Search PubMed⌕ Search

Biomedical subjects

C A Horswill

Publications and source records attributed to C A Horswill.

31 records · Page 2Linked to original sources
PubMed1991

Effects of tolbutamide on growth and body composition of nondiabetic children with cystic fibrosis.

Previously, we reported that nondiabetic children with cystic fibrosis show a blunted insulin response to a meal stimulus. In the study presented here, using tolbutamide, we determined the effects of augmented insulin secretion/action on height and lean body mass of children with cystic fibrosis. Twelve subjects (mean +/- SEM age, 11.0 +/- 0.5 y) were studied for three 4-mo periods: 1) pretreatment, 2) treatment, consisting of 750 mg/d of tolbutamide, and 3) posttreatment. Before the pretreatment period, insulin response to a meal stimulus was evaluated in relation to three doses of tolbutamide: 0, 250, and 500 mg. Growth was monitored during each period, and incremental changes in lean body mass were calculated from height data. To validate the change in lean body mass based on height measurements, we determined lean body mass in seven subjects during the treatment period by using a criterion method (H218O). Growth velocity (cm/4 mo) significantly increased (p less than 0.05) during the treatment (2.58 +/- 0.31) compared with the pretreatment period (0.88 +/- 0.20). The increase in lean body mass calculated from height was greater during the treatment (1.61 +/- 0.29 kg/4 mo) than during the pretreatment period (0.44 +/- 0.18 kg/4 mo) (p less than 0.05). There was also a significant increase (p less than 0.05) in lean body mass during the treatment as measured with H218O (1.91 +/- 0.65 kg/4 mo). Acute administration of either 250 or 500 mg of tolbutamide reduced (p less than 0.05) the area under the glucose concentration curve in response to a meal compared with the control condition of no tolbutamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Elevated blood pressure in obese children: influence of gender, age, weight and serum insulin levels.

Prepubescent and early pubescent obese children (n = 114, mean percent IBW = 165, mean age 7.3 years) were studied to determine the relationship of weight (WT), percent of ideal body weight (percent IBW), gender, and insulin (I) to systolic (SBP) and diastolic (DBP) blood pressure. Subjects were assessed for weight, height, percent IBW, systolic and diastolic blood pressure, and Tanner stage; subjects with Tanner stage greater than 3 were excluded. Multiple regression revealed that body weight accounted for the greatest variance in SBP (adj. R2 = 0.34, P less than 0.05), followed by the age. For DBP, weight also accounted for the greatest variance (adj. R2 = 0.16, P less than 0.05) followed by gender. A subgroup (n = 50) was evaluated for oral glucose tolerance. Subjects ingested 1.75 g glucose (GLU)/kg weight and had blood samples drawn at 0, 30, 60, 90, 120 and 180 min. Pearson correlations showed SBP correlated significantly to I at 0 (r = 0.44) and the total integrated area for insulin (r = 0.45); however, adjusting SBP for age by using z-score transformations negated all correlations between SBP and insulin. GLU at 0 and the total integrated area were not significantly correlated to SBP or DBP in absolute or age-adjusted terms. These data on prepubescent, nondiabetic, obese children suggest an association between insulin and elevations in SBP, but not DBP, that is largely due to a mutual association between age and weight. Also, insulin resistance as reflected in GLU response was not related to SBP or DBP.

Age Factors↗
PubMed1990

Changes in the protein nutritional status of adolescent wrestlers.

The protein nutritional status of adolescent wrestlers was studied to determine whether changes occur during a season of competition and weight loss. Subjects (N = 18) were measured prior to the start of the season (PRE), twice in the midseason, and once during late season (LATE) for weight, percent body fat, and height. At each of these times, a venous blood sample was obtained from the subjects, who were fasted, and analyzed for concentrations of albumin, prealbumin, retinol binding protein (RBP), blood urea nitrogen (BUN), hemoglobin, hematocrit, and 23 amino acids. Diet records were kept by subjects to assess daily energy, protein, fat, and carbohydrate intake. Data were analyzed by repeated measures ANOVA. Results showed that wrestlers decreased weight by an average of 6.6 +/- 0.9% and that percent body fat, fat-free weight, plasma levels of prealbumin and RBP, the ratio of total essential amino acids to total amino acids, and dietary energy nutrient intakes were significantly lower at LATE compared to PRE. RBP decreased during midseason and averaged (+/- SE) 3.21 +/- 0.15 mg.100 ml-1 at LATE; prealbumin was significantly lower at LATE with a mean value of 19.8 +/- 1.0 mg.100 ml-1. Total energy intake decreased from PRE values by 35%, to approximately 27 kcal.kg-1.d-1 during the season. In conclusion, in these high school wrestlers who lost approximately 6.6% of weight, there were adverse effects on some of the indices of protein nutritional status.

Adolescent↗
PubMed1990

Weight loss, dietary carbohydrate modifications, and high intensity, physical performance.

Well trained subjects (N = 12) were studied before and after losing approximately 6% of body weight to determine whether physical performance could be maintained while consuming a hypocaloric, high percentage carbohydrate diet. During a 4-d period of weight loss, subjects were randomly assigned to a high carbohydrate (HC) or low carbohydrate (LC) diet. A crossover design was used; subjects were measured before (PRE) and after (POST) weight loss on both diets for a 6-min bout of high intensity arm cranking, weight, skinfold thickness, and profile of mood states (POMS). Hemoglobin, hematocrit, and glycerol concentrations were analyzed for resting blood samples, while lactate, pH, and base excess were analyzed for blood samples drawn at rest and 1, 3, and 5 min after arm cranking. A three-way ANOVA of sprint work revealed a weight loss effect, a diet by weight loss interaction, and an order by diet by weight loss interaction (P less than 0.05). Total sprint work (mean +/- SE) PRE and POST HC was 37.7 +/- 2.1 kJ and 37.4 +/- 2.2 kJ, respectively. Sprint work was higher for PRE LC vs POST LC, with mean values of 37.4 +/- 2.1 kJ and 34.4 +/- 2.2 kJ, respectively. Post-arm cranking lactate was significantly higher PRE compared to POST for both HC and LC. Post-exercise blood pH was lower (P less than 0.05) at PRE vs POST, with no diet effect. Regardless of the diet, POMS variables tension, depression, anger, fatigue, and confusion were significantly elevated from PRE to POST; vigor was significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Estimation of minimal weight of adolescent males using multicomponent models.

The purpose of this study was to determine whether the estimation of minimal weight (the body weight at which 5% of the weight is fat) of adolescent males could be improved by accounting for differences in hydration state and bone mineral content. Improvement was defined as a larger value for minimal weight and a smaller standard deviation compared to minimal weight estimated from body density. Forty adolescent males (mean age +/- SD, 15.5 +/- 1.4 yr) were measured for height, weight, body density (hydrostatic weighing), total body water (deuterium oxide dilution), and bone mineral content (single photon absorptiometry). Twenty-two adult males (mean age +/- SD, 23.6 +/- 2.2 yr) were measured as a reference group. Percent body fat and minimal weight were calculated from the body density (MWD), body density adjusted for total body water (MWDW), and body density adjusted for body water and bone mineral content (MWDWB). Repeated-measures ANOVA was used to test for differences between the methods and for trends in the data. The results showed a slight but nonsignificant increase in minimal weight for the adolescent group when body water and bone mineral data were added. The means +/- SD for MWD, MWDW, and MWDWB values of the adolescents were 54.6 +/- 9.0 kg, 54.8 +/- 8.6 kg, and 55.4 +/- 8.4 kg, respectively. It was concluded that the multicomponent methods, which accounted for hydration and bone mineral status, did not significantly improve the estimates of minimal weight of adolescent males compared to the single component method, i.e., minimal weight from body density.

Adipose Tissue↗
PubMed1989

Comparison of maximum aerobic power, maximum anaerobic power, and skinfold thickness of elite and nonelite junior wrestlers.

The purpose of this investigation was to identify physiologic differences between elite high school-age wrestlers and nonelite wrestlers of comparable age, weight, and training experience. Two groups of junior wrestler, elite (n = 18) and nonelite (n = 18) were measured for maximum aerobic power (treadmill run), maximum anaerobic power of the arms and legs (Wingate test), and skinfold thickness. On the average (+/- SE) elite juniors had a VO2max of 52.6 +/- 2.0 ml/kg.min-1, 376 +/- 20 W for arm power, and 540 +/- 25 W for leg power. The nonelite group had a VO2max of 51.5 +/- 1.4 ml/kg.min-1 and 331 +/- 22 W and 467 +/- 29 W for arm and leg power, respectively. Ttests were computed to identify differences between the groups. The results revealed significant differences in four skinfold thicknesses, absolute anaerobic leg power, and relative anaerobic power of arms and legs. It was concluded that relative maximum anaerobic power is distinctly greater in elite high school wrestlers than less successful peers. In light of the results, it may be of benefit for wrestlers of lower caliber to decrease body fat, increase fat-free weight, and increase total body power through training.

Adolescent↗
PubMed1989

Total-body electrical conductivity (TOBEC): relationship to estimates of muscle mass, fat-free weight, and lean body mass.

A comparison of methods for estimating body composition (BC) of 12 subjects was made by using fat-free weight from total-body electrical conductivity (FFWT), muscle mass from 3-methylhistidine excretion (MM3MH) and creatinine excretion (MMCRE), fat-free weight from hydrostatic weighing (FFWBD), and lean body mass from whole-body potassium counting (LBMK). Data were analyzed for day-to-day variability and regression analyses were applied to compare the different methods of measuring BC. Mean values (+/- SEM, kg) for the estimates were 53.9 +/- 3.5 (FFWT), 26.9 +/- 2.9 (MM3MH), 25.3 +/- 2.5 (MMCRE), 53.2 +/- 3.6 (FFWBD), and 52.8 +/- 3.5 (LBMK). Regression analyses revealed that TOBEC estimates of fat-free weight had an adjusted r2 (+/- SEE, kg) of 0.95 +/- 2.2, 0.50 +/- 7.9, 0.95 +/- 1.8, and 0.88 +/- 4.0 for MM3MH, MMCRE, FFWBD, and LBMK, respectively. It was concluded that TOBEC is a potentially reliable method for estimating the muscle mass within the fat-free compartment, as well as fat-free weight and lean body mass.

Adipose Tissue↗
PubMed1988

Sodium bicarbonate ingestion improves performance in interval swimming.

In an effort to determine the effects of bicarbonate (NaHCO3) ingestion on exercise performance, ten male college swimmers were studied during five different trials. Each trial consisted of five 91.4 m (100-yd) front crawl swims with a two-minute rest interval between each bout. The trials consisted of two NaHCO3 treatments, two placebo trials and one test with no-drink. One hour before the onset of swimming, the subjects were given 300 ml of citric acid flavored solution containing either 17 mmol of NaCl (placebo) or 2.9 mmol of NaHCO3.kg-1 body weight (experimental), or received no drink (no-drink). Performance times for each 91.4 m swim were recorded. Blood samples were obtained before and one hr after treatment, two min after warmup, and two min after the final 91.4 m sprint. Blood pH, lactate, standard bicarbonate (SBC) and base excess (BE) were measured. No differences were found for performance or the blood measurements between the placebo and no-drink trials. Bicarbonate feedings, on the other hand, produced a significant (P less than 0.05) improvement in performance on the fourth and fifth swimming sprints. Blood lactate, pH, SBC and BE were significantly higher (P less than 0.05) at post-exercise in NaHCO3 treatments. These data are in agreement with previous findings that during repeated bouts of exercise pre-exercise administration of NaHCO3 improves performance, possibly by facilitating the efflux of hydrogen ions from working muscles and thereby delaying the onset of fatigue.

Bicarbonates↗
PubMed1988

Excretion of 3-methylhistidine and hydroxyproline following acute weight-training exercise.

Changes in urine excretion of 3-methylhistidine (3MH) and hydroxyproline (OHP) were investigated following a single session of weight training that produced delayed onset muscle soreness (DOMS). The subjects (n = 18) maintained meat-free diets for 6 days and collected 24-h urine volume on day 4 (PRE), day 5 (POST1), and day 6 (POST2) for analysis of 3MH, OHP, and creatinine (CRE). At the end of PRE, nine subjects (EX) performed intensive weight-training exercises. The remaining subjects (NE) served as a nonexercised group. All subjects were measured for fat free weight (FFW) and rated DOMS at the end of each urine collection period, i.e., PRE, POST1, and POST2. The results were significant DOMS ratings on POST1 and POST2 compared with PRE2 for EX only. Excretion of 3MH (x +/- SE in mumol/day) by group were, for EX, PRE 271 +/- 18, POST1 243 +/- 16, POST2 259 +/- 23; for NE, PRE 203 +/- 23, POST1 209 +/- 27, POST2 225 +/- 32. Excretion of OHP (x +/- SE in mg/day) were, for EX, PRE 30.0 +/- 5.4, POST1 32.8 +/- 6.4, POST2 29.6 +/- 6.1; for NE, PRE 22.5 +/- 5.2, POST1 21.6 +/- 6.0, POST2 22.7 +/- 6.0. Changes in urine 3MH and OHP were not statistically significant, whether analyzed in absolute terms or relative to CRE and FFW. It was concluded that the acute session of weight training which produced muscle soreness did not effect excretion of 3MH or OHP.

Adult↗
PubMed1988

Influence of sodium bicarbonate on sprint performance: relationship to dosage.

The purpose of this investigation was to determine the minimum oral dosage of bicarbonate needed to significantly elevate blood bicarbonate and the influence of induced alkalosis on performance in high-intensity, short-duration exercise. Nine endurance-trained cyclists performed four 2-min sprints on separate occasions using an isokinetic cycle ergometer (Fitron, Cybex, Inc.). One hour before each test, the cyclists consumed either a placebo (A), a solution of 0.10 g NaHCO3.kg-1 body weight (B), a solution of 0.15 g NaHCO3.kg-1 body weight (C), or a solution of 0.20 g NaHCO3.kg-1 body weight (D) in random order. Arterialized venous blood was taken before (PRE) and after (POST) ingestion, and 1, 3, 5, 10, and 15 min following the 2-min bike sprint. The results showed a significant increase in POST blood bicarbonate, and the elevation was incrementally related to the dosage. There was, however, no significant improvement in performance. Total work (mean +/- SE) for each treatment (N.m per 2 min) were: A, 47,267 (+/- 2,472); B, 47,004 (+/- 3,094); C, 46,312 (+/- 2,964); and D, 47,190 (+/- 2,621). The results of this study show that incremental doses of NaHCO3 of 0.20 g.kg-1 and below produce incremental elevations in blood bicarbonate but do not produce improvements in performance for a sprint bout lasting 2 min.

Acid-Base Equilibrium↗
PubMedDate not supplied

Feeding-induced changes in energy expenditure in children with cystic fibrosis.

Seven children with cystic fibrosis (aged 7 to 12 years) were studied in the fasted and fed states. Using a primed, constant, intravenous infusion of NaH13CO3, the rate of appearance of CO2 (RaCO2) was estimated. Net CO2 excretion (VCO2) was also measured. Energy expenditure was calculated using the food quotient. RaCO2 (mean +/- SD) (mumol.kg-1.min-1) in the fasted and fed states (297 +/- 59 and 359 +/- 67) was 117% and 105% of VCO2 (259 +/- 48 and 352 +/- 72). Feeding induced a 23% and a 37% increase in RaCO2 and VCO2, respectively, and respective 19% and 33% increases in energy expenditure (p < .05). Measurement of CO2 production by isotopic dilution is a useful index of group changes in energy expenditure, including those induced by feeding.

Body Temperature Regulation↗