Evaluation of pulmonary resistance and maximal expiratory flow measurements during exercise in humans. (25/4418)

To evaluate methods used to document changes in airway function during and after exercise, we studied nine subjects with exercise-induced asthma and five subjects without asthma. Airway function was assessed from measurements of pulmonary resistance (RL) and forced expiratory vital capacity maneuvers. In the asthmatic subjects, forced expiratory volume in 1 s (FEV1) fell 24 +/- 14% and RL increased 176 +/- 153% after exercise, whereas normal subjects experienced no change in airway function (RL -3 +/- 8% and FEV1 -4 +/- 5%). During exercise, there was a tendency for FEV1 to increase in the asthmatic subjects but not in the normal subjects. RL, however, showed a slight increase during exercise in both groups. Changes in lung volumes encountered during exercise were small and had no consistent effect on RL. The small increases in RL during exercise could be explained by the nonlinearity of the pressure-flow relationship and the increased tidal breathing flows associated with exercise. In the asthmatic subjects, a deep inspiration (DI) caused a small, significant, transient decrease in RL 15 min after exercise. There was no change in RL in response to DI during exercise in either asthmatic or nonasthmatic subjects. When percent changes in RL and FEV1 during and after exercise were compared, there was close agreement between the two measurements of change in airway function. In the groups of normal and mildly asthmatic subjects, we conclude that changes in lung volume and DIs had no influence on RL during exercise. Increases in tidal breathing flows had only minor influence on measurements of RL during exercise. Furthermore, changes in RL and in FEV1 produce equivalent indexes of the variations in airway function during and after exercise.  (+info)

Exposure to trichloroethylene I. Uptake and distribution in man. (26/4418)

Fifteen healthy male subjects were exposed to about 540 and 1,080 mg/m3 of trichloroethylene (TRI) in the air during rest and exercise on a bicycle ergometer. Each subject was exposed during four 30-min periods. The arterial blood concentration increased linearly with the concentration in the alveolar air. The uptake of TRI was about 55% of the supplied amount at rest. At a work load of 150 W during the fourth period the percentage uptake decreased to about 25%. For one fairly thin subject the uptake was near zero at the end of exposure. This development was probably due to the relatively low solubility of TRI in blood and tissues. The uptake of TRI may be estimated from pulmonary ventilation and the concentration in alveolar and inspiratory air.  (+info)

Exposure to trichloroethylene II. Metabolites in blood and urine. (27/4418)

Fifteen men were exposed to trichloroethylene (TRI) in three different ways with regard to the concentration of TRI in the air as well as exercise on a bicycle ergometer. The total amount of TRI supplied and taken up by each person was measured. The concentrations of trichloroethanol (TCE) and trichloroacetic acid (TCA) were determined in blood and urine. In spite of large differences in uptake, there were only small differences in the concentration of TCA in blood during the day of exposure. There was a large scatter for the values of TCA in urine within each group. The concentration of TCE in arterial blood increased during exposure. Thereafter the concentrations were almost constant for 2 h and differed among the groups. These results can be interpreted as being due to balanced rates of the formation and elimination of TCE. The levels mentioned were related to the uptake of TRI. The same was found for the rate of excretion of TCE in urine when calculations were made from the morning sample obtained the day after exposure.  (+info)

Correlates of individual differences in body-composition changes resulting from physical training in obese children. (28/4418)

BACKGROUND: No studies have been reported in children that assess correlates of body-composition changes in response to a physical training intervention. OBJECTIVE: The hypothesis studied was that variation in diet and physical activity would explain a significant portion of the interindividual variation in the response of body composition to physical training. DESIGN: The participants were 71 obese children aged 7-11 y (22 boys, 49 girls; 31 whites, 40 blacks). Body composition was measured by dual-energy X-ray absorptiometry, physical activity by a 7-d recall interview, and diet by two, 2-d recalls. The children underwent 4 mo of physical training. RESULTS: The mean attendance was 4 d/wk, the mean (+/-SD) heart rate for the 40-min sessions was 157 +/- 7 beats/min, and the mean energy expenditure was 946 +/- 201 kJ/session. On average, the percentage body fat decreased significantly in the total group, and total mass, fat-free soft tissue, bone mineral content, and bone mineral density increased, but there was a good deal of individual variability. Multiple regression models indicated that in general, more frequent attendance, being a boy, lower energy intake, and more vigorous activity were associated with healthier body-composition changes with physical training. Ethnicity was not retained as a correlate of the change of any component of body composition. CONCLUSIONS: In obese children, age, vigorous activity, diet, and baseline percentage body fat together accounted for 25% of the variance in the change in percentage body fat with physical training.  (+info)

Postexercise net protein synthesis in human muscle from orally administered amino acids. (29/4418)

We examined the response of net muscle protein synthesis to ingestion of amino acids after a bout of resistance exercise. A primed, constant infusion of L-[ring-2H5]phenylalanine was used to measure net muscle protein balance in three male and three female volunteers on three occasions. Subjects consumed in random order 1 liter of 1) a mixed amino acid (40 g) solution (MAA), 2) an essential amino acid (40 g) solution (EAA), and 3) a placebo solution (PLA). Arterial amino acid concentrations increased approximately 150-640% above baseline during ingestion of MAA and EAA. Net muscle protein balance was significantly increased from negative during PLA ingestion (-50 +/- 23 nmol. min-1. 100 ml leg volume-1) to positive during MAA ingestion (17 +/- 13 nmol. min-1. 100 ml leg volume-1) and EAA (29 +/- 14 nmol. min-1. 100 ml leg volume-1; P < 0.05). Because net balance was similar for MAA and EAA, it does not appear necessary to include nonessential amino acids in a formulation designed to elicit an anabolic response from muscle after exercise. We concluded that ingestion of oral essential amino acids results in a change from net muscle protein degradation to net muscle protein synthesis after heavy resistance exercise in humans similar to that seen when the amino acids were infused.  (+info)

Carbohydrate ingestion can completely suppress endogenous glucose production during exercise. (30/4418)

The purposes of this study were 1) to investigate the effect of carbohydrate (CHO) ingestion on endogenous glucose production (EGP) during prolonged exercise, 2) to study whether glucose appearance in the circulation could be a limiting factor for exogenous CHO oxidation, and 3) to investigate whether large CHO feedings can reduce muscle glycogen oxidation during exercise. Six well-trained subjects exercised three times for 120 min at 50% maximum workload while ingesting water (FAST), a 4% glucose solution (LO-Glc), or a 22% glucose solution (HI-Glc). A primed continuous intravenous [6, 6-2H2]glucose infusion was given, and the ingested glucose was enriched with [U-13C]glucose. Glucose ingestion significantly elevated CHO oxidation as well as the rates of appearance (Ra) and disappearance. Ra glucose equaled Ra of glucose in gut (Ra gut) during HI-Glc, whereas EGP was completely suppressed. During LO-Glc, EGP was partially suppressed, whereas Ra gut provided most of the total glucose Ra. We conclude that 1) high rates of CHO ingestion can completely block EGP, 2) Ra gut may be a limiting factor for exogenous CHO oxidation, and 3) muscle glycogen oxidation was not reduced by large glucose feedings.  (+info)

Regulation of protein synthesis after acute resistance exercise in diabetic rats. (31/4418)

These studies determined whether insulin-like growth factor-I (IGF-I) involvement in exercise-stimulated anabolic processes becomes more evident during hypoinsulinemia. Male Sprague-Dawley rats (n = 6-12/group) were made diabetic (blood glucose congruent with 300 mg/dl) by partial pancreatectomy (PPX) or remained nondiabetic (glucose congruent with 144 mg/dl). Rats performed acute resistance exercise by repetitive standing on the hindlimbs with weighted backpacks (ex), or they remained sedentary (sed). Resistance exercise caused increases in rates of protein synthesis (nmol Phe incorporated. g muscle-1. h-1, measured for gastrocnemius muscle in vivo 16 h after exercise) for both nondiabetic [sed = 154 +/- 6 (SE) vs. ex = 189 +/- 7] and diabetic rats (PPXsed = 152 +/- 11 vs. PPXex = 202 +/- 14, P < 0.05). Arterial plasma insulin concentrations in diabetic rats, congruent with180 pM, were less than one-half those found in nondiabetic rats, congruent with444 pM, (P < 0.05). The activity of eukaryotic initiation factor 2B (eIF2B; pmol GDP exchanged/min) was higher (P < 0.05) in ex rats (sed = 0.028 +/- 0.006 vs. ex = 0.053 +/- 0.015; PPXsed = 0.033 +/- 0.013 vs. PPXex = 0.047 +/- 0.009) regardless of diabetic status. Plasma IGF-I concentrations were higher in ex compared with sed diabetic rats (P < 0.05). In contrast, plasma IGF-I was not different in nondiabetic ex or sed rats. Muscle IGF-I (ng/g wet wt) was similar in ex and sed nondiabetic rats, but in diabetic rats was 2- to 3-fold higher in ex (P < 0.05) than in sed rats. In conclusion, moderate hypoinsulinemia that is sufficient to alter glucose homeostasis does not inhibit an increase in rates of protein synthesis after acute moderate-intensity resistance exercise. This preserved response may be due to a compensatory increase in muscle IGF-I content and a maintained ability to activate eIF2B.  (+info)

Effect of long-term caloric restriction and exercise on muscle bioenergetics and force development in rats. (32/4418)

We evaluated the hypothesis that long-term caloric restriction and exercise would have beneficial effects on muscle bioenergetics and performance in the rat. By themselves, each of these interventions is known to increase longevity, and bioenergetic improvements are thought to be important in this phenomenon. Accordingly, we investigated rats that underwent long-term caloric restriction and were sedentary, ad libitum-fed rats permitted to exercise by daily spontaneous wheel running (AE), and the combination of the dietary and exercise interventions (RE). Ad libitum-fed, sedentary rats comprised the control group. 31P NMR spectra of the gastrocnemius muscle (GM) were collected in vivo at rest and during two periods of electrical stimulation. Neither caloric restriction nor exercise affected the ratio of phosphocreatine to ATP or pH at rest. During the first stimulation and after recovery, the RE group had a significantly smaller decline in pH than did the other groups (P < 0.05). During the second period of stimulation, the decrease in pH was much smaller in all groups than during the first stimulation, with no differences observed among the groups. The combination of caloric restriction and exercise resulted in a significant attenuation in the decline in developed force during the second period of stimulation (P < 0.05). A biochemical correlate of this was a significantly higher concentration of citrate synthase in the GM samples from the RE rats (32.7 +/- 5.4 micromol. min-1. g-1) compared with the AE rats (17.6 +/- 5.7 micromol. min-1. g-1; P < 0.05). Our experiments thus demonstrated a synergistic effect of long-term caloric restriction and free exercise on muscle bioenergetics during electrical stimulation.  (+info)