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Biomedical subjects

F Brouns

Publications and source records attributed to F Brouns.

At least 19 recordsLinked to original sources
PubMed1992

Physiological changes and gastro-intestinal symptoms as a result of ultra-endurance running.

One hundred and seventy-two competitors of the Swiss Alpine Marathon, Davos, Switzerland, 1988, volunteered for this research project. Of these volunteers 170 (158 men, 12 women) finished the race (99%). The race length was 67 km with an altitude difference of 1,900 m between the highest and lowest points. Mean age was 39 (SEM 0.8) years. Average finishing times were 8 h 18 min (men) and 8 h 56 min (women). Loss of body mass averaged 3.4% body mass [mean 3.3 (SEM 0.2)%; 4.0 (SEM 0.4)%; men and women, respectively]. Blood samples from a subgroup of 89 subjects (6 women and 83 men) were taken prior to and immediately after completion of the race. Changes in haemoglobin (9.3 mmol.l-1 pre-race, 9.7 mmol.l-1 post-race) and packed cell volume (0.44 pre, 0.48 post-race) were in line with the moderate level of dehydration displayed by changes in body mass. Mean plasma volume decreased by 8.3%. No significant changes in plasma osmolality, sodium, or chloride were observed but plasma potassium did increase by 5% (4.2 mmol.l-1 pre-race, 4.4 mmol.l-1 post-race). Mean fluid consumption was 3290 (SEM 103) ml. Forty-three percent of all subjects, and 33% of those who gave blood samples, complained of gastro-intestinal (GI) distress during the race. No direct relationship was found between the quantity or quality of beverage consumed and the prevalence of GI symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Exogenous carbohydrate oxidation from maltose and glucose ingested during prolonged exercise.

Intestinal perfusion studies have shown that glucose absorption from maltose occurs faster than from isocaloric glucose. To determine whether ingested maltose might be a superior source of carbohydrate (CHO) for endurance athletes, we compared the rates of gastric emptying, absorption and oxidation of 15 g.100 ml-1 solutions of maltose and glucose. Six endurance-trained cyclists drank 1200 ml of either U-14C maltose or U-14C glucose as a 400-ml loading bolus immediately before exercise, and as 8 x 100-ml drinks at 10-min intervals during a 90-min ride at 70% of maximal oxygen consumption. The rates of gastric emptying [maltose 690 (SD 119) ml.90 min-1; glucose 655 (SD 93) ml.90 min-1], the appearance of U-14C label in the plasma, and the peak rates of exogenous CHO oxidation [maltose 1.0 (SD 0.09) g.min-1; glucose 0.9 (SD 0.09) g.min-1] were not significantly different. Further, the 51 (SD 8) g of maltose and the 49 (SD 9) g of glucose oxidised during exercise were similar. Each accounted for approximately 20% of the total CHO oxidised during the 90 min of exercise. Since only half of the CHO delivered to the intestine was oxidised in the 90-min ride (maltose 49%; glucose 50%), we conclude that neither the rate of gastric emptying, nor digestion limited the rate of ingested CHO utilisation during the early stages of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Gastric emptying of carbohydrate--medium chain triglyceride suspensions at rest.

Nine male volunteers participated in 4 gastric emptying (GE) tests of liquid equicaloric mixtures of CHO (maltodextrins) and MCT of the following composition (% CHO-% MCT): Drink (Dr) 1:70%-30%, Dr2: 80%-20%, Dr3: 90%-10%, Dr4: 100%-0%. GE was measured at rest for 90 min according to the modified double sampling technique. GE rate, expressed as t1/2 (SEM), was 23 (2.3), 24 (1.6), 27 (2.2) and 36 (2.9) min, respectively, from drink 1 to drink 4. Statistical analysis showed that all MCT containing drinks emptied faster than the 100% CHO drink. Two mechanisms may explain this observation: 1) the CHO content and osmolality increases from Dr 1 to Dr 4 (both are regulators of GE); 2) MCT may not inhibit GE as common fat does, due to a better water solubility and absorption in the small intestine, resulting in a decreased duodenal-gastric feedback.

Adult↗
PubMed1992

Nutritional aspects of health and performance at lowland and altitude.

One of the most important nutritional goals amongst athletes is to maintain adequate energy and fluid balance, since these are subject to relatively rapid changes and are directly related to performance and health. This may especially be the case when exercise intensity is high. Furthermore, when due to exercise and environmental stress food and fluid intake become depressed. In such conditions there may be a dramatic increase in the utilization of carbohydrate (CHO), fluid, and in some instances protein. These increased requirements may then not be covered. Insufficient replacement of CHO may lead to hypoglycemia, altered protein metabolism, central fatigue and exhaustion. Large sweat losses may pose a risk to health by inducing severe dehydration, impaired blood circulation and heat transfer, leading to heat exhaustion and collapse. Inadequate CHO and protein intake leads to a negative nitrogen balance, which over the long term will lead to a loss of muscle mass. In the scope of this presentation we will refer to the most important nutritional factors which are known to affect performance over a short term, at sea level and altitude.

Altitude↗
PubMed1992

Gastrointestinal complaints in relation to dietary intake in triathletes.

This study examined the relationship between gastrointestinal (GI) symptoms and dietary intake in triathletes. Fifty-five male triathletes (age 31 +/- 6 yrs) were surveyed regarding the most recently completed half Iron Man triathlon. Questions were asked regarding GI symptoms and dietary intake. Fifty-two percent complained of eructation and 48% of flatulence. Other symptoms were abdominal bloating, vomiting urge, vomiting, nausea, stomachache, intestinal cramps, and diarrhea. More symptoms occurred while running than at other times. All individuals who had eaten within 30 min of the start vomited while swimming. Fat and protein intake was greater in those who vomited or had the urge to vomit than in those without these symptoms. Of the former, 93% had consumed a hypertonic beverage. Forty percent of those who drank a hypertonic beverage and only 11% of those who drank an iso- or hypotonic beverage had severe complaints. Four of five individuals with stomachache had consumed a strongly hypertonic beverage. All subjects with intestinal cramps had eaten fiber-rich foods in the prerace meal; only 10% of those without cramps had done so.

Adult↗
PubMed1992

Rationale for upper limits of electrolyte replacement during exercise.

The addition of carbohydrate and sodium to sport drinks has been recommended to enhance fluid intake and absorption and to delay fatigue. Other electrolytes (E) which are lost through sweating are also commonly added. However, too many E may lead to increased serum E and osmolality levels, which may negatively influence thermoregulation, depress sweating, and cause gastrointestinal distress. On the other hand, drinking large amounts of plain water to compensate sweat loss may induce hyponatremia. Therefore, literature describing sweat E losses was examined in order to estimate average whole-body E loss and to determine an upper limit for replacement of E with sport drinks. Mean E loss was determined from 13 studies, with +/- 1 SD resulting in a hypothetical range for E losses. Correction for net absorption resulted in an upper limit fo electrolyte replacement. It is suggested that the E levels in sport rehydration drinks should not exceed the upper limit of the range given.

Electrolytes↗
PubMed1992

Gastric emptying, absorption, and carbohydrate oxidation during prolonged exercise.

This study was designed to examine aspects of digestive function that may limit assimilation of water and oxidation of orally ingested carbohydrate (CHO) during exercise. Eight males completed a crossover study in which each cycled on four occasions for 80 min at 70% maximal O2 consumption. Beverage was consumed at 0, 20, 40, and 60 min. Beverages were water, 4.5% glucose (4.5G), 17% glucose (17G), and 17% maltodextrin (17MD). CHO beverages contained 20 meq/l NaCl and were 13C enriched to measure exogenous CHO oxidation. Gastric (beverage) volume was measured at 80 min. Water uptake was estimated by including 2H2O in the beverage and measuring 2H accumulation in blood. Jejunal perfusion tests were conducted at rest with the same subjects and beverages. In 60 min, 1,294 +/- 31 (SE) ml were ingested; at 80 min, volumes emptied with H2O (1,257 +/- 32 ml) and 4.5G (1,223 +/- 32 ml) were greater than with 17G (781 +/- 56 ml) and 17MD (864 +/- 71 ml; P less than 0.05). Total CHO oxidized was similar with all beverages, but there was a greater increase in exogenous CHO oxidation over time with 17G and 17MD than with 4.5G; 54, 19, and 18% of the CHO ingested with 4.5G, 17G, and 17MD, respectively, was oxidized. This represents 57, 32, and 27%, respectively, of the CHO emptied from the stomach. 2H accumulation in the blood was more rapid with H2O and 4.5G than with 17G or 17MD. Net jejunal water absorption was greater from 4.5G than from water. Net water absorption was also observed from 17MD, whereas net secretion was observed with 17G.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Energy expenditure climbing Mt. Everest.

Weight loss is a well-known phenomenon at high altitude. It is not clear whether the negative energy balance is due to anorexia only or an increased energy expenditure as well. The objective of this study was to gain insight into this matter by measuring simultaneously energy intake, energy expenditure, and body composition during an expedition to Mt. Everest. Subjects were two women and three men between 31 and 42 yr of age. Two subjects were observed during preparation at high altitude, including a 4-day stay in the Alps (4,260 m), and subsequently during four daytime stays in a hypobaric chamber (5,600-7,000 m). Observations at high altitude on Mt. Everest covered a 7- to 10-day interval just before the summit was reached in three subjects and included the summit (8,872 m) in a fourth. Energy intake (EI) was measured with a dietary record, average daily metabolic rate (ADMR) with doubly labeled water, and resting metabolic rate (RMR) with respiratory gas analysis. Body composition was measured before and after the interval from body mass, skinfold thickness, and total body water. Subjects were in negative energy balance (-5.7 +/- 1.9 MJ/day) in both situations, during the preparation in the Alps and on Mt. Everest. The loss of fat mass over the observation intervals was 1.4 +/- 0.7 kg, on average two-thirds of the weight loss (2.2 +/- 1.5 kg), and was significantly correlated with the energy deficit (r = 0.84, P < 0.05). EI on Mt. Everest was 9-13% lower than during the preparation in the Alps.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[The effect of beverage composition and gastrointestinal function on fluid and nutrient availability during physical exertion: e review].

Intensive exercise affects digestion and absorption. Nevertheless, athletes involved in intensive endurance exercise are advised to ingest fluid and energy supplying nutrients, to compensate for the losses and to delay fatigue. The present review describes the effects of exercise on the gastrointestinal tract and the aspects which determine optimal fluid and nutrient delivery during exercise in different climatological and exercise conditions.

Carbohydrate Metabolism↗
PubMed1991

Heat--sweat--dehydration--rehydration: a praxis oriented approach.

In any situation where heat production as a result of physical exercise exceeds heat elimination from the body by radiation and convection, the body will depend on sweat secretion and evaporation for its thermoregulation. Sweat secretion will reach maximal levels at high energy expenditures in the heat but will be limited when exercising in the cold climate. Athletes and their coaches should understand some of the principles of thermoregulation in order to make an adequate decision about optimal fluid and carbohydrate replacement in a specific situation. In general it is advised that the carbohydrate content of rehydration drinks should be low (max 80 g l-1) when sweat loss is maximal, may be intermediate when both carbohydrate availability and moderate dehydration influence performance (up to 110 g l-1), and may be maximal (up to 160 g l-1) when the sweat loss is minimized and carbohydrate is the major determinant of the rate of fatigue development. Sodium should be added to rehydration drinks in order to maximize fluid and carbohydrate absorption. A range of electrolyte values for replacement of sweat induced losses, based on whole body wash down procedure is presented.

Body Temperature Regulation↗
PubMed1991

Carbohydrate supplementation, glycogen depletion, and amino acid metabolism during exercise.

Eight highly trained cyclists were studied during exercise after glycogen depletion (test A) and during carbohydrate (CHO) loading (test B). In test B subjects were able to complete 2 h of exercise at 70-75% maximal workload (Wmax), whereas the initial intensity of 70% Wmax had to be reduced to 50% in test A. Plasma ammonia increased more rapidly, and plasma alanine, glutamate, and glutamine were lower in test A. Exercise caused a 3.6-fold increase in the proportion of active branched-chain 2-oxoacid dehydrogenase (BC) complex in muscle in test A. No activation occurred in test B. There was an inverse correlation between the activity of the BC complex and the glycogen content of the postexercise biopsies. Exercise did not cause changes in the muscle content of ATP, ADP, AMP, IMP, hypoxanthine, and lactate. It is concluded that CHO loading abolishes increases in branched-chain amino acid (BCAA) oxidation during exercise and that part of the ammonia production during prolonged exercise originates from deamination of amino acids. The data appear to confirm the hypothesis (A.J. M. Wagenmakers, J.H. Coakley, and R.H.T. Edwards. Int. J. Sports Med. 11: S101-S113, 1990) that acceleration of the BCAA aminotransferase reaction may drain the tricarboxylic acid cycle and that glycogen is a carbon chain precursor of tricarboxylic acid cycle intermediates and glutamine.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1991

High rates of exogenous carbohydrate oxidation from starch ingested during prolonged exercise.

This study compared the gastric emptying and oxidation of two 15% carbohydrate (CHO) solutions: a 22-chain-length glucose polymer (GP) and soluble starch (SS). Six endurance-trained subjects ingested 1,200 ml of either GP or SS while cycling for 90 min at 70% of maximal oxygen consumption (VO2max). Whereas the calculated total CHO oxidation (GP 266.8 +/- 41.9 g; SS 263.6 +/- 28.9 g) and the volume emptied from the stomach (GP 813 +/- 130 ml; SS 919 +/- 116 ml) were similar, the appearance of the 14C label in plasma occurred more rapidly from ingested SS than from GP (P less than 0.001). This resulted in a significantly greater rate of SS oxidation than that from GP (SS 105.9 +/- 21.9 g, GP 49.6 +/- 10.2 g; P less than 0.001). Exogenous CHO oxidation from GP accounted for 19% of total CHO oxidation, whereas the corresponding value for SS was 40%. This study suggests that the oxidation of SS and GP solutions ingested during exercise at 70% VO2max is not limited by gastric emptying. Rather, it appears to be either the rate of digestion or absorption of these solutions that determines their utilization.

Adult↗
PubMed1991

Daily variation in gastric emptying when using the double sampling technique.

The purpose of this study was to establish the intra-individual variation in the rate of gastric emptying (GE) by using the double sampling technique of George. Eight healthy male volunteers, all familiar with gastric intubation and testing, participated in four GE tests, using an isotonic fluid as a test meal. Conditions were kept constant during all four tests, and each test was separated by at least 48 h. The within-subjects coefficient of variation proved to be 29%. The findings demonstrate that, given standard conditions, GE is reproducible from day to day.

Adult↗
PubMed1990

Gastric emptying with repeated drinking during running and bicycling.

The high prevalence of gastrointestinal complaints in long-distance runners makes the movements specific to this type of exercise suspected of causing a disruption of normal gastrointestinal function. Gastric emptying rate is one indicator thereof. In the present study trained volunteers performed similar repeated fluid ingestion tests while running and while bicycling for 80 min at 70% VO2max. Control tests at rest were also conducted. Two drinks containing carbohydrate were tested, one hypertonic, and one isotonic. Artificially sweetened water was used as a control. Gastric emptying rate of the isotonic drink, expressed as a percentage of the volume in the stomach at the beginning of each measurement period, did not differ between cycling and running during the first 40 min and was faster during cycling than during running between 40 and 80 min. With the hypertonic drink no differences between cycling and running were observed. In comparing gastric emptying rates after each sequential bolus, at rest, the isotonic drink was observed to maintain a high emptying rate, equal to that of water, whereas the hypertonic drink emptied more slowly after the first 20-min period. A similar pattern was observed during both running and cycling. The isotonic drink continued to empty quickly after the initial 20 min, whereas GE rate of the hypertonic drink decreased after the initial 20 min.

Adult↗
PubMed1990

Ammonia accumulation during highly intensive long-lasting cycling: individual observations.

In a number of individual cycling tests lasting 2.5-5 h with alternating exercise intensities of 50%-85% of maximal working capacity, it was observed that plasma ammonia levels may rise above 250 mumol/l when reaching exhaustion, while lactate levels remain relatively low. Acute quantitative ammonia production during intensive endurance exercise may be enhanced by a reduced glycogen availability in muscle. However, adequate amounts of glycogen itself do not prevent ammonia production when exercise is at high intensity and long-lasting. The continuous ammonia accumulation in blood during endurance exercise in trained individuals may be the result of a relatively low blood flow to the liver and thereby low clearance in contrast to lactate which may not accumulate due to a high clearance rate in both active and nonactive oxidative muscle fibers. In a number of subjects it was observed that exhaustion, when performing endurance exercise at high exercise intensities, occurred when plasma ammonia levels were high. Muscle cramps occurred in subjects who reached their highest individual ammonia values and seemed not to be related to serum potassium, plasma lactate, or muscle glycogen. These individual observations give rise to the hypothesis that high intramuscular ammonia levels may be related to the etiology of muscle exhaustion and muscle cramping during highly intensive endurance exercise.

Ammonia↗
PubMed1990

Effects of dehydration on gastric emptying and gastrointestinal distress while running.

Gastrointestinal distress is commonly reported by athletes after ingestion of a beverage. We speculate that ingestion may be occurring after dehydration has taken place. The high prevalence of GI disorders in marathon runners who have lost greater than or equal to 4% body weight supports this theory. To test this theory, the effects of dehydration, and dehydration in combination with endurance running, on gastric emptying (GE) and frequency of gastrointestinal (GI) complaints were tested in this experiment. A complete cross-over study was designed. Sixteen subjects ingested 8 ml.kg BW-1 of a 7% carbohydrate (296 mOsm.kg-1), solution after a euhydration or dehydration regime. Dehydration (4% BW loss) was produced by 60% maximal speed running at 30 degrees C or by intermittent sauna exposure at 100 degrees C. Euhydration experiments were conducted with a 2 h rest period with water administered at 20 and 40 min. Gastric drink volumes were measured every 10 min for 40 min. Emptying curves were compared using semi-log transformation of the percentage emptying data and simple linear regression. The slope of each line was used as a measure of average GE rate. Dehydration-exercise resulted in slower GE than in all other treatments (P less than 0.05). ANOVA revealed significant effects of dehydration (P less than 0.05) and exercise (P less than 0.05), these two effects being additive in delaying GE. GI complaints were reported by 37.5% of the subjects during dehydration-exercise experiments. No GI disturbance was reported in other tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Fluid intake and gastrointestinal problems in runners competing in a 25-km race and a marathon.

A group of 114 previously untrained subjects, 31 females and 83 males, was followed for 18 months while training for a marathon. Forty-four of the subjects completed a survey regarding fluid intakes and gastrointestinal (GI) disturbances during competition for both their first 25-km race (run after 1 year of training) and their first marathon. GI problems were common. Among the individuals surveyed, 25% had GI complaints in the 25-km race. In the marathon, 52% complained of GI distress. In general, fluid consumption was low (25 km means = 109 ml; marathon w = 577 ml). Body weight losses in the marathon were substantial (w = 3.2%, BW; range 1.5%-6.2%) indicating sweat losses greater than fluid replacement. These losses were greater in men than in women (men w = 3.4% BW; women w = 2.6% BW). GI complaints were not associated with larger drink intakes. In contrast, dehydration above a certain limit appears to increase the frequency of GI disorders. In the marathon, 80% of the runners who lost greater than 4% BW had GI problems. It is possible that reduced blood flow to the GI region is compromised via the exercise itself as well as by a reduced blood volume, which may disrupt normal secretion/absorption of the digestive tract. It may also be that a rising core body temperature, associated with decreased sweating at high levels of dehydration, may be related to GI dysfunction.

Adult↗