PubMed Health⌕ Search

Biomedical subjects

W J Fink

Publications and source records attributed to W J Fink.

At least 91 records · Page 5Linked to original sources
PubMed1981

The role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running.

This study examined the effect of the type, amount, and the frequency of feeding of carbohydrates on muscle glycogen resynthesis after running. Trained male runners performed a 16.1 km run at 80% VO2 max to decrease gastrocnemius glycogen levels. A complex or simple carbohydrate diet (approximately 3000 kcal) resulted in similar muscle glycogen levels 24 h after exercise. Forty-eight hours after exercise the complex carbohydrate diet resulted in significantly higher (p less than 0.05) muscle glycogen levels. Consuming increasing amounts of carbohydrate, between 88 to 648 g carbohydrate/day, resulted in increasingly larger amounts of muscle glycogen resynthesis (24 h) after exercise. Frequent feedings of a high carbohydrate diet did not enhance muscle glycogen synthesis when compared to equal amounts of carbohydrates in two meals. It appears that muscle glycogen can be normalized between daily strenuous running activity.

Adult↗
PubMed1979

Lipid metabolism in skeletal muscle of endurance-trained males and females.

Bipsies were obtained from the gastrocnemius muscle of 13 male and 12 female distance runners and analyzed for [14C]palmitoyl-CoA oxidation, fiber composition, and the activities of selected enzymes. The male and female runners were similar in terms of maximal oxygen uptake (VO2max), training mileage, fiber compositions, and data collected during a 60-min treadmill run at 70% VO2max. Muscle succinate dehydrogenase and carnitine palmitoyl transferase activities were, however, significantly greater (P less than 0.05) in the male than in female runners. In addition, the male runners' muscle also showed a greater capacity to oxidize palmitoyl CoA. Little relationship, however, was found between muscle lipid metabolism, enzyme activities, and the calculated (respiratory exchange) fraction of energy derived from fat during 60 min of running at 70% VO2max. Although these data support the concept that endurance training (80-115 km/wk) markedly enhances the capacity of muscles to metabolize fats, the factors that regulate the usage of lipids during prolonged exercise do not appear to be limited by the capacity of the fibers to oxidize fatty acids, as determined by in vitro measurements.

Adult↗
PubMed1979

Training adaptations in skeletal muscle of juvenile diabetics.

Skeletal muscles from 12 male, juvenile-onset diabetics (JD) and 13 nondiabetics (ND) were studied to determine the effects of endurance training on mitochondrial enzyme activities, lipoprotein lipase (LPL) activity, and the oxidation of lipids (14C-palmityl CoA) in vitro. Ten weeks of endurance running (30 min/day, 5 days/wk) resulted in 11.0 and 12.9% gains in aerobic capacity for the JD and ND groups (P greater than 0.05), respectively. Both groups showed significant (P less than 0.05) increases in muscle LPL, carnitine palmityl transferase, succinate dehydrogenase, and hexokinase activities with training. Though the pretraining capacities for 14C-palmityl CoA oxidation were similar for both ND and JD groups, the diabetics showed a 41% greater improvement in the measurement of muscle lipid oxidation after training than did the ND group. The principal finding of this research was that skeletal muscle of juvenile diabetics who are in moderate insulin balance shows adaptations to endurance training that are similar to those of nondiabetic men.

Adult↗
PubMed1979

Influence of caffeine and carbohydrate feedings on endurance performance.

Nine trained cyclists were studied to determine the effects of caffeine (CAF), and glucose polymer (GP) feedings on work production (kpm) during two hr of isokinetic cycling exercise (80 rpm). Ingestion of 250 mg of CAF 60 min prior to the ride was followed by ingestion of an additional 250 mg fed at 15 min intervals over the first 90 min of the exercise. This treatment significantly increased work production by 7.4% and Vo2 by 7.3% as compared to control (C) while the subjects' perception of exertion remained unchanged. Ingestion of approximately 90 g of GP during the first 90 min (12.8 g/15 min) of the exercise had no effect on total work production or Vo2. It was, however, effective in reducing the rate of fatigue over the last 30 min of cycling. Although GP maintained blood glucose and insulin levels (P less than or equal to 0.05) above those of the C and CAF trials, total CHO utilization did not differ between treatments. During the last 70 min of the CAF trial, however, fat oxidation was elevated 31% and appeared to provide the substrate needed for the increased work production during this period of exercise. These data, therefore, demonstrate an enhanced rate of lipid catabolism and work production following the ingestion of caffeine.

Adult↗
PubMed1979

Effects of preexercise feedings on endurance performance.

Eight male and female students were studied during exercise to exhaustion on a bicycle ergometer at 80 and 100% of Vo2max following the ingestion of water (W), 75 g of glucose (G) or a liquid meal (M) (10 g protein, 12.5 g fat, 15 g CHO). When compared to the endurance ride (80% Vo2max) in the W treatment, endurance performance time was reduced by 19%, (p less than .05) (53.2 to 43.2 min) as a result of the preexercise glucose feeding (Trial G). No difference in performance at 80% Vo2max was found between the W and M trials. The preexercise feedings had no effect on exercise time to exhaustion at 100% Vo2max. During the G and M trials at 80% Vo2max, most of the subjects demonstrated a transient decline in serum glucose (less than 3.5 mM). After 30-40 min. of exercise, however, serum glucose returned to normal and was seldom low at the time of exhaustion. Serum free fatty acids (FFA) were depressed throughout the G trial. The results of these experiments indicate impaired lipid mobilization following CHO ingestion. The present data support our earlier findings (11) which demonstrate that glucose feedings 30-45 minutes before endurance exercise increase the rate of CHO oxidation and impede the mobilization of FFA, thereby reducing exercise time to exhaustion.

Adult↗
PubMed1978

Skeletal muscle enzyme activity, fiber composition and VO2 max in relation to distance running performance.

Muscle biopsy samples were obtained from the gastrocnemius of 26 well-trained runners of widely varying ability. Portions of the sample were analyzed for succinate dehydrogenase (SDH) activity and for muscle fiber composition. VO2 max was determined during uphill treadmill running. Mean values for muscle SDH activity (14.6 U/g), fiber composition (55% slow twitch) and VO2 max (60.9 ml/kg x min(-1)) were lower than reported previously for groups of elite and sub-elite runners. The physiological data were consistent with the performance ability of the sample [5 : 12,11 : 20 and 36 : 40 (min :s) for 1, 2 and 6 miles, respectively]. Within the sample, performance was most strongly related to VO2 max (r=-0.84,-0.87 and -0.88 for 1, 2, and 6 miles). There was little relationship between muscle SDH activity and either performance (r=-0.11, -0.14, -0.20 for 1,2, and 6 miles) or VO2 max (r=0.23). The relationship between muscle fiber composition and performance was only modestly strong (r=-0.52,-0.54, -0.55 for 1,2, and 6 miles). The results indicate that the primary determinant of cross-sectional differences in running performance is VO2 max. Skeletal muscle metabolism apparently contributes little to these cross-sectional differences and may be of much greater importance to variations in performance within an individual.

Humans↗
PubMed1978

Effects of caffeine ingestion on metabolism and exercise performance.

In an effort to assess the effects of caffeine ingestion on metabolism and performance during prolonged exercise, nine competitive cyclists (two females and seven males) exercised until exhaustion on a bicycle ergometer at 80% of Vo2 max. One trial was performed an hour after ingesting decaffeinated coffee (Trial D), while a second trial (C) required that each subject consume coffee containing 330 mg of caffeine 60 min before the exercise. Following the ingestion of caffeine (Trial C), the subjects were able to perform an average of 90.2 (SE +/- 7.2) min of cycling as compared to an average of 75.5 (SE +/- 5.1) min in the D Trial. Measurements of plasma free fatty acids, glycerol and respiratory exchange ratios evidenced a greater rate of lipid metabolism during the caffeine trial as compared to the decaffeinated exercise treatment. Calculations of carbohydrate (CHO) metabolism from respiratory exchange data revealed that the subjects oxidized roughly 240 g of CHO in both trials. Fat oxidation, however, was significantly higher (P less than 0.05) during the C Trial (118 g or 1.31 g/min) than in the D Trial (57 g or 0.75 g/min). On the average the participants rated (Perceived Exertion Scale) their effort during the C Trial to be significantly (P less than 0.05) easier than the demands of the D treatment. Thus, the enhanced endurance performance observed in the C Trial was likely the combined effects of caffeine on lipolysis and its positive influence on nerve impulse transmission.

Adult↗
PubMed1978

Muscle strength and power changes during maximal isokinetic training.

This study investigated the effects of short duration, high intensity training on skeletal muscle. The extensors and flexors of the knee were tested and exercised by means of an isokinetic dynamometer. Measurements of peak torque were obtained at velocities ranging from 0 degrees/sec (isometric) to 300 degrees/sec through a distance of 90 degrees. Total work output was measured during repeated knee extensions and flexions for work tasks of 6 sec and 30 sec duration. A 1-min test of repeated maximal contractions was administered to examine muscular fatiguability before and after training. The subjects trained one leg with repeated 6 sec exercise bouts, while the other leg was trained using repeated 30 sec bouts. All training and testing was executed at near maximal force and at a constant velocity (180 degrees/sec). The subjects trained four times per week for a period of seven weeks. The daily work output was equal for the 6 and 30 sec training legs. Results indicate that: (1) isokinetic training programs of 6 and 30 seconds duration can significantly (P less than .05) increase peak muscular torque; (2) training velocity may be an important consideration in improving peak torque; (3) total work output was increased an average of 30% with either training at relatively slow (60 degrees/sec) or fast (180 degrees/sec) velocities; (4) both training programs significantly reduced the fatiguability of the knee extensor muscles.

Adult↗
PubMed1977

Submaximal and maximal working capacity of elite distance runners. Part II. Muscle fiber composition and enzyme activities.

The present study confirms earlier observations that the musculature of elite distance runners is characterized by a high predominance of ST fibers. Although the percent ST fibers effectively discriminates between good and elite distance runners, fiber composition alone is a poor predictor of distance running success within the group of elite runners. Muscle enzyme measurements suggest that the 11 to 20 miles (17.7 to 32.2 km) of daily training performed by the elite runners produced a significantly greater increase in muscle SDH activity than was observed in the good distance runners, who were running 7 to 11 miles (11.3 to 17.7 km) per day, Although such endurance training enhances the oxidative capacity of the muscle, it apparently has little influence on the enzymes of glycogenolysis.

Energy Metabolism↗
PubMed1976

Treatment of postoperative reactive hypoglycemia by a reversed intestinal segment.

Eleven men with disabling reactive hypoglycemia, in a range of 12 to 50 mg per 100 ml, were treated an average of seven years after gastric surgery with a 10 cm reversed jejunal segment. The reversal was placed at the gastric outlet in six patients and just below the ligament of Treitz in five. The former technic produced a somewhat better correction of hypoglycemia than did the latter. A good result was obtained in all eleven and none has had recurrence of seizures or fainting. Whereas the average minimal blood sugar before reversal was 34 mg per 100 ml, after reversal it was increased to 64 mg per 100 ml. The most severe hypoglycemia was noted in a patient after vagotomy and pyloroplasty. We recommend that all patients with dumping syndrome undergo glucose tolerance tests and plasma insulin determinations to ascertain whether they have reactive hypoglycemia. It is our conclusion that introduction of a reversed jejunal segment can control refractory reactive hypoglycemia resulting from previous gastric surgery.

Adult↗
PubMed1976

Muscle fiber composition and enzyme activities of elite distance runners.

Muscle biopsies were obtained from the gastrocnemius of 14 elite distance runners, 18 middle distance runners, and 19 untrained men. The middle distance runners were all highly trained, but had significantly slower performance times than the elite runners at distances greater than 3 miles. Fiber composition and mean cross-sectional areas were determined from muscle sections incubated for histochemical activity. A portion of the specimen was used to determine succinate dehydrogenase (SDH), lactate dehydrogenase (LD/Y and phosphorylase activities. All subjects were tested for maximal oxygen uptake on a treadmill. As previously demonstrated by others, the elite runners' muscles were characterized by a high percentage (79%) of slow twitch (ST) fibers. On the average, the crosssectional area of their ST fibers was found to be 22% larger than the FT fibers (P less than 0.05). SDH activity of whole muscle homogenates from elicte and middle distance runners was 3.4- and 2.8- fold greater, respectively, than that measured in the untrained men. Since the LDH and phosphorylase activities were similar for the runners and untrained men, it appears that training for distance running has little influence on the enzymes of glycogenolysis.

Glycolysis↗
PubMed1975

Leg muscle metabolism during exercise in the heat and cold.

In an effort to assess the effects of environmental heat stress on muscle metabolism during exercise, 6 men performed work in the heat (Tdb = 44 degrees C, RH = 15%) and cold (Tdb = 9 degrees C, RH = 55%). Exercise consisted of three 15-min cycling bouts at 70 to 85% VO2max, with 10-min rest between each. Muscle biopsies obtained from the vastus lateralis before and after each work bout were analyzed for glycogen and triglyceride content. Venous blood samples drawn before and after exercise were assayed for lactate, glucose, free fatty acids, hemoglobin, and hematocrit. Oxygen uptake, heart rates and rectal temperatures were all significantly higher during exercise in the heat. Blood lactate concentration was roughly twice as great during the heat experiments as that measured in the 9 degrees C environment. Muscle glycogen utilization per 60 min was significantly greater in the heat ( - 74 m moles/kg-wet muscle) as compared to the cold exercise (- 42 m moles/kg-wet muscle). On the average, muscle triglyceride declined 23% during exercise in the cold and 11% in the heat. The findings of an enhanced glycolysis during exercise in the heat is compatible with earlier studies which demonstrate a decreased availability of oxygen due to a reduction in muscle blood flow.

Adult↗