Association between time spent in sedentary,moderate to vigorous physical activity,body mass index,cardiorespiratory fitness and blood pressure

Background: Elevated blood pressure (BP) has been reported in young people and seems to be associated with body mass index (BMI) and reduced physical activity (PA).

Aim: This study sought to analyse the association of BP with BMI, PA intensity patterns and cardiorespiratory fitness (CRF) in youth.

Subjects and methods: A cross-sectional study was carried out including 66 boys (13.91±1.76) and 97 girls (14.02±1.71). Anthropometric characteristics, CRF and BP were assessed during school time and accelerometers were utilized to determine intensity of PA.

Results: The linear regression model, adjusted for age, sex and height, showed that higher values of BMI were associated (p≤0.05) with higher values of systolic blood pressure (SBP) (1.39; 95% CI: 0.56; 2.23) and diastolic blood pressure (DBP) (1.52; 95% CI: 0.68; 2.37). Additionally, SBP, but not DBP, was inversely associated (p≤0.05) with moderate PA (?0.25; 95% CI: ?0.47; ?0.02) and positively correlated with sedentary activities (0.04; 95% CI: 0.00; 0.08).

Conclusion: The present study showed that BMI and time spent in sedentary activities were inversely associated with SBP. However, time spent in moderate PA was positively associated with SBP. BMI was the single predictor of DBP.     

Changes in aerobic fitness and body fat during army recruit training

Summary Aerobic fitness and related indices were evaluated in 254 soldiers at the beginning and near the end of initial army recruit training. Aerobic fitness in terms of maximal aerobic power was predicted from the Astrand-Ryhming submaximal heart rate bicycle test. Estimated vO₂ max increased by 8%, 42.0–45.3 ml/kg·min. Accompanying this increase in aerobic capacity was a decline in body fat content without a change in body weight. It is concluded that army recruit training at the time of this study was effective in terms of increasing aerobic work capacity and reducing excess body fat.HQ UNFICYP BFPO 567     

Association among basal serum BDNF, cardiorespiratory fitness and cardiovascular disease risk factors in untrained healthy Korean men

Evidence suggests that serum brain-derived neurotrophic factor (serum BDNF) can be affected by cardiorespiratory fitness (CRF), but this relationship is far from clear. Recent reports show an inverse relationship between serum BDNF and CRF in healthy individuals, and other studies suggest a possible association between serum BDNF and cardiovascular disease. However, the possible interaction between serum BDNF, CRF, and cardiovascular disease risk has not been studied. The purpose of this study was to examine the association among serum BDNF, CRF, and cardiovascular disease risk factors in healthy men. The investigation involved a large sample of men (n = 995, age range: 20-76 years) who live in the central area of South Korea and were recruited into the Preventive Health Study. Our study showed a significant inverse relationship between serum BDNF and relative VO(2)max (r = -0.412, p < 0.0001) and heart rate reserve (r = -0.194, p < 0.0001). Serum BDNF was positively correlated with body mass index (r = 0.80, p < 0.0001), total cholesterol (r = 0.185, p < 0.0001), and triglyceride (r = 0.320, p < 0.0001). Our data suggest that serum BDNF may be associated with effects of increased CRF on cardiovascular disease. However, more research is clearly needed before a determination of whether, and to what extent, serum BDNF may be responsible for some of the health benefits associated with CRF.     

Concurrent improvements in cardiorespiratory and muscle fitness in response to total body recumbent stepping in humans

A group of 26 sedentary adults [mean age 48.4 (SD 6.4) years] were allocated randomly into either a non-exercising control group (CON, n=9) or an exercise group (EX, n=17) that trained 3 days a week for 12 weeks using a total body recumbent stepper (TBRS). Training intensity and duration progressed from 50% of heart rate reserve maximum (HRR_max) for 20 min to 75% HRR_max for 40 min. Maximal exercise responses were measured during incremental treadmill (TM) and TBRS tests to examine the specificity of the adaptations to training. Muscle strength was measured using a one repetition maximum (1 RM) test for the leg press (LP), chest press (CP), and seated row (SR). Muscle endurance (END) was evaluated for LP, CP, and SR as the number of repetitions achieved before failure when exercising at an intensity of 60% of baseline 1 RM. Body composition was estimated using the sum of seven skinfolds. After training, significant increases (P<0.05) in maximal oxygen uptake and exercise time were observed in the EX group on both the TM (9.3% and 4.8%, respectively) and TBRS (18.2% and 70.5%, respectively). The TBRS training resulted in significant increases (P<0.01) in 1 RM and END of the legs, chest, and back, with greater magnitude of improvements observed for END. Furthermore, TBRS training resulted in a significant increase in lean body mass and significant reductions in fat mass and percentage body fat (P<0.01). The CON did not show changes in any measurement (P>0.05). These data indicated concurrent improvements in both cardiovascular and muscle fitness. The greater improvements observed on the TBRS test and in muscle endurance suggest the adaptations are specific to the mode of training. Electronic Publication     

Association of adiposity, cardiorespiratory fitness and exercise practice with the prevalence of type 2 diabetes in Brazilian elderly women

BACKGROUND: Diabetes incidence in people with advanced age is increasing at an alarming rate, and for this reason the screening of high-risk individuals such as elderly women is critically important. OBJECTIVE: To analyze the association of adiposity, cardiorespiratory fitness and exercise practice with type 2 diabetes (T2D) in elderly Brazilian women. METHODS: Participated of this cross sectional study 1,059 elderly women (mean 69.5 yr; SD 6.1), who self-reported family history of cardiovascular disease, smoking status, hypertension, and T2D diagnosed previously by a physician. The following independent variables were assessed: exercise practice, body mass index, waist circumference, and cardiorespiratory fitness. Logistic regression analysis was used to investigate the association between each independent variable with T2D using adjusted-models. RESULTS: T2D prevalence was 16%. General and central adiposity were directly associated with T2D, whereas cardiorespiratory fitness was inversely related with T2D. The joint effect of exercise practice and central adiposity showed that inactive women had higher odds ratio for T2D when compared with active ones, within the same WC group. Inactive women with WC > or = 94.0 cm had an odds ratio of 5.8 (95%IC 1.3-25.3). CONCLUSIONS: A direct positive association was found between general and central adiposity, as well as an inverse relation between CRF and exercise practice with T2D. Elderly women who practice exercise regularly had lower odds for T2D. Health professionals should encourage individuals of all ages to engage on regular exercise practice, which could reduce body fatness and may be beneficial in reducing the prevalence of T2D in older ages.     

Aerobic fitness and body fat of young British males entering the army

Summary Aerobic fitness and percent body fat were measured in a sample of 438 male Army recruits between the ages of 17 and 30 prior to the commencement of training. The sample came from all areas of England and Wales. Aerobic fitness, as represented by maximal oxygen uptake ( O₂ max), was predicted from the Astrand submaximal bicycle heart rate test. Body fat was predicted from four skinfold measurements. Total group means ±SD were: age, 19.5±2.5 years; O₂ max 41.7 ±8.3 ml/kg·min; and body fat, 14.5±4.8% of body weight. O₂ max varied with age, athletic participation and aptitude score. No relationship was found with occupation of parent, prior civilian occupation or smoking severity. When adjusted for methodological differences, O₂ max was slightly below similar Army entrants in Norway and the United States.     

Body fat, menarche, fitness and fertility

Many well-trained athletes, ballet dancers and women who dietexcessively have secondary or primary amenorrhoea. Less extensivetraining or weight loss may result in anovulatory menstrualcycles, or a shortened luteal phase. These disruptions of reproductiveability are due to hypothalamic dysfunction, which is correlatedwith weight loss or excessive leanness. It is proposed thatthese associations are causal and that the high percentage ofbody fat (26–28%) in the mature human female may influencereproduction directly. Four mechanisms are known: (i) adiposetissue converts androgens to oestrogen by aromatization. Bodyfat is thus a significant extragonadal source of oestrogen;(ii) body weight, hence fatness, influences the direction ofoestrogen metabolism to more potent or less potent forms; leanerwomen make more catechol oestrogens, the less potent form; (iii)obese women and young, fat girls have a diminished capacityfor oestrogen to bind sex-hormonebinding-globulin; (iv) adiposetissue can store steroid hormones. An indirect mechanism maybe signals of abnormal control of temperature and changes inenergy metabolism, which accompany excessive leanness. The hypothalamicreproductive dysfunction results in abnormal gonadotrophin secretion:there is an age inappropriate secretory pattern of luteinizinghormone (LH) and follicle stimulating hormone (FSH), resemblingthat of prepubertal children. The secretion of LH and the responsesto LHRH are reduced in direct correlation with the amount ofweight loss. Other evidence from non-athletic and athletic womenand mammals is presented in support of the hypothesis that aparticular, minimum ratio of fat to lean mass is normally necessaryfor menarche ({small tilde}17% fat/body wt) and the maintenanceof female reproductive ability ({small tilde}22% fat/body wt).Nomograms are given for the prediction of these critical weightsfor height from a fatness index; these weights are useful clinicallyin the evaluation of nutritional amenorrhoea and the restorationof fertility in underweight women. Evidence is presented thatundernutrition and hard physical work can affect the naturalfertility of populations, by the delay of menarche, a longerperiod of adolescent subfecundity, a longer birth interval andan earlier age of menopause. Data from a study of the longtermreproductive health of 2622 former college athletes comparedwith 2766 non-athletes show that the former college athleteshad a significantly lower lifetime occurrence of breast cancerand cancers of the reproductive system, and a lower lifetimeoccurrence of benign tumours of these tissues, compared withthe non-athletes. Over 82% of the former athletes began theirtraining in high school or earlier. A possible explanation maybe that long-term, the former athletes had lower levels of oestrogenbecause they were leaner, and more of the oestrogen was metabolizedto the non-potent catechol oestrogens. The observed reductionof cancer risk associated with physical exercise has potentialfor public health.     

Physical activity,cardiorespiratory fitness,motor performance,and growth of senegalese pre-adolescents

Profiles of usual physical activity, cardiorespiratory fitness, motor performance, and growth were measured regularly for 2 years in 40 rural Senegalese (Wolof) children—20 boys and 20 girls—who were 10 or 11 years of age and clinically healthy at the beginning of the study. Compared to National Center for Health Statistics (NCHS) reference data, the children showed lower weight-for-age and height-for-age throughout the period of observation; the increments of height from year to year were not remarkable and growth spurts were not observed during the study period. The motor performance (running, jumping, throwing) and spirometer test results were inferior to age-matched American children. When adjusted for actual weight and height, jumping and throwing results were similar to those of American children, but running results remained inferior. Cardiorespiratory function appeared inferior to American children of the same age, although speed of recovery after exertion demonstrated good cardiorespiratory efficiency. Physical activity, directly observed over 2-day periods on 4 occasions, corresponded to an average energy expenditure of 1.66 Mets (multiples of basal metabolic rate) (boys) and 1.76 Mets (girls), which are close to the FAO/WHO/UNU values for age. The higher energy expenditure of girls could be explained by their participation in domestic tasks. Both boys and girls spent an average of 42 minutes/day on activities equivalent to energy consumption rates equal or greater than 4.8 Mets. Significant correlations existed between the activity index and cardiorespiratory fitness in boys, and between the activity index and motor performances in girls. Physical aptitudes of sampled children appear compatible with the demands of their social and agricultural tasks. However, it appears that persistent malnutrition may have stunted their growth and motor performances. © 1993 Wiley-Liss, Inc.     

Relationships between anthropometry, cardiorespiratory fitness indices and physical activity levels in different age and sex groups in rural Senegal (West Africa)

BACKGROUND: A high level of activity is commonplace in traditional subsistence societies. Physiological characteristics of individuals, including body composition and physical fitness, could be limiting factors when performing daily tasks. OBJECTIVES: The study investigated the relationships between cardiorespiratory fitness, nutritional status and physical activity patterns, so as to test the hypothesis that these relationships are less straightforward in children than in adults. STUDY DESIGN: Four different groups of individuals from rural Senegal were investigated: 99 10-13-year-old children of both sexes (11.1 +/- 1.5 years old) from two settings in Senegal (Lambaye and Podor), 43 adolescent girls (15.5 +/- 0.5 years), and 30 adult women (17-40 years). METHODS: Subjects undertook a step test, and anthropometric measurements were collected. Continuous heart rate (HR) monitoring was performed for 8-12 h. The flex-HR method was used to estimate levels of activity (per cent of time spent under or over the flex-HR). RESULTS: Ten to 13-year-old children and adolescent girls presented slight degrees of malnutrition. Adult women were apparently not nutritionally deprived. Differences in cardiorespiratory fitness were found among 10-13-year-old children, while adult women performed better than adolescent girls. Children from Lambaye had a higher level of activity than children from Podor. Similarly, adult women were more active than adolescent girls. No relationships were found between cardiorespiratory or anthropometric measurements and per cent of time spent above the flex-HR (> flex-HR) in 10-13-year-old children. In contrast, in adult women and adolescent girls, body composition and cardiorespiratory indices were significant predictors of activity levels. CONCLUSION: Our data support the hypothesis that activity levels are less dependent upon physiological characteristics in children than in adults in traditional subsistence societies.     

Relationships between anthropometry,cardiorespiratory fitness indices and physical activity levels in different age and sex groups in rural Senegal (West Africa)

Background: A high level of activity is commonplace in traditional subsistence societies. Physiological characteristics of individuals, including body composition and physical fitness, could be limiting factors when performing daily tasks.

Objectives: The study investigated the relationships between cardiorespiratory fitness, nutritional status and physical activity patterns, so as to test the hypothesis that these relationships are less straightforward in children than in adults.

Study design: Four different groups of individuals from rural Senegal were investigated: 99 10–13-year-old children of both sexes (11.1?±?1.5 years old) from two settings in Senegal (Lambaye and Podor), 43 adolescent girls (15.5?±?0.5 years), and 30 adult women (17–40 years).

Methods: Subjects undertook a step test, and anthropometric measurements were collected. Continuous heart rate (HR) monitoring was performed for 8–12?h. The flex-HR method was used to estimate levels of activity (per?cent of time spent under or over the flex-HR).

Results: Ten to 13-year-old children and adolescent girls presented slight degrees of malnutrition. Adult women were apparently not nutritionally deprived. Differences in cardiorespiratory fitness were found among 10–13-year-old children, while adult women performed better than adolescent girls. Children from Lambaye had a higher level of activity than children from Podor. Similarly, adult women were more active than adolescent girls. No relationships were found between cardiorespiratory or anthropometric measurements and per?cent of time spent above the flex-HR (>flex-HR) in 10–13-year-old children. In contrast, in adult women and adolescent girls, body composition and cardiorespiratory indices were significant predictors of activity levels.

Conclusion: Our data support the hypothesis that activity levels are less dependent upon physiological characteristics in children than in adults in traditional subsistence societies.     

Physical activity, fat intake and body fat

The body fatness of a subject is a long-term reflection of the energy balance, the more intake exceeds expenditure the more energy is stored as fat. There is not yet a clear answer on the question whether the current obesity epidemic is a consequence of gluttony or sloth. Review studies do not show a reduction of physical activity over the years, and food intake is difficult to measure in daily life conditions. Food intake can only be derived from self-report, where under-reporting of food intake and selective underreporting of fat intake are major issues. Fat intake might be an important factor in the increase of body weight. Many studies suggest the capacity of the body to oxidize dietary fat is a major risk factor for a positive energy balance. Additionally, there is evidence that most of the fat consumed is stored before oxidation. Obesity prone subjects might be characterized by a higher storage of dietary fat. The only way to increase the oxidation of dietary fat, other than consuming more dietary fat, is to increase energy expenditure by an increase of physical activity. Indeed, there are indications that physical activity is an important determinant of fat oxidation. Based on the evidence presented, it is concluded that the obesity epidemic is mainly due to a high dietary intake, especially as fat, and that physical activity can be a tool to modulate the effect of fat intake on body fat.     

Genomics of body fat percentage may contribute to sex bias in anorexia nervosa

Anorexia nervosa (AN) occurs nine times more often in females than in males. Although environmental factors likely play a role, the reasons for this imbalanced sex ratio remain unresolved. AN displays high genetic correlations with anthropometric and metabolic traits. Given sex differences in body composition, we investigated the possible metabolic underpinnings of female propensity for AN. We conducted sex‐specific GWAS in a healthy and medication‐free subsample of the UK Biobank (n = 155,961), identifying 77 genome‐wide significant loci associated with body fat percentage (BF%) and 174 with fat‐free mass (FFM). Partitioned heritability analysis showed an enrichment for central nervous tissue‐associated genes for BF%, which was more prominent in females than males. Genetic correlations of BF% and FFM with the largest GWAS of AN by the Psychiatric Genomics Consortium were estimated to explore shared genomics. The genetic correlations of BF%_male and BF%_female with AN differed significantly from each other (p < .0001, δ = ?0.17), suggesting that the female preponderance in AN may, in part, be explained by sex‐specific anthropometric and metabolic genetic factors increasing liability to AN.     

Characteristics of body fat, body fat percentage and other body composition for Koreans from KNHANES IV

Accurate measurement of fat mass has become increasingly important with the increasing incidence of obesity. We assessed fat and muscle mass of Koreans with the Korea National Health and Nutrition Examination Survey IV (KNHANES IV). We studied 10,456 subjects (aged 20 to 85 yr; 4,476 men, 5,980 women). Fat and muscle mass were measured by dual-energy x-ray absorptiometry. Reference values of body compositions were obtained using the LMS method. The fat mass index (FMI, body fat mass/height(2); kg/m(2)) of Korean men did not correlate with age (P = 0.452), but those of Korean women (P < 0.001) did. The ratio of percentage of fat in the trunk and legs was positively related with age in both the genders. The appendicular lean mass/height(2) (kg/m(2)) of Korean men was negatively related to age (P < 0.001). In women, this ratio increased with age (P < 0.001). When we defined obesity according to the FMI classification, the rates of obesity were 6.1% (FMI > 9 kg/m(2)) in men and 2.7% (FMI > 13 kg/m(2)) in women. It is concluded that the muscle mass decreases and obesity increases with aging in Korean men, whereas both fat mass and obesity increase with aging in Korean women.