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PubMed1995

Fatness and physical fitness of girls 7 to 17 years.

A two-fold approach was used to investigate the association between fatness and fitness of girls 7 to 17 years of age: first, age-specific correlations between fatness and measures of health-related and motor fitness, and second, comparisons of fitness levels of girls classified as fat and lean. A representative sample of 6700 between 7 to 17 years was surveyed. Adiposity (fatness) was estimated as the sum of five skinfolds (biceps, triceps, subscapular, suprailiac, medial calf). Physical fitness included health-related items (step test, PWC170, the sit and reach, sit-ups and leg lifts, flexed arm hang) and motor performance items (standing long jump, vertical jump, arm pull strength, flamingo stand, shuttle run, plate tapping). Age-specific partial correlations between fatness and each fitness item, controlling for stature and weight, were calculated. In addition, in each age group the fattest 5% (presumably the obese) and the leanest 5% were compared on each fitness test. After controlling for stature and weight, subcutaneous fatness accounts for variable percentages of the variance in each fitness item. Estimates for health-related fitness items are: cardiorespiratory endurance-step test (3% to 5%) and PWC170 (0% to 16%), flexibility-sit and reach (3% to 8%), functional strength-flexed arm hand (6% to 17%) and abdominal strength-sit-ups/leg lifts (1% to 8%). Corresponding estimates for motor fitness items are more variable: speed of limb movement-plate tapping (0% to 3%), balance-flamingo stand (0% to 5%), speed and agility-shuttle run (2% to 12%), static strength-arm pull (4% to 12%), explosive strength-standing long jump/vertical jump (11% to 18%). At the extremes, the fattest girls have generally poorer levels of health-related and motor fitness.

Adolescent↗
PubMed1982

Plasma high density lipoproteins HDL2, HDL3 and postheparin plasma lipases in relation to parameters of physical fitness.

A number of studies has shown that the plasma levels of high density lipoprotein (HDL) are increased by regular aerobic exercise. The plasma HDL, particularly HDL2, is regulated by the activity of 2 endothelial lipases, viz. lipoprotein lipase (LPL) and hepatic lipase (HL), which both can be assayed in postheparin plasma. In the present study the plasma levels of HDL2 and HDL3 cholesterol and the postheparin plasma lipase activities were related to parameters of physical fitness obtained from a pulse conducted maximal bicycle ergometer test. There was a significant positive correlation between HDL2 cholesterol and physical fitness (r = 0.52, P less than 0.01). On the other hand, the postheparin plasma hepatic lipase activity showed a significant negative correlation to physical fitness (r = -0.57, P less than 0.01). The HDL2 cholesterol was inversely correlated with the HL activity (r = 0.57, P less than 0.001). Application of partial correlation analysis to the data showed that the relationship between HDL2 cholesterol and fitness disappeared by keeping the HL activity constant whereas the correlation between HDL2 and HL was not influenced by fitness. The relation of HDL2 to fitness was independent in body fat and basal plasma insulin level; in addition the relationship between HL and fitness was not accounted for by body fatness. No relationship was found between physical fitness and LPL activity or between HDL3 and fitness. The results support the hypothesis that hepatic endothelial lipase has a role in the regulation of plasma HDL2 cholesterol and that the activity of this enzyme decreases upon increase of physical fitness.

Adult↗
PubMed2004

The association between cardiorespiratory fitness and C-reactive protein in subjects with the metabolic syndrome.

OBJECTIVES: We sought to study relationship between cardiorespiratory fitness and C-reactive protein (CRP) in subjects with the metabolic syndrome. BACKGROUND: Recent studies have shown an association between the metabolic syndrome and chronic subclinical inflammation, as determined by elevated CRP. Cardiorespiratory fitness is associated with a lower risk of diabetes and improved insulin resistance. METHODS: Physical fitness was assessed in 1,640 subjects using the Bruce treadmill protocol and expressed as maximal metabolic equivalents. The level of CRP was measured using a high-sensitivity assay. RESULTS: Geometric mean CRP was calculated across quartiles of fitness after adjustment for age, gender, smoking, use of medications, and coronary disease. A strong inverse trend toward decreasing CRP levels with increasing fitness quartiles was present in subjects without metabolic abnormalities, subjects with one or two metabolic abnormalities, and subjects with the metabolic syndrome (all p <or= 0.001). The effect of fitness was particularly robust among subjects with the metabolic syndrome. The adjusted mean CRP in subjects in the upper and lower fitness quartiles was 1.48 versus 0.93 mg/dl in subjects without metabolic abnormalities, 2.40 versus 1.66 mg/dl in subjects with one or two metabolic abnormalities, and 4.62 versus 2.20 mg/l in subjects with the metabolic syndrome (p = 0.049 for the interaction between fitness and number of metabolic abnormalities). CONCLUSIONS: Subjects with the metabolic syndrome who maintain a high fitness level have markedly lower CRP concentrations, as compared with those with a low fitness level.

C-Reactive Protein↗
PubMed2006

Aerobic physical fitness in relation to blood lipids and fasting glycaemia in adolescents: influence of weight status.

BACKGROUND AND AIMS: We explored the associations between aerobic physical fitness with blood lipids and a composite index of blood lipids and fasting glycaemia in adolescents, analysing possible interactions with weight status. METHODS AND RESULTS: Body mass index and aerobic physical fitness was measured in 2090 adolescents (1034 males and 1056 females) 13-18.5 years by using the 20-m shuttle run test. Plasma glucose, total, high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol, triglycerides, apolipoprotein (apo) A-I, apo B-100 and lipoprotein(a) [Lp(a)] were measured in 460 of the 2090 subjects. After adjustment for confounding factors, a continuously distributed summary score for blood lipids and fasting glycaemia was significantly related to aerobic fitness in males (P=0.018) and females (P=0.045, from the 2nd to the 4th quartile of aerobic fitness). After adjustment for gender, age, sexual maturation and economic status, aerobic fitness was related to the composite index of blood lipids and glycaemia in both overweight and non-overweight adolescents (P< 0.05). However, for the same level of aerobic fitness, the composite index of blood lipids and glycaemia was significantly higher in overweight adolescents (P=0.001). After setting the minimal aerobic fitness standards to present a healthy lipid profile, about 50% of males did not reach such values. CONCLUSION: Our data suggest that both aerobic fitness and weight management are associated with a composite index of blood lipids and glycaemia in adolescents. Our study also provides the minimal levels of aerobic physical fitness associated with a favourable lipid profile in male adolescents, a new tool which should be adopted by schools as "aerobic fitness standards".

Adolescent↗
PubMed2001

Usefulness of cardiorespiratory fitness as a predictor of all-cause and cardiovascular disease mortality in men with systemic hypertension.

There is an inverse gradient of mortality across levels of cardiorespiratory fitness in healthy adults; however, the association of fitness to mortality in persons with comorbidities such as hypertension is not fully understood. This study quantifies the relation of cardiorespiratory fitness to all-cause mortality and cardiovascular disease (CVD) mortality in hypertensive men. In this observational cohort study, we calculated death rates for low, moderate, and high fitness categories in normotensive (n = 15,726) and hypertensive (n = 3,184) men, and in men without a history of hypertension but with elevated blood pressure (BP) (systolic BP > or = 140 or diastolic BP > or = 90 mm Hg) at baseline (n = 3,257). The participants were 22,167 men (average age 42.6 +/- 9.2 years [mean +/- SD]) who underwent a medical examination that included a maximal exercise test during 1970 to 1993, with mortality follow-up to December 31, 1994. We identified 628 deaths (188 from CVD) during 224,173 man-years of observation. There was an inverse linear trend across fitness groups for all-cause and CVD mortality. The relative risk (95% confidence interval [CI]), using the low fitness group as reference, for all-cause mortality in hypertensive men was 0.45 (95% CI 0.31 to 0.65) and 0.42 (95% CI 0.27 to 0.66) for moderate and high fitness groups, respectively, and in men with elevated BP, 0.49 (95% CI 0.34 to 0.70) and 0.44 (95% CI 0.29 to 0.68) for moderate and high fitness groups, respectively. The pattern of results was similar for CVD mortality. There was an inverse linear relation between fitness and death rate for all-cause mortality in both the uncontrolled and controlled hypertensive groups. This study provides evidence that moderate to high levels of cardiorespiratory fitness provide protection against all-cause and CVD mortality in hypertensive men and men without a history of hypertension but with elevated BP at examination.

Adult↗
PubMed2003

The association between high blood pressure, physical fitness, and body mass index in adolescents.

BACKGROUND: The aim of this study was to analyze the association of fitness and fatness with blood pressure (BP) and hypertension. This was a cross-sectional study of 13,557 boys and girls 15-20 years of age. Fitness was estimated from a shuttle run test, fatness from body mass index (BMI), and BP was measured sitting after 5 min of rest. Other lifestyle variables were self-reported. RESULTS: Boys had a higher systolic BP (SBP) than girls. A low physical fitness level and high BMI were independently associated with a high BP and risk of having hypertension in both girls and boys. Interaction was found between BMI and fitness. In a stratified analysis an odds ratio (OR) of 3.99 was found for hypertension in girls with a BMI > 25 kg m(-2) compared to lean girls if all had a low fitness level, and an OR of 2.14 for a high BMI in girls with a high fitness level. In boys, OR for high versus low BMI were 3.23 in the low fit and 2.34 and 2.50 in the middle and upper tertile of fitness, respectively. CONCLUSIONS: Fitness and BMI were independently associated to BP. BMI was a stronger predictor of hypertension in those with a low fitness level, especially in girls.

Adolescent↗
PubMed2000

A fifteen-year longitudinal study in young adults on the relation of physical activity and fitness with the development of the bone mass: The Amsterdam Growth And Health Longitudinal Study.

Although positive effects of physical activity are often reported, there are still uncertainties about the type, intensity, duration, and frequency of these activities that are most effective for (re)modeling bone mass during youth. In the Amsterdam Growth and Health Longitudinal Study, daily physical activity and fitness were monitored from age 13 to 29 years in a group of 182 males and females. At a mean age of 28 years, bone mineral density (BMD) was measured at three sites with dual X-ray absorptiometry (DXA): in the lumbar region (lumbar BMD), the femoral neck (hip BMD), and the distal radius (wrist BMD). Physical activity (PA) was estimated from a cross-check activity interview taking in consideration all daily physical activities during the last 3 months; PA was scored in two different ways: (1) metabolic physical activity score (METPA) by weighting the intensity (multiples of basic metabolic rate [METs]) and duration (minutes per week); and (2) mechanic physical activity score (MECHPA) by weighting the peak strain (ground reaction forces as multiples of body mass) irrespective of frequency and duration of the physical activities. Physical fitness was measured with a neuromotor fitness test (composite of six strength, flexibility, and speed tests) and as cardiopulmonary fitness (maximal oxygen uptake). The physical activity and fitness scores were calculated over two age periods: during adolescence (13-16 years) and during adulthood (21-27 years). The standardized regression coefficients (corrected for gender, biological age, body composition, and calcium intake) show that weight, physical activity (both METPA and MECHPA), and neuromotor fitness during adolescence and in young adulthood are significantly and positively related with the lumbar BMD (beta = 0. 11-0.40) and hip BMD (beta = 0.18-0.26), measured at the mean age of 28 years. This was not the case for cardiorespiratory fitness. No significant correlations at all are found with wrist BMD, a bone site that is less involved in physical activity and fitness. It can be concluded that daily physical activity during adolescence and in the young adult period is significantly related to the BMD at the lumbar spine and femoral neck at age 28 of males and females. Only neuromotor fitness and not cardiopulmonary fitness during adolescence and young adulthood is related to the BMD of males and females at age 28 years.

Adolescent↗
PubMed2006

The association between low physical fitness and high body mass index or waist circumference is increasing with age in children: the 'Québec en Forme' Project.

OBJECTIVE: To evaluate physical fitness and body composition of children involved in the 'Québec en Forme' (QEF) Project and to compare data obtained to the reference values of the 1981 Canada Fitness Survey (CFS). DESIGN: Cross-sectional study. SUBJECTS: A total of 1140 children (591 boys and 549 girls) of first (7 years), second (8 years) and fourth (10 years) grade from primary schools in the City of Trois-Rivières (Québec) were selected to participate in this study. MEASUREMENTS: Body mass index (BMI) and waist circumference (WC) were measured. The physical fitness tests included standing long jump, 1-min speed sit-ups and speed shuttle run. RESULTS: The prevalence of overweight in children ranged between 20 and 30%, which represents a substantial increase compared to the 1981 CFS. The relationship between BMI and WC was highly significant in boys and girls (r=0.90 and 0.86, respectively, P<0.0001). The negative correlations between BMI or WC and the performance in all physical fitness tests were mostly significant in children of both genders (-0.16 < or = r < or = -0.45, at least P<0.05), and these relationships were significantly greater in older children (P<0.05). Based on the 1981 CFS, only 4.7-14.1% of QEF boys still performed in the upper quartile of the distribution (fit boys), whereas 32.1-69% performed not much higher than the lower quartile (unfit boys) for each fitness test. In girls, the relative fitness decrease observed in 2003 was more pronounced since only 1-9.9% of subjects performed in the upper quartile of the distribution compared to 42.8-81.4% who did not perform higher than the lower quartile of the 1981 reference scores of the CFS. CONCLUSION: This study shows that BMI and WC are negatively correlated with physical fitness and that these associations are more pronounced in older children. Furthermore, physical fitness of our cohort, especially in girls, was much lower than what was documented in the 1981 CFS in subjects of the same age. This study thus emphasizes the necessity to develop early interventions to improve physical fitness in children and to prevent the increase of childhood obesity.

Body Composition↗
PubMed2004

Comparison of three procedures for initial fitting of compression hearing aids. III. Inexperienced versus experienced users.

We assessed whether gain requirements differ for experienced users and new users when fitted with multi-band compression hearing aids Three procedures for initial fitting were used: the Cambridge method for loudness equalization (CAMEQ), the Cambridge method for loudness restoration (CAMREST), and the desired sensation level input/output (DSL[i/o]) method. Twenty experienced hearing aid users and 20 new users with mild-to-severe sensorineural loss were fitted with Danalogic 163D digital hearing aids, using each procedure in turn in a counter-balanced order. The new users were given a pre-fitting with slightly reduced gains prior to the 'formal' fitting. Immediately after formal fitting with a given procedure, and 1 week after fitting, the gains were adjusted by the minimum amount necessary to achieve acceptable fittings. The amount of adjustment required provided the main measure of the adequacy of the initial fitting. On average, new users required decreases in gain for all procedures, the decreases being larger for DSL[i/o] than for CAMEQ or CAMREST. For experienced users, gain adjustments were small for CAMEQ and CAMREST, but were larger and mostly negative for DSL[i/o]. After these gain adjustments, users wore the aids for at least 3 weeks before filling out the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire and taking part in laboratory measurements of the speech reception threshold (SRT) for sentences in quiet and in steady and fluctuating background noise at levels of 60 and 75 dBSPL. The scores on the APHAB test and the SRTs did not differ significantly for the three procedures. We conclude that the CAMEQ and CAMREST procedures provide more appropriate initial fittings than DSL[i/o]. For inexperienced users, gains typically need to be reduced by about 3dB relative to those prescribed by CAMEQ or CAMREST, although the amount of reduction may depend on hearing loss. An analysis of gain adjustments as a function of order of testing provided some evidence for increased tolerance to high-frequency amplification with increasing experience during the 4-month course of the trial, but this effect did not differ for the experienced and new users.

Acoustic Stimulation↗
PubMed1998

Cardiorespiratory fitness and cardiovascular disease risk factors in postmenopausal women.

PURPOSE: The purpose of the present study was to determine if individuals with high levels of cardiorespiratory fitness have better levels of the cardiovascular disease (CVD) risk factors of total cholesterol (TC), HDL cholesterol (HDL), total cholesterol/HDL cholesterol ratio (TC/HDL), triglycerides (TG), and fibrinogen (FIB) when compared with those with low fitness, in 283 nonsmoking, postmenopausal women. Second, we examined the relation between fitness and CVD risk after controlling for use of hormones and other possible confounding factors. METHODS: These analyses were done on a subset of nonsmoking, postmenopausal women in the Aerobics Center Longitudinal Study (ACLS). Records of postmenopausal women who completed a preventive medicine physical examination between 1987 and 1995 were examined. Cardiorespiratory fitness level was determined by total treadmill time to exhaustion on a graded exercise test; CVD risk factors were assessed via blood analysis. RESULTS: On cross-sectional regression analysis, fitness was significantly associated (P < or = 0.005) with TC (r2 = 0.08), TC/HDL (r2 = 0.12), TG (r2 = 0.09), and FIB (r2 = 0.06), and an increase in HDL (r2 = 0.04). After controlling for hormone status, age, year of testing, and blood glucose, each outcome variable remained significantly associated with cardiorespiratory fitness (P < 0.05). TC/HDL and TG continued to be significantly related to cardiorespiratory fitness after adjusting for body mass index (BMI) as a control variable (P < 0.01). The lack of significance between TC, HDL, and FIB with cardiorespiratory fitness after adjusting for BMI is likely due to the biological relationship between cardiorespiratory fitness and BMI (r2 = 0.19). CONCLUSIONS: We conclude that cardiorespiratory fitness is an important independent determinant of blood lipid and FIB levels in nonsmoking postmenopausal women, with or without HRT.

Cardiovascular Diseases↗
PubMedDate not supplied

Determinants of exercise blood pressure response in normotensive and hypertensive women: role of cardiorespiratory fitness.

PURPOSE: Exaggerated blood pressure (BP) response during physical exertion is associated with increased risk for cardiovascular events. Furthermore, it may be the predisposing factor for myocardial infarction triggered by physical exertion. The authors have shown that systolic BP achieved after 6 minutes of exercise is the strongest predictor of left ventricular hypertrophy. Furthermore, a 37 mm Hg increase in systolic BP above resting BP at 6 minutes of exercise was the threshold for left ventricular hypertrophy. The purpose of this study was to determine predictors of exercise BP response in normotensive and hypertensive women. METHODS: An exercise tolerance test (Bruce) was performed by 1411 normotensive (resting BP < 140/90 mm Hg) and hypertensive (resting BP > or = 140/90 mm Hg) women. These women were faculty, students, and staff at the University of Maryland, College Park, Maryland, and the George Washington University Medical Center, as well as patients undergoing a routine exercise tolerance test at West Coast Cardiology, Pinellas Park, Florida. Two fitness categories (low-fit and high-fit) were established on the basis of treadmill time to exhaustion adjusted for age. RESULTS: Significant associations were observed among the 6-minute exercise BP and age, body mass index, resting systolic and diastolic BP, heart rate, and exercise time to exhaustion. In a stepwise multiple-regression analysis, the determinants of BP after 6 minutes of exercise were resting systolic BP and treadmill time to exhaustion (R2 = 0.36) for normotensive women and treadmill time to exhaustion and resting systolic BP (R2 = 0.30) for hypertensive women. When fitness categories were contrasted, low-fit women in both the normotensive and hypertensive categories had higher BP and rate-pressure product after 6 minutes of exercise than the high-fit women (P <.05). CONCLUSIONS: Resting systolic BP and cardiorespiratory fitness are determinants of a submaximal exercise BP response for both hypertensive and normotensive women. Low cardiorespiratory fitness is associated with a higher BP response during submaximal exercise, suggesting that increased fitness may attenuate this abnormal rise in BP. Thus, low- to moderate-intensity physical activities for most days of the week should be encouraged for all women to increase cardiorespiratory fitness. This is likely to attenuate an abnormal rise in systolic BP that may occur during routine daily activities and protect against the associated health consequences.

Adult↗
PubMed2005

An evaluation of pain and "fitness" during labor and its acceptability to women.

BACKGROUND: Labor experiences involve many dimensions that change during labor but are rarely measured contemporaneously and longitudinally. We examined pain and "fitness" aspects of women's labor experience and assessed the acceptability to participants. METHODS: Thirty nulliparas and 20 multiparas in term labor indicated pain and fitness every 45 minutes in contraction-free intervals on visual analog scales from 0 to 10. Fitness implied both physical and psychological strength. Data were analyzed cross-sectionally and longitudinally, with adjustment for analgesia and time dependency. Women received feedback and evaluated their participation on the first day postpartum. RESULTS: Measurements of pain and fitness ranged from 2 to 22 per woman (mean +/- SD: 7.4 +/- 4.4). Pain scores showed various patterns, mostly increasing from 1.4 (+/- 1.9) at the first to 6.6 (+/- 3.8) at the last measurement in nulliparas and from 1.3 (+/- 2.1) to 6.2 (+/- 4.0) in multiparas. One half of the women declined steadily in fitness throughout labor, occasionally after a slight increase early on. Multiparas entered labor more fit (5.9 +/- 3.0) than nulliparas (3.9 +/- 2.7), but showed a sharper decline so that the difference leveled out just before birth. Although fitness at any one time did not reflect pain levels, fitness and pain were inversely related, especially in nulliparas (p = 0.003). Analgesia affected pain scores but affected fitness only a little. Women's responses were mainly positive, especially in appreciating the feedback. Nevertheless, 32 percent of women skipped one or more measurements, often toward the end or when too close to a contraction. CONCLUSIONS: Pain and "fitness" are two distinctly different dimensions of labor experience. Repeated longitudinal measurements of elements of well-being are clearly feasible and acceptable to laboring women. They may be useful to assess how labor events and interventions affect women's well-being.

Cross-Sectional Studies↗
PubMed2006

Graded associations between cardiorespiratory fitness, fatness, and blood pressure in children and adolescents.

OBJECTIVE: To measure the graded relation between cardiorespiratory fitness and sum of skinfolds, waist circumference, and blood pressure in children and adolescents participating in the European youth heart study. METHODS: The participants were 4072 children and adolescents (aged 9 and 15) from Denmark, Portugal, Estonia, and Norway. Cardiorespiratory fitness was indirectly determined using a maximal ergometer cycle test. The sum of four skinfolds, waist circumference, and blood pressure were assessed with a standardised protocol. Linear regression analysis was used to test the graded relation between cardiorespiratory fitness and the dependent variables adjusted for pubertal stage, sex, and country. RESULTS: A significant curvilinear graded relation was found between cardiorespiratory fitness and waist circumference and sum of skinfolds (partial r2 for cardiorespiratory fitness was 0.09-0.26 for the different sexes and age groups). Systolic and diastolic blood pressure also showed a curvilinear relation with cardiorespiratory fitness, and fitness explained 2% of the variance in systolic blood pressure. The difference in systolic blood pressure between the least and most fit was 6 mm Hg. CONCLUSION: A curvilinear graded relation was found between cardiorespiratory fitness and waist circumference, sum of skinfolds, and systolic blood pressure. The greatest difference in these health variables was observed between low and moderate fitness levels.

Adolescent↗
PubMed1986

Health, fitness, physical activity, and morbidity of middle aged male factory workers. I.

A description of the fitness, physical activity of lifestyle, and some aspects of health status and attitudes in a population of male factory workers aged 35-60 is presented as the first part of a report on a study of morbidity in this population. A total of 1394 subjects were included, undergoing medical examination, fitness testing by bicycle ergometry, assessment of body fat, and interview questionnaire. The inter-relation of fitness, body composition, habitual exertion, health risk factors, and attitudes to exercise are discussed. Fitness levels are compared with those reported in other studies and discussed in terms of capacity for walking and running and in relation to criteria for health benefit. In these two latter respects fitness appears to be inadequate among the great majority of those tested, although it is comparable with that reported by several other recent studies. Fitness is associated with physical activity of leisure but not that of work. Only relatively strenuous physical activity in leisure time appears to be related to fitness, and is only participated in by some 28% of the sample. Cycling has the strongest association with fitness of all the physical activity variables. Blood pressure and percentage body fat are also associated, inversely, with fitness, the latter not unexpectedly because of the weight related measure of fitness.

Adult↗
PubMed2005

Physical fitness and the metabolic syndrome in adults from the Quebec Family Study.

Physically fit individuals have a lower risk of cardiovascular disease and type 2 diabetes. However, it is unknown whether the associations between physical fitness and the metabolic syndrome are independent of total and abdominal adiposity. Physical fitness was defined as the physical work capacity on a cycle ergometer at heart rate of 150 bpm (PWC 150) in a sample of 158 men and 198 women 20-60 years of age. PWC 150 was adjusted for fat-free mass prior to the analyses. Percent body fat was estimated by hydrostatic weighing. Visceral and subcutaneous abdominal fat were measured by computed tomography. The prevalence of the metabolic syndrome was based on two definitions. The metabolic syndrome decreased with increasing fitness in men (approx. 6 times higher in less fit vs. most fit tertile, p < 0.05) and in women (approx. 4 times higher in less fit vs. most fit tertile, p < 0.05). Fitness was negatively associated with most individual components of the metabolic syndrome, except HDL-cholesterol for which the correlation was positive. However, in men and in women, the effects of physical fitness on the individual components of the metabolic syndrome were attenuated after considering total and abdominal adiposity.

Adipose Tissue↗
PubMed1994

Free fatty acid metabolism in aerobically fit individuals.

The impact of aerobic fitness level on the production and disposal of serum free fatty acids was investigated in 26 normal young volunteers. The fitness level was ascertained by history and confirmed by determination of maximal aerobic capacity. Energy expenditure and substrate oxidation at rest were measured with indirect calorimetry. Free fatty acid turnover was measured with an infusion of [14C]palmitic acid. All tests were done > or = 48 h after the last bout of exercise. The sedentary (SED) volunteers had higher rates of systemic delivery of fatty acids than aerobically fit (FIT) individuals (532 +/- 53.4 vs. 353 +/- 62.3 mumol/min; P = 0.05). This difference was accentuated when the values were normalized to fat-free mass (9.2 +/- 0.8 and 5.9 +/- 0.98 mumol.kg-1.min-1 for SED and FIT, respectively). Fatty acid oxidation was similar between FIT and SED volunteers in absolute numbers (209 +/- 25 vs. 202 +/- 21 mumol/min, respectively; NS) as well as when normalized to fat-free mass (3.8 +/- 0.9 vs. 3.6 +/- 1.4 mumol.kg-1.min-1, respectively; NS). In contrast, the nonoxidative disposal of serum fatty acids was higher in SED (330 +/- 46.1 mumol/min) than in FIT individuals (144 +/- 52 mumol/min; P = 0.026). Thus, the ratio of nonoxidative to oxidative disposal rates of fatty acids was higher in SED than in FIT individuals (1.65 +/- 0.29 vs. 0.75 +/- 0.17; P = 0.021). The data support the hypothesis that high aerobic fitness level is associated with a low rate of systemic delivery of fatty acids at rest. Nevertheless, subjects with high aerobic fitness levels have fat oxidation at the same rate as unfit individuals.

Adolescent↗
PubMed1996

Aerobic fitness effects on exercise-induced low-frequency diaphragm fatigue.

We used bilateral phrenic nerve stimulation (BPNS; at 1, 10, and 20 Hz at functional residual capacity) to compare the amount of exercise-induced diaphragm fatigue between two groups of healthy subjects, a high-fit group [maximal O2 consumption (VO2max) = 69.0 +/- 1.8 ml.kg-1.min-1, n = 11] and a fit group (VO2max = 50.4 +/- 1.7 ml.kg-1.min-1, n = 13). Both groups exercised at 88-92% VO2max for about the same duration (15.2 +/- 1.7 and 17.9 +/- 2.6 min for high-fit and fit subjects, respectively, P > 0.05). The supramaximal BPNS test showed a significant reduction (P < 0.01) in the BPNS transdiaphragmatic pressure (Pdi) immediately after exercise of -23.1 +/- 3.1% for the high-fit group and -23.1 +/- 3.8% (P > 0.05) for the fit group. Recovery of the BPNS Pdi took 60 min in both groups. The high-fit group exercised at a higher absolute workload, which resulted in a higher CO2 production (+26%), a greater ventilatory demand (+16%) throughout the exercise, and an increased diaphragm force output (+28%) over the initial 60% of the exercise period. Thereafter, diaphragm force output declined, despite a rising minute ventilation, and it was not different between most of the high-fit and fit subjects. In summary, the high-fit subjects showed diaphragm fatigue as a result of heavy endurance exercise but were also partially protected from excessive fatigue, despite high ventilatory requirements, because their hyperventilatory response to endurance exercise was reduced, their diaphragm was utilized less in providing the total ventilatory response, and possibly their diaphragm aerobic capacity was greater.

Adult↗
PubMed1998

A role for gastrointestinal endotoxins in enhancement of heat tolerance by physical fitness.

To further elucidate mechanisms underlying the higher heat tolerance of physically fit compared with sedentary people, we have investigated the possibility that endotoxins (of gastrointestinal origin) act, as in the normal development of fever, to raise body temperature and therefore reduce heat tolerance. In an initial series of experiments, five physically fit and four sedentary sheep were exposed twice at rest to an environment of 42/35 degrees C (dry/wet bulb temperature). When animals were given normal saline i.v., rectal temperature (Tre) rose at a significantly higher rate in sedentary than in fit animals; this confirms that heat tolerance is improved by physical fitness. Treatment with i.v. indomethacin did not affect the rate of rise of Tre in fit animals. In sedentary animals, however, Tre was lowered to approximate that of fit animals. Because indomethacin blocks prostaglandin pathways involved in endotoxin-induced fever, the indomethacin-induced improvement of heat tolerance of sedentary but not fit animals supports the contention that endotoxins play a role in determining that difference in heat tolerance. In a second series of experiments, quantitative cardiovascular measurements were made by using radioactive microspheres. Under normothermic conditions, blood flows in the brain, ileum, and diaphragm were higher in fit than in sedentary animals. During hyperthermia up to Tre of 42 degrees C (in a 42/39 degrees C environment), fit compared with sedentary animals exhibited 1) a greater increase in cardiac output, 2) an increase in blood flow through arteriovenous anastomoses to higher and better maintained levels, 3) less reduction in blood flow to the ileum, and 4) greater increase in blood flows to the myocardium, turbinates, nasal mucosa, and respiratory muscles. Endotoxins are likely to come from the gut lumen, because reduction of gut blood flow forms part of the normal response to heat stress. We suggest that improvement of heat tolerance by physical fitness is caused by a greater cardiovascular capacity that permits not only greater perfusion of heat-loss tissues but the maintenance of a better gastrointestinal tract blood supply, thereby better maintaining the normal barrier to movement of endotoxins from gut lumen to plasma. Sedentary people, with their lower cardiovascular capacity, redistribute more blood flow away from the gut during environmentally induced hyperthermia, thus allowing endotoxin-induced fever to aggravate hyperthermia.

Animals↗