Search

Hypothesis: Physically active occupations may protect against the risk of abdominal obesity., Objectives: This study assessed the interaction between non-occupational physical activity (NOA) (leisure-time, transport and domestic activity) and occupational activity (OA) in relation to abdominal obesity., Methods: A total of 3539 adults over the age of 20, with no work limitations, employed in one of the 17 occupations classified as low OA (LOA) or high OA (HOA) were identified in the 1999-2004 National Health and Nutrition Examination Survey. Waist circumference (WC) was used to categorize individuals into either non-obese or abdominally obese (WC>88 cm in women and >102 cm in men) categories. NOA was divided into three categories based upon physical activity guidelines: (1) no NOA; (2) insufficient NOA; and (3) sufficient NOA. Logistic regression was used to examine possible associations between NOA, OA and abdominal obesity., Results: In those who are sedentary outside of work, a high-activity occupation reduces the odds risk ratio of being categorized with abdominal obesity to 0.37 in comparison with those who work in low-activity occupations. For people working in low-activity occupations, there was a clear association with activity outside of work and the odds risk ratio of being categorized with abdominal obesity. In these adults, a reduced odds ratio was found only among those who met the physical activity guidelines through NOA (odds ratio=0.55; 95% confidence interval (CI)=0.40-0.75)., Conclusion: HOA is associated with a reduced risk of abdominal obesity. Thus, it is important to include OA in studies seeking to understand the association between physical activity and abdominal adiposity.

Background/objective: The Actiheart (Mini Mitter, Sunriver, OR, USA) uses heart rate (HR) and activity data to predict activity energy expenditure (AEE). Currently, the Actiheart has only been tested during laboratory conditions. Therefore, the objective of this study was to validate the Actiheart prediction method against indirect calorimetry during a wide range of activities in a field setting., Subjects/methods: Forty-eight participants (age: 35+/-11.4 years) were recruited for the study. Eighteen activities were split into three routines of six activities and each routine was performed by 20 participants. During each routine, the participants wore an Actiheart and simultaneously, AEE was measured with a Cosmed K4b(2) portable metabolic system. The manufacturer's HR algorithm, activity algorithm, and combined activity and HR algorithm were used to estimate AEE., Results: The mean error (and 95% prediction intervals) for the combined activity and HR algorithm, HR algorithm, and activity algorithm versus the Cosmed K4b(2) were 0.02 kJ kg(-1) min(-1) (-0.17, 0.22 kJ kg(-1) min(-1)), -0.03 kJ kg(-1) min(-1) (-0.24, 0.18 kJ kg(-1) min(-1)), and 0.14 kJ kg(-1) min(-1) (-0.12, 0.40 kJ kg(-1) min(-1)), respectively., Conclusion: The Actiheart combined activity and HR algorithm and HR algorithm provide similar estimates of AEE on both a group and individual basis.

Objective: The objective of this study was to develop a new 2-regression model relating Actical activity counts to METs., Methods: Forty-eight participants (mean (SD) age 35 (11.4) years) performed 10 min bouts of various activities ranging from sedentary behaviours to vigorous physical activities. Eighteen activities were split into three routines with each routine being performed by 20 individuals. Forty-five routines were randomly selected for the development of a new 2-regression model and 15 tests were used to cross-validate the new 2-regression model and compare it against existing equations. During each routine, the participant wore an Actical accelerometer on the hip and oxygen consumption was simultaneously measured by a portable metabolic system. The coefficient of variation (CV) of four consecutive 15 s epochs was calculated for each minute. For each activity, the average CV and the counts min(-1) were calculated for minutes 4-9. If the CV was < or =13% a walk/run regression equation was used and if the CV was >13% a lifestyle/leisure time physical activity regression was used., Results: An exponential regression line (R(2) = 0.912; standard error of the estimate (SEE) = 0.149) was used for activities with a CV< or =13%, and a cubic regression line (R(2) = 0.884, SEE = 0.804) was used for activities with a CV>13%. In the cross-validation group the mean estimates, using the new 2-regression model with an inactivity threshold, were within 0.56 METs of measured METs for each of the activities performed (p> or =0.05), except cycling (p<0.05)., Conclusion: For most activities examined the new 2-regression model predicted METs more accurately than currently available equations for the Actical accelerometer.

Background: The goal of this study was to establish preliminary criterion-referenced cut points for adult pedometer-determined physical activity (PA) related to weight status defined by body mass index (BMI)., Methods: Researchers contributed directly measured BMI and pedometer data that had been collected (1) using a Yamax-manufactured pedometer, (2) for a minimum of 3 days, (3) on ostensibly healthy adults. The contrasting groups method was used to identify age- and gender-specific cut points for steps/d related to BMI cut points for normal weight and overweight/obesity (defined as BMI <25 and >or=25 kg/m2, respectively)., Results: Data included 3127 individuals age 18 to 94 years (976 men, age = 46.8 +/- 15.4 years, BMI = 27.3 +/- 4.9; 2151 women, age = 47.4 +/- 14.9 years, BMI = 27.6 +/- 6.4; all gender differences NS). Best estimated cut points for normal versus overweight/obesity ranged from 11,000 to 12,000 steps/d for men and 8000 to 12,000 steps/d for women (consistently higher for younger age groups)., Conclusions: These steps/d cut points can be used to identify individuals at risk, or the proportion of adults achieving or falling short of set cut points can be reported and compared between populations. Cut points can also be used to set intervention goals, and they can be referred to when evaluating program impact, as well as environmental and policy changes.

Electronic pedometers are accurate for assessing steps taken while walking in normal weight adults but the accuracy of these devices has not been tested in overweight and obese men and women. The primary purpose of this study was to assess the accuracy of an electronic pedometer for measuring steps taken at various walking speeds in groups of adults with variations in body mass index (BMI). The secondary purpose was to determine if the manufacturer recommended position is the best placement position for overweight and obese adults. Participants were categorized into one of three BMI categories identified by the World Health Organization: normal (N = 25; < 25 kg x m(-2)), overweight (N = 24; 25 - 29.9 kg x m(-2)), or obese (N = 17; > or = 30 kg x m(-2)). Participants walked on a treadmill for 3 min at 54, 67, 80, 94, and 107 m x min(-1) for a total of 15 min. During the treadmill walking, three electronic pedometers tallied steps taken. The pedometers were placed at the waist level, one on the anterior mid-line of the thigh (front; manufacturer recommended placement), one on the mid-axillary line (side), and one on the posterior mid-line of the thigh (back). Concurrently, a researcher counted steps using a hand-tally counter. Category of BMI did not affect the accuracy of the pedometer at any walking speed (54 m x min(-1), p = 0.991; 67 m x min(-1), p = 0.556; 80 m x min(-1), p = 0.591; 94 m x min(-1), p = 0.426; 107 m x min(-1), p = 0.869). At 54 m x min(-1), the front, side, and back pedometers significantly underestimated hand-tally counted steps by 20 % (p < 0.001), 33 % (p < 0.001), and 26 % (p < 0.001), respectively. At 67 m x min(-1) the front, side, and back pedometers significantly underestimated hand-tally counted steps by 7 % (p = 0.027), 13 % (p < 0.001), 11 % (p = 0.002), respectively. The steps recorded by the electronic pedometers placed at the front, side and back of the waist were not significantly different than steps counted by the hand-tally counter at speeds of 80 m x min(-1) and higher for all subjects combined. An electronic pedometer accurately quantified steps walked at speeds of 80 m x min(-1) or faster in persons with a normal BMI and those classified as overweight or obese. The placement of the pedometer on the front, side or back of the waistband did not affect accuracy of the pedometer for counting steps.

The purpose of this study was to establish the accuracy of five published accelerometer regression equations that predict time spent in different intensity classifications during free-living activities. Ten participants completed physical tasks in a field setting for a near-continuous 5 - 6 h-period while oxygen uptake and accelerometer data were collected. The amount of time spent in resting/light, moderate and hard activity was computed from 3 and 6 MET cut-points associated with five existing regression formulas relating accelerometer counts x min -1 to energy expenditure. The Freedson cut-points over-estimated resting/light activity by 34 min (13 %) and under-estimated moderate activity by 38 min (60 %). The Hendelman cut-points for all activities underestimated resting/light activity by 77 min (29 %), and overestimated moderate activity by 77 min (120 %). The Hendelman cut-points developed from walking activities over-estimated resting/light activity by 37 min (14 %) and under-estimated moderate activity by 38 min (60 %). Estimates from the Swartz cut-points for estimating time spent in resting/light, moderate and hard intensity activity were not different from the criterion measure. The Nichols cut-points over-estimated resting/light activity by 31 min (12 %) and under-estimated moderate activity by 35 min (55 %). Even though the Swartz method did not differ from measured time spent in moderate activity on a group basis, on an individual basis, large errors were seen. This was true for all regression formulas. These errors highlight some of the limitations to using hip-mounted accelerometers to reflect physical activity patterns. The finding that different accelerometer cut-points gave substantially different estimates of time spent data has important implications for researchers using accelerometers to predict time spent in different intensity categories.

Purpose: Heart rate (HR) and motion sensors represent promising tools for physical activity (PA) assessment, as each provides an estimate of energy expenditure (EE). Although each has inherent limitations, the simultaneous use of HR and motion sensors may increase the accuracy of EE estimates. The primary purpose of this study was to establish the accuracy of predicting EE from the simultaneous HR-motion sensor technique. In addition, the accuracy of EE estimated by the simultaneous HR-motion sensor technique was compared to that of HR and motion sensors used independently., Methods: Thirty participants (16 men: age, 33.1 +/- 12.2 yr; BMI, 26.1 +/- 0.7 kg.m(-2); and 14 women: age, 31.9 +/- 13.1 yr; BMI, 27.2 +/- 1.1 kg.m(-2) (mean +/- SD)) performed arm and leg work in the laboratory for the purpose of developing individualized HR-VO2 regression equations. Participants then performed physical tasks in a field setting for 15 min each. CSA accelerometers placed on the arm and leg were to discriminate between upper and lower body movement, and HR was then used to predict EE (METs) from the corresponding arm or leg laboratory regression equation. A hip-mounted CSA accelerometer and Yamax pedometer were also used to predict EE. Predicted values (METs) were compared to measured values (METs), obtained via a portable metabolic measurement system (Cosmed K4b(2))., Results: The Yamax pedometer and the CSA accelerometer on the hip significantly underestimated the energy cost of selected physical activities, whereas HR alone significantly overestimated the energy cost of selected physical activities. The simultaneous HR-motion sensor technique showed the strongest relationship with VO(2) (R(2) = 0.81) and did not significantly over- or underpredict the energy cost (P = 0.341)., Conclusion: The simultaneous HR-motion sensor technique is a good predictor of EE during selected lifestyle activities, and allows researchers to more accurately quantify free-living PA.

Purpose: The American College of Sports Medicine and the Centers for Disease Control and Prevention (ACSM-CDC) recommend 30 min of daily moderate-intensity physical activity for health; however, the effectiveness of this recommendation in lowering blood pressure (BP) in hypertensives is unclear. The present study tested the hypothesis that walking activity following the ACSM-CDC physical activity recommendation would lower BP in postmenopausal women with high BP., Methods: Resting BP was measured in 24 postmenopausal women with borderline to stage 1 hypertension at baseline, 12 wk, and 24 wk. Fifteen women in the exercise (EX) group walked 3 km.d-1 above their daily lifestyle walking, whereas 9 women in the control (CON) group did not change their activity. Walking activity was self-measured with a pedometer in both groups., Results: Resting systolic BP was reduced in the EX group after 12 wk by 6 mm Hg (P < 0.005) and was further reduced by 5 mm Hg at the end of 24 wk (P < 0.005). There was no change in diastolic BP with walking. The CON group experienced no change in BP at either 12 or 24 wk. Body mass was modestly reduced by 1.3 kg in the EX group after 24 wk (P < 0.05); however, it was not correlated with the change in BP. There were no changes in selected variables known to impact BP including percent body fat, fasting plasma insulin, or dietary intake., Conclusion: In conclusion, a 24-wk walking program meeting the ACSM-CDC physical activity recommendation is effective in lowering systolic BP in postmenopausal women with borderline to stage 1 hypertension.

The accuracy of a computerized metabolic system, using inspiratory and expiratory methods of measuring ventilation, was assessed in eight male subjects. Gas exchange was measured at rest and during five stages on a cycle ergometer. Pneumotachometers were placed on the inspired and expired side to measure inspired (VI) and expired ventilation (VE). The devices were connected to two systems sampling expired O(2) and CO(2) from a single mixing chamber. Simultaneously, the criterion (Douglas bag, or DB) method assessed VE and fractions of O(2) and CO(2) in expired gas (FE(O(2)) and FE(CO(2))) for subsequent calculation of O(2) uptake (VO(2)), CO(2) production (VCO(2)), and respiratory exchange ratio. Both systems accurately measured metabolic variables over a wide range of intensities. Though differences were found between the DB and computerized systems for FE(O(2)) (both inspired and expired systems), FE(CO(2)) (expired system only), and VO(2) (inspired system only), the differences were extremely small (FE(O(2)) = 0.0004, FE(CO(2)) = -0.0003, VO(2) = -0.018 l/min). Thus a computerized system, using inspiratory or expiratory configurations, permits extremely precise measurements to be made in a less time-consuming manner than the DB technique.

Objective: To assess the interaction between leisure-time physical activity (LTPA) and occupational activity (OA) on the prevalence of obesity., Design: Secondary data analysis of a population based cross-sectional US national sample (NHANES III)., Subjects: A total of 4889 disease-free, currently employed adults over age 20 y., Measurements: Subjects body mass index (BMI) was categorized as (1) obese (BMI> or =30 kg/m(2)), or (2) non-obese (BMI<30 kg/m(2)). LTPA was divided into four categories: (1) no LTPA; (2) irregular LTPA; (3) regular moderate intensity LTPA; and (4) regular vigorous intensity LTPA. OA was grouped as (1) high OA and (2) low OA. Age, gender, race-ethnicity, smoking status, urbanization classification, alcohol consumption and income were statistically controlled., Results: In all, 16.8% (s.e. 0.7) of the total subject population were obese (15.1% (s.e. 1.1) of men and 19.1% (s.e. 1.1) of women). Logistic regression revealed that compared to those who engage in no LTPA and have low levels of OA, the likelihood of being obese is 42% (95% CI 0.35, 0.96) lower for those who engage in no LTPA and have high OA, 48% (95% CI 0.32, 0.83) lower for those who have irregular LTPA and have high levels of OA, and about 50% lower for all those who have regular LTPA through moderate or vigorous activity levels regardless of OA level., Conclusion: When considering disease free adults above 20 y of age employed in high and low activity occupations, a high level of occupational activity is associated with a decreased likelihood of being obese.

The purpose of this investigation was to assess the accuracy of the COSMED K4 b2 portable metabolic measurement system against the criterion Douglas bag (DB) method. During cycle ergometry on consecutive days, oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and respiratory exchange ratio (R) were measured at rest and during power outputs of 50, 100, 150, 200, and 250W. No significant differences (P > 0.05) were observed in VO2 between the K4 b2 and DB at rest and at 250W. Though the K4 b2 values were significantly higher (P<0.05) than DB values at 50, 100, 150, and 200 W, the magnitude of these differences was small (0.088, 0.092, 0.096, and 0.088 L x min(-1), respectively). VCO2 and VE values from the K4 b2 were significantly lower than the DB at 200 and 250 W, while no significant differences were observed from rest through 150W. The slight overestimation of VO2 (50-200 W) combined with the underestimation of VCO2 (200 and 250W) by the K4 b2 resulted in significantly lower R values at every stage. These findings suggest the COSMED K4 b2 portable metabolic measurement system is acceptable for measuring oxygen uptake over a fairly wide range of exercise intensities.

Unlabelled: To further develop our understanding of the relationship between habitual physical activity and health, research studies require a method of assessment that is objective, accurate, and noninvasive. Heart rate (HR) monitoring represents a promising tool for measurement because it is a physiological parameter that correlates well with energy expenditure (EE). However, one of the limitations of HR monitoring is that training state and individual HR characteristics can affect the HR-VO2 relationship., Purpose: The primary purpose of this study was to examine the relationship between HR (beats x min(-1)) and VO2 (mL x kg(-1 x -1) min(-1)) during field- and laboratory-based moderate-intensity activities. In addition, we examined the validity of estimating EE from HR after adjusting for age and fitness. This was done by expressing the data as a percent of heart rate reserve (%HRR) and percent of VO2 reserve (%VO2R)., Methods: Sixty-one adults (18-74 yr) performed physical tasks in both a laboratory and field setting. HR and VO2 were measured continuously during the 15-min tasks. Mean values over min 5-15 were used to perform linear regression analysis on HR versus VO2. HR data were then used to predict EE (METs), using age-predicted HRmax and estimated VO2max., Results: The correlation between HR and VO2 was r = 0.68, with HR accounting for 47% of the variability in VO2. After adjusting for age and fitness level, HR was an accurate predictor of EE (r = 0.87, SEE = 0.76 METs)., Conclusion: This method of analyzing HR data could allow researchers to more accurately quantify physical activity in free-living individuals.

Purpose: This study tested the validity of four motion sensors for measuring energy expenditure (EE) during moderate intensity physical activities in field and laboratory settings. We also evaluated the accuracy of the EE values for selected moderate activities listed in the 1993 Compendium of Physical Activities., Methods: A total of 81 participants (age 19-74 yr) completed selected tasks from six general categories: yardwork, housework, occupation, family care, conditioning, and recreation. Twelve individuals performed each of the 28 activities examined. During each activity, EE was measured using a portable metabolic measurement system. Participants also wore three accelerometers (Computer Science and Applications [CSA], Inc. model 7164; Caltrac; and Kenz Select 2) and the Yamax SW-701 electronic pedometer. For the CSA device, three previously developed regression equations were used to convert accelerometer scores to EE., Results: The mean error scores (indirect calorimetry minus device) across all activities were: CSA1, 0.97 MET; CSA2, 0.47 MET, CSA3, 0.05 MET; Caltrac, 0.83 MET; Kenz, 0.96 MET; and Yamax, 1.12 MET. The correlation coefficients between indirect calorimetry and motion sensors ranged from r = 0.33 to r = 0.62. The energy cost for power mowing and sweeping/mopping was higher than that listed in the 1993 Compendium (P < 0.05), and the cost for several household and recreational activities was lower (P < 0.05)., Conclusion: Motion sensors tended to overpredict EE during walking. However, they underpredicted the energy cost of many other activities because of an inability to detect arm movements and external work. These findings illustrate some of the limitations of using motion sensors to predict EE in field settings.

Purpose: This study was designed to establish prediction models that relate hip and wrist accelerometer data to energy expenditure (EE) in field and laboratory settings. We also sought to determine whether the addition of a wrist accelerometer would significantly improve the prediction of EE (METs), compared with a model that used a hip accelerometer alone., Methods: Seventy participants completed one to six activities within the categories of yardwork, housework, family care, occupation, recreation, and conditioning, for a total of 5 to 12 participants tested per activity. EE was measured using the Cosmed K4b2 portable metabolic system. Simultaneously, two Computer Science and Applications, Inc. (CSA) accelerometers (model 7164), one worn on the wrist and one worn on the hip, recorded body movement. Correlations between EE measured by the Cosmed and the counts recorded by the CSA accelerometers were calculated, and regression equations were developed to predict EE from the CSA data., Results: The wrist, hip, and combined hip and wrist regression equations accounted for 3.3%, 31.7%, and 34.3% of the variation in EE, respectively. The addition of the wrist accelerometer data to the hip accelerometer data to form a bivariate regression equation, although statistically significant (P = 0.002), resulted in only a minor improvement in prediction of EE. Cut points for 3 METs (574 hip counts), 6 METs (4945 hip counts), and 9 METs (9317 hip counts) were also established., Conclusion: The small amount of additional accuracy gained from the wrist accelerometer is offset by the extra time required to analyze the data and the cost of the accelerometer.

Purpose: Three methods for measuring time spent in daily physical activity (PA) were compared during a 21-d period among 83 adults (38 men and 45 women)., Methods: Each day, participants wore a Computer Science and Applications, Inc. (CSA) monitor and completed a 1-page, 48-item PA log that reflected time spent in household, occupational, transportation, sport, conditioning, and leisure activities. Once a week, participants also completed a telephone survey to identify the number of minutes spent each week in nonoccupational walking and in moderate intensity and hard/very hard-intensity PA. Data were analyzed using descriptive statistics and Spearman rank-order correlations. Three equations developed to compute CSA cut points for moderate and hard/very hard PA were also compared with the PA logs and PA survey., Results: There was modest to good agreement for the time spent in different PA intensity categories between the three CSA cut point methods (r = 0.43-0.94, P < 0.001). Correlations between the CSA and PA logs ranged from r = 0.22 to r = 0.36, depending on the comparisons. Correlations between the survey items and PA logs were r = 0.26-0.54 (P < 0.01) for moderate and walking activities and r < 0.09 (P > 0.05) for hard/very hard activities. Correlations between the survey items and the CSA min per day varied according to the method used to compute the CSA intensity cut points., Conclusions: The results were consistent with findings from other PA validation studies that show motion sensors, PA logs, and surveys reflect PA; however, these methods do not always provide similar estimates of the time spent in resting/light, moderate, or hard/very hard PA.

We provide an updated version of the Compendium of Physical Activities, a coding scheme that classifies specific physical activity (PA) by rate of energy expenditure. It was developed to enhance the comparability of results across studies using self-reports of PA. The Compendium coding scheme links a five-digit code that describes physical activities by major headings (e.g., occupation, transportation, etc.) and specific activities within each major heading with its intensity, defined as the ratio of work metabolic rate to a standard resting metabolic rate (MET). Energy expenditure in MET-minutes, MET-hours, kcal, or kcal per kilogram body weight can be estimated for specific activities by type or MET intensity. Additions to the Compendium were obtained from studies describing daily PA patterns of adults and studies measuring the energy cost of specific physical activities in field settings. The updated version includes two new major headings of volunteer and religious activities, extends the number of specific activities from 477 to 605, and provides updated MET intensity levels for selected activities.

Major technical advances have occurred within the last 10 years in the field of physical activity monitoring. The biggest one is real-time data acquisition, and the development of computer microchips that allow vast amounts of information to be stored and later recalled. It is evident that no single motion sensor will provide an accurate estimate of energy expenditure across all activities. Future directions for research include the use of combined instruments such as an accelerometer plus questionnaire, multiple motion sensors, or dual HR-motion sensor technology.

Purpose: This study compared measurements of daily walking distance on the College Alumnus questionnaire (CAQ) and a pedometer., Methods: A total of 96 men and women (25-70 yr of age) with a wide range of physical activity habits were studied. Physical activity index was computed from the College Alumnus questionnaire (PAI-CAQ) as the sum of the energy expended in stair climbing, walking, and sports and recreational physical activity. Data on walking distance were compared with values obtained from the Yamax electronic pedometer (DW-500B). Participants wore the pedometer for 7 consecutive days, except when sleeping, showering, or performing sports and recreational activities., Results: Subjects underestimated their daily walking distance on the CAQ, compared with the pedometer (1.43 +/- 1.01 vs 4.17 +/- 1.61 km x d(-1)). The energy expended in walking was correspondingly lower on the CAQ, compared with the pedometer-derived values (555 +/- 405 versus 1608 +/- 640 kcal x wk(-1))., Conclusions: These findings suggest that electronic pedometers are useful for examining questions about walking distance on physical activity questionnaires.

In the exercising human, maximal oxygen uptake (VO2max) is limited by the ability of the cardiorespiratory system to deliver oxygen to the exercising muscles. This is shown by three major lines of evidence: 1) when oxygen delivery is altered (by blood doping, hypoxia, or beta-blockade), VO2max changes accordingly; 2) the increase in VO2max with training results primarily from an increase in maximal cardiac output (not an increase in the a-v O2 difference); and 3) when a small muscle mass is overperfused during exercise, it has an extremely high capacity for consuming oxygen. Thus, O2 delivery, not skeletal muscle O2 extraction, is viewed as the primary limiting factor for VO2max in exercising humans. Metabolic adaptations in skeletal muscle are, however, critical for improving submaximal endurance performance. Endurance training causes an increase in mitochondrial enzyme activities, which improves performance by enhancing fat oxidation and decreasing lactic acid accumulation at a given VO2. VO2max is an important variable that sets the upper limit for endurance performance (an athlete cannot operate above 100% VO2max, for extended periods). Running economy and fractional utilization of VO2max also affect endurance performance. The speed at lactate threshold (LT) integrates all three of these variables and is the best physiological predictor of distance running performance.

Purpose: The world hour record in cycling has increased dramatically in recent years. The present study was designed to compare the performances of former/current record holders, after adjusting for differences in aerodynamic equipment and altitude. Additionally, we sought to determine the ideal elevation for future hour record attempts., Methods: The first step was constructing a mathematical model to predict power requirements of track cycling. The model was based on empirical data from wind-tunnel tests, the relationship of body size to frontal surface area, and field power measurements using a crank dynamometer (SRM). The model agreed reasonably well with actual measurements of power output on elite cyclists. Subsequently, the effects of altitude on maximal aerobic power were estimated from published research studies of elite athletes. This information was combined with the power requirement equation to predict what each cyclist's power output would have been at sea level. This allowed us to estimate the distance that each rider could have covered using state-of-the-art equipment at sea level. According to these calculations, when racing under equivalent conditions, Rominger would be first, Boardman second, Merckx third, and Indurain fourth. In addition, about 60% of the increase in hour record distances since Bracke's record (1967) have come from advances in technology and 40% from physiological improvements., Results and Conclusions: To break the current world hour record, field measurements and the model indicate that a cyclist would have to deliver over 440 W for 1 h at sea level, or correspondingly less at altitude. The optimal elevation for future hour record attempts is predicted to be about 2500 m for acclimatized riders and 2000 m for unacclimatized riders.

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) were made at rest and at power outputs of 50, 100, 150, 200, and 250 W. No significant differences (P > 0.05) were observed for VE, VO2, and VCO2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (FEO2) and carbon dioxide (FECO2) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable metabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L x min(-1), using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

During an incremental run test, some researchers consistently observe a heart rate (HR) deflection at higher speeds, but others do not. The present study was designed to investigate whether differences in test protocols could explain the discrepancy. Additionally, we sought to determine whether the HR deflection point accurately predicts lactate threshold (LT). Eight trained runners performed four tests each: 1) a treadmill test for maximal O(2) uptake, 2) a Conconi test on a 400-m track with speeds increasing approximately 0.5 km/h every 200 m, 3) a continuous treadmill run with speeds increasing 0.5 km/h every minute, and 4) a continuous LT treadmill test in which 3-min stages were used. All subjects demonstrated an HR deflection on the track, but only one-half of the subjects showed an HR deflection on the treadmill. On the track the shortening of stages with increasing speeds contributed to a loss of linearity in the speed-HR relationship. Additionally, the HR deflection point overestimated the LT when a continuous treadmill LT protocol was used. In conclusion, the HR deflection point was not an accurate predictor of LT in the present study.

Normotensive individuals who exhibit an exaggerated blood pressure (BP) response to exercise have an increased risk of future hypertension. However, previous studies failed to control for resting BP despite the fact that an elevated resting BP in the normotensive range is also a strong predictor of future hypertension. Therefore, we determined whether maximal systolic BP is associated with resting BP. Resting BP was measured in 68 healthy normotensive men on three separate days. The subjects then performed a graded, maximal exercise test on a Monark cycle ergometer. Maximal systolic BP was strongly correlated with resting systolic BP (r = 0.64, P < 0.0001). Subjects with elevations in systolic BP during maximal exercise (> 220 mmHg) also had higher (P < 0.005) resting BP than those without (< 220 mmHg). When stepwise regression analyses were performed, systolic BP at rest was a significant independent predictor of maximal systolic BP, explaining over 40% of the variability. These results suggest that exaggerated BP response as a predictor of future hypertension reported in previous studies may be little more than a simple reflection of elevated resting BP. Specifically, these studies should not be interpreted as demonstrating that exercise BP is a better predictor of future hypertension than resting BP alone. In the future, defining the BP 'response' to exercise as a change score (i.e. maximal BP minus resting BP) may be advantageous as it permits the effects of exercise to be examined independently of the level of resting BP.

Substrate utilization during and after low- and moderate-intensity exercise of similar caloric expenditure was compared. Ten active males [age: 26.9 (4.8) years; height: 181.1 (4.8) cm; Mass: 75.7 (8.8) kg; maximum O2 consumption (VO2max): 51.2 (4.8) ml x kg(-1) x min(-1)] cycled at 33% and 66% VO2max on separate days for 90 and 45 min, respectively. After exercise, subjects rested in a recumbent position for 6 h. Two h post-exercise, subjects ate a standard meal of 66% carbohydrate (CHO), 11% protein, and 23% fat. Near-continuous indirect calorimetry and measurement of urinary nitrogen excretion were used to determine substrate utilization. Total caloric expenditure was similar for the two trials; however, significantly (P < 0.05) more fat [42.4 (3.6) g versus 24.0 (12.2) g] and less CHO [142.5 (28.5) g versus 188.8 (45.2) g] was utilized as a substrate during the low-intensity compared to the moderate-intensity trial. Protein utilization was similar for the two trials. The difference in substrate use can be attributed to the exercise period because over twice as much fat was utilized during low-intensity [30.0 (11.0) g] compared to moderate-intensity exercise [13.6 (6.6) g]. Significantly more (P < 0.05) CHO was utilized during the moderate-intensity [106.0 (27.8) g] compared to the low-intensity exercise [68.7 (20.0) g]. Substrate use during the recovery period was not significantly different. We conclude that low-intensity, long-duration exercise results in a greater total fat oxidation than does moderate intensity exercise of similar caloric expenditure. Dietary-induced thermogenesis was not different for the two trials.

The purpose of this study was to compare muscle fibre type proportions and capillary density in untrained, college-aged blacks (n = 14) and whites (n = 14). Both groups were similar in terms of peak oxygen uptake (VO2peak), measured during cycle ergometry (blacks: 42.6 +/- 4, whites: 44.3 +/- 4 ml.kg-1 min-1, mean +/- SD). Muscle samples were obtained from the quadriceps femoris (vastus lateralis) by the needle biopsy technique. Fibre type was determined by myosin ATPase stain (pH = 4.54) and capillaries were identified by amylase-periodic acid Schiff (PAS) stain. The percentage of type I, IIa, and IIb fibres in the blacks was 39.5 +/- 11.5, 40.0 +/- 8.4, and 22.8 +/- 9.8, respectively. In whites the percentage of type I, IIa, and IIb fibres was 44.9 +/- 8.5, 36.6 +/- 6.9, and 18.3 +/- 9.6, respectively. No significant differences were noted between the two racial groups for type I, IIa, or IIb fibres. Capillary density was 277 +/- 39/mm2 in the blacks compared to 289 +/- 32/mm2 in the whites. Capillary density was positively correlated to percentage of type I fibres (r = 0.497) and negatively correlated to percentage of type IIa fibres (r = -0.389), in the overall study population. These data suggest that if racial differences in fibre type do exist, such differences are small compared to the variability in this measure.

The major symptoms of overtraining including decreased exercise performance, altered mood states, and depleted muscle glycogen stores closely resemble the effects of brain serotonin, the level of which is dependent on the plasma ratio of tryptophan to branched-chain amino acids (BCAA). To examine the relation between plasma amino acids and overtraining, ten highly-trained endurance runners underwent two weeks of base training (normal training) before increasing their training volume by 40% for two weeks to achieve a state of short-term overtraining (or overreaching). The overtraining period was followed by two weeks of recovery in which training volume was reduced by 41% of the base training. For the whole group, no significant changes were observed in running economy and maximum oxygen uptake. There were no changes in resting heart rate, blood pressure, resting metabolic rate, and serum cortisol level in response to the changes in training volume. The runners experienced a significant increase (p < 0.05) in fatigue score for the profile of mood states when the training volume was increased. The elevated fatigue score returned to baseline when the training volume was reduced. Plasma free or total tryptophan, BCAA, and the tryptophan/BCAA ratio were not significantly altered throughout the course of this study. We concluded that proposed physiological markers of overtraining, including plasma tryptophan and BCAA levels, were unchanged despite a 40% increase in training volume.

The traditional view of VO2max owes a great deal to the work of A. V. Hill, who conducted experiments on exercising man in Manchester, England, in the 1920's. Hill and colleagues proposed that there is an upper limit to oxygen uptake (VO2max), that there are inter-individual differences in this variable, and that VO2max is limited by the circulatory and/or respiratory systems. They demonstrated that oxygen uptake increases linearly with running speed, but in some subjects it eventually "reaches a maximum beyond which no effort can drive it," a phenomenon now referred to as the VO2 plateau. In recent years, Timothy Noakes has strongly criticized Hill's concept of VO2max. He maintains that the absence of a VO2 plateau in some subjects is proof that oxygen delivery is not a limiting factor for VO2max. This view fails to recognize that the plateau is not the principal evidence for a cardiorespiratory limitation. Noakes rejects the VO2max paradigm of A. V. Hill in its entirety. The alternative paradigm he proposes is that endurance performance is limited by "muscle factors." Noakes suggests that the best distance runners have muscle characteristics that allow them to achieve higher running speeds, and since running speed is linearly related to oxygen uptake, an indirect consequence of this is that they will have higher VO2max values. This is exactly the opposite of how the relationship between VO2max and running speed at the end of a maximal exercise test should be viewed. Noakes offers little evidence to support his views, and they conflict with a vast body of scientific evidence showing that oxygen transport is a major determinant of endurance performance. After carefully reviewing the evidence on both sides of the issue, we conclude that the older "classical" VO2max paradigm of A. V. Hill is the correct one.

Objectives: The objectives of the present study were (1) to evaluate the pressor response to an isometric handgrip exercise in normotensive black and white males; (2) to measure plasma catecholamine levels pre- and post-exercise, as an index of sympathetic nervous system activity; and (3) to quantify the pressor response to bolus intravenous injections of phenylephrine (an alpha-specific agonist)., Methods: Cardiovascular and catecholamine responses to an isometric handgrip exercise (3 minutes at 30% MVC) were measured in 15 normotensive blacks and whites. In another phase of the study, pressor responses to bolus injections of phenylephrine were assessed to evaluate alpha-adrenergic sensitivity., Results: The blood pressure in the blacks increased from 119/69 to 160/120 mm HG during isometric exercise, while in the whites it increased from 118/67 to 153/110 mm HG. The blacks exhibited a greater diastolic blood pressure reactivity, as evidenced by a significant race x time interaction (p < 0.05). The heart rate responses were not significantly different between the two groups. The plasma levels of norepinephrine were similar at rest, but were 25% lower in the blacks than in the whites following isometric exercise (p < 0.01). Black subjects also demonstrated an increased pressor response to intravenous injections of phenylephrine at rest (p < 0.05)., Conclusions: The enhanced vascular sensitivity to norepinephrine may have contributed to the greater exercise pressor response in the blacks.

Recent studies have suggested that an exaggerated blood pressure response to maximal exercise may be useful in detecting individuals who are prone to developing hypertension in later years. To examine the hypothesis that regular aerobic exercise results in a smaller blood pressure response to maximal exercise, 26 endurance-trained and 31 untrained individuals (matched on age and physical characteristics) performed graded maximal exercise tests on a cycle ergometer. Trained subjects achieved a significantly (P < .05) higher level of maximal oxygen uptake (mean +/- SE: 59.4 +/- 1.4 v 44.7 +/- 1.0 mL/kg/min), as well as a greater maximal work rate. Although there was no significant difference in resting blood pressure between the groups, endurance-trained individuals demonstrated significantly higher maximal systolic blood pressure levels compared to untrained subjects during maximal exercise (225 +/- 3 v 204 +/- 4 mm Hg). The group differences in systolic blood pressure were also significant (P < .05) at work rates of 180 W and higher. It is concluded that physically active individuals show higher blood pressure responses to maximal exercise, despite their reduced risk of future hypertension. This finding indicates that an exaggerated blood pressure response is not a valid prognostic test to indicate the likelihood of future hypertension in this population.

Black Americans have been shown to exhibit increased blood pressure responses to a variety of physical stressors. However, few investigators have examined hemodynamic responses to cold stress. Additionally, no studies have compared blood pressure responses to forehead and foot stress in blacks. Therefore, in this study, hemodynamic responses to cold pressor tests were compared in 30 blacks (15 males, 15 females) utilizing two application sites. Baseline comparisons of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), forearm blood flow (FBF) and forearm vascular resistance (FVR) were not different prior to forehead and foot cold stress. Following baseline measurements, ice was applied separately to the forehead and foot for 90 seconds with hemodynamic measurements being recorded at 45 and 90 seconds. During application of ice to the forehead, FVR-90 was significantly higher (P < .002, 97.0 units vs. 66.4 units) compared to the foot. The application of ice to the foot resulted in significantly greater SBP-45 responses (P < .0001, 147 mmHg vs. 139 mmHg), HR-45 responses (P < .0043, 80, b.min-1 vs. 69 b.min-1). HR-90 responses (P < .0001, 78 b.min-1 vs. 64 b.min-1), and FBF-45 responses (P < .05, 2.74 ml.min-1.100ml-1 vs. 1.98 ml.min-1.100ml-1). These findings suggest that blacks exhibit disparate patterns of reactivity in response to cold stress as a function of application site. Therefore, investigators should consider the application site when interpreting studies examining a biracial cohort.

This is a three-part study that examined the accuracy of five brands of electronic pedometers (Freestyle Pacer, Eddie Bauer, L.L. Bean, Yamax, and Accusplit) under a variety of different conditions. In Part I, 20 subjects walked a 4.88-km sidewalk course while wearing two devices of the same brand (on the left and right side of the body) for each of five different trials. There were significant differences among pedometers (P < 0.05), with the Yamax, Pacer, and Accusplit approximating the actual distance more closely than the other models. The Yamax pedometers showed close agreement, but the left and right Pacer pedometers differed significantly (P = 0.0003) and the Accusplit displayed a similar trend (P = 0.0657). In Part II, the effects of walking surface on pedometer accuracy were examined. Ten of the original subjects completed an additional five trials around a 400-m rubberized outdoor track. The devices showed similar values for sidewalk and track surfaces. In Part III, the effects of walking speed on pedometer accuracy were examined. Ten different subjects walked on a treadmill at various speeds (54, 67, 80, 94, and 107 m.min-1). Pedometers that displayed both distance and number of steps were examined. The Yamax was more accurate than the Pacer and Eddie Bauer at slow-to-moderate speeds (P < 0.05), though no significant differences were seen at the fastest speed. While there are variations among brands in terms of accuracy, electronic pedometers may prove useful in recording walking activities in free-living populations.

The equilibrium CO2 rebreathing technique has been widely used for the noninvasive determination of cardiac output. Recently, several investigators have used this technique in conjunction with auscultatory blood pressure measurements to calculate total peripheral resistance. To examine the validity of this approach, we attempted to determine whether the CO2 rebreathing procedure has a significant effect on blood pressure. The participants in the present study were 10 male subjects, 24 +/- 1 yr of age (mean +/- SE). Each subject performed two trials-one with CO2 rebreathing and one without. Both trials consisted of three stages (rest, 25%, and 50% VO2peak), each stage lasting 15 min. During the rebreathing trial, the CO2 rebreathing technique was administered at 10 min into each stage. There were no statistically significant differences in the heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure responses between the two trials. These results indicate that the equilibrium CO2 rebreathing technique does not alter auscultatory blood pressures at rest and during exercise up to intensities of 50% VO2peak.

High-intensity resistance (HIR) training has been associated with muscle hypertrophy and decreased microvascular density that might produce a blood flow limitation. The effect of HIR training on lower leg maximal blood flow and minimum vascular resistance (Rmin) during reactive hyperemia were investigated in 7 healthy males. The gastrocnemius-soleus muscles of one leg were trained using maximal isokinetic concentric contractions for 4 weeks; the nontrained leg was the control. Lower leg blood flow was measured by venous occlusion plethysmography. Lower leg muscle volume was determined using magnetic resonance imaging. Peak isokinetic torque increased in both the trained (T) and nontrained (NT) legs (p < .05). Lower leg muscle volume increased by 2% in the T leg only (p < .05). In the T leg, maximal blood flow decreased and Rmin increased (p < .05); no hemodynamic change was detected in the NT leg. It is concluded that HIR training of the calf muscles is associated with a decrease in hyperemia-induced blood flow; thereby, indicating a blood flow limitation to the calf muscles.

Seven competitive road cyclists (M +/- SE = 23.7 +/- 1.5 yr, 70.5 +/- 1.7 kg) participated to determine the effects of cycling body position on physiological responses during uphill cycling and maximal oxygen uptake (VO2max). There was no significant difference in VO2max between seated and standing positions on a cycle ergometer (66.4 +/- 1.6 vs. 66.4 +/- 1.7 ml . kg-1 . min-1). When the subjects rode their own bicycle on a treadmill, oxygen uptake and heart rate were significantly (p < 0.05) higher during standing when subjects bicycled at 20.0 km . h-1 (4% grade), but no difference was observed when riding at 12.3 km . h-1 (10% grade). Leg RPE was significantly (p < 0.05) lower for standing position up a 10% grade. The results suggest that the standing position is less economical during moderate hill climbing, but during steep hill climbing, it results in a decreased sensation of effort in the legs.

The carbon dioxide rebreathing technique is widely used for determination of cardiac output during exercise. The equilibration method of Collier et at. (J. Appl. Physiol. 9:25, 1956) is generally preferred over the exponential method of Defares (J. Appl. Physiol. 13:159, 1968). However, the equilibration method requires the volume and initial CO2 percentage in the rebreathing bag to be adjusted according to the work rate. A device for mixing two gases (100% O2 and 20% CO2/80% O2) was constructed for this purpose. Multistage regulators are attached to the gas tanks and connected to a medical gas mixer via high-pressure air hoses. A variable time-delay switch causes a solenoid valve to open for 1.0-10s to deliver a predetermined gas volume. The device was found to accurately deliver a preset volume and concentration of gas to the rebreathing bag. A gas mixing apparatus simplifies the equilibration CO2 rebreathing technique by allowing the investigator to easily select the initial volume and percentage of CO2.

In an attempt to determine whether the lactate threshold (LT) is the result of a sudden increase in plasma epinephrine (Epi), eight healthy college-aged males (22.4 +/- 0.4 yr) were recruited to perform three cycle ergometer exercise tests. Each subject performed a graded exercise test (GXT) to determine LT, Epi threshold, and norepinephrine threshold (64.6 +/- 2.4, 62.5 +/- 2.4, and 60.8 +/- 4.3% peak oxygen uptake, respectively). Each subject also completed, in random order, two 30-min submaximal (20% peak oxygen uptake below LT) exercise tests. During one test, graded Epi infusions were carried out at rates of 0.02-0.12 micrograms.kg-1.min-1; the other served as a control test. Infusion resulted in plasma Epi concentrations similar to those observed during GXT. The increase in blood lactate with Epi infusion was significantly greater than that during the control test (3.0 +/- 0.3 vs. 1.4 +/- 0.1 mmol/l at minute 30) but did not approach levels exhibited during GXT. We suggest an interaction of the increasing plasma Epi with other factors may be responsible for the sudden increase in blood lactate during graded exercise.

Historically, the achievement of maximal oxygen uptake (VO2max) has been based on objective criteria such as a leveling off of oxygen uptake with an increase in work rate, high levels of lactic acid in the blood in the minutes following the exercise test, elevated respiratory exchange ratio, and achievement of some percentage of an age-adjusted estimate of maximal heart rate. These criteria are reviewed relative to their history, the degree to which they have been achieved in published research, and how investigators and reviewers follow them in current practice. The majority of the criteria were based on discontinuous protocols, often carried out over several days. Questions are raised about the applicability of these criteria to modern continuous graded exercise test protocols, and our lack of consistency in the terminology we use relative to the measurement of maximal oxygen uptake.

The purpose of this study was to examine the cardiovascular responses of sprinters and distance runners to isometric (IE) and dynamic exercise (DE). Normotensive males were selected and grouped according to prior running performance: sprinter (N = 6) or distance runner (N = 6). Each subject completed an incremental DE (cycle ergometry) test (6-min stages) at 20%, 40%, and 60% of VO2peak, and 3 min of isometric handgrip at 30% of MVC. Blood pressure (BP), heart rate (HR), cardiac output (Q), oxygen uptake, and blood lactate were measured, while mean arterial blood pressure (MABP), cardiac index (CI), and systemic vascular resistance (SVR) were calculated during each stage of DE. BP and HR were measured during each minute of IE. Muscle biopsies of the vastus lateralis revealed a significant difference in capillary density (capillaries per mm2 and capillaries per fiber) between the sprinters and distance runners (323 +/- 23 vs 409 +/- 27 and 2.2 +/- 0.2 vs 3.2 +/- 0.3, P < 0.05) and for the percentage of Type I fibers (46.4 +/- 4% vs 64.8 +/- 7%, P < 0.05). The IE challenge elicited a greater BP response at minute 3 in the sprinters, which was associated with a greater HR response. During DE, there were no significant differences in BP or HR between the groups. However, at 60% of VO2peak, the distance runners had a significantly higher cardiac index and a lower systemic vascular resistance than the sprinters (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Polylactate (PL), a semi-soluble amino acid/lactate salt, is a newly developed carbohydrate supplement purported to increase endurance. Our purpose was to determine if the addition of PL to a glucose polymer solution (GP) extends exercise time relative to a pure GP solution. In a double blind and random crossover design, 5 subjects exercised twice to exhaustion at 70% of VO2max. During the trials, they consumed GP or a GP/PL mixture at the rate of 0.3 g carbohydrate per kg of body wt in a 7% solution every 20 min until exhaustion. The GP/PL mixture contained 6.25 g GP to 0.75 g PL per 100 ml of water. Mixture composition was critical because PL, as supplied by the manufacturer and under our experimental conditions, produced severe gastro-intestinal efflux in concentrations > or = 2.5%; PL was tolerable in concentrations < or = 0.75%. At 20 min intervals, we measured VO2, respiratory exchange ratio, heart rate, and perceived exertion. At 30 min intervals, we measured serum glucose, insulin, free fatty acids, and glycerol as well as whole blood lactate and pH. We found that the addition of PL to a GP solution had no measurable physiological or performance effects.

Recent studies have reported that skeletal muscle characteristics are altered in hypertension, insulin resistance, and android obesity. These conditions represent cardiovascular risk factors that are often "clustered" together, and have begun to be recognized as part of a metabolic/cardiovascular syndrome. This paper reviews the evidence correlating skeletal muscle characteristics to cardiovascular risk factors, and outlines the proposed mechanisms for the relationships. Muscle characteristics (e.g., fiber type, capillary density, oxidative capacity, insulin binding, GLUT 4 levels, and glucose uptake) are discussed. Although aerobic training does not appear to alter the ratio of Type I/II fibers, it favorably affects other skeletal muscle characteristics that are mechanistically linked to cardiovascular risk factors. These muscle adaptations are important in understanding how exercise training helps to prevent cardiovascular disease.

Objective: To study exercise blood pressure response in association with exercising muscle maximal vasodilatory capacity in normotensives with a positive and negative family history of hypertension., Subjects: Twenty-eight normotensive healthy subjects were recruited. Of these, two females and 13 males had a positive, and three females and 10 males had a negative, family history of hypertension., Methods: Both groups of subjects rode a bicycle ergometer while systolic blood pressure, diastolic blood pressure and heart rate were measured at 30%, 60% and peak oxygen uptake rate. The vasodilatory capacity was examined in the lower leg by measuring the minimal vascular resistance during peak reactive hyperemia after 10 min arterial occlusion., Results: Age, body weight, resting blood pressure, peak oxygen uptake rate and casual lower leg vascular resistance were not significantly different between the two groups of subjects. Significantly higher exercise systolic blood pressure (9%) and diastolic blood pressure (9%) were seen in the subjects with positive family history of hypertension compared with the subjects with negative family history of hypertension. Exercise heart rate was significantly higher in the subjects with negative than in those with positive family history of hypertension. The vascular resistance at peak vasodilation was 22% higher in the subjects with positive than in the subjects with negative family history of hypertension., Conclusions: This study demonstrates that the dynamic exercise blood pressure is exaggerated and skeletal muscle vasodilatory capacity is limited in normotensives with genetic risk of hypertension. This suggests that the higher pressor response to physical stress that is found in normotensives with a family history of hypertension may be attributed to the resistance vessels in the exercising muscle.

The purpose of this study was to characterize the aerobic and anaerobic capabilities of United States Cycling Federation cyclists in different categories. To determine aerobic and anaerobic power, 38 competitive road cyclists (32 males, 6 females) performed a VO2max test and a Wingate anaerobic test, respectively. Male cyclists in category II had the highest VO2max, both in absolute and relative terms. Their VO2max was 6% and 10% higher than category III and IV cyclists, respectively (4.98 +/- 0.14 vs 4.72 +/- 0.15 vs 4.54 +/- 0.12 l/min). A significant difference existed between category II and IV male cyclists (p < 0.05). VO2max for female cyclists (3.37 +/- 0.13 l/min) was significantly (p < 0.05) lower than those for males. The Wingate anaerobic test revealed that male cyclists in category II also had the highest anaerobic power output. The peak power output in category II, III and IV was 13.86 +/- 0.23, 13.55 +/- 0.25, and 12.80 +/- 0.41 W/kg, respectively. The mean power output in category II, III, and IV was 11.22 +/- 0.18, 11.06 +/- 0.15, and 10.40 +/- 0.30 W/kg, respectively. The difference in the mean power output between category II and IV was significant (p < 0.05). Female cyclists recorded significantly less peak and mean power output than their male counterparts (p < 0.05). However, when expressed relative to lean body mass, anaerobic power was similar for both sexes. No inter-correlation was found in any measurement between the aerobic and anaerobic power values. On the whole, category II male cyclists were characterized by higher aerobic and anaerobic power outputs.(ABSTRACT TRUNCATED AT 250 WORDS)

The application of automated blood pressure measurement during exercise has been limited by inaccuracies introduced by the effects of accompanying motion and noise. We evaluated a newly developed automated blood pressure monitor for measuring exercise blood pressure (Colin STBP-680; Colin, San Antonio, Texas, USA). The STBP-680 uses acoustic transduction with the assistance of the electrocardiogram R-wave to trigger the sampling period for blood pressure measurement. The automated monitor readings were compared with simultaneous technician mercury sphygmomanometric readings in the same arm. Blood pressure was measured in 18 men at rest and during exercise at 40% VO2 peak, (low intensity), 70% VO2 peak (moderate intensity) and VO2 peak (high intensity) on the cycle ergometer. Mean(s.d.) systolic blood pressure difference between the automated monitor and mercury manometer readings at rest and during exercise at low, moderate and high work intensities were 3(0) mmHg, 3(2) mmHg, 1(1) mmHg, and 0(11) mmHg respectively (analysis of variance; P > 0.05). Resting diastolic blood pressure obtained with the STBP-680 was similar to the mercury manometer readings (78(10) versus 81(7) mmHg (P > 0.05). Exercise diastolic pressure at the low level of work intensity was almost identical between the automated monitor and mercury manometer readings (64(8) versus 65(10) mmHg (not significant)). Diastolic blood pressure readings between the STBP-680 and mercury manometer showed a greater difference at the moderate and high workloads (11 mmHg and 9 mmHg, respectively), but this difference was not significant (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

This study was performed to determine whether alterations in vascular structure exist in a biracial population of young (age 22.3 +/- 0.6 yrs [mean + SE]) normotensive men. We examined maximal vasodilatory capacity in 21 blacks and 20 whites (average blood pressure = 122/75 and 118/72 mm Hg, respectively). Forearm blood flow was determined at rest and after 10 min of ischemic handgrip exercise using venous occlusion plethysmography. Forearm vascular resistance was computed from blood flow and mean arterial blood pressure determined by auscultation. Minimum forearm vascular resistance was 23% higher in blacks (2.60 +/- 0.60) than in whites (2.11 +/- 0.41) (P = .005), and was unrelated to parental history of hypertension. The regression equation for minimum forearm vascular resistance (Y) and casual blood pressure (X) for blacks was Y = -1.782 + 0.0487X (r = 0.522); for whites it was Y = -1.165 + 0.0367X (r = 0.418). When the data were covaried on resting mean arterial blood pressure, blacks still had a higher minimum forearm vascular resistance (P = .014). The results suggest a racial difference in the vascular structure of the forearm resistance vessels.

This study was conducted to determine whether the pedaling frequency of cycling at a constant metabolic cost contributes to the pattern of fiber-type glycogen depletion. On 2 separate days, eight men cycled for 30 min at approximately 85% of individual aerobic capacity at pedaling frequencies of either 50 or 100 rev.min-1. Muscle biopsy samples (vastus lateralis) were taken immediately prior to and after exercise. Individual fibers were classified as type I (slow twitch), or type II (fast twitch), using a myosin adenosine triphosphatase stain, and their glycogen content immediately prior to and after exercise quantified via microphotometry of periodic acid-Schiff stain. The 30-min exercise bout resulted in a 46% decrease in the mean optical density (D) of type I fibers during the 50 rev.min-1 condition [0.52 (0.07) to 0.28 (0.04) D units; mean (SEM)] which was not different (P > 0.05) from the 35% decrease during the 100 rev.min-1 condition [0.48 (0.04) to 0.31 (0.05) D units]. In contrast, the mean D in type II fibers decreased 49% during the 50 rev.min-1 condition [0.53 (0.06) to 0.27 (0.04) units]. This decrease was greater (P < 0.05) than the 33% decrease observed in the 100 rev.min-1 condition [0.48 (0.04) to 0.32 (0.06) units). In conclusion, cycling at the same metabolic cost at 50 rather than 100 rev.min-1 results in greater type II fiber glycogen depletion. This is attributed to the increased muscle force required to meet the higher resistance per cycle at the lower pedal frequency.(ABSTRACT TRUNCATED AT 250 WORDS)