, lighter personnel have an advancement advantage, although they tend to be poorer performers on many tests of work-related fitness. Several strategies have been proposed to rectify this incongruence including balanced tests, scaled scores, and correction factors--yet most need large-scale validation. Because nearly all subjects in such research have been men, future investigations should focus on women and elucidate the feasibility of universal physical fitness tests for all that include measures of health- and work-related fitness while imposing no systematic body mass bias.     

Occupational physical activity and non-Hodgkin's lymphoma

PURPOSE: The purpose of this study was to evaluate the role of physical activity in the development of non-Hodgkin's lymphoma (NHL). METHODS: Incident NHL cases and population-based controls were identified from three case-control studies conducted in four midwestern states: Iowa, Kansas, Minnesota, and Nebraska. A total of 1177 cases (993 men, 184 women) and 3625 controls (2918 men, 707 women) were interviewed. Usual occupation (all states) and lifetime occupational histories (Iowa and Minnesota only), obtained from interviews, were classified for energy expenditure (EE) and sitting time. Odds ratios (OR) and 95% confidence intervals were calculated comparing moderate and high activity levels with sedentary levels. RESULTS: There was no evidence of an association between NHL and occupational physical activity measured either by EE or sitting time. Among men, the OR associated with usual occupation moderate and high EE were 1.1 and 1.0, respectively. For sitting time, the OR were also 1.1 and 1.0 for moderate and high activity, respectively. Among women, slight nonsignificant elevations in risk of NHL were observed among the high energy level and high activity sitting categories. The trends were not significant. There was no evidence of confounding or effect modification by vital status, hair dye use, or solvent exposure. Among subjects with lifetime occupational histories, there were no significant increases or trends for cumulative or average EE or sitting time. There was no association between occupational physical activity and NHL. CONCLUSION: Research on nonoccupational physical activity, which in the U.S. is likely the more important component of daily activity than occupational activity, may still be warranted given the laboratory evidence linking physical activity and immune function, an important factor in the etiology of NHL.     

Occupational physical activity across occupational categories

This study investigated the amount of physical activity that occurs during normal working hours, highlighting the occupational differences in physical activity by occupational category. Data were collected by means of a self-administered questionnaire (Tecumseh Occupational Physical Activity Questionnaire [TOQ]), which measures past year Occupational Physical Activity (OPA) and by a motion-sensing device (Yamax DigiWalker Pedometer SW - 700). Ninety male and female participants aged 18-62 years participated in the study. Participants were stratified by occupational category according to the Australian Standard Classification of Occupations (ASCO), which was then condensed into professional, white-collar and blue-collar workers. The results showed significant (p < .05) increases in OPA from the professional category (least active) through to the blue-collar workers (most active) in terms of walking activity. Mean daily step counts were 2,835, 3,616 and 8,757 for professional, white-collar and blue-collar respectively. Occupational Physical Activity Scores and Work Activity Units (WAU) in MET - min x wk(-1) from the TOQ showed similar patterns, with blue collar reporting significantly (p < .05) more past year OPA than their white-collar and professional workers. Significant correlations were also shown between the pedometer (step-count data) and the TOQ (r = .38 - .74, p < .01).     

Current physical activity is related to bone mineral density in males but not in females

The purpose of the present study was to investigate the association between high-, medium-, and low-impact physical activity in males and females at the time of peak bone mineral density in young adulthood. The cohort consisted of 62 male medical students (aged 28.1 +/- 3.9) and 62 female medical students (aged 25.1 +/- 3.9). The bone mineral density (aBMD, g/cm (2)) of the total body, femoral neck, and lumbar spine, and the bone mineral content (BMC, grams) and area (cm (2)) of the femoral neck and lumbar spine was measured using dual energy X-ray absorptiometry. Volumetric BMD (vBMD, mg/cm (3)) of the femoral neck and lumbar spine was estimated. The total amount of physical activity per week, which was recorded in a questionnaire, was divided into high-impact, medium-impact, and low-impact activity. In the male cohort, hours of high-impact physical activity per week was associated with aBMD and BMC of all sites (r=0.27 - 0.53, p<0.05) and bone area of the femoral neck (r=0.38, p<0.01). Total amount of physical activity per week was associated with aBMD of the total body and femoral neck, BMC of femoral neck and lumbar spine, femoral neck vBMD, and the lumbar spine area (p<0.05 for all). Using multiple linear regression, high-impact physical activity was independently associated with aBMD (beta=0.27, p<0.05) and BMC (beta=0.34, p<0.01) of the femoral neck. In the female cohort there was no association between amount or type of physical activity to aBMD, BMC, vBMD, or the bone area of any site. Instead body weight, lean body mass, or fat mass were significantly related to aBMD and all BMC sites in this group. The results of the present study suggest that present physical activity level has a stronger relation to different aspects of bone mass in the male compared to the female adult skeleton.     

Relationship of measures of leisure time physical activity to physical fitness indicators in Spanish adults

BACKGROUND: The purpose of our study was to examine the association between estimates of energy expenditure obtained by the Minnesota Leisure Time Physical Activity questionnarie (LTPA) and physical fitness indicators. METHODS. PARTICIPANTS: An adaptation of the LTPA was assessed in a sample of Spanish population: male (n = 44) and female (n = 38). Interventions: the LTPA 1 year recall questionnaire was administered twice with a 12-month interval and participants also responded monthly the Four Week Physical Activity History (FWH) questionnaire. Measures: test-retest reliability of the LTPA and the relationships between changes in V.O2max, percent body fat and leisure time physical activity were examined. RESULTS: Corresponding components of the LTPA and the FHW were highly correlated and scores in heavy leisure time activities and household chores showed a relatively low variance ratio, indicating an acceptable reliability of the questionnaire. Heavy intensity physical activity and household chores were highly related to V.O2max and there was a weaker association to moderate or light activity. CONCLUSIONS: Our results suggest that the Spanish version of the LTPA is a relatively valid and reliable measure of regular physical activity and a valid estimator of cardiorespiratory fitness in adults.     

Relationships of perceived benefits and barriers to physical activity, physical activity participation and physical fitness in Hong Kong female adolescents

AIM: Previous studies that examined participation in physical activity suggested that female adolescents were less active compared with males. However, the relationship between physical fitness, physical activity participation, and perceived benefits and barriers for physical activity to adolescents, irrespective of gender, has not been made clear. This study examines the association of these factors in female adolescents. METHODS: Physical activity participation and perceived benefits and barriers to physical activity were determined in 206 secondary school female subjects (aged 11 to 18) using a validated questionnaire. RESULTS: Subjects with a correct concept about optimal physical activity participation to maintain health engaged in an activity level higher than the group without a correct concept (t=2.37, p=0.02). A significant correlation was established between the physical activity participation with "health" (r=0.22, p<0.001) and "body image" (r=0.17, p=0.02) in the perceived benefit category. The individual factor, "make me feel better in general" in the "health" category (p=0.04) and the intention to participate (p<0.001) were shown to be significant predictors for physical activity participation. The combined effects of the regression model explained 35.9% of the variance in participation in physical activity. CONCLUSION: Policies to support regular physical activity participation at school and out-of-school should be strategically developed and promoted, highlighting the promotion of health benefits in exercise and the reinforcement of initial intent towards exercise.     

Association of physical fitness with LDL and HDL subfractions in young healthy men.

A dyslipoproteinemia of increased concentrations of small, dense LDL particles and reduced HDL2 cholesterol has shown to be associated with coronary heart disease (CHD). In contrast, an increase in physical fitness and a reduction of body mass index (BMI) improve the lipoprotein profile and reduce the incidence of cardiovascular events. The association of physical exercise, physical fitness, and body weight with an atherogenic lipoprotein subfraction profile has been investigated before in obese subjects, but the relationship is unknown in a healthy non-obese population without insulin resistance or CHD. Therefore, a detailed lipoprotein subfraction profile of 3 HDL and 6 LDL subfractions was determined in 125 healthy men (26+/-5 years). Physical fitness (maximal oxygen consumption, VO2max) was assessed by ergometry and physical activity by questionnaire. Those men with the lowest physical fitness (VO2max < 40 ml/kg/min) and the lowest physical activity score had a significantly less favourable lipoprotein subfraction profile of increased concentration of small, dense LDL particles (d: > 1.044 g/ml) and reduced HDL2a cholesterol than those with a VO2max >50 ml/kg/min. Multivariate regression analysis revealed that concentrations of small, dense LDL particles were primarily determined by BMI whereas HDL2a cholesterol and apolipoprotein A-I were primarily determined by physical fitness. These findings underline the relationship between a good physical fitness, a low body weight, and a favourable lipoprotein subfraction profile even in a healthy young male population.     

Tracking physical fitness and physical activity from childhood to adolescence: the muscatine study

PURPOSE: Physical fitness and physical activity tracking data enhance our understanding as to when children settle into their long-term exercise and fitness patterns and, therefore. provide insight as to when programs focusing on preventing sedentary adults behaviors should be initiated. METHODS: In this paper, the tracking of physical fitness and physical activity was examined in a 5-yr population-based study of children and adolescents in Muscatine, IA. Study subjects (N = 126) were pre- or early-pubescent at baseline (mean age boys 10.8 yr and girls 10.3 yr). Physical fitness was measured using direct determination of oxygen uptake and maximal voluntary isometric contraction while physical activity was assessed via questionnaire. RESULTS: Boys classified as sedentary based on initial measurements of TV viewing and video game playing were 2.2 times more likely than their peers to also be classified as sedentary at follow-up. Tracking of most physical fitness and physical activity variables was moderate to high, indicating some predictability of early measurements for later values. Sedentary behavior tracked better in boys, whereas vigorous activity tended to track better in girls. CONCLUSION: These observations suggest that preventive efforts focused on maintaining physical fitness and physical activity through puberty will have favorable health benefits in later years.