The Role of Body Habitus in Predicting Cardiorespiratory Fitness: The FRIEND Registry.

This study aimed to validate and cross-validate a non-exercise prediction model from a large and apparently healthy US cohort of individuals who underwent an analysis of body habitus (waist circumference (WC) and body mass index (BMI)) with measured CRF. The large cohort (5 030 individuals) was split into validation (4 030) and cross-validation (1 000) groups, whereby waist circumference and maximal aerobic capacity (VO2max) were assessed by rigorously approved laboratories. VO2max was estimated in 2 multiple regression equations using age, sex and either WC (r=0.77; standard error of the estimate (SEE) 6.70 mLO2∙kg(-1)∙min(-1)) or BMI (r=0.76; SEE 6.89 mLO2∙kg(-1)∙min(-1)).Cross-validation yielded similar results. However, as VO2max increased, there was increased bias, suggesting VO2max may be underestimated at higher values. Both WC and BMI prediction models yielded similar findings, with WC having a slightly smaller SEE. These measures of body habitus appear to be adequate in predicting CRF using non-exercise parameters, even without a measure of physical activity. Caution should be taken when using these equations in more fit individuals.

The influence of acute resistance training and body composition on coagulation and fibrinolytic activity in low-risk women.

This study explored the coagulation and fibrinolytic responses to acute resistance training in young women and aimed to determine the influence of body composition on these variables. Healthy young women aged 23+/-5 yrs participated in the study. Body fat and fat distribution were assessed using DEXA. Each subject performed 6 sets of 10 leg extension repetitions at an intensity associated with 70% of 1-repetition maximum. Markers of coagulation (TAT), fibrinolytic stimulation (tPA) and inhibition (PAI-1) were assessed before and immediately after exercise. tPA activity increased in response to acute resistance exercise (p<0.05), however, there was no change in TAT or PAI-1 activity. Percent body fat was negatively correlated to the tPA response to exercise (r=-0.44), and positively related to PAI-1 at baseline (r=0.47) and post-exercise (r=0.47), and to post-exercise TAT (r=0.44). Android/gynoid fat ratio was negatively related to post-exercise tPA (r=-0.43), positively related to PAI-1 at baseline (r=0.61) and post-exercise (r=0.62) and to post-exercise TAT (r=0.43). These physiological responses suggest women with elevated body fat may be at increased risk of an adverse thrombosis-related event both at rest and during exercise compared to leaner women.

Relationships of aerobic capacity and percent body fat with plasma free fatty acid following walking.

We investigated relationships of peak VO2 and percent body fat with postexercise plasma free fatty acid (FFA) and glycerol concentrations in 14 men using multiple-regression techniques. During 1 h of walking (36% of peak VO2), no significant differences in plasma-FFA response were attributed to either peak VO2 or percent body fat. However, individuals with higher peak VO2S tended to have greater elevations in plasma-glycerol concentration during exercise (p = 0.074). They also had greater peak FFA concentrations and FFA X glycerol(-1)-molar ratios immediately after exercise and faster subsequent clearing of excess FFA from the blood (p less than 0.05). Percent fat was not related to postexercise plasma glycerol, FFA, FFA X glycerol-1 responses. Differing postexercise FFA responses, as related to peak VO2, were due, not to varying rates of lipolysis but rather to different rates of FFA mobilization and utilization.

The long-term treatment of stable angina pectoris with verapamil.

In a double-blind 16-week crossover study, the effectiveness of verapamil therapy for chronic stable angina was evaluated in 19 patients (Phase I). Twelve of these patients were then followed for 38 to 58 months of open-label treatment (Phase II). Clinical responses were assessed with traditional indices, treadmill exercise tests, and a newly developed Performance Index (PI). During Phase I, verapamil resulted in a 50% mean reduction in the number of patients developing effort angina on treadmill exercise, a 15% mean increase in treadmill exercise time, and an 18% mean improvement in the PI. In eight of ten patients, diastolic blood pressure rises during exercise were significantly lowered during verapamil treatment in Phase I. In a limited population of patients followed for long periods of time, our data show that verapamil remains acceptably effective in the treatment of angina pectoris. Though diastolic blood pressure rises were decreased during Phase I, we could not confirm that effect over longer periods of time. Functional capacity as determined by the PI was sustained in Phase II.

Evaluation of within-day precision of serum cholesterol measured by a portable analyzer.

The use of dry-chemistry analyzers for the measurement of cholesterol in mass screening settings has received considerable attention. Less is known about the efficacy of these types of analyzers in the clinical office or laboratory setting. Thus, we investigated the within-day precision of cholesterol measurements performed by the Reflotron method with specific comparisons made between two trained technicians and two instruments. Forty serum specimens were analyzed eight times (twice by each technician on both instruments) with the identity of the specimen blinded from the technician. Each specimen was also analyzed by two different methods commonly accepted in the clinical laboratory to estimate the accuracy of the Reflotron cholesterol measures. Small, significant (P less than 0.05) main effect differences were observed in cholesterol concentrations between technicians (1.8%) and instruments (0.8%). The overall coefficient of variation (CV) of the serum cholesterol measures was 2.5%, which meets the Laboratory Standardization Panel's "ideal" goal. However, three individual cases (one specimen's eight analyses) had CV greater than 5%, and three other cases had CV greater than 3%. Most of these cases could be traced to one outlier value. Review of all 320 Reflotron analyses revealed that only 10 (3.1%) were outliers (greater than 5% from specimen mean value). When operated in a laboratory with regular quality control procedures, the Reflotron method can meet national standards for precision. In this setting, differences between technicians and instruments are not of clinical importance.

The effect of exercise training on the severity and duration of a viral upper respiratory illness.

PURPOSE: The purpose of this investigation was to determine whether exercise training affects the severity and duration of a rhinovirus-caused upper respiratory illness (URI). METHODS: Subjects who were rhinovirus 16 (RV 16) antibody-free completed a graded exercise test. Thirty-four individuals (ages 18-29 yr) of moderate fitness (32 mL.kg-1.min-1 to 60 mL.kg-1.min-1) were randomly assigned to the exercise group (EX) while 16 additional individuals of similar age and fitness served as a nonexercise (NEX) control group. All EX and NEX subjects were inoculated with RV 16 on 2 consecutive days. EX subjects completed 40 min of supervised exercise every other day at 70% of heart rate (HR) reserve for a 10-d period. Every 12 h, all subjects completed a 13-item symptom severity checklist and a physical activity log. Used facial tissues were collected and weighed (symptom severity measure) during these same reporting periods. RESULTS: A two group by nine measure (2 x 9) repeated measures ANOVA procedure showed no difference in symptom questionnaire mean scores and the mucous weights of the EX and NEX groups for days 2-10 of the experiment. A two measure by five measure (2 x 5) repeated measures ANOVA procedure indicated no differences between the pre- and post-exercise questionnaire means for the five sessions that EX subjects exercised. Statistical significance was set at P < 0.05. CONCLUSION: These results suggest that moderate exercise training during a rhinovirus-caused URI under the conditions of this study design do not alter the severity and duration of the illness.

Plasma volume changes and cardiovascular responses associated with weight lifting.

Ten experienced weight lifters were studied to determine the influence of strenuous, free-weight, squat lift exercise on changes in plasma volume, mean arterial pressure, and the rate pressure product. After a 40-min postural adjustment prior to upright exercise, each subject completed eight sets of eight repetitions of the squat exercise at 55% of the one-repetition maximum. Electrocardiogram heart rate was monitored throughout the test, and blood pressure was determined at the completion of each exercise set. Arterialized capillary blood was drawn during sitting and standing pre-exercise and at the end of the second, fourth, sixth, and eighth sets for the measurement of hemoglobin, hematocrit, and plasma protein concentration, and after the last set for blood lactate. Five additional subjects participated in a postural control comparison. The results of the ANOVA showed a significant loss in plasma volume over the trials which was 2 1/2 times greater than for the control subjects (17.9 vs 7.7% loss) over the same period of time. Exercise rate pressure product increased by 2.85 times resting while only 1.1 times resting for the control subjects. An elevation in mean arterial pressure was found to be correlated to changes in plasma volume, r = -0.98. This study found that plasma volume is reduced while the rate pressure product is increased during the squat lift exercise.

Predictors of over- and underachievement of age-predicted maximal heart rate.

The age-predicted maximal heart rate (PMHR) formula, 220--age, is frequently used for identifying exercise training intensity, as well as determining endpoints for submaximal exercise testing. This study was designed to identify variables discriminating those with actual maximal heart rates considerably above or below that predicted from the 220--age equation. Subjects included 2010 men and women ranging in age from 14 to 77 yr. Stepwise discriminant analysis was performed using maximal heart rate error groups as the dependent variable, and selected preexercise test characteristics as predictors. The HR error groups were based on the difference between the measured and PMHR as follows: below (> or = 15 beats.min-1 below PMHR), within (+/- 14 beats.min-1 of PMHR), and above (> or = 15 beats.min-1 above PMHR). A contrast of the below and above groups identified age, resting HR, body weight, and smoking status as predictors of group membership (P < 0.01) for both men and women. The overall canonical correlation was 0.282 and 0.294 for the men and women, respectively. Older age, higher resting HR, lower weight, and non-smoking were related to the above group, while the inverse was related to the below group. Standardized coefficients suggest that age and resting heart rate for the men, and age and smoking status for the women were the most potent variables for discriminating extreme deviations between measured and PMHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a rhinovirus-caused upper respiratory illness on pulmonary function test and exercise responses.

Upper respiratory illness (URI) may cause more frequent acute disability among athletes than all other diseases combined. The purposes of this study were to determine the impact of a rhinovirus-caused URI on resting pulmonary function submaximal exercise responses and on maximal exercise functional capacity. Twenty-four men and 21 women (18-29 yr) of varying fitness levels were assigned to the experimental group (URI), and 10 additional individuals served as a control group (CRL). An initial serological screening was performed on all URI group subjects to exclude those with the rhinovirus 16 (HRV16) antibody. All subjects completed both a baseline pulmonary function test and a graded exercise test to volitional fatigue. URI subjects were inoculated with HRV 16 on two consecutive days within 10 d of completing these tests. The day following the second inoculation (peak of illness), post-inoculation pulmonary function and graded exercise tests were performed. A noninfected control group completed these same pulmonary and exercise tests 1 wk apart. ANOVA identified no significant differences (P < 0.05) at minutes 2, 5, and 8 for the physiological responses measured between the pre- and post-exercise tests for both the URI and CRL, groups. Furthermore, there were no significant differences between maximal exercise performance between running trials for either group. There was also no significant interaction between treatment (pre/post URI) and group for any of the pulmonary function measures obtained. In conclusion, physiological responses to pulmonary function testing and submaximal and maximal exercise do not appear to be altered by an URI.

Failure of predicted VO2peak to discriminate physical fitness in epidemiological studies.

Previous investigators reported that peak oxygen uptake (VO2peak) could be accurately predicted from nonexercise test variables, and that this score would be suitable for categorizing cardiorespiratory fitness (CRF) within epidemiological studies. However, the accuracy of these models has varied considerably. The purposes of this study were: 1) assess the accuracy of predicting VO2peak with a new nonexercise model, and 2) assess the utility of the predicted VO2peak for categorizing CRF in epidemiological studies. Subjects included 2,350 men and women. Cross-validated multiple regression models revealed that age, sex, resting heart rate, body weight, percentage body fat, smoking, and physical activity were significant predictors (P < 0.001) of VO2peak. The multiple regression model for relative VO2peak (ml.kg-1.min-1) had R2 = 0.733 (SEE = 5.38), whereas the model for absolute VO2peak (l.min-1) had R2 = 0.773 (SEE = 0.425). The 95% confidence intervals for the predicted VO2peak were large (+/- 10.6 ml.kg-1.min-1 and +/- 0.833 l.min-1). These results support the notion that VO2peak can be predicted from a multiple regression model devoid of exercise test variables. However, due to the extreme variability in the predicted scores, the regression models were unable to effectively distinguish CRF categories. Therefore, despite statistical success in predicting VO2peak for the nonexercise test regression models, we conclude that such models fail to provide the accuracy needed for categorizing CRF within large epidemiological cohorts where the purpose is to assess mortality risk.

Evaluation of the ACSM submaximal ergometer test for estimating VO2max.

The purpose of this investigation was to assess the reliability and validity of maximal oxygen uptake estimates (ESTmax) from the ACSM submaximal cycle ergometer test. Subjects included 15 men and 15 women aged 21-54 yr who performed two submaximal tests and one maximal cycle ergometer test to determine maximal oxygen uptake (VO2max). During the submaximal tests, heart rates (HR) were recorded from a radio telemetry monitor. ESTmax was predicted for both submaximal trials by extrapolating HR to an age-predicted maximal HR. Correlation coefficient and standard error of measure (SEmeas) for ESTmax between submaximal trials were r = 0.863 and SEmeas = 0.40 l.min-1, while a t-test revealed no significant difference between trials. Although trial means were not significantly different, large variation in individual cases was evident by the high SEmeas (0.40 l.min-1) and by a large SEmeas expressed as a percentage of the mean (13%). The mean of the two ESTmax significantly overestimated measured VO2max with percent error, total error, and mean error equal to 25.7%, 0.89 l.min-1, and 0.63 l.min-1, respectively. The standard error of estimate expressed as a percentage of the mean was equal to 16% and 15% for both ESTmax. In summary, the ACSM protocol failed to be reliable as represented by the large differences found between submaximal trials. Furthermore, the protocol significantly overestimates VO2max and should not be used when an accurate assessment of VO2max is required.

Evaluation of a shallow water running test for the estimation of peak aerobic power.

The purpose of this investigation was to assess the validity of a 500-yard shallow water run test to determine peak aerobic power (VO2peak) and to compare it with the commonly used 1.5-mile run test. Subjects included 15 men and 28 women who completed two trials each of a 500-yard shallow water run test and a 1.5-mile run and then completed a graded exercise test on a treadmill to determine VO2peak. Correlation coefficients with measured VO2peak were -0.89 and -0.80 for the 1.5-mile and 500-yard water runs, respectively. Multiple regression analyses revealed that prediction of VO2peak from 1.5-mile run time was significantly improved by including the 1.5-mile run peak HR (R2 = 0.82, SEE = 3.52 ml.kg-1.min-1). Similarly, for the 500-yard water run test, percent body fat and height were significant additional predictors of VO2peak (R2 = 0.86, SEE = 3.19 ml.kg-1.min-1). We conclude that the 500-yard shallow water run test, especially when used with the descriptive measures of percent body fat and height, can provide a reasonable estimate of an individuals' cardiorespiratory fitness classification. However, caution is advised when administering these tests in older populations or in those with multiple coronary risk factors.

Fluid intake during an ultramarathon running race: relationship to plasma volume and serum sodium and potassium.

To assess the relationship between self-selected fluid intake patterns and changes in plasma volume and serum electrolytes during prolonged exercise, five men completed ultramarathon runs ranging from 50 to 100 km. There was a significant relationship between fluid intake and plasma volume changes but no changes occurred in either serum sodium or potassium. Subjects who ingested the most fluid during the race had a modest hemodilution without any changes in serum or potassium. This response may have been influenced by the consumption of beverages containing osmotically active solutes such as sodium and glucose.

Differences in estimates of percent body fat using bioelectrical impedance.

The purpose of the present investigation was to analyze the replicability of percent body fat (% fat) determined from Bioelectrical Impedance Analyses (BIA) after 2 different postprandial time periods and by 2 different technicians. The BIA % fat measures were also compared to those determined from skinfold measurements (SF) and hydrostatic weighing (HW). Fifteen physically active men had body composition determined on 4 separate days over a 2 week period under controlled conditions, once each week after fasting for 12 hours and once after 3 hours. Each day the subjects had BIA and SF measures taken by different trained technicians. Once each week the subjects also were hydrostatically weighed (HW). There were no differences for either BIA or SF between the 2 postprandial time periods. There were significant differences between technicians for both BIA and SF (p < 0.01), although the relationships between technicians were good (r = 0.90 and 0.95, respectively). Mean values for BIA (11.8 +/- 3.2%) and HW (11.0 +/- 7.2%) were similar, however, the correlation was only r = 0.50. These results indicate that although BIA gave relatively consistent values, it regressed both low and high % fat values towards the mean of the sample.

Postprandial lipemia in obese men with abdominal fat patterning.

OBJECTIVE: The purpose of this study was to assess differences in measures of postprandial triglyceride (TG) clearance between obese men with abdominal fat patterning (OAF) and men of desirable weight (DW). It was hypothesized that the OAF men would have impaired postprandial TG clearance. EXPERIMENTAL DESIGN: A comparative design was used. SETTING: Data were collected in a research laboratory with access to blood analysis instrumentation. PARTICIPANTS: Fourteen healthy, physically active, normolipemic men (7 OAF and 7 DW) were studied. INTERVENTIONS: Each subject consumed an oral fat load (78 grams of fat) and blood samples were collected every hour for 8 hours. MEASURES: Measures of postprandial lipemia included: incremental TG area, total TG area, time to peak TG concentration, maximal change in TG concentration, and time to return to baseline TG concentration. RESULTS: OAF men had significantly greater total area under the TG curve (24.7 +/- 1.09 vs 16.1 +/- 1.3 mmol-L(-1).8 hours, p = 0.003) and greater maximum TG change (2.0 +/- 0.3 vs 1.2 +/- 0.2 mmol-L-1, p = 0.03) following the oral fat load. Additionally, the total area under the TG curve was positively correlated with baseline TG concentrations (r = 0.53) and inversely correlated with baseline HDL2 concentrations (r = 0.64). Baseline HDL2 concentrations were inversely correlated with time to return to TG baseline (r = 0.57). CONCLUSIONS: Normal fasting lipoprotein profiles and regular physical activity do not preclude OAF men from having pronounced postprandial lipemia.

Caffeine consumption habits do not influence the exercise blood pressure response following caffeine ingestion.

BACKGROUND: The purpose of this study was to determine if the BP response during walking following caffeine ingestion differed between those who regularly consume caffeine and those who do not. METHODS: A double-blind cross-over experimental design was used. Data were collected in a research laboratory with a clinical exercise testing room. Eight regular caffeine users and eight men who did not habitually consume caffeine were studied. Each subject consumed of a beverage once with and once without 4.5 mg caffeine/kg fat-free mass added to the drink. Following consumption each subject walked at three intensities of exercise (30, 50, and 70% of VO2peak). Measures of BP were obtained by the auscultatory technique. RESULTS: Caffeine consumption resulted in significant increases in both systolic BP and diastolic BP at rest and during exercise. The elevation during exercise was 7-8 mmHg at all three exercise intensities for systolic BP; however, for diastolic BP there was only a significant elevation (4 mmHg) at the highest exercise intensity. No differences were noted between those men who regularly consume and those who regularly abstain from caffeine. There was a wide range in the resting BP response to caffeine (combined SBP and DBP ranged from 10-39 mmHg) suggesting that there are marked differences in sensitivity to caffeine, irrespective of individuals' consumption habits. CONCLUSIONS: Consideration should be given to caffeine intake prior to exercise in patients for whom an additional increase in BP during exercise would not be desirable.

Precision of total and regional body fat estimates from dual-energy X-ray absorptiometer measurements.

OBJECTIVES: To evaluate the precision of both total %fat and all the regional %fat measures acquired from both the Lunar Prodigy and Lunar iDXA software. DESIGN: Cross-sectional study. SETTING: University-based research laboratory. PARTICIPANTS: The sample consisted of 300 individual test records from men and women who had volunteered to participate in dual-energy x-ray absorptiometer (DXA) technician precision training studies. Subjects ranged in age from 20-84 years and in body mass index from 15.7-52.0 kg.m-2. MEASUREMENTS: A total of 27 different technicians performed three total body scan measurements on 10-15 different subjects. The Lunar Prodigy and Lunar iDXA were used for 253 and 47 precision training evaluations, respectively. The regions of interest (ROI) were automatically determined by the enCORE software (autoROI) for total body, android, gynoid, trunk, legs, and arms regions and the region %fat data were used for analyses. RESULTS: The CV for total body %fat was 1.9% and 0.9% for the Prodigy and iDXA, respectively. CV's for %fat measures at regional sites ranged from 1.2-4.4% for the Prodigy measures and 0.9-2.4% for the iDXA measures. The ICC for both devices ranged from 0.990 to 0.999. CONCLUSION: Monitoring the status of body composition changes with age is gaining more clinical acceptance. Thus, it is important that practitioners use measures that are both precise and accurate. The findings from the current study add support that DXA measurements can be used with a high level of confidence for serial testing of patients.