Insulin sensitivity, cardiorespiratory fitness, and physical activity in overweight Hispanic youth

OBJECTIVE: To determine whether cardiorespiratory fitness and/or physical activity (PA) were related to measures of insulin sensitivity and secretion independent of body composition in overweight Hispanic children. RESEARCH METHODS AND PROCEDURES: Ninety-five Hispanic children (n = 55 boys; n = 40 girls; 8 to 13 years old) participated in this investigation. The frequently sampled intravenous glucose tolerance test was used to determine the insulin sensitivity index (SI), the acute insulin response, and the disposition index. Cardiorespiratory fitness [maximal oxygen uptake (VO(2max))] was evaluated using a treadmill protocol, and PA was determined by an interviewer-administered questionnaire. Body composition was measured using DXA. RESULTS: Unadjusted correlations indicated that VO(2max) (milliliters of O(2) per minute) was negatively related to SI (r = -0.46, p < 0.05) and disposition index (r = -0.31, p < 0.05) and positively associated with fasting insulin (r = 0.29, p < 0.05), but these relationships were no longer significant once gender, Tanner stage, fat mass, and soft lean tissue mass were included as covariates (all p > 0.05). Multivariate linear regression analysis showed that body fat mass explained 53% of the variance in SI and that VO(2max) (milliliters of O(2) per minute) was not independently related to SI. Cardiorespiratory fitness was positively related to both fat mass (r = 0.43, p < 0.001) and soft lean tissue mass (r = 0.89, p < 0.001). PA was not related to any measure of insulin sensitivity and secretion. DISCUSSION: Cardiorespiratory fitness, as determined by VO(2max) (milliliters of O(2) per minute), was not independently related to insulin sensitivity or secretion, suggesting that VO(2max) influences insulin dynamics indirectly through fat mass.     

Non-esterified fatty acid levels and physical inactivity: the relative importance of low habitual energy expenditure and cardio-respiratory fitness

The fasting concentration of non-esterified fatty acids (NEFA) and the degree to which it declines during an oral glucose tolerance test are closely associated with insulin resistance and glucose intolerance. However, relatively few studies have described possible environmental determinants of NEFA concentrations. Physical activity is likely to be related to NEFA levels, but habitual activity level is difficult to quantify in epidemiological studies. In particular, it is unclear whether NEFA is more closely related to cardio-respiratory fitness or to habitual energy expenditure. In order to quantify these relationships, we analysed data from the Ely prospective population-based study in which 931 subjects underwent a glucose tolerance test with measurements of cardio-respiratory fitness and 4 d energy expenditure by heart-rate monitoring, a technique previously validated against whole-body calorimetry and doubly-labelled water. In order to estimate the latent variables of usual fitness and energy expenditure, a subset of 190 subjects underwent repeat testing on three further occasions over 1 year. In analyses adjusting only for age and sex, energy expenditure and cardio-respiratory fitness were both negatively correlated with the total area under the NEFA curve following the oral glucose load (standardised beta coefficients -0.030 and -0.039 respectively; both P<0.001) However, further adjustment for degree of obesity and bivariate measurement error suggested that the effect of energy expenditure was significantly greater than that for fitness (-0.047 and -0.005 respectively). These results suggest that the area under the NEFA curve in the oral glucose tolerance test, a measure of insulin sensitivity, is strongly associated with the habitual level of physical activity.     

Trends in body fat, body mass index and physical fitness among male and female college students

There have been many publications in recent years reporting on the quantity of physical activity among college students using indirect indicators such as steps walked per day or time spent on physical activities. The purpose of this study was to describe the trends of physical fitness related to BMI and body fat among university students between 1996 and 2008. The results showed a significant decline in the average fitness levels measured as an estimation of VO(2max) for male and female students (p < 0.001 for both sexes). The linear trend for BMI by years was not significant for both sexes (p for males = 0.772, p for females = 0.253). On average, in the last 13 years, % body fat was increasing 0.513%/year for males and 0.654%/year for females. There is a significant indirect correlation between the student's VO(2max) levels and % body fat, r = -0.489; p < 0.001 for males; and r = -0.416, p < 0.001 for females. Approximately 23.9% of the variance in the VO(2max) levels in males and 17.3% in females can be explained by the variance in % body fat. The results support recent findings that physical fitness among college students is declining and body fatness is increasing.     

The role of exercise physical activity in varying the total energy expenditure in healthy Japanese men 30 to 69 years of age

This study was designed to examine 1) the role of exercise physical activity (EPA), and then 2) physical fitness and body composition upon variation of the total energy expenditure (TEE) in healthy Japanese men aged 30 to 69 y (n = 40). EPA and TEE were assessed over 14 d using an accelerometer and a doubly labeled water (DLW) method, respectively. Basal metabolic rate (BMR) was measured after 10 h fasting on the morning of the day of DLW dosing. Physical activity-induced energy expenditure (PAEE) was calculated by subtracting BMR and diet-induced thermogenesis (DIT = 101 TEE) from TEE. EPA was subdivided into three intensities: low, moderate and high and the accumulated duration (time expressed in minutes) of each of these was calculated. Body composition and physical fitness (VO2max) were determined using an underwater weighing method and a treadmill exercise test, respectively. BMR (mean +/- SD: 1,459 +/- 181 kcal/d) declined significantly with age (r = -0.37. p < 0.05), but PAEE (946 +/- 320 kcal/d) and TEE (2,672 +/- 369 kcal/d) did not. A multiple stepwise regression analysis was used to develop an empirical model that relates energy expenditure measured by the DLW (TEE) to age, height, body mass index, FM, FFM, percentage body fat, VO2max, and accumulated duration spent for low-, moderate-, and high-intensity EPA. The results revealed that FFM and high-intensity EPA were identified as important determinants of TEE and accounted for 51%. We may therefore conclude that 1) high-intensity EPA appears to be relevant in determining TEE, especially among active individuals, and 2) body composition was more important than physical fitness in determining TEE in this population.     

Quantifying the association between habitual energy expenditure and blood pressure

BACKGROUND: Previous studies have demonstrated an association between physical inactivity and hypertension, but the methods used to assess activity have been subjective and imprecise. Recently methods have become available allowing measurement of energy expenditure in free-living populations. Our aim was to employ these methods to assess the independent association between energy expenditure, cardio-respiratory fitness and blood pressure. METHODS: In a cross-sectional study of 775 people (45-70 years) participating in a continuing population-based cohort study, energy expenditure was assessed by 4 days of heart rate monitoring with individual calibration of the relationship between heart rate and energy expenditure, a method validated against doubly-labelled water and whole body calorimetry. Cardio-respiratory fitness was assessed in a sub-maximal test. To adjust for measurement error in the assessment of usual energy expenditure and fitness, 190 subjects repeated both tests on three further occasions at 4-monthly intervals. RESULTS: A highly significant linear trend in blood pressure was found across quintiles of the physical activity level, the ratio of total energy expenditure to basal metabolic rate. The differences in the mean systolic/diastolic blood pressure between the top and bottom quintile was 6.3/4.4 mmHg in men and 10.7/5.9 mmHg in women. These effects were independent of obesity and cardio-respiratory fitness. Correction for measurement error suggests that the true underlying relationship between usual energy expenditure and blood pressure is stronger still. CONCLUSIONS: These findings are compatible with a strong association between usual energy expenditure and blood pressure and support public health strategies aimed at increasing overall energy expenditure.     

Culturally tailored aerobic exercise intervention for low-income Latinas

PURPOSE: To determine the efficacy of community-based, culturally tailored exercise intervention on the moderate and vigorous physical activity and physiologic outcomes of low-income Latino women (Latinas). DESIGN: A randomized trial contrasted safety education to an aerobic dance intervention. SETTING: Interventions were held in a "store-front" exercise site near a community clinic. SUBJECTS: Sedentary low-income Latinas (N = 151; 18-55 years; 70% overweight/obese) were recruited. Retention was 91% for follow-up measures. INTERVENTION: Three sessions per week of supervised aerobic dance were provided for 6 months. Controls attended 18 safety education sessions over 6 months. MEASURES: Physical activity and aerobic fitness (VO2max) were primary outcomes. RESULTS: Participants in the exercise group reported more vigorous exercise (p < .001) and walking (p = .005) at post-test than controls. Aerobic dance and unsupervised activity resulted in a five-fold greater increase in relative VO2max compared with controls (p < .001). Although exercise and fitness decreased at follow-up, vigorous exercise (p = .001) and relative VO2max (p < .001) remained higher in the exercise group, suggesting maintenance at 1 year. CONDUSION:. Culturally tailored aerobic dance can increase vigorous physical activity, possibly generalizing to walking, and the combination can improve cardiorespiratory fitness in low-income, overweight, sedentary Latinas.     

Assessing the perceived environment among minimally active adolescent girls: validity and relations to physical activity outcomes

PURPOSE: This study examined how adolescents' perceptions of exercise resources in the environment relate to physical activity outcomes. METHODS: Perceptions of the availability and use of environmental resources, vigorous physical activity (VIG), daily energy expenditure (KCAL), lifestyle activities (LA), and cardiovascular fitness (Vo2peak) were assessed cross-sectionally among 87 minimally active adolescent girls (ages 14-17). To validate adolescent reports, the perceived availability of environmental resources was also assessed from 47 parents. RESULTS: Adolescent-parent agreement over the availability of resources was modest for the home domain (r = .62, p < .001) and weak for the community domain (r = .14, p > .05). Adolescents' perceptions of resource availability in both the home and community domains were positively associated with VO2peak (p < .05) but unrelated to VIG, KCAL, and LA. Adolescents' use of home resources was positively correlated with both VIG and LA (p < .05). CONCLUSION: Minimally active adolescent girls were more attuned to and likely to use the resources for physical activity located in their home environment as opposed to the community environment.     

Physical activity, cardiorespiratory fitness and body mass index as predictors of substantial weight gain and obesity: the Canadian physical activity longitudinal study

BACKGROUND: Obesity is a growing health issue in Canada and the identification of the determinants of obesity is important for the development of prevention strategies. The purpose of this investigation was to determine the relationships between physical activity, cardiorespiratory fitness, body mass index (BMI), and the development of future obesity. METHODS: The sample included 459 adults (18+ y; 223 men, 236 women) from the Canadian Physical Activity Longitudinal Study (PALS; 2002-04). Data on physical activity, smoking, alcohol consumption, BMI, and cardiorespiratory fitness (VO2max) were collected in 1981 and 1988. The mean BMI, physical activity, and VO2max were calculated across the 1981 and 1988 measures. Self-reported height and weight were collected in the 2002-04 survey, and participants were classified as overweight (BMI 25 to 29.9 kg/m2) or obese (BMI 230 kg/m2). Logistic regression was used to predict overweight, obesity or substantial weight gain (10 kg or more) in 2002-04, controlling for age, sex, smoking and alcohol use. RESULTS: Higher VO2max in 1981-88 was associated with lower odds of obesity in 2002-04 (OR = 0.87; 95% Cl: 0.76-0.99, p < 0.05), and higher BMI in 1981-88 was associated with higher odds of obesity in 2002-04 (1.84; 1.52-2.20, p < 0.0001). In women, higher VO2max (0.82; 0.72-0.93) resulted in lower odds of a 10 kg weight gain. CONCLUSIONS: The results indicate that cardiorespiratory fitness and previous BMI are important predictors of future weight gain and obesity, and should be incorporated in strategies to identify individuals at increased risk of obesity.     

Physical training augments plasma catecholamines and natural killer cell activity

To elucidate the effects of a 10-week exercise training period on physical fitness and plasma catecholamine concentration at rest, and on natural killer cell activity in young healthy untrained females, subjects (20-22 years old. N = 16) carried out physical training by a protocol which consisted of treadmill jogging at a work-intensity of 50% of their VO2max, two hours a day three times a week for ten weeks. VO2max was increased significantly from 33.1 +/- 3.4 ml/kg/min to 38.3 +/- 6.6 ml/kg/min by the ten weeks of physical training (P < 0.005), and natural killer cell activity was also increased significantly from 31.9 +/- 14.3% to 46.4 +/- 18.4% (P < 0.05). The concentrations of epinephrine and norepinephrine before and after physical training were 18.3 +/- 8.7 pg/ml and 20.4 +/- 8.9 pg/ml, and 134.1 +/- 52.2 pg/ml and 248.1 +/- 106.8 pg/ml (P < 0.005), respectively. Changes in norepinephrine and epinephrine correlated with the change in VO2max (r = 0.780, P < 0.005; r = 0.556, P < 0.05). While the change in natural killer cell activity correlated with the change in epinephrine (r = 0.623, P < 0.01), the correlation of the change in natural killer cell activity with change in norepinephrine did not reach statistical significance (r = 0.497, P = 0.0503). From these results we concluded that physical training augments plasma catecholamine levels and natural killer cell activity at rest in young healthy females.     

Cardiovascular disease risk factors in 6-7-year-old Danish children: the Copenhagen School Child Intervention Study

OBJECTIVE: To describe population values in cardiovascular disease (CVD) risk factors such as blood lipids, fasting insulin and glucose and blood pressure in this young age group, and calculate associations to fitness and fatness. METHODS: Participants were 369 boys (6.8 +/- 0.4 years) and 327 girls (6.7 +/- 0.4 years) from preschool classes in Copenhagen. Peak VO2, blood pressure (BP), fat content and anthropometry were determined. A fasting blood sample was analysed for insulin, glucose and blood lipids. Physical activity was measured using accelerometry. RESULTS: Mean BMI, BP and blood lipids were not different between sexes. Fat percentage assessed from skinfolds was higher (21.5% vs. 16.5%) in girls than in boys (P < 0.001). Peak VO2 and physical activity were higher in boys than in girls (8% and 9%, respectively). Peak VO2 associated to fatness independent of body weight (r = 0.41; P < 0.001). Among the CVD risk factors, fitness was associated to high-density lipoprotein (HDL) (r = 0.14; P < 0.01) and physical activity (r = 0.12; P < 0.01). Fatness assessed by skinfold was associated to blood pressure (r = 0.19-0.28; P < 0.001), to fasting glucose (r = 0.11, P < 0.05) and insulin (r = 0.17; P < 0.001). CONCLUSIONS: Mean BP in 6-7-year-old Danish children has decreased since 1979 and BMI has increased modestly since 1986/1987. The lipid profile was similar compared with data from 1973 and 1978 in Danish children. Weak relationships were found between CVD risk factors, fitness and fatness.     

Energy expenditure of agricultural workers in an area of endemic schistosomiasis in the Sudan.

Indices of physiological performance in the field under natural working conditions were measured in 46 Sudanese Gezira villagers and related to exercise performance under controlled laboratory conditions. The effect of Schistosoma mansoni infection on energy expenditure in the field was also investigated. A highly significant positive association between the maximal aerobic power output (VO2 max) measured in the laboratory with energy expenditure in the field (r = + 0.51, p less than 0.001) and with changes in body weight during work (r = 0.41, p less than 0.01) was found. The villagers' energy expenditure in field work amounted to 25-28 KJ/min, which corresponded to more than 50% of their predicted VO2 max. They maintained that relative work level for more than an hour. The differences in energy expenditure between moderately infected and non-infected villagers with schistosomiasis did not attain statistical significance but the number of non-infected subjects on which the comparison was based was small.     

The association between physical fitness and diagnosed chronic disease in health maintenance organization members

PURPOSE: The purpose of this investigation was to determine the relationship between predicted cardiorespiratory fitness (predicted VO2max) and diagnosed chronic disease. DESIGN: A stratified random sample of individuals was surveyed. SETTING: Large Health Maintenance Organization (HMO) in the upper Midwest. SUBJECTS: HMO members (N = 8000), age 40 and over, with none, one, or two or more of the following diagnosed chronic conditions: hypertension, diabetes, dyslipidemia, and heart disease. MEASURES: Predicted VO2max was estimated for those respondents who completed the survey providing all critical data elements (n = 4121; representing 51.5% of total sample). Predicted VO2max was compared across chronic conditions using analysis of variance. The proportion of subjects across fitness quintiles by number of chronic conditions was tested using the chi 2 test. RESULTS: Subjects without chronic conditions showed higher predicted VO2max values (29.8 +/- 7.7 ml/kg/min) than those with one (25.9 +/- 7.8 ml/kg/min) or two or more conditions (25.7 +/- 7.9 ml/kg/min) (p < .0001). Subjects with diabetes, hypertension, and heart disease reported lower predicted VO2max than their healthier counterparts (p < .0001), but this was not the case for dyslipidemia subjects (27.6 +/- 7.6 vs. 27.4 +/- 8.2 ml/kg/min, respectively; p > .58). A larger proportion of diseased subjects was in the lowest fitness quintile for diabetes, hypertension, and heart disease, but not for dyslipidemia. CONCLUSIONS: As a group, chronic disease patients appear to have lower levels of physical fitness than subjects without chronic disease. Physical fitness improvement in diseased populations should be supported in the clinical setting.     

Low-frequency physical activity insufficient for aerobic conditioning is associated with lower body fat than sedentary conditions

We aimed to show the relationships between reported physical activity, fitness level, and body composition in healthy adult office-working Kuwaiti males (n = 45). Reported level of physical activity (group 0 = no routine exercise, n = 10; group 1 = routine exercise once per wk, n = 19; group 2 = routine exercise two or more times per wk, n = 16) was determined from recall questionnaires. Aerobic fitness levels were assessed from resting exercise heart rates and measurement of maximal oxygen uptake (treadmill exercise, Bruce protocol). Body composition was estimated from measurements of body weight, body height, and seven skin-folds. None of the subjects reported dieting to reduce or maintain their body weight. Despite minimal and not statistically significant differences in resting heart rates, VO(2)max, VO(2)max/kg body weight, and VO(2)max/kg lean body mass, the sedentary group (group 0) had a much higher (12--14 kg) average body weight, higher (12--13 kg) body fat, and thicker skin folds than the more physically active groups 1 and 2. Groups 1 and 2 did not differ significantly from each other with regard to fitness and body composition parameters. Thus, routine physical activities insufficient to result in aerobic conditioning were found to be associated with lower body weight and lower body fat compared to those present in subjects reporting the total absence of any routine physical activity. These data are consistent with the hypothesis that even mild levels of routine physical activity are associated with levels of energy turnover that allow less intense and/or frequent periods of positive energy balance, resulting in maintenance of lower body fat than in totally sedentary people. Frequency of participation in routine physical activities may also reflect the level of non-exercise related physical activities and thus relate to the ability to minimize weight gain.     

Energy expenditure of agricultural workers in an area of endemic schistosomiasis in the Sudan

Indices of physiological performance in the field under natural working conditions were measured in 46 Sudanese Gezira villagers and related to exercise performance under controlled laboratory conditions. The effect of Schistosoma mansoni infection on energy expenditure in the field was also investigated. A highly significant positive association between the maximal aerobic power output (VO2 max) measured in the laboratory with energy expenditure in the field (r = + 0.51, p less than 0.001) and with changes in body weight during work (r = 0.41, p less than 0.01) was found. The villagers' energy expenditure in field work amounted to 25-28 KJ/min, which corresponded to more than 50% of their predicted VO2 max. They maintained that relative work level for more than an hour. The differences in energy expenditure between moderately infected and non-infected villagers with schistosomiasis did not attain statistical significance but the number of non-infected subjects on which the comparison was based was small.     

Reliability and validity of self-reported physical activity in the Nord-Trøndelag Health Study: HUNT 1

BACKGROUND: A large health survey was previously conducted in 1984-86, the Nord-Tr?ndelag Health Study (HUNT 1), and another was conducted in 1995-97 (HUNT 2). A third, HUNT 3, started in 2006. However, the physical activity (PA) questionnaires have not yet been validated. AIMS: To assess the reliability and validity of the self-reported physical activity questionnaire in the Nord-Tr?ndelag Health Study (HUNT 1). METHODS: The HUNT 1 questionnaire was administered to a random sample of 108 healthy men aged 20-39 years. Repeatability was assessed with a repeat questionnaire after one week, and validity by comparing results with direct measurement of VO(2) during maximal work on a treadmill, with ActiReg, an instrument that measures PA and energy expenditure (EE) and with the International Physical Activity Questionnaire (IPAQ). ActiReg records the main body positions (stand, sit, bent forward and lie) together with the motion of the trunk and/or one leg each second. RESULTS: The results indicated strong, significant agreement on test-retest (weighted kappa frequency, r=0.80, intensity, r=0.82, and duration, r=0.69). We found a moderate, significant correlation, r=0.48 (p< or =0.01), between the index based on questionnaire responses and VO(2max.) Metabolic equivalent (MET) values of 6 or more from ActiReg and "vigorous activity' from the IPAQ most strongly correlated with the index (r=0.39, r=0.55, respectively). Associations of other measures obtained from ActiReg with questionnaire responses were weaker. CONCLUSIONS: Our results indicate that the PA questionnaire in HUNT 1 is reproducible and provides a useful measure of leisure-time PA for men. The questionnaire is very short, and compared favourably with much longer instruments for assessment of more vigorous PA. It should be an appropriate tool for use in further epidemiological studies, particularly when the interest is in aspects of PA reflected in fitness or METs greater than 6.     

Validity and repeatability of the EPIC-Norfolk Physical Activity Questionnaire

BACKGROUND: Physical activity is an important lifestyle which is often poorly assessed in epidemiological studies. The European Prospective Investigation into Cancer Study-Norfolk cohort (EPIC-Norfolk), a large population-based cohort study, has developed a comprehensive questionnaire to assess activity in different domains of life aimed at assessing total energy expenditure. We report the repeatability of this instrument and its validity against repeated objective measures of fitness and energy expenditure undertaken throughout the time frame of reference of the questionnaire. METHODS: The validity of the instrument was measured in 173 individuals randomly selected from a continuing population-based cohort study. Energy expenditure was assessed by four separate episodes of 4-day heart-rate monitoring, a method previously validated against whole body calorimetry and doubly-labelled water. Cardio-respiratory fitness was assessed by four repeated measures of sub-maximum oxygen uptake. At the end of the 12-month period, participants completed the physical activity questionnaire that assesses past-year activity at home, work and in recreation. Repeatability was assessed in a separate group of 399 randomly selected participants in EPIC who completed the physical activity questionnaire twice with a 3-month interval. RESULTS: The age- and sex-adjusted correlation between the objective measure of daytime energy expenditure and the sum of recreational and occupational reported physical activity (in MET h per week) was 0.28 (P < 0.001). The reported time spent in vigorous activity was correlated with cardio-respiratory fitness (0.16, P < 0.05) and with the proportion of time when energy expenditure was more than five times basal (0.17, P < 0.05). The repeatability of the sum of recreational and occupational reported activity was high, r = 0.73. CONCLUSIONS: The indices of physical activity derived from this questionnaire have levels of validity and repeatability comparable to other physical activity instruments that are used in large epidemiological studies and which have undergone such intense development and testing.     

The effects of short- vs. long-bout exercise on mood, VO2max, and percent body fat

BACKGROUND: To compare the ACSM-CDC physical activity accumulation recommendation to the traditional recommendation, for impact on mood and physiological markers of fitness. METHODS: Randomized controlled trial with sedentary male (n = 21) and female (n = 19) subjects assigned to walk either long bouts (LB; 30 min/day), short bouts (SB; 3 x 10 min/day), or a nonexercise control (CTL) group for 8 weeks. Pre- and post-measures were collected for V02max and percent body fat. Pre-, mid-, and post-measures were collected for the Profile of Mood States (POMS). RESULTS: VO2max increased in the SB group (+7.2%) and LB (+6.7%; P < or = 0.05). Percent body fat decreased in the LB group (-6.7%; P < or = 0.05). Total mood disturbance (TMD) decreased in the LB and SB groups (P < or = 0.05); only the LB group showed reductions compared to the CTL group (P < or = 0.05). Tension-anxiety and vigor-activity were altered in the LB group compared to the other two groups (P < or = 0.05). Reductions in percent body fat correlated with TMD (r = 0.38; P < or = 0.05) and Tension-anxiety reduction (r = 0.40; P < or = 0.05). CONCLUSIONS: LB and SB walking produced similar and significant improvements in VO2max LB walking was more effective at reducing percent body fat, tension-anxiety and total mood disturbance, and increasing vigor compared to the control group.     

Lifestyle and blood pressure levels in male twins in Utah

Healthy male monozygotic (MZ) and dizygotic (DZ) twin pairs (MZ pairs = 77; DZ pairs = 88) were studied to assess the effect of dietary intake, physical activity, physical fitness, body mass index (BMI), sum of the triceps and subscapular skinfold measurements, alcohol and caffeine consumption, and smoking patterns on blood pressure. Data on physical activity, detailed dietary intake, medical history, and demographics were obtained from a questionnaire. A bicycle ergometer was used to estimate level of fitness; other medical information was ascertained from physical examination. After normalizing the study variables, intraclass correlations for BMI and the sum of the triceps and subscapular skinfold measurements were higher in MZ than in DZ twin pairs (BMI: MZ r = 0.76, DZ r = 0.48; skinfolds: MZ r = 0.73, DZ r = 0.28), as were VO2max(MZ r = 0.63, DZ r = 0.25) and post-bike heart rate (MZ r = 0.69, DZ r = 0.19). Both systolic (SBP) and diastolic blood pressure (DBP) had high heritability estimates (SBP = 0.60, and DBP = 0.66). Using factor analysis, four major lifestyle factors were identified and categorized as: 1) dietary intake; 2) a factor heavily weighted by cigarette smoking, alcohol and caffeine consumption; 3) fatness; 4) physical activity and physical fitness. Adjustment for these factors did not alter heritability estimates for either SBP or DBP.     

Physical activity, physical fitness, blood pressure, and fibrinogen in the Northern Ireland health and activity survey.

STUDY OBJECTIVE: To investigate the relationship between physical activity, physical fitness, blood pressure, and fibrinogen. DESIGN: This was a cross sectional population study using a two stage probability sample. SETTING: Northern Ireland. PARTICIPANTS: A sample of 1600 subjects aged 16-74 years from the population of Northern Ireland. MAIN OUTCOME MEASURES: Physical activity profile from computer assisted interview using the Allied Dunbar national fitness survey scales. Physical fitness using estimation of VO2 max by extrapolation from submaximal oxygen uptake while walking on a motor driven treadmill. Systolic and diastolic blood pressure measured with a Hawksley random zero sphygmomanometer. Measurement of fibrinogen using the Clauss method. MAIN RESULTS: There were significant relationships between both current and past activity and blood pressure. These were of a magnitude that would have been clinically significant, but for the fact that, with the exception of the relationship between habitual activity and diastolic pressure (p = 0.03) and past activity and systolic pressure (p = 0.03) in men, they were not sustained after adjustment for the effect of age using analysis of variance. After adjustment for other potentially confounding factors using multiple regression, there was an inverse relationship between systolic blood pressure and past activity in men, so that those with a life-time of participation compared with a life-time of inactivity had a lower systolic blood pressure of 6 mmHg (p < 0.05). There was a highly significant (p < 0.001) inverse association between both systolic and diastolic blood pressure and physical fitness (VO2 max) which was not sustained after adjustment for possible confounding factors. There were relationships between fibrinogen and highest recorded activity (p < 0.001), habitual activity (p < 0.01), and past activity (p < 0.01) in men but no significant relationship in women. The relationship between fibrinogen and activity was no longer sustained after adjustment for possible confounding factors. There was a highly significant (p < 0.001) inverse relationship with physical fitness using VO2 max. This relationship was sustained after adjustment for possible confounding factors in both men (p < 0.05) and women (p < 0.001). CONCLUSIONS: There was a relationship between physical activity, physical fitness, and blood pressure but the relationship was greatly influenced by age. A reduction of 6 mmHg in systolic blood pressure associated with past activity is of clinical significance and supports the hypothesis that physical activity is of benefit in reducing cardiovascular risk. There was a lower level of fibrinogen in those who were most active but this relationship was not significant after adjustment for possible confounding factors. There was also a lower level of fibrinogen those who were most fit (VO2 max) and this relationship persisted even after adjustment for possible confounding factors.