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Biomedical subjects

F Brouns

Publications and source records attributed to F Brouns.

87 records · Page 5Linked to original sources
PubMed1989

Eating, drinking, and cycling. A controlled Tour de France simulation study, Part II. Effect of diet manipulation.

Field studies during the Tour de France indicated that cyclists consume 30% of daily energy intake as liquid carbohydrate (CHO)-enriched nutrition with the goal of maintaining energy and CHO balance. The aim of the present investigation was to study the effect of such dietary manipulation during 2 days of long-lasting exhausting cycling on food and fluid intake, energy balance, nitrogen balance, and nutrient oxidation. Thirteen highly trained cyclists were divided into two subgroups receiving ad libitum either a primarily maltodextrin-based beverage (Mf) (20% w/v, 85% maltodextrin, 15% fructose) or a 50/50% composed fructose-maltodextrin (FM) beverage in addition to their normal diet. The study was performed during a 7-day stay in a respiration chamber (2 preparation days, 1 standardized resting day, 2 cycling days, 1.5 standardized recovery days), allowing for continuous gas analysis, weighed food and fluid intake procedure, and collection of excretes. The data of this study were compared with data from the same subjects receiving a normal CHO-rich diet (N) (60 En%) in a separate experiment. The results showed that the cyclists receiving Mf were able to maintain EB during sustained exercise days in contrast to when receiving N and to subjects receiving FM. With Mf treatment CHO intake increased, up to 80 En% (17.5 +/- 1.0 g.kg-1 BW) and carbohydrate balance remained positive. The subjects receiving FM had the largest CHO oxidation, calculated from R. Protein oxidation significantly increased in N and FM as a result of exercise but not in Mf. The latter subjects were in slightly negative nitrogen balance at a protein intake level of 1.4 g.kg-1 BW.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Metabolic changes induced by sustained exhaustive cycling and diet manipulation.

Thirteen highly trained subjects were studied concerning the effect of consuming a normal carbohydrate-rich diet (N) on energy exchange, substrate metabolism, and performance. Six of these subjects performed the same protocol receiving N supplemented with a high-maltodextrin, low-fructose beverage (Mf). The studies were performed in random order. The subjects performed 2 days of sustained exhausting cycling, preceded and followed by a standardized resting day, in a respiration chamber, allowing continuous gas analysis, weighed food and fluid intake procedures, collection of excretes, and drawing of blood samples at 7:00 AM, 12:00 AM (halfway exercise) and 3:00 PM at exhaustion. Muscle biopsies were taken prior to, 45 min after, and 24 h after exercise (energy expenditure 25.2-26.6 MJ.day-1). The results showed that while consuming a normal diet, the cyclists developed a negative energy balance (-9 MJ.day-1) and regulated their hormone levels in such a way that fat oxidation and protein breakdown were increased and CHO oxidation became depressed. When supplemented with Mf, the subjects showed increased blood glucose, insulin and decreased glucagon levels. Fat metabolism was significantly depressed as indicated by the levels of blood fatty acids, glycerol, and ketones. A significant glycogen sparing, as well as supercompensation within 24 h of recovery, was observed after Mf supplementation. The normal CHO-rich diet, available ad libitum, was insufficient to fully restore glycogen within 24 h. The changes in substrate availability and glycogen depletion were accompanied by a significant performance improvement, 126% when cycling a final 90% Wmax bout, when supplemented with Mf compared with N.

Adult↗
PubMed1989

Glycogen synthesis during exercise and rest with carbohydrate feeding in males and females.

Since it has been demonstrated that endurance-trained cyclists are able to synthesize glycogen during mild exercise, glycogen synthesis was investigated in non-endurance-trained males and females as well. Seven males and nine females exercised on a cycle ergometer to deplete muscle glycogen. After the exhaustive exercise and taking a muscle biopsy, the males either exercised 2.5 h at 40% of maximal work load (trial A) or rested for 2.5 h (trial B). In both trials the subjects drank a 25% maltodextrin-fructose solution. After 2.5 h of exercise or rest, a second muscle biopsy was taken for determination of glycogen and for histochemistry (ATPase and PAS). In the females glycogen synthesis was only studied during 2.5 h rest, after prior glycogen depletion. In the male subjects, during mild exercise with carbohydrate feeding muscle glycogen did not increase. During rest muscle glycogen increased in the males from 123 +/- 49 mmol/kg DW at exhaustion to 229 +/- 70 mmol/kg DW (P less than 0.001), resulting in a net increase of 42 mmol/kg DW/h. Glycogen synthesis during rest occurred both in type I and type II fibers. In the females, during 2.5 h of rest, muscle glycogen increased from 130 +/- 56 mmol/kg DW at exhaustion to 224 +/- 51 mmol/kg DW, resulting in a net increase of 37 mmol/kg DW/h. The results demonstrate that glycogen synthesis during mild exercise does not occur in non-endurance-trained athletes, whereas in the resting state glycogen synthesis in non-endurance-trained males is not different from endurance-trained cyclists. In addition, glycogen synthesis during rest is similar in males and females.

Adult↗
PubMed1989

Effect of carbohydrate intake during warming-up on the regulation of blood glucose during exercise.

It has been shown that the intake of carbohydrate (CHO)-containing beverages under resting conditions may lead to a rebound hypoglycemia and decreased performance when exercise is performed thereafter. The aim of the present investigation was to study the effect of CHO beverage consumption with different CHO sources and different concentrations, during warming-up under practice-like circumstances, on the regulation of blood glucose during exercise. Eighteen highly trained cyclists consumed a standardized breakfast at 8:00 AM and performed a warming-up procedure at 10:00 AM for 20 min. Warming-up was followed by a 7-min break after which the subjects cycled for 45 min at a heart rate of 150. During warming-up a CHO-containing beverage (either sucrose, fructose, maltodextrin, or glucose) or a placebo was consumed in random order. The test was performed twice, with 300 ml and 600 ml intake, to study a possible dose-response effect. The results of the study showed that warming-up and final exercise lead to an increase of the catecholamines and a decrease of insulin. During the 7-min break this response was reversed. Glucose and maltodextrin induced the same insulin response. Increasing volume and higher CHO concentrations induced a longer increase in blood glucose level compared with the placebo intake. The results showed that intake of CHO-containing beverages during warming-up followed by a small break does not lead to rebound hypoglycemia, independent of the amount of CHO ingested, but instead increases blood glucose.

Adult↗
PubMed1989

Adequacy of vitamin supply under maximal sustained workloads: the Tour de France.

In the Tour de France competing cyclists must pedal about 4000 km over a period of three weeks with only one day allowed for rest. The course includes 30 mountains, the highest of which reaches an altitude of approximately 2700 m. The energy expenditure values of these cyclists range from a mean of 25.4 MJ/day to peak values of 32.7 MJ/day. These are the highest values that have ever been reported for a period longer than seven days. On the basis of the food records of 5 cyclists, it turned out that 62 En.% is derived from CHO, 15 En.% from protein, and 23 En.% from fat. Since the food choice is primarily focused on digestibility and energy content, this results in a frequent consumption of sweet cakes and CHO-rich fluids. Some 49% of the energy is consumed in between meals. Such a nutritional pattern leads to a lowering of the nutrient density especially with respect to the B-vitamins. Intake of vitamins B1, B2, B6, and C, including contribution from enriched sport drinks, was 1.97 mg, 4.96 mg, 2.40 mg, and 158 mg, respectively. Besides this, intramuscular injections of megadosis vitamins of B1, B2, B6, nicotinamide, pantothenic acid, and especially B12 did increase the intake drastically. This was reflected in high blood concentrations of vitamins. Except for folic acid, vitamins (B1, B2, B6, and B12) exceeded the upper limits of the values from a reference group, particularly B12, which exceeded the reference values by up to 400%. During the Tour, vitamin concentrations remained essentially unchanged.

Bicycling↗
PubMed1989

Exercise and training effects on gastric emptying of carbohydrate beverages.

Carbohydrate containing drinks are commonly consumed as an ergogenic aid during endurance sports activities. The efficacy of a given drink is limited by the rate of absorption, which is in turn limited by gastric emptying. A myriad of factors influence gastric emptying. The influence of several of these factors (training status, exercise intensity, and carbohydrate composition) was investigated by repeated experiments using a nasogastric tube and a modification of the technique of George. A group of well-trained bicyclists and a group of untrained subjects performed similar experiments. Three different carbohydrate containing drinks (15 g.100 ml-1 glucose (G), 15 g.100 ml-1 maltodextrin plus 3 g.100 ml-1 fructose (MD), 7 g.100 ml-1 sucrose (I] and artificially sweetened water were compared during rest and 50 and 70% Wmax bicycling. Experimental design was crossover. There was a trend for the carbohydrate drinks to empty initially more slowly under the influence of exercise. Differences in drink volume remaining in the stomach were significant (P less than 0.05), with I at 10 min (70%, mean = 48.9%; rest, mean = 30.5%) and at 20 min (70%, mean = 28.9%; rest, mean = 23.8%) and with MD at 10 min (70%, mean = 71.1%; rest, mean = 55.9%). A similar trend was also seen with 50% Wmax exercise; however, this trend was only significant with MD at 10 min (50%, mean = 72.1%; rest, mean = 55.9%). Drink composition was a much stronger inhibitor of gastric emptying. However, all drinks emptied exponentially with fast-phase initial emptying rates. No differences in gastric emptying or secretion were observed between trained and untrained subjects.

Adolescent↗
PubMed1988

Determination of total gastric volume, gastric secretion and residual meal using the double sampling technique of George.

In literature several techniques are described for the measurement of gastric emptying. One of these is the double sampling technique of George which has the advantage that it enables multiple measurements of total gastric volume in one experiment. In order to estimate net gastric emptying, however, it is important to differentiate between the test meal volume present in the stomach and gastric secretion. In the present study George's technique was extended with a calculation procedure to estimate gastric secretion and net test meal outflow. An in vitro experiment was carried out which showed an accuracy of 5-10% for this method. An in vivo comparison was made with Hunt's chloride technique, which is used for estimating gastric secretion. Sixteen subjects participated in a 60 minute test with water as a test meal. Regression analysis showed a high degree of correlation (R2 = 0.99) between Hunt's method and the proposed method. The data obtained indicate that the proposed method gives a reliable estimation of net gastric emptying and is simple to do as no further measurements have to be carried out other than those needed for George's method.

Adult↗
PubMed1988

Comparison of doubly labeled water with respirometry at low- and high-activity levels.

In previous studies the doubly labeled water method for measuring energy expenditure in free-living humans has been validated against respirometry under sedentary conditions. In the present investigation, energy expenditure is measured simultaneously with doubly labeled water and respirometry at low- and high-activity levels. Over 6 days, five subjects were measured doing mainly sedentary activities like desk work; their average daily metabolic rate was 1.40 +/- 0.09 (SD) times sleeping metabolic rate. Four subjects were measured twice over 3.5 days, including 2 days with heavy bicycle ergometer work, resulting in an average daily metabolic rate of 2.61 +/- 0.25 (SD) times sleeping metabolic rate. At the low-activity level, energy expenditures from the doubly labeled water method were on the average 1.4 +/- 3.9% (SD) larger than those from respirometry. At the high-activity level, the doubly labeled water method yielded values that were 1.0 +/- 7.0% (SD) lower than those from respirometry. Results demonstrate the utility of the doubly labeled water method for the determination of energy expenditure in the range of activity levels in daily life.

Adult↗
PubMed1987

Carbohydrate feeding and glycogen synthesis during exercise in man.

In 7 male cyclists glycogen synthesis during exercise and rest was studied. Each subject did two exercise trials (A and B), in random order. In both trials, after determining the maximal workload (Wmax), intermittent exercise was given to exhaustion. After the exhaustive exercise and taking a muscle biopsy the subjects either exercised at 40% Wmax for 3 h (trial A) or rested for 3 h (trial B), during which they consumed approximately 2 l of a 25% malto-dextrine drink in both trials. After 3 h rest (trial A) or 3 h of mild exercise (trial B) a second muscle biopsy was taken for total glycogen and histochemistry (ATPase and PAS). Blood glucose and insulin levels were elevated during the first 2 h of exercise (p less than 0.05). Glycogen depletion was most pronounced in type I and to a less extent in type IIA fibers. In trial A muscle glycogen increased from 136 +/- 66 to 199 +/- 71 mmol/kg DW, and in trial B from 145 +/- 56 to 257 +/- 79 mmol/kg DW. During exercise glycogen repletion was restricted to type IIA and IIB fibers, whereas during rest glycogen synthesis occurred both in type I and type II fibers. The present study demonstrates that oral carbohydrate administered during exercise may not only provide substrate for energy metabolism, but can also be utilized for glycogen synthesis in the non-active muscle fibers.

Adult↗
PubMedDate not supplied

Effects of 2-week ingestion of (-)-hydroxycitrate and (-)-hydroxycitrate combined with medium-chain triglycerides on satiety and food intake.

The aim of this study was to assess the effects of 2 weeks of supplementation with (-)-hydroxycitrate (HCA) and HCA combined with medium-chain triglycerides (MCT) on satiety and energy intake. The experimental design consisted of three intervention periods of 2 weeks separated by washout periods of 2 or 6 weeks in a double-blind, placebo-controlled, randomized, and crossover design. Seven male and 14 female normal to moderately obese subjects (mean+/-S.D.; age, 43+/-10 years; body mass index, 27.6+/-2.0 kg/m(2)) participated in this study. Subjects consumed three self-selected meals and four isoenergetic snacks daily with either no supplementation (PLA), with 500 mg HCA (HCA), or 500 mg HCA and 3 g MCT (HCA+MCT). Each intervention period ended with a test day, consisting of a standardized breakfast and ad libitum a lunch and a dinner. There was a significant body weight (BW) loss during the 2 weeks of intervention (PLA, -0.5+/-0.3 kg, P<.05; HCA, -0.4+/-0.2 kg, P<.05; HCA+MCT, -0.7+/-0.2 kg, P<.01), but this reduction was not different between treatments. Twenty-four-hour energy intake (PLA, 8.1+/-0.3 MJ; HCA, 8.3+/-0.3 MJ; HCA+MCT, 8.4+/-0.3 MJ) and the area under the curve of the appetite-related parameters during the test day were similar for all treatments. Two weeks of supplementation with HCA and HCA combined with MCT did not result in increased satiety or decreased energy intake compared to placebo in subjects losing BW.

Adult↗
PubMedDate not supplied

Osmolarity does not affect the gastric emptying rate of oral rehydration solutions.

BACKGROUND: The objective of this study was to determine the effect of either carbohydrate content or osmolarity on gastric emptying rate in normal healthy subjects. METHODS: In total 12 test drinks were ingested as a single 8 mL/kg per body weight bolus on an empty stomach. Six of these drinks had a different carbohydrate content, increasing stepwise from 45 to 90 g/L, but all with the same osmolarity (330 mOsm/kg). The other six drinks all contained 60 g carbohydrate/L but differed stepwise in osmolarity because of the use of maltodextrins with a difference in chain length (243 to 374 mOsm/kg). RESULTS: The results show a significant negative relation between carbohydrate content and gastric emptying in the six drinks with a uniform osmolarity but progressively increasing carbohydrate content. The six drinks, which had the same carbohydrate-energy content but different osmolarities, emptied all at the same rate from the stomach. The delivery of carbohydrate-energy per minute from the stomach to the small intestine was the same for all drinks. CONCLUSIONS: From these data we conclude that the rate of gastric emptying of carbohydrate-containing solutions is triggered by the carbohydrate-energy drink content or by the delivery rate of carbohydrate-energy to the gut. Osmolarity in the range studied here had no effect.

Administration, Oral↗
PubMedDate not supplied

Infection assessment of totally implanted long-term venous access devices.

AIM: Comparison of catheter tip versus port content culture techniques to assess infection in totally implanted vascular access devices (TIVAD). MATERIALS AND METHODS: Comparison of pocket swab, catheter-tip and port content cultures after removing the silicon puncture septum in a prospectively collected consecutive series of 102 TIVAD removed for clinical suspicion of infection, between May 2000 and March 2003. RESULTS: 102 totally implanted port-catheters in 98 patients, age ranging from 1 to 90 years (median 53 years), were removed 7 to 2616 days after insertion (median 210 days). Infection of the pocket surrounding the port was found in 21 cases, all proven by a positive culture of the pocket swab. Out of the remaining 81 cases without pocket infection, 32 had only a positive catheter tip culture, whereas 56 had a positive port content culture (p = 0.0002). Always the same microorganism was isolated in the 32 patients with positive catheter tip and port content cultures. The main organisms identified within TIVAD were Coagulase Negative Staphylococcus (CNS) (41 cases) and Candida sp (15 cases). Eight out of the 21 pocket infections were caused by Staphylococcus aureus. CONCLUSION: In the presence of local signs of infection, taking cultures of the pocket surrounding the port is sufficient for diagnostic purposes. When infection is localized within the device only, port content cultures taken after removal of the silicon septum are more often positive than cultures of the catheter tip, and constitute therefore a more reliable tool for the assessment of TIVAD infection.

Adolescent↗