Kirk J. Cureton

Muscle hypertrophy in men and women.

It is widely believed that women experience less skeletal muscle hypertrophy consequent to heavy-resistance training than men. The purpose of this study was to test this hypothesis using both traditional indirect indicators as well as a direct measure of muscle size. Seven male experimental (ME), 8 female experimental (FE), and 7 control subjects were studied before and after a 16-wk weight training program, in which ME and FE trained 3 days.wk-1 at 70 to 90% of maximum voluntary contraction using exercise designed to produce hypertrophy of the upper arm and thigh. Strength increased significantly (P less than 0.05) in ME and FE, respectively, on elbow flexion (36.2 and 59.2%), elbow extension (32.6 and 41.7%), knee flexion (12.8 and 24.4%), and knee extension (28.8 and 33.9%) tests. Absolute changes were significantly greater in ME than FE in 2 of the 4 tests, whereas percentage changes were not significantly different. Substantial muscle hypertrophy occurred in the upper arms of both ME and FE as evidenced by significant increases in upper arm circumference (7.9 and 7.9%), bone-plus-muscle (B+M) cross-sectional area (CSA) estimated by anthropometry (17.5 and 20.4%), and muscle CSA determined from computed tomography scanning (15.9 and 22.8%). Changes by ME and FE were not significantly different, except for the absolute increase in estimated B+M CSA, which was significantly greater in ME (11.2 vs 7.4 cm2). No muscle hypertrophy occurred in the thigh of either ME and FE as evidenced by non-significant changes in thigh circumference (1.7 and 2.3%), B+M CSA (4.9 and 6.1%), and muscle CSA (2.9 and 2.9%). Changes by ME and FE in body weight, fat-free weight, and fat weight were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Ratings of perceived exertion at the lactate threshold in trained and untrained men and women.

The purpose of this study was to investigate the effects of state of training and gender on ratings of perceived exertion (RPE) at the lactate threshold (LT), and to determine whether RPE during moderate to heavy sub-maximal exercise is more closely associated with LT or %VO2max. RPE at the LT (RPELT) and at various percentages of VO2max were compared in 10 male and 10 female trained distance runners, and 10 male and 10 female untrained subjects, 18 to 35 yr of age. Mean (+/- SD) VO2max [ml X kg FFW-1 (fat-free weight) X min-1] of the trained men and women (72.3 +/- 1.4 and 73.1 +/- 1.6) was significantly higher (P less than 0.05) than for the untrained men and women (60.2 +/- 1.4 and 53.2 +/- 1.8), confirming their higher cardiorespiratory capacity. Similarly, the mean LTs (%VO2max) of the trained men and women (79.2 +/- 1.7% and 73.3 +/- 1.8%) were significantly higher (P less than 0.05) than for the untrained men and women (66.5 +/- 3.3% and 58.9 +/- 3.3%), and mean values for the men were significantly higher (P less than 0.05) than for the women. The means for RPELT for the four groups, 13.6 +/- 2.1, 13.5 +/- 1.6, 13.5 +/- 1.5, and 12.9 +/- 1.3, respectively, were not significantly different (P greater than 0.05), even though the ratings were given at markedly different levels of VE, VO2 (1 X min-1), heart rate, and %VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Responses to preferred intensities of exertion in men differing in activity levels

We compared ratings of perceived exertion (RPE), state anxiety, percentage of peak oxygen uptake (% VO2peak), percentage of ventilatory threshold (% Tvent), and blood lactate concentration [HLa] in 11 high-active and 12 low-active men (23 +/- 3 yr) at self-selected power outputs during 20 min of cycling. The high-active group selected higher power outputs than did the low-active group, but % VO2peak and % Tvent were lower for the high-active subjects during the initial 5-10 min of cycling. Both groups reported increased RPE across time, but contrary to past studies of load-incremented cycling, RPE was identical for the groups despite their differences in relative intensity. No differences were found for [HLa] or state anxiety during cycling. The groups did not differ on exertional symptoms, but the high-active subjects reported a significant reduction in state anxiety immediately after cycling. A preferred exertion protocol provides an alternative approach to identifying influences on perceived exertion during prolonged exercise. The influence of physical activity history/status on the association between the concomitant pattern of self-selected power outputs and postexercise anxiety reduction merits study.

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.

A generalized equation for prediction of VO2peak from 1-mile run/walk performance.

The purpose of this study was to develop and cross-validate a generalized equation for predicting VO2peak from 1-mile run/walk (MRW) time and demographic variables in youth and young adults. Data for 753 males and females 8-25 yr of age were divided into validation (N = 495) and cross-validation (N = 258) samples. The validation sample was used to develop a multiple regression equation for predicting treadmill VO2peak (ml.kg-1.min-1) from gender (0 = F, 1 = M), age (yr), body mass index (kg.m-2; BMI) and MRW time (min). The multiple correlation (R) and standard error of estimate (SEE) were: R = 0.71, SEE = 4.8 ml.kg-1.min-1. The accuracy of this equation was confirmed when applied to the cross-validation sample. The regression equation for the total sample was: VO2peak = -8.41 (MRW) + 0.34 (MRW)2 + 0.21 (Age x Gender) -0.84 (BMI) + 108.94, R = 0.72, SEE = 4.8 ml.kg-1.min-1. We conclude that the generalized equation provides valid estimates of VO2peak in youth and young adults. The equation should be useful for educators, clinicians, and researchers who would like to interpret results of the MRW test in terms of VO2peak.

Development of Youth Aerobic-Capacity Standards Using Receiver Operating Characteristic Curves

BACKGROUND Cardiovascular fitness has important implications for current and future health in children. PURPOSE In this paper, criterion-referenced standards are developed for aerobic capacity (an indicator of cardiovascular fitness) based on receiver operating characteristic (ROC) curves. METHODS The sample was drawn from participants aged 12-18 years in the National Health and Nutrition Examination Survey (1999-2002, N=1966). Subjects completed a treadmill exercise test from which maximal oxygen uptake (VO(2)max) was estimated from heart rate response. Metabolic syndrome was classified using previously published standards based on the National Cholesterol Education Program/Adult Treatment Panel III adult values at age 20 years. Using aerobic fitness z-scores as the test and metabolic syndrome as the criterion, ROC curve analysis was used to identify aerobic-capacity thresholds. RESULTS The area under the curve (AUC) value for boys (83.1%) was high, indicating good utility for detecting risk of metabolic syndrome with aerobic fitness values. The AUC for girls (77.2%) was slightly below the recommended value of 80%. Although the ROC plots identified a defensible point for classifying levels of fitness, the approach in the present study was to establish two independent thresholds, one aimed at high specificity and one aimed at high sensitivity. The resulting z values for the low- and higher-risk threshold lines were then converted back to VO(2)max estimates using published LMS (L=skewness, M=median, and S=coefficient of variation) parameters. Values at the low-risk threshold ranged from 40 to 44 mL/kg/min for boys and from 38 to 40 mL/kg/min for girls. CONCLUSIONS In summary, aerobic fitness can be used with moderate accuracy to differentiate between adolescents with and without metabolic syndrome. Age- and gender-specific aerobic-capacity thresholds for creating separate risk groups were identified using nationally representative growth percentiles.

Metabolic and Circulatory Responses to Walking and Jogging in Water

Abstract To compare the metabolic and circulatory responses to walking and jogging in water with similar exercise performed in air, oxygen uptake ([Vdot]O2), ventilation ([Vdot]E), respiratory exchange ratio (R), and heart rate (HR) were measured in six male subjects during 6-minute bouts of walking or jogging through waist-deep water (30 to 31°C) at five different speeds (.7–1 m/second). Work bouts of similar metabolic intensity were also carried out in air (27 to 29°C) on the treadmill. Approximately one-half to one-third the speed was required to work at the same level of energy expenditure during walking and jogging in water as compared with the exercise in air (2.6 to 3.5 vs. 5.5 to 13.4 km/ hour). During the water exercise, [Vdot]O2, HR, and R increased nearly linearly with increased speed, whereas the increase in [Vdot]E was somewhat curvilinear. These responses were similar to those during exercise in air. HRs at any given level of [Vdot]O2 were not significantly different (p < .05) for the exerci...

Effect of training on the rating of perceived exertion at the ventilatory threshold

SummaryThe purpose of this study was to determine the effect of training on the rating of perceived exertion (RPE) at the ventilatory threshold. College students were assigned to either training (n=17) or control (n=10) groups. Trainers completed 18 interval training sessions (five × 5 min cycling at 90–100%

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

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