Douglas S. King

Improvement in Glucose Tolerance After 1 Wk of Exercise in Patients With Mild NIDDM

We investigated the effects of 1 wk of intense exercise on glucose tolerance in 10 men with abnormal glucose tolerance [7 had mild non-insulin-dependent diabetes mellitus (NIDDM), and 3 had impaired glucose tolerance]. The 7 days of exercise did not result in significant changes in body weight or maximal oxygen uptake. Plasma glucose concentration at 120 min averaged 227 ± 23 mg/dl in an oral glucose tolerance test (OGTT) before and 170 ± 18 mg/dl after the 7 days of exercise (P < .001). There was a 36% reduction in the area under the glucose tolerance curve. Plasma insulin concentration at 120 min of the OGTT averaged 172 ± 27μU/ml before and 106 ± 13 μU/ml after 7 days of exercise (P < .001); the area under the insulin curve was decreased by 32%. In contrast to the response to 7 days of exercise, one bout of exercise did not result in an improvement in glucose tolerance. These results provide evidence that regularly performed, vigorous exercise can be effective in decreasing insulin resistance and improving glucose tolerance within 7 days in some patients with mild NIDDM.

Effect of carbohydrate feeding frequencies and dosage on muscle glycogen use during exercise

Nine men were studied during three 4-h cycling bouts to determine the effect of frequency and dosage of solid carbohydrate (CHO) feedings (86 g) on muscle glycogen utilization and exercise performance. In the frequency trial (F), the subjects ingested 10.75 g of CHO along with 200 ml of water at 30-min intervals; in the dosage trial (D), the subjects ingested 21.5 g of CHO with 400 ml of water at 60-min intervals. During the control trial (C), the subjects ingested 400 ml of an artificially sweetened placebo at 60-min intervals. Respiratory exchange ratios were significantly elevated in both trials D and F (P less than 0.05). Blood glucose was significantly elevated in trial D 20 min post-feeding but had returned to control levels by 50 min. In trial F, blood glucose was maintained at a constant level throughout the entire 4 h. In trial C, blood glucose declined steadily during the entire 4 h. Despite the differences in blood glucose levels between the three trials, there were no significant differences in the rate of muscle glycogen utilization in any of the trials (D = 82.9 +/- 6.6 [SE] mmol X kg-1 vs C = 80.9 +/- 6.9 mmol X kg-1 vs F = 74.4 +/- 12.2 mmol X kg-1). In a sprint ride (100% VO2max) to exhaustion at the end of each trial, the subjects performed significantly longer in trial F compared to C (120.97 +/- 9.6 vs 81.0 +/- 7.1 s).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pre-exercise carbohydrate feedings on endurance cycling performance

Six men were studied to compare the effects of pre-exercise carbohydrate feedings on endurance performance and muscle glycogen utilization during prolonged exercise. Trials consisted of a cycling ride to exhaustion at 75% maximal oxygen uptake preceded by the ingestion of either 75 g of glucose in 350 ml of water (GLU), 75 g of fructose in 350 ml of water (FRU), or 350 ml of an artificially sweetened and flavored placebo (CON). No differences were observed between trials for oxygen uptake, respiratory exchange ratio, heart rate, or exercise time to exhaustion (CON = 92.7 +/- 5.2 min, FRU = 90.6 +/- 12.4, and GLU = 92.8 +/- 11.3, mean +/- SE). Blood glucose was elevated as a result of the GLU feeding, but fell rapidly with the onset of exercise, reaching a low of 4.02 +/- 0.34 mmol X l-1 at 15 min of exercise. Serum insulin also increased following the GLU feeding but had returned to pre-drink levels by 30 min of exercise. No differences in blood glucose and insulin were observed between FRU and CON. Muscle glycogen utilization during the first 30 min of exercise (CON = 46.3 +/- 8.2 mmol X kg-1 wet weight, FRU = 56.3 +/- 3.0 mmol X kg-1 wet weight, GLU = 50.0 +/- 4.9 mmol X kg-1 wet weight) and total glycogen use (CON = 93.4 +/- 11.1, FRU = 118.8 +/- 10.9, and GLU = 99.5 +/- 4.3) were similar in the three trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Reduced Training on Muscular Power in Swimmers.

In brief: Seventeen male collegiate swimmers were studied before, during, and after 14 days of reduced training (tapering). Maximal arm power was measured using a bio- kinetic swim bench and during a tethered (power) swim test, and each swimmer also swam 200 yards (182.9 meters) at an evenly paced velocity corresponding to 90% of his best performance of the season. Tapering had no influence on postexercise acid-base balance, but there was a significant increase (p <.05) in power output on both the biokinetic swim bench and the power swim test. Performance times improved an average of 3.1%. The improvements are in part due to significant gains in muscular power.

Endocrine and Lipid Responses to Chronic Androstenediol-Herbal Supplementation in 30 to 58 Year Old Men

Objective: The effectiveness of an androgenic nutritional supplement designed to enhance serum testosterone concentrations and prevent the formation of dihydrotestosterone and estrogen was investigated in healthy 30 to 58 year old men. Design: Subjects were randomly assigned to consume a nutritional supplement (AND-HB) containing 300-mg androstenediol, 480-mg saw palmetto, 450-mg indole-3-carbinol, 300-mg chrysin, 1,500 mg gamma-linolenic acid and 1,350-mg Tribulus terrestris per day (n = 28), or placebo (n = 27) for 28 days. Subjects were stratified into age groups to represent the fourth (30 year olds, n = 20), fifth (40 year olds, n = 20) and sixth (50 year olds, n = 16) decades of life. Measurements: Serum free testosterone, total testosterone, androstenedione, dihydrotestosterone, estradiol, prostate specific antigen and lipid concentrations were measured before supplementation and weekly for four weeks. Results: Basal serum total testosterone, estradiol, and prostate specific antigen (PSA) concentrations were not different between age groups. Basal serum free testosterone concentrations were higher (p < 0.05) in the 30- (70.5 ± 3.6 pmol/L) than in the 50 year olds (50.8 ± 4.5 pmol/L). Basal serum androstenedione and dihydrotestosterone (DHT) concentrations were significantly higher in the 30- (for androstenedione and DHT, respectively, 10.4 ± 0.6 nmol/L and 2198.2 ± 166.5 pmol/L) than in the 40- (6.8 ± 0.5 nmol/L and 1736.8 ± 152.0 pmol/L) or 50 year olds (6.0 ± 0.7 nmol/L and 1983.7 ± 147.8 pmol/L). Basal serum hormone concentrations did not differ between the treatment groups. Serum concentrations of total testosterone and PSA were unchanged by supplementation. Ingestion of AND-HB resulted in increased (p < 0.05) serum androstenedione (174%), free testosterone (37%), DHT (57%) and estradiol (86%) throughout the four weeks. There was no relationship between the increases in serum free testosterone, androstenedione, DHT, or estradiol and age (r2 = 0.08, 0.03, 0.05 and 0.02, respectively). Serum HDL-C concentrations were reduced (p < 0.05) by 0.14 mmol/L in AND-HB. Conclusions: These data indicate that ingestion of androstenediol combined with herbal products does not prevent the formation of estradiol and dihydrotestosterone.

Effects of pre-exercise carbohydrate feedings on muscle glycogen use during exercise in well-trained runners

SummaryThe purpose of this study was to examine the effects of pre-exercise glucose and fructose feedings on muscle glycogen utilization during exercise in six well-trained runners (

Effects of dietary sodium on body and muscle potassium content during heat acclimation.

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Effect of preexercise electrolyte ingestion on fluid balance in men and women.

=68.2±3.4 ml·kg−1·min−1). On three separate occasions, the runners performed a 30 min treadmill run at 70%