Biomedical subjects

K J Cureton

Publications and source records attributed to K J Cureton.

At least 19 recordsLinked to original sources

PubMed1992

Validation of the 12-minute swim as a field test of peak aerobic power in young women.

The purposes of this study were to validate the 12-min swim as a field test of VO2 peak in female recreational swimmers and to compare its validity with that of the 12-min run. The results are contrasted with those previously reported on a comparable group of male recreational swimmers. Thirty-four young women completed 12-min swim, 12-min run, tethered swimming VO2 peak, and treadmill running VO2 peak tests within 3 weeks. Mean (+/- SD) 12-min swim and run distances were 597 +/- 82 and 2,313 +/- 317 m, and mean tethered swim and treadmill run VO2 peak values were 39.2 +/- 4.9 and 45.4 +/- 6.3 ml.kg BW-1.min-1, respectively. Correlation coefficients and standard errors of estimate for predictions of swimming VO2 peak from the 12-min swim (.42 and 4.5 ml.kg BW-1.min-1) and run (.58 and 4.1 ml.kg BW-1.min-1) and for predictions of treadmill run VO2 peak from the 12-min swim (.34 and 6.0 ml.kg BW-1.min-1) and run (.87 and 3.2 ml.kg BW-1.min-1) indicated that the 12-min run was a more accurate predictor of tethered swim or treadmill run VO2 peak than the 12-min swim. These data are in close agreement with our previous study on young male recreational swimmers. We conclude that the 12-min swim has relatively low validity as a field test of peak aerobic power and that it is not an equally valid alternative to the 12-min run in young adult female recreational swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Breathlessness predicts perceived exertion in young women with mild asthma.

We examined ratings of breathlessness (BRE) as a predictor of perceived exertion (RPE) during incremental cycling at power outputs of 50, 75, and 100 W. Young females (21 yr +/- 1.9) diagnosed with mild asthma (N = 25) were compared with females having normal lung function (N = 25) matched for age, VO2peak, trait anxiety, activity history (7-d recall), and BMI (kg.m-2). Relative oxygen consumption (%VO2peak), blood lactate concentration, VE.VO2(-1), and state anxiety were statistically controlled in hierarchical multiple linear regression analyses. For each group, %VO2peak explained 60% of the variance in RPE across power outputs (P less than 0.001); R2 was unchanged (P greater than 0.10) with the addition of blood lactate, VE.VO2(-1), and state anxiety. Absolute RPE and BRE did not differ between groups at any power output, but partial standardized (beta) and unstandardized (b) regression coefficients and increases in R2 showed that BRE had a greater effect (P less than 0.01) on RPE for asthmatics [adjusted R2 increased to 0.89; (beta) = 0.75; (b) = 0.79 +/- 0.06] than for controls [adjusted R2 increased to 0.74; (beta) = 0.52; (b) = 0.51 +/- 0.09]. The standard error of the prediction was 0.79 for asthmatics and 1.16 for controls. The prediction of RPE by BRE was not moderated by variation in forced expiratory volume for 1 s (FEV1), forced vital capacity (FVC) or peak inspiratory flow (VI). Physiological responses were similar for the groups, but blood lactate was higher in asthmatics at rest, at each power output, and at VO2peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Effect of varying levels of hypohydration on responses during submaximal cycling.

The effect of varying levels of hypohydration on hemodynamic, cardiorespiratory, and metabolic responses to progressive incremental submaximal cycling was examined in nine male subjects. Subjects cycled in a neutral (22 degrees C) environment under euhydration (EU), moderate hypohydration (MH), and severe hypohydration (SH). To achieve the desired level of hypohydration, subjects cycled at 50% VO2max for 1.5 h in a 38 degrees C environment on two separate occasions, 36 h prior to testing. Mean (+/- SE) percent losses in body weight from baseline during EU, MH, and SH were 0.6 +/- 0.3%, 3.3 +/- 0.1%, and 5.6 +/- 0.4%, respectively. Ventilation, O2 uptake, respiratory exchange ratio, heart rate, plasma free fatty acids, plasma glycerol, blood lactate, and hematocrit were not significantly altered by hypohydration. During EU, hemoglobin concentration was significantly lower than during both MH and SH, but no significant difference was observed for plasma volume loss. Plasma glucose was significantly higher during SH compared with EU and MH. These results suggest that hypohydration of up to 5.6% caused by exercise and fluid manipulation over 36 h does not alter cardiorespiratory or blood lactate responses during progressive incremental submaximal cycling in a neutral environment. However, hepatic metabolism may be altered during hypohydration as indicated by higher plasma glucose levels.

Adult↗

PubMed1992

Differential effects of dietary carbohydrate on RPE at the lactate and ventilatory thresholds.

This study used manipulation of dietary intake and substrate utilization to dissociate the ventilatory (TVE) and lactate (TLAC) thresholds, and investigated the role of the thresholds in perception of effort as measured by the Borg 15-category rating of perceived exertion (RPE) scale. Thirteen males performed graded exercise tests following: a) glycogen depletion (GD) and 3 d on a high-carbohydrate diet (HC, 93% total daily energy intake as carbohydrate), b) GD and 3 d on a low-carbohydrate diet (LC, 21%), and c) a mixed-carbohydrate diet (NC, 51%). During submaximal exercise at intensities between 30 and 90% of peak oxygen uptake (VO2peak), significant differences among conditions (P less than 0.05) were obtained for carbon dioxide elimination, respiratory exchange ratio, and plasma lactate, with HC greater than NC greater than LC. Mean (+/- SD) TLAC occurred at different (P less than 0.05) percentages of VO2peak, with HC (55.6 +/- 2.9%) less than NC (59.6 +/- 2.9%) less than LC (63.8 +/- 2.8%). Means for TVE were not different. RPE at TLAC were significantly different (P less than 0.01) among conditions, with HC (12.6 +/- 0.6) less than NC (13.8 +/- 0.6) less than LC (14.3 +/- 0.7), but RPE at TVE were not different. It was concluded that the perception of exertion as becoming "somewhat hard" to "hard" is more closely linked to TVE than to TLAC.

Adult↗

PubMed1992

No effects of glycogen depleting exercise and altered diet composition on mood states.

To investigate the effects of glycogen depleting exercise and dietary composition on mood, 14 males completed the Profile of Mood States (POMS) questionnaire under four conditions. A control condition (CON) of ad libitum diet preceded any experimental manipulation. Subsequently, three treatments were administered randomly in a counterbalanced design: a) following a glycogen-depletion protocol and 3 d on a high-carbohydrate diet (93% of total caloric intake as carbohydrate [CHO]), b) following a glycogen-depletion protocol and 3 d on a low-CHO diet (23% of total caloric intake as CHO), and c) following 3 d of recorded ad libitum dietary consumption. Conditions a and b simulated phases of popular glycogen-loading protocols, and condition c served as a second control condition confirmed by records of dietary intake. The POMS measured tension-anxiety, depression-dejection, anger-hostility, vigor-activity, fatigue-inertia, and confusion-bewilderment. A composite score of total mood disturbance (TMD) was computed by summing the subscale scores (weighting vigor-activity negatively). Dietary composition (fat, protein, and CHO content) differed significantly (P less than 0.001) among the three treatments, but total caloric intake was not different. No significant differences were found among the treatment and control conditions for TMD or any POMS subscale score. We find no evidence that the 3-d glycogen loading protocol we employed with healthy, moderately fit, young males can be expected to confound performance measures by altering mood.

Adult↗

PubMed1991

Relationship of cardiac size to maximal oxygen uptake and body size in men and women.

It has been suggested in previous studies that the difference in endurance performance between males and females is related to gender-specific differences in cardiac function. Other studies have not equated males and females for physical condition, and this may have contributed to the findings. The purpose of this study was to determine the extent to which the difference in VO2max in groups of similarly trained males and females was explained by gender differences in cardiac size, fat-free weight (FFW) and hemoglobin concentration [( Hb]). Measurements of VO2max, FFW, [Hb] and cardiac size (LVM) were made on 19 males and 20 females comparable in age and cardiorespiratory capacity. The difference between men and women in LVM accounted for 68.3% of the gender difference in VO2max, and the combination of LVM and FFW accounted for 98.7% of the gender-related difference in VO2max. It was concluded that the gender difference in LVM accounts for a majority of the difference in VO2max in males and females, with other aspects of body size accounting for nearly all the remaining difference. The gender difference in heart size primarily reflects the smaller overall dimensions of women.

Body Constitution↗

PubMed1991

Interactive effects of body posture and exercise training on maximal oxygen uptake.

To determine the effect of posture on maximal O2 uptake (VO2 max) and other cardiorespiratory adaptations to exercise training, 16 male subjects were trained using high-intensity interval and prolonged continuous cycling in either the supine or upright posture 40 min/day 4 days/wk for 8 wk and 7 male subjects served as non-training controls. VO2 max measured during upright cycling and supine cycling, respectively, increased significantly (P less than 0.05) by 16.1 +/- 3.4 and 22.9 +/- 3.4% in the supine training group (STG) and by 14.6 +/- 2.0 and 6.0 +/- 2.0% in the upright training group (UTG). The increase in VO2 max measured during supine cycling was significantly greater (P less than 0.05) in the STG than in the UTG. The increase in VO2 max in the UTG was significantly greater (P less than 0.05) when measured during upright exercise than during supine exercise. However, there was no significant difference in posture-specific VO2 max adaptations in the STG. A postural specificity was also evident in other maximal cardiorespiratory variables (ventilation, CO2 production, and respiratory exchange ratio). In the UTG, maximal heart rate decreased significantly (P less than 0.05) only during supine cycling; there was no significant difference in maximal heart rate after training in the STG. We conclude that posture affects maximal cardiorespiratory adaptations to cycle training. Additionally, supine training is more effective than upright training in increasing maximal cardiorespiratory responses measured during supine exercise, and the effects of supine training generalize to the upright posture to a greater extent than the effects of upright training generalize to the supine posture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1991

Red blood cell pulmonary capillary transit time during exercise in athletes.

The purpose of this study was to test the hypothesis that the exercise-induced hypoxemia observed in endurance athletes is due to a reduction in the mean red blood cell pulmonary capillary transit time consequent to a plateau in pulmonary capillary blood volume (Vc) as exercise intensity progresses from moderate to heavy levels. Measurements of Vc, mean transit time, arterial O2 tension (PaO2), and end tidal-arterial O2 tension difference (AaDO2) were made in 16 subjects (mean maximal oxygen uptake (VO2max) = 4.90 l.min-1) at rest and during five cycle exercise bouts designed to elicit 55, 65, 75, 85, and 95% VO2max. Mean PaO2 fell from 101 mm Hg at rest to 85 mm Hg during heavy exercise. Mean AaDO2 increased linearly from one stage to the next and at the highest work rate equaled 22.3 mm Hg. Mean Vc failed to plateau with increasing exercise intensity and increased on average by 16 ml from one stage to the next. Mean transit time, on average, dropped from 1.05 s at rest to 0.46 s at the lowest work rate. Mean transit time did not decrease further with increasing exercise intensity (range, 0.42-0.46 s). We conclude that, under the conditions of this study, the AaDO2 increases and PaO2 decreases observed in endurance athletes during exercise of increasing intensity is not caused by a plateau in Vc and a consequent reduction in mean transit time.

Adult↗

PubMed1991

Validation of the 12-min swim as a field test of peak aerobic power in young men.

The purposes of this study were to validate the 12-min swim as a field test of VO2max and to compare its validity with that of the 12-min run. Thirty-six young men completed 12-min swim, 12-min run, tethered swimming (TS) VO2peak, and treadmill running (TR) VO2peak tests within 3 wk. Mean (+/- SD) 12-min swim and run distances were 581 +/- 88 and 2797 +/- 290 m, and mean TS and TR VO2peak values were 50.3 +/- 6.2 and 57.2 +/- 5.5 ml.kg BW-1.min-1, respectively. Correlation coefficients and standard errors of estimate for predictions of TS VO2peak from the 12-min swim (0.40 and 5.7 ml.kg BW-1.min-1) and run (0.74 and 4.2 ml.kg BW-1.min-1) and for predictions of TR VO2peak from the 12-min swim (0.38 and 5.1 ml.kg BW-1.min-1) and run (0.88 and 2.6 ml.kg BW-1.min-1) indicated that the 12-min run was a more accurate predictor of TS or TR VO2peak than the 12-min swim. We conclude that the 12-min swim has relatively low validity as a field test of peak aerobic power and that it should not be considered an equally valid alternative to the 12-min run in young male recreational swimmers. However, the accuracy of predicting VO2peak from the 12-min swim is as good as some other commonly used methods, and, therefore, it may be adequate for fitness classification in situations in which a high level of accuracy is not needed.

Adult↗

PubMed1991

Metabolic determinants of 1-mile run/walk performance in children.

The 1-mile run/walk test is the field test of choice for evaluating maximal aerobic power (VO2max) in school-aged children. The objective of this study was to determine the relative importance of selected metabolic determinants of mile run/walk performance in children 6-14 yr of age. Mile run/walk time (MRWT), VO2max, running economy (VO2 in ml.kg-1.min-1 at 8.05 km.h-1; VO2econ), and the percentage of VO2max utilized at the average mile run/walk speed (%VO2max) were measured in 59 children (33 boys and 26 girls); 27 6-8 yr olds (group 1), 17 9-11 yr olds (group 2), and 15 12-14 yr olds (group 3). Partial correlations between MRWT and VO2max, VO2econ, and %VO2max, holding constant the effects of age and sex, were as follows: group 1: -0.26, 0.03, and -0.82; group 2; -0.43, 0.09, and -0.88; and group 3, -0.60, 0.45, and -0.80. Multiple regression analysis indicated that the combination of the three metabolic measures accounted for 90%, 97%, and 90% of the variance in MRWT in the three age groups, respectively. Standardized regression coefficients for VO2max, VO2econ, and %VO2max in group 1 (-0.66, 0.19, and -0.83), group 2 (-0.45, 0.33, and -0.92), and group 3 (-0.76, 0.27, and -0.50) indicated that the %VO2max utilized at the average mile run/walk speed was the most important determinant of MRWT variance in children 6-11 yr old, whereas VO2max was the most important determinant for children 12-14 yr old. We conclude that the relative importance of the metabolic determinants of the 1-mile run/walk test, as typically administered in the schools, changes with age.

Adolescent↗

PubMed1991

Relationship of heart rate to oxygen uptake during weight lifting exercise.

To define the relation of heart rate to oxygen uptake during weight lifting (WL), heart rate (HR) and oxygen uptake (VO2) were determined during bouts of WL at four intensities (40, 50, 60, and 70% of one-repetition maximum (1-RM)) in 15 males. The 11.5-min bouts of WL consisted of three circuits using four exercises (bench press, bent-over row, arm curl, and parallel squat), with each performed for ten repetitions over a 30-s period with a 1:1 work/rest ratio. During lifting at the four intensities, mean (+/- SE) VO2 values were 1.31 +/- 0.04, 1.50 +/- 0.07, 1.72 +/- 0.07, and 1.86 +/- 0.08 l.min-1, or 33-47% of treadmill-determined VO2max. Mean (+/- SE) HR values were 124 +/- 4, 134 +/- 4, 148 +/- 5, and 161 +/- 4 beats.min-1, or 63-82% of maximal HR. The slope of the linear regression equation predicting %VO2max from %HRmax (Y = 0.582X - 1.7911, r = 0.86, SEE = 3.4%) was approximately half that reported for dynamic low-resistance exercise such as running or cycling. At a given %HRmax, %VO2max was consistently lower than predicted for dynamic low-resistance exercise. It was concluded that the HR/VO2 relationship during dynamic high-resistance exercise for intensities between 40 and 70% of 1-RM is linear but is different from that reported for dynamic low-resistance exercise. The data are consistent with the conclusion in previous studies that using HR to prescribe the metabolic intensity of WL exercise results in a substantially lower level of aerobic metabolism than during dynamic low-resistance exercise.

Adult↗

PubMed1990

Is the gender difference in peak VO2 greater for arm than leg exercise?

Based on observations that the difference between men and women in estimates of arm musculature is greater than the difference in leg musculature, it was hypothesized that the gender difference in peak oxygen uptake (VO2; l.min-1) would be greater for arm exercise than leg exercise. To test this hypothesis, 19 (10 men, 9 women) highly trained swimmers (HT) and 20 (10 men, 10 women) untrained students (UT) were tested for peak VO2 on cycle and arm-crank ergometers. Arm and leg fat-free volumes (FFV) were measured to provide an estimate of muscle distribution. No gender difference was observed in either the arm-to-leg peak VO2 ratio (0.699 for the men vs 0.696 for the women) or in the arm-to-leg FFV ratio (0.410 for the men vs 0.402 for the women). Although the proportion of musculature in the arms as assessed by the FFV appeared to be the same in men and women, the similarity in muscle distribution was probably not responsible for the identical average arm-to-leg peak VO2 ratios. The variance in the muscle distribution accounted for only 2-4% of the variance in the arm-to-leg peak VO2 differences within individuals. We conclude that factors other than arm and leg muscle dimensions account for the variability in the arm-to-leg peak VO2 ratio and that the gender difference in peak VO2 is the same for arm and leg exercise.

Adult↗

PubMed1990

Prediction of oxygen uptake on a bicycle wind-loaded simulator.

The primary purpose of this study was to determine the accuracy of estimating oxygen uptake (VO2) from the flywheel revolution rate of a bicycle wind-loaded simulator. VO2 at four different flywheel revolution rates was measured on a Findlay Road Machine (FRM). Ten male trained cyclists, 10 male untrained cyclists, 10 female trained cyclists and 10 female untrained cyclists served as subjects. Significant curvilinear relationships (P less than 0.01) were found between road speed estimated from flywheel revolution rate and VO2 expressed as 1.min-1, ml.kg-1.min-1, 1.min-1.m-2 (r = 0.97, 0.96, 0.98, respectively). The absolute standard error of the mean VO2 was 0.21 l.min-1 (9.6%), 3.71 ml.kg-1.min-1 (11.5%) and 0.10 l.min-1.m-2 (7.9%), respectively. The relationship between VO2 and speed was similar to that reported during road cycling. To determine the magnitude of between-machine differences in VO2, six subjects randomly performed cycling using two different FMR. Significant (P less than 0.05) differences between machines were found at only the highest speed. The present study indicates that it is possible to accurately predict VO2 from flywheel revolution rate using a FRM. Since the FRM appears to approximate the resistance a cyclist experiences on the road and allows cyclists to use their own bicycle, it provides a good alternative to traditional laboratory ergometers.

Bicycling↗

PubMed1990

Criterion-referenced standards for youth health-related fitness tests: a tutorial.

A new development in the testing of physical fitness of youth is the use of criterion-referenced standards (CRS). Although three national youth health-related physical fitness (HRPF) tests currently have CRS, a detailed description of the procedures used in their development has not been published nor have the standards been validated. Consequently, the scientific basis of these standards has been questioned. The purposes of this tutorial are (a) to discuss briefly issues related to the development of CRS for HRPF tests, (b) to provide a detailed description of procedures used in development of mile run/walk test CRS as an example, and (c) to illustrate how these standards can be validated. The objective is to stimulate discussion and critical evaluation of CRS for youth HRPF tests.

Adolescent↗

PubMed1990

Postural specificity of cardiovascular adaptations to exercise training.

The purposes of this study were to determine 1) whether posture affects the magnitude of cardiovascular adaptations to training and 2) whether cardiovascular adaptations resulting from exercise training in the supine posture transfer (generalize) to exercise in the upright posture and vice versa. Sixteen sedentary men, aged 18-33 yr, were trained using high-intensity interval and prolonged continuous cycling in the supine (STG; supine training group) or upright (UTG; upright training group) posture 4 days/wk, 40 min/day, for 8 wk, while seven male subjects served as nontraining controls. After training, maximal O2 uptake measured during supine and upright cycling, respectively, increased significantly (P less than 0.05) by 22.9 and 16.1% in the STG and by 6.0 and 14.6% in the UTG. No significant cardiovascular adaptations were observed at rest. During submaximal supine cycling at 100 W, significant increases in end-diastolic volume (21%) and stroke volume (22%) (radionuclide ventriculography and CO2 rebreathing) and decreases in heart rate, blood pressure, and systemic vascular resistance occurred in the STG, whereas only a significant decrease in blood pressure occurred in the UTG. During upright cycling at 100 W, a significant decrease in blood pressure occurred in the STG, whereas significant increases in end-diastolic volume (17%) and stroke volume (18%) and decreases in blood pressure and systemic vascular resistance occurred in the UTG. Volume of myocardial contractility, ejection fraction, and systolic blood pressure-to-end-systolic volume ratio did not change significantly after training when measured during supine and upright cycling in either training group. Blood volume increased significantly in the UTG but remained unchanged in the STG.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed1989

Does lung function limit performance in a 24-hour ultramarathon?

Based on observations of impaired lung function after marathon and ultramarathon running, it was hypothesized that the decline in running speed during a 24-h ultramarathon may be explained, in part, by ventilatory muscle fatigue. To test this hypothesis, ten competitors in the 1988 TAC/USA National 24-h Championship performed a battery of pulmonary function tests every 3 h during the race. The tests included measurement of inspiratory capacity, peak flow, forced vital capacity, forced expiratory volume in 1 sec, maximum voluntary ventilation for 12 sec (MVV12), and maximal respiratory pressures. Running speed was averaged over 3-h periods. MVV12 was significantly decreased (17%), but only after 24 h of running. All other ventilatory measures tended to decrease over time but the changes were not significant. However, after correcting for between-subject differences in running speed, the variance in MVV12 accounted for 39% (P less than 0.0001) of the variance in running speed. It was concluded that the decrease in ventilatory muscle endurance may constrain running speed in extremely prolonged running events.

Adult↗

PubMed1989

Circadian specificity in exercise training.

The purpose of this study was to determine whether metabolic and cardiorespiratory adaptations to exercise training are greater at the time of day of training than at another time. Twenty-seven subjects performed cycle ergometer tests in the morning (AM) and in the afternoon (PM) before and after a 6-wk period during which ten subjects trained regularly in the morning, seven subjects trained in the afternoon, and ten did not train. Training caused decreases in HR, VE, and rating of perceived exertion during submaximal exercise; a 7.7% increase (p less than 0.01) in VO2 max; and a 9.1% increase (p less than 0.01) in performance time. Adaptations (training effects) were independent of time of day of training for all variables except VO2 at the ventilatory threshold. Compared with each other, subjects who trained in the morning had relatively higher post-training thresholds in the morning, while subjects who trained in the afternoon had relatively higher values in the afternoon (p less than 0.05). This is evidence of circadian specificity in training and supports the notion of planning physical preparation to coincide with the time of day at which one's critical performance is scheduled.

Adult↗

PubMed1989

Effect of time of day on perceived exertion at work rates above and below the ventilatory threshold.

The effect of time of day on ratings of perceived exertion (RPE) at various intensities of cycling exercise, both below and above the ventilatory threshold, was studied in 32 subjects, 18 to 35 years of age. The ventilatory threshold occurred at the same (p greater than .05) mean (+/- SD) work rate in the morning (110.6 +/- 27.0 watts) and in the afternoon (111.9 +/- 23.9 watts) and was perceived as equally strenuous (p greater than .05) in the morning (RPE = 13.8 +/- 2.4) and in the afternoon (RPE = 13.6 +/- 2.8). At intensities below the ventilatory threshold, RPE was the same (p greater than .05) in the morning and in the afternoon; above the ventilatory threshold, RPE was lower (p less than .05) in the morning. We conclude that, during incremental submaximal cycling exercise above the ventilatory threshold, a particular work rate is perceived as less strenuous in the morning than in the afternoon. About 20% of this difference in RPE is explained by lower ventilatory demands in the morning.

Adolescent↗