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Biomedical subjects

A Weltman

Publications and source records attributed to A Weltman.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of carbohydrate supplementation on performance during 1 hour of high-intensity exercise.

The effects of carbohydrate supplementation on high-intensity exercise performance were examined in 5 moderately-trained subjects (age = 28.4 +/- 1.5 yr; ht = 171.0 +/- 4.3 cm; wt = 66.25 +/- 6.32 kg). High-intensity exercise tests (initiated at the power output (PO) associated with 90% VO2 peak [mean = 201 +/- 21 watts] x 60 min, with drop-off in PO allowed over time) were completed under the following randomized double blind conditions: 1) pre-exercise glucose polymer (G)/placebo during exercise (G/P), 2) G pre-exercise and during exercise (G/G), and 3) placebo pre-exercise and during exercise (P/P). Subjects ingested 300 ml of a sweetened placebo or a similarly flavored 10% G solution, immediately prior to and every 15 min during exercise. No differences were observed in PO among the 3 treatments until min 40-60 where PO was greater with G. This resulted in significantly greater total work (and less drop-off in PO) with G (G/P = 619 +/- 234kJ [14.5% lower than the value associated with 201 watts maintained for 60 min (724kJ)], G/G = 599 +/- 235 kJ [17.3% lower than the value associated with 201 watts maintained for 60 min]) compared with placebo (P/P = 560 +/- 198 kJ [22.7% drop-off in average PO]) (p < 0.05). VO2 followed a similar pattern with no difference in VO2 over min 0-40 and significantly higher VO2 in G/P and a trend for higher VO2 in G/G during min 40-60 compared to placebo. Results of the present study indicate that, compared to placebo, pre-exercise ingestion of G (30 g in 10% solution) results in less drop-off in PO during 1 hour of high-intensity exercise performance, and that no further benefit is observed when the same amount of G is also ingested every 15 min during exercise.

Adult↗
PubMed1995

Differential impact of age, sex steroid hormones, and obesity on basal versus pulsatile growth hormone secretion in men as assessed in an ultrasensitive chemiluminescence assay.

A chemiluminescence-based GH assay with 30- to 100-fold increased sensitivity recently disclosed combined basal and pulsatile GH secretion in men. However, how age, sex steroid hormones, and obesity singly and jointly influence the basal vs. pulsatile modes of GH release is not known. We used the foregoing assay (detection threshold, 0.002-0.005 microgram/L) and high sensitivity and specificity (> or = 90% each) deconvolution analysis to quantitate basal and pulsatile GH secretion from 24-h serum GH concentration profiles in 26 healthy lean and obese men, whose ages spanned 18-63 yr and whose percentage body fat ranged from 12-47%. Concentrations of serum insulin-like growth factor I (IGF-I), IGF-I-binding protein-1 (IGFBP-1), and IGFBP-3 were related to specific measures of basal or pulsatile GH release. We observed that mean (24-h) serum GH concentrations embraced a 140-fold range from 0.013-1.8 micrograms/L and were related negatively to age (r = -0.50; P < 0.01), percentage body fat (r = -0.620; P < 0.01), and their interaction (r = -0.610; P < 0.01). In contrast, testosterone was a robustly positive statistical determinant of mean serum GH values (r = 0.628; P = 0.0006). Stepwise multivariate regression analysis disclosed that percentage body fat alone and jointly with the serum testosterone concentration controlled, respectively, 38% and 50% of the total variability in GH levels (P = 0.0013 and P = 0.0008). As assessed by deconvolution analysis, GH secretory burst mass was negatively related to percentage body fat (r = -0.621; P < 0.01) and positively to serum testosterone (r = 0.529; P = 0.0054). The calculated half-life of GH correlated positively with serum estradiol (r = 0.447; P = 0.032), and negatively with percentage body fat (r = -0.437; P = 0.048). Basal GH secretion rates were negatively related to serum estradiol (r = -0.485; P = 0.016). In contrast, GH secretory burst frequency and duration were unrelated to age, percentage body fat, or sex steroids. The fraction of total GH secreted in bursts was negatively correlated with the body mass index (r = -0.540; P < 0.01). Serum IGF-I concentrations were positively related to total pulsatile GH secretion (r = 0.690; P = 0.0011) and negatively to age (r = -0.597; P = 0.007) and percentage body fat (r = -0.611; P = 0.009).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1994

Effects of acute caffeine withdrawal on habituated male runners.

This study investigated the effects of caffeine withdrawal on six trained caffeine-habituated male runners: age 29.8 +/- 5.8 (SD) yr, height 180.4 +/- 5.4 cm, weight 77.3 +/- 6.7 kg, maximal O2 uptake 63.0 +/- 5.4 ml.kg-1.min-1, and daily caffeine intake 674 +/- 128 mg. The subjects received a loading dose (5 mg/kg body wt) of caffeine 48 h before each testing session. They were then given (using a repeated-measures double-blind design) additional doses of caffeine (5 mg/kg body wt) or a placebo 36, 24, 12, and 2 h before testing. They ran at a velocity corresponding to their lactate threshold for 60 min in a caffeine withdrawal or caffeinated condition. Caffeine withdrawal resulted in no significant differences in absolute O2 uptake, O2 uptake relative to maximal O2 uptake, respiratory exchange ratios, or free fatty acid concentrations. Glycerol concentrations were significantly attenuated in the withdrawal condition. No significant differences were revealed in calculated substrate utilization. It was concluded that caffeine withdrawal significantly affects lipolysis but not substrate utilization during prolonged running.

Adult↗
PubMed1994

Catecholamine and blood lactate responses to incremental rowing and running exercise.

Ten collegiate rowers performed discontinuous incremental exercise to their tolerable limit on two occasions: once on a rowing ergometer and once on a treadmill. Ventilation and pulmonary gas exchange were monitored continuously, and blood was sampled from a venous catheter located in the back of the hand or forearm for determination of blood lactate ([La]) and plasma epinephrine ([Epi]) and norepinephrine ([NE]) concentrations. Thresholds for lactate (LT), epinephrine (Epi-T), and norepinephrine (NE-T) were determined for each subject under each condition and defined as breakpoints when plotted as a function of O2 uptake (VO2). For running, LT (3.76 +/- 0.18 l/min) was lower (P < 0.05) than Epi-T (4.35 +/- 0.14 l/min) and NE-T (4.04 +/- 0.19 l/min). For rowing, LT (3.35 +/- 0.16 l/min) was lower (P < 0.05) than Epi-T (3.72 +/- 0.22 l/min) and NE-T (3.70 +/- 0.18 l/min) and was lower (P < 0.05) than LT for running. Within each mode of exercise, Epi-T and NE-T did not differ. Because LT occurred at a significantly lower VO2 than either Epi-T or NE-T, we conclude that catecholamine thresholds, per se, were not the cause of LT. However, for both modes of exercise LT occurred at a plasma [Epi] of approximately 200-250 pg/ml (rowing, 221 +/- 48 pg/ml; running, 245 +/- 45 pg/ml); these concentrations are consistent with the plasma [Epi] reported necessary for eliciting increments in blood [La] during Epi infusion at rest. Plasma [NE] at LT differed significantly between modes (rowing, 820 +/- 127 pg/ml; running, 1,712 +/- 217 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Relationship between age, percentage body fat, fitness, and 24-hour growth hormone release in healthy young adults: effects of gender.

We investigated whether gender affects the physiological relationships between the release of GH and age, body composition, and levels of physical fitness in humans. We studied 32 eumenorrheic females (age = 31 +/- 5 yr) and 12 males (age = 27 +/- 5 yr). Significant gender differences were found for peak oxygen consumption [VO2 peak = 40.5 +/- 6.9 (females) vs. 50.1 +/- 11.6 (males) ml/kg.min-1, P < 0.05] and body composition [hydrostatic weighing, percentage body fat = 28.7 +/- 5.4 (females) vs. 18.1 +/- 9.8 (males), P < 0.05] but not for body mass index [BMI = 23.7 +/- 3.1 (females) vs. 24.0 +/- 3.3 (males)]. Blood samples were drawn every 10 min for 24 h from 0800 h to determine integrated serum GH concentration [2350 +/- 1260 (females) vs. 3110 +/- 1760 (males) microgram/L x min]; females were studied during the early follicular phase (days 4-5) of the menstrual cycle. In females, a significant relationship existed between 24-h integrated serum GH concentration and age (r = -0.35, P = 0.05) but not BMI (r = -0.19, P = 0.29); the relationship between 24-h integrated serum GH concentration and VO2 peak (r = 0.31, P = 0.08) and percentage body fat (r = 0.29, P = 0.11) approached significance. In males, significant relationships existed between 24-h integrated serum GH concentration and age (r = -0.79, P = 0.002), percentage body fat (r = -0.75, P = 0.005), and VO2 peak (r = 0.58, P = 0.05) but not between 24-h integrated serum GH concentration and BMI (r = -0.53, P = 0.08). Standardized regression coefficients revealed that for each SD change in age, BMI, percentage body fat, or VO2 peak the associated change in 24-h integrated serum GH concentration was 1.9-2.6 times greater in males than in females. We conclude that age, percentage body fat (but not BMI), and fitness are related to 24-h GH release in young adults and that these relationships are considerably stronger in males than females.

Adipose Tissue↗
PubMed1994

Rating of perceived exertion and blood lactate concentration during submaximal running.

We examined whether the relation between of ratings of perceived exertion (RPE) and exercise intensities associated with the lactate threshold (LT) and blood lactate concentrations (BLC) of 2.5 and 4.0 mM, established with an incremental protocol, held during 30-min treadmill run at constant velocity (V). RPE (11.6, 14.9, 16.8, 18.9), oxygen uptake (VO2) (3.2, 3.7, 3.9, 4.2 l.min-1), and V (168, 196, 215, 227 m.min-1) at LT, BLC of 2.5, and 4.0 mM and peak were determined for nine males during incremental exercise. Subjects then completed three 30-min runs at the V associated with LT and BLC of 2.5 and 4.0 mM, with RPE, VO2, and blood [HLa] determined every 5 min. After min 10 during the 30-min runs, RPE, VO2, and BLC were not significantly different from corresponding values observed during the incremental protocol. Regression equations predicting BLC from RPE were generated from results obtained during the incremental protocol. RPE values from the 30-min runs were used to predict BLC, and the measured BLC was used to validate the use of RPE as a predictor of BLC. Correlations ranged from r = 0.79 to r = 0.98 [total error (TE) ranged from 0.6-1.3 mM]. We conclude that RPE is a physiologically valid tool for prescribing exercise intensity when the intent is to use LT and/or BLC as the intensity criterion.

Adult↗
PubMed1993

Cholinergic and opioid involvement in release of growth hormone during exercise and recovery.

Cholinergic and opioid pathways have been implicated as mediators of the increased growth hormone (GH) release observed during exercise. This study compared the GH responses induced by a moderate-intensity exercise bout during treatment with placebo (Plac), the opioid receptor antagonist naltrexone (Nalt), the indirect cholinergic agonist pyridostigmine (PD), or a combination of the two drugs (P + N). Ten active males served as subjects (age, 25.1 +/- 0.6 yr; wt, 79.7 +/- 2.5 kg; % body fat, 14.9 +/- 1.4; peak oxygen consumption, 46.2 +/- 2.7 ml.kg-1 x min-1). Blood samples were drawn at 5-min intervals during the 4.5-h testing period to determine the GH concentration. The testing period was divided as follows: 0600-700 h = baseline, 0700-0800 h = preexercise, 0800-0830 h = exercise, and 0830-1030 h = recovery. Drugs were administered 1 h before exercise (at 0700 h). Exercise consisted of 30 min of cycling at an individualized work load previously found to elicit a blood lactate concentration of 2.5 mM. Heart rate, oxygen consumption, blood lactate, and blood glucose were measured throughout the exercise period. Results indicated that neither the resting GH concentration nor the metabolic parameters during exercise were altered by the treatments. Peak serum GH concentration was not significantly altered by the treatments (range 7.3 +/- 2.0 to 12.6 +/- 4.4 micrograms/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The effects of assistive devices on the oxygen cost, cardiovascular stress, and perception of nonweight-bearing ambulation.

Nonweight-bearing ambulation with the aid of an assistive device is often prescribed in the clinical setting. Little is known about the oxygen cost, cardiovascular stress, and perception of effort of these devices when applied to the same sample of subjects. Therefore, the present study compared the oxygen cost, cardiovascular stress [measured by heart rate (HR), blood pressure (BP) responses, and rate pressure product (RPP)], and perception of effort [measured by ratings of perceived exertion (RPE)] of unassisted ambulation (UA), nonweight-bearing ambulation using axillary crutches (AC), a standard walker (SW), and a wheeled walker (WW). Nine female subjects ambulated at self-selected velocities for 7 minutes during each ambulation mode. Oxygen consumption, HR, BP, and RPEs were obtained. As expected, UA resulted in the lowest VO2 (11.2 +/- 1.4 ml/kg.min-1) and greatest velocity (1.24 +/- 0.27 m/sec). Results also indicated that AC ambulation resulted in lower oxygen consumption per meter (0.4 +/- 0.1 ml/kg.m-1) and greater velocity (0.74 +/- 0.18 m/sec) than either SW ambulation (0.6 +/- .1 ml/kg.-1, 0.39 +/- 0.09 m/sec) or WW ambulation (0.6 +/- .1 ml/kg.m-1, 0.40 +/- 0.12 m/sec) (p < .05). No differences were observed among assisted ambulation modes for HR, BP responses, RPP, or RPE values. Because patients typically ambulate for a set distance (rather than a set time) and because the oxygen cost per unit distance was lowest for AC, it is suggested that, when possible, AC should be prescribed for non-weight-bearing ambulation.

Adult↗
PubMed1993

Effect of preload and range of motion on isokinetic torque in women.

The purposes of this study were to compare the effects of two preload settings (0 N, 75 N) and two ranges of motion (5-90 degrees ROM, 25-70 degrees ROM) on torque output of the knee musculature. Twenty females were randomly assessed for isokinetic concentric (CON) and eccentric (ECC) torque of the knee extensor (EXT) and flexor (FLEX) musculature at a velocity of 1.62 rads.s-1. Two four-way ANOVAs (muscle x mode x range of motion x preload) revealed significant differences in average torque between the preload and range of motion conditions (CONEXT: 5-90 degrees ROM, 75 N = 74.3 +/- 17.2 Nm; 5-90 degrees ROM, 0 N = 68.3 +/- 17.2 Nm; 25-70 degrees ROM, 75 N = 79.0 +/- 13.0 Nm; 25-70 degrees ROM, 0 N = 71.5 +/- 20.8 Nm) (ECCEXT: 5-90 degrees ROM, 75 N = 85.6 +/- 28.6 Nm; 5-90 degrees ROM, 0 N = 82.8 +/- 27.8 Nm; 25-70 degrees ROM, 75 N = 97.7 +/- 23.4 Nm; 25-70 degrees ROM, 0 N = 93.6 +/- 26.5 Nm) (CONFLEX: 5-90 degrees ROM, 75 N = 43.5 +/- 9.2 Nm; 5-90 degrees ROM, 0 N = 43.1 +/- 5.6 Nm; 25-70 degrees ROM, 75 N = 44.2 +/- 8.9 Nm; 25-70 degrees ROM, 0 N = 41.2 +/- 8.9 Nm) (ECCFLEX: 5-90 degrees ROM, 75 N = 56.7 +/- 16.3 Nm; 5-90 degrees ROM, 0 N = 55.6 +/- 17.8 Nm; 25-70 degrees ROM, 75 N = 57.3 +/- 14.0 Nm; 25-70 degrees ROM, 0 N = 51.8 +/- 14.0 Nm) (P < 0.05). No differences in peak torque values were observed. Based on the findings of this study, preload and range of motion should remain constant between and among subjects if average torque is used as a criterion measure.

Adult↗
PubMed1992

Exercise training at and above the lactate threshold in previously untrained women.

We examined the effects of training at and above the lactate threshold in previously untrained women. Twenty-four untrained eumenorrheic women (age = 31.3 +/- 4.0 yrs, wt = 66.2 +/- 7.6 kg, ht = 166.4 +/- 5.8 cm) were assessed at baseline [during days 1-3 of the menstrual cycle (MC)] and every 4 MC after that (for 1 year) for VO2 and velocity (V) at LT, fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM, and Max. Subjects were assigned to control (C, n = 7), at LT/LT, trained 6 days/week at the velocity associated with LT, (n = 9) or above LT (greater than LT, trained 3 days/week at the velocity midway between V LT and V Max and 3 days/week at V LT, n = 8) groups. Exercise prescriptions were adjusted after each assessment and each group progressed similarly in weekly mileage. No between group differences were observed before training. After training the greater than LT group had significantly higher values than the C and /LT groups for LT (p less than 0.05). For FBLC of 2.0, 2.5, and 4.0 mM and Max, the greater than LT group values were greater than the C group (p less than 0.05). No differences were observed after training between the /LT and C groups. Although the greater than LT group had higher VO2 and V Max values than the /LT group after training, these differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The effect of training intensity on ratings of perceived exertion.

We examined the effects of intensity of training on ratings of perceived exertion (RPE) at the lactate threshold (LT), fixed blood lactate concentrations (FBLC) of 2.0, 2.5 and 4.0 mM and peak in 25 untrained eumenorrheic women (mean +/- SD: age = 30.9 +/- 4.1 yrs; height = 165.7 +/- 5.9 cm; weight = 65.5 +/- 7.6 kg) who completed one year of run training. Subjects were recruited as sedentary controls or were randomly assigned to one of two training groups: 1) at the lactate threshold (at LT) or 2) above the lactate threshold (greater than LT). The at LT group trained at velocity LT and the greater than LT group trained at the velocity midway between velocity LT and peak velocity. Training subjects were reevaluated every fourth menstrual cycle and training intensity was adjusted. The control group was reassessed at menstrual cycle 12. Before training no among group differences were observed for VO2 or velocity at LT, FBLC and peak. Both training groups increased VO2 at LT, FBLC and peak as a result of training (p less than 0.05), with the greater than LT group exhibiting greater improvement than the at LT group (VO2 at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak increased by 6.4, 5.3, 5.1, 4.0 and 4.7 ml/kg.min-1 for at LT and by 10.4, 9.2, 8.6, 5.1 and 5.9 ml/kg.min-1 for greater than LT; p less than 0.05). Similar findings were observed for the velocity associated with these lactate concentrations. No pre/post differences were observed in VO2 or velocity for the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Dietary patterns, eating behaviors, and bone mineral density in women runners.

Although reduced gonadal steroid hormone concentrations appear to play a major role in lower trabecular bone mineral density (BMD) in women with athletic amenorrhea, dietary deficiencies and eating behaviors may also affect BMD in women runners. To investigate this possibility, dietary patterns (7-d records), eating-disorders inventory (EDI), and BMD were examined in nine nonrunning eumenorrheic control (Contl) and 32 women runners classified as eumenorrheic (n = 19, Eumen) and oligo/amenorrheic (a group in which some were oligomenorrheic and some were amenorrheic; Ol/Am, n = 13). Runner groups had similar cardiorespiratory fitness, body composition, and training characteristics. Lumbar spine BMD was lower in the Ol/Am runners (-12%, P less than 0.05) but proximal femur BMD did not differ. Dietary intake and EDI subscale scores were similar among the groups. However, there was an inverse trend between EDI subscale scores for bulimia and ineffectiveness and femoral BMD in the Ol/Am runners (r = -0.62 to -0.71, P less than 0.05). These results suggest that self-reported dietary intake and/or eating behaviors do not predict reproductive-function alterations in women runners, but eating behaviors may be associated with lower BMD in Ol/Am runners.

Adolescent↗
PubMed1992

Durability of the reproductive axis in eumenorrheic women during 1 yr of endurance training.

Menstrual cycle (MC) alterations occur in some endurance-training women. We hypothesized that a prospective running program would evoke alterations in MC phase lengths and in the physiological frequency of pulses of luteinizing hormone (LH) and/or diminish 24-h integrated serum LH concentrations in some women. In addition, we postulated that women who train more intensively (above the lactate threshold) would show alterations in gonadotropin release earlier in the training program or to a greater degree. To test these hypotheses, we examined the effects of different exercise intensities on physiological and endocrine responses. Twenty-three healthy eumenorrheic gynecologically mature (postmenarchal age 17.8 +/- 0.9 yr) untrained women undertook a 1-yr training program at one of two exercise intensities, one at a velocity corresponding to the lactate threshold (LT) and the other halfway between that of LT and peak running velocity, or served as controls. Training distance was the same in each exercise group. Physiological measurements were repeated every four MC to track changes in fitness and readjust training velocities. The lengths of the MC and the follicular and luteal phases were determined from hormonal concentrations. Body composition, nutritional intake, and pulsatile release of LH were determined. The women ran approximately 790 miles. Each group improved physiologically, with the greater than LT group improving to a greater degree. A less than 2-day decrease in the luteal phase length was observed only in the greater than LT group. No significant changes for any parameter of pulsatile LH release were noted between exercise groups. No significant changes in nutritional intake and only small changes in body composition were noted in either exercise group despite the added energy expenditure of exercise. We conclude that a progressive exercise program of moderate distance and intensity does not adversely affect the robust reproductive system of gynecologically mature eumenorrheic women.

Adult↗
PubMed1992

Reproductive hormones and bone mineral density in women runners.

We examined the relationships among reproductive hormone concentrations and bone mineral density (BMD) in 43 women runners classified as eumenorrheic (n = 24), oligomenorrheic (n = 8), or amenorrheic (n = 11). Results were compared with a eumenorrheic nonrunner control group (n = 11). Serum 17 beta-estradiol, progesterone, and dehydroepiandrosterone sulfate concentrations were determined in daily blood samples for 21 days, and integrated concentrations (areas under the curve) were calculated. BMD was assessed at the lumbar spine and proximal femur by dual-photon absorptiometry. As expected, 17 beta-estradiol, progesterone, and lumbar spine BMD were higher in the control and eumenorrheic runner groups than in the oligomenorrheic and amenorrheic runner groups (P less than 0.05). Progesterone concentration was significantly correlated with lumbar spine BMD in the eumenorrheic runners (r = 0.61). None of the steroid hormones was significantly related to BMD in the oligomenorrheic/amenorrheic group. The present data suggest that circulating levels of gonadal steroid hormones affect axial BMD in eumenorrheic runners.

Adolescent↗
PubMed1992

Endurance training amplifies the pulsatile release of growth hormone: effects of training intensity.

The effects of intensity of run training on the pulsatile release of growth hormone (GH) were investigated in 21 eumenorrheic untrained women. The O2 consumption (VO2) at the lactate threshold (LT); fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM; peak VO2; maximal VO2; body composition; and pulsatile release of GH were measured. Subjects in both the at-lactate threshold (/LT, n = 9) and above-lactate threshold (greater than LT, n = 7) training groups increased VO2 at LT and FBLC of 2.0, 2.5, and 4.0 mM and VO2max after 1 yr of run training. However, the increase observed in the greater than LT group was greater than that in the /LT group (P less than 0.05). No change was observed for the control group (n = 5). No among- or within-group differences were observed for body weight, although trends for reductions in percent body fat (P less than 0.06) and fat weight (P less than 0.15) were observed in the greater than LT group, and both training groups significantly increased fat-free weight (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗