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A Bonen

Publications and source records attributed to A Bonen.

137 records · Page 8Linked to original sources
PubMed1979

Prediction of maximal oxygen uptake in boys, ages 7-15 years.

Predictions of Vo2max (1 min-1 and ml kg-1 min-1) were obtained via multiple regression procedures from a sample of 100 boys, ages 6.7-14.8 years. Prediction equations for Vo2max (1 min-1) were obtained from the subjects' height, and the Vo2 (1 min-1) and heart rate observed during the third min of a treadmill walk (R = 0.95; CV = +/- 9.3%). A similar prediction was obtained when the subjects' age, height and weight were used (R = -0.94; CV = +/- 9.7%). Vo2max (ml kg-1 min-1) was predicted with similar accuracy (CV = +/- 8.4%) from age, and heart rate, VCO2(1 min-1), Vo2 (ml kg min-1), or from simply age, height and weight (CV = +/- 9.2%). Cross-validation of the equations with another sample of 39 boys demonstrated that the prediction equations based on laboratory data were quite stable, % errors approximately 1-2 +/- 9%. However, the equations based on age, height and weight underestimated the Vo2max slightly, both in 1 min (X = -0.091 min) and ml kg min (X = -2.2 ml kg min, P less than 0.05). The results indicate that reasonably reliable and accurate estimates of Vo2max for children may be obtained from either laboratory data, or simply from their age, height and weight.

Adolescent↗
PubMed1979

Muscle fiber composition and performance capacities of women.

The purpose of the present study was to determine whether the fast-twitch (FT) fiber composition in muscle was a) correlated with performance capacities, b) related to the trainability of the subjects, and c) whether the FT fiber composition could be predicted with standard laboratory tests. From twenty-four young women (ages 24.3 +/- 3.0 yrs) muscle biopsies were obtained from the vastus lateralis of both the left and right legs. In addition, each subject completed four laboratory tests: i) a maximal oxygen intake test on the cycle ergometer, ii) a high-kp power test, iii) a low-kp power test, and iv) a Sargent jump. Prior to training the correlations between %FT fibers and each of the tests (r equal to or less than 0.19) were not significant (P less than 0.05). After training anaerobically (N = 20) significant improvements (P less than 0.05) occurred in a) the high-kp test (delta = + 0.12 +/- 0.02 kpm/sec.kg) b) the low-kp test (delta = + 0.10 +/- 0.01 kpm/sec.kg) and c) the Sargent jump (delta = + 2.5 +/- 1.1 cm). However, these training-induced changes (delta) were not correlated with %FT fiber composition (r equal to or less than 0.35), nor were the post-training performances on the tests correlated with the %FT fibers (r equal to or less than 0.12). Performance capacities before and after training were not significantly different in groups with a low %FT fiber composition (35.8 +/- 1.6%) or a high %FT fiber composition (63.6 +/- 2.2%). None of the performance tests either singly, or in combination in a multiple regression equation, provided a suitable prediction of the FT muscle fiber composition. The results of this study indicate that athletic performances and/or susceptibility for training cannot be determined a priori from simple measurements of muscle fiber composition.

Adult↗
PubMed1976

Effects of exercise on excretion rates of urinary free cortisol.

Excretion rates of urinary free cortisol were studied in 20 men assigned to four treadmill exercise groups: walking at 3 mph for 10 min or 30 min, or running at 7.5 mph for 10 min or 30 min. Free cortisol in urine was measured before and 30, 60, and 90 min after exercise, and again on a control day. Patterns of free-cortisol excretions after exercise at 7.5 mph for 10 and 30 min were significantly different from the control day (P less than 0.05) with the largest changes occurring in the 30-min group. Exercise and control patterns were not different for the other two conditions (P greater than 0.05). Within the 7.5 mph-30 min group the postexercise cortisol excretion rates were directly related to the relative intensity of exercise (%VO2max) and the respiratory exchange ratio. It is concluded that changes in free cortisol excretion rates depend on the duration as well as the intensity of exercise.

Adult↗
PubMed1976

Comparison of self-selected recovery methods on lactic acid removal rates.

The purpose of this study was to compare lactic acid removal rates during three modes of recovery from a standardized exercise bout. Each subject (N = 6) completed a 1 mile run (92.2 +/- 3.7% Vo2max). Thereafter, lactic acid removal rates were compared in the runners at each of three different modes of recovery: a) rest; b) a self-selected, continuous jogging pace (free-jogging); and c) completely uncontrolled recovery (free-intermittent) normally practiced by athletes. Venous blood samples were taken immediately after the mile run and every 5 min thereafter for 20 min. Data were expressed relative to the initial post-exercise blood sample (100%). Lactic acid removal was significantly faster during the free-jogging recovery than during the free-intermittent and the resting recoveries (P less than 0.001). Removal rates during the free-intermittent recovery were significantly faster than during the resting recovery (P less than 0.001). The results indicated that nearly optimal lactic acid removal rates were attained during the free-jogging recovery.

Adolescent↗
PubMed1975

Lactic acid removal rates during controlled and uncontrolled recovery exercise.

After a standardized 6-min bicycle ergometer exercise (89% VO2max) lactic acid removal rates were compared during recovery at rest and exercies at 29.7, 45.3, 61.8, and 80.8% VO2max, and twice while the subjects (N = 7) regulated their own recovery exercise. Blood samples were taken after the standardized exercise and every 5 min during the 30-min recovery periods. During the controlled recovery periods lactic acid removal rates were dependent on the intensity of the recovery (Y' = 0.103 + 0.218chi - 0.464 X 10(-2)chi2 + 0.252 X 10(-4)chi3). Optimal removal was predicted to occur at 32% VO2max. Removal rates during the self-regulated recoveries were not different (P greater than 0.05), but these removal rates were faster than during recovery at rest and exercise at 61.8 and 80.8% VO2max (P less than 0.01). Removal rates during the self-regulated recovery and recovery at 29.7 and 45.3% VO2max were not different (P greater than 0.05). The subjects were therefore able to remove lactic acid effectively when selecting their own recovery exercise.

Adult↗
PubMedDate not supplied

Cellular fatty acid uptake is acutely regulated by membrane-associated fatty acid-binding proteins.

Cellular long-chain fatty acid uptake is believed to occur largely by protein-mediated transmembrane transport of fatty acids, and also by passive diffusional uptake. It is postulated that the membrane proteins function in trapping of fatty acids from extracellular sources, whereafter their transmembrane translocation occurs by passive diffusion through the lipid bilayer. The key membrane-associated proteins involved are plasma membrane fatty acid-binding protein (FABP(pm)) and fatty acid translocase (FAT/CD36). Their plasma membrane contents are positively correlated with rates of fatty acid uptake. In studies with heart and skeletal muscle we observed that FAT/CD36 is regulated acutely, in that both contraction and insulin can translocate FAT/CD36 from an intracellular depot to the sarcolemma, thereby increasing the rate of fatty acid uptake. In addition, from studies with obese Zucker rats, an established rodent model of obesity and insulin resistance, evidence has been obtained that in heart, muscle and adipose tissue FAT/CD36 is permanently relocated from an intracellular pool to the plasma membrane, resulting in increased fatty acid uptake rates in this condition. These combined observations indicate that protein-mediated fatty acid uptake is a key step in cellular fatty acid utilization, and suggest that malfunctioning of the uptake process could be a critical factor in the pathogenesis of insulin resistance.

Animals↗
PubMedDate not supplied

Predicting submaximal oxygen consumption during treadmill running in mice.

Treadmill exercise is the most common form of exercise used in studies involving laboratory rodents. However, oxygen consumption (VO2) is not usually monitored since the measurement of this parameter is particularly difficult in small, exercising animals. The purpose of this study was to develop a regression equation for predicting submaximal VO2 in mice during treadmill running. Twenty female mice of three strains were tested, in an Oxyscan metabolic treadmill, on different days at running speeds of 10, 13, 15, 17, and 20 m/min at a 0% grade. Each mouse was placed in the treadmill chamber for a 10-min period before running commenced. Running speed was increased in 2-min intervals by 5 m/min until the assigned speed was reached. Each mouse then ran for 10 min to reach steady state, followed by another 20 min at the steady-state plateau. During this period a 30-s expired gas sample was collected every minute. Gas samples were analyzed for O2 and CO2, using an Oxyscan gas analyzer. Trials were conducted during the nocturnal phase of the animals' photoperiod, and running speeds were assigned randomly to minimize order effects. This approach provided highly reliable measures of oxygen consumption (r = 0.96). By using the running speeds (10-20 m/min) and the animal's body weight it was possible to predict the submaximal oxygen consumption (mL/min) during running with a high degree of accuracy (i.e., R2 = 0.85). In an independent group of animals (n = 14) we compared the predicted VO2 with the measured VO2. This yielded a good correlation coefficient (r = 0.79) and a low prediction error (+2.4 +/- 2.9%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Involvement of membrane-associated proteins in the acute regulation of cellular fatty acid uptake.

The transport of long-chain fatty acids across cellular membranes most likely occurs to some extent by passive diffusion and additionally is facilitated by a number of membrane-associated and cytoplasmic proteins. In this overview we focus on the involvement of the membrane proteins fatty acid translocase (FAT/CD36), plasma membrane fatty acid-binding protein (FABPpm) and fatty acid-transport protein (FATP). Newly obtained evidence is presented that in skeletal muscle, fatty acid uptake is subject to short-term regulation by translocation of FAT/CD36 from intracellular stores to the plasma membrane, analogous to the regulation of muscular glucose uptake by GLUT-4 translocation. These new findings establish a significant role of membrane-associated proteins in the cellular fatty acid-uptake process. Possible implications for the uptake and transport of long-chain fatty acids by the brain are discussed.

Albumins↗