Search

Abstract Objectives--(a) To investigate the effects of reduced training on physical condition and performance in well trained cyclists; (b) to study whether an intermittent exercise programme would maintain physiological training [...]

Background/objectives: To investigate (1) the association of four VDR polymorphisms (TaqI/rs731236, ApaI/rs7975232, FokI/rs10735810, and Bsml/rs1544410) with markers of adiposity and tissue-specific insulin resistance at baseline, after weight loss and weight maintenance; (2) the effect of the VDR polymorphisms in the SAT transcriptome in overweight/obese Caucasians of the DiOGenes cohort. Methods: We included 553 adult obese individuals (mean BMI 34.8 kg/m2), men (n= 197) and women (n= 356) at baseline, following an 8-week weight loss intervention and 26 weeks weight maintenance. Genotyping was performed using an Illumina 660W-Quad SNP chip on the Illumina iScan Genotyping System. Tissue-specific IR was determined using Hepatic Insulin Resistance Index (HIRI), Muscle Insulin Sensitivity Index (MISI), and Adipose Tissue Insulin Resistance Index (Adipo-IR). Expression quantitative trait loci (eQTL) analysis was performed to determine the effect of SNPs on SAT gene expression. Results: None of the VDR polymorphisms were associated with HIRI or MISI. Interestingly, carriers of the G allele of VDR FokI showed higher Adipo-IR (GG + GA 7.8 ± 0.4 vs. AA 5.6 ± 0.5, P= 0.010) and higher systemic FFA (GG + GA: 637.8 ± 13.4 vs. AA: 547.9 ± 24.7 µmol/L, P= 0.011), even after adjustment with age, sex, center, and FM. However, eQTL analysis showed minor to no effect of these genotypes on the transcriptional level in SAT. Also, VDR polymorphisms were not related to changes in body weight and IR as result of dietary intervention (P> 0.05 for all parameters). Conclusions: The VDR Fokl variant is associated with elevated circulating FFA and Adipo-IR at baseline. Nevertheless, minor to no effect of VDR SNPs on the transcriptional level in SAT, indicating that putative mechanisms of action remain to be determined. Finally, VDR SNPs did not affect dietary intervention outcome in the present cohort.

There are no standardised serving/portion sizes defined for foods consumed in the European Union (EU). Typical serving sizes can deviate significantly from the 100?g/100?ml labelling specification required by the EU legislation. Where the nutritional value of a portion is specified, the portion size is determined by the manufacturers. Our objective was to investigate the potential for standardising portion sizes for specific foods, thereby ensuring complementarity across countries. We compared portion size for 156 food items measured using a food frequency questionnaire across the seven countries participating in the Food4me study. The probability of consuming a food and the frequency of consumption differed across countries for 93% and 58% of the foods, respectively. However, the individual country mean portion size differed from the average across countries in only 16% of comparisons. Thus, although dietary choices vary markedly across countries, there is much less variation in portion sizes. Our results highlight the potential for standardisation of portion sizes on nutrition labels in the EU.

For early prevention or inhibition of postmenopausal and age-related bone loss, nutritional interventions might be a first choice. For some vitamins and minerals an important role in bone metabolism is known or suggested. Calcium and vitamin D support bone mineral density and are basic components in most preventive strategies. Magnesium is involved in a number of activities supporting bone strength, preservation, and remodeling. Fluorine and strontium have bone-forming effects. However, high amounts of both elements may reduce bone strength. Boron is especially effective in case of vitamin D, magnesium, and potassium deficiency. Vitamin K is essential for the activation of osteocalcin. Vitamin C is an important stimulus for osteoblast-derived proteins. Increasing the recommended amounts (US RDA 1989), adequate intakes (US DRI 1997), or assumed normal intakes of mentioned food components may lead to a considerable reduction or even prevention of bone loss, especially in late postmenopausal women and the elderly.

The aim of the present study was to establish whether gastro-intestinal (GI) complaints observed during and after ultra-endurance exercise are related to gut ischaemia-associated leakage of endotoxins [lipopolysaccharide (LPS)] into the circulation and associated cytokine production. Therefore we collected blood samples from 29 athletes before, immediately after, and 1, 2 and 16 h after a long-distance triathlon for measurement of LPS, tumour necrosis factor-α and interleukin-6 (IL-6). As the cytokine response would trigger an acute-phase response, characteristic variables of these responses were also measured, along with creatine kinase (CK) to obtain an indicator of muscle damage. There was a high incidence (93% of all participants) of GI symptoms; 45% reported severe complaints and 7% of the participants abandoned the race because of severe GI distress. Mild endotoxaemia (5–15 pg/ml) was evident in 68% of the athletes immediately after the race, as also indicated by a reduction in IgG anti-LPS levels. In addition, we observed production of IL-6 (27–fold increase immediately after the race), leading to an acute-phase response (20-fold increase in C-reactive protein and 12% decrease in pre-albumin 16 h after the race). The extent of endotoxaemia was not correlated with the GI complaints or the IL-6 response, but did show a correlation with the elevation in C-reactive protein (rs 0.389; P = 0.037). Creatine kinase levels were increased significantly immediately post-race, and increased further in the follow-up period. Creatine kinase levels did not correlate with those of either IL-6 or C-reactive protein. It is therefore concluded that LPS does enter the circulation after ultra-endurance exercise and may, together with muscle damage, be responsible for the increased cytokine response and hence GI complaints in these athletes.

The use of dobutamine as selective β1-adrenoceptor agonist in in vivo studies on human thermogenesis and lipid utilization was investigated in 20 men. At 2.5, 5, and 10 μg ⋅ kg−1⋅ min−1, dobutamine induced significant increases in energy expenditure, lipid oxidation, and lipolysis. The β1-adrenoceptor antagonist atenolol (bolus: 42.5 μg/kg, infusion: 1.02 μg ⋅ kg−1⋅ min−1) blocked all dobutamine-induced effects on thermogenesis and lipid utilization. All parameters remained at levels comparable to those during saline infusion. The dose of atenolol used did not inhibit β2-adrenoceptor-specific changes in energy expenditure, lipid oxidation, and lipolysis during salbutamol infusion (85 ng ⋅ kg−1⋅ min−1). This indicates that atenolol was specific for β1-adrenoceptors and did not camouflage concomitant β2-adrenoceptor stimulation during dobutamine infusion. Therefore, we conclude that dobutamine can be used as a selective β1-adrenoceptor agonist at dosages ≤10 μg ⋅ kg−1⋅ min−1in in vivo studies on human thermogenesis and lipid utilization.

This study examined the effect of exercise training on body composition and sleeping metabolic rate (SMR) in 15 men and 13 women who participated in a 20-week training programme aimed at running a half marathon. Body mass (BM) was measured after waking up, fasted and with an empty bladder. Body composition was assessed using densitometry. The SMR was measured from 0300–0600 hours during an overnight sleep in a respiration chamber. Assessment of SMR was at least 36 h after the last period of exercise training. After 20 weeks of endurance training no change in BM was observed. However, body composition changed significantly. On average men lost 2.4 kg body fat (P< 0.01) and gained 1.7 kg fat free mass (FFM) (P<0.01). In women fat loss averaged 0.9 kg after 20 weeks (P<0.01), while FFM increased by 1.0 kg (P<0.05). Loss of fat mass was significantly larger in males (P<0.05). No changes in SMR were found, either in absolute terms, or when normalised for BM or FFM. Therefore, we have concluded that exercise training has no chronic, long-term effect on SMR: A possible explanation for this outcome in view of the different findings in similar studies is discussed.

The effect of a 5-month endurance training programme on physical activity and average daily metabolic rate (ADMR) was studied. Subjects were 16 males and 16 females preparing for a half marathon. Total physical activity, measured using an accelerometer, had increased by 62% and 63% after 20 weeks in males and females, respectively. Physical activity during the non-exercise part of the day did not change although in males it tended to increase (15%, NS). The ADMR had increased significantly in males after 8 and 20 weeks (+2.3 and +3.3 MJ· day-1, respectively,P<0.05) and exceeded the net energy expenditure for endurance-training three to four times. In females no significant increase in ADMR was found (+ 1.5 and + 1.3 MJ·day-1, after 8 and 20 weeks, respectively). In females the change in ADMR could be largely attributed to the net cost of running itself and a small increase (10%) in resting metabolic rate during the time of day they were awake. In males a discrepancy was observed between the increase of ADMR and the expenditure due to exercise and non-exercise activities. We suggest exercise stimulates habitual physical activity and diet-induced thermogenesis in males but not in females.

The validity of the pedometer and actometer for estimating the daily physical activity was evaluated by means of an observation study. The physical activity in a classroom of 11 pupils of a kindergarten was assessed by means of a pedometer, actometer and by observation. Besides this an activity questionnaire was completed by the infant-quide. On basis of the individual observation it is clear that the infant-guide can give valuable information about the activity of the children at school.

The purpose of this study was a critical evaluation of pedometer and actometer for estimating daily physical activity.

This paper provides a brief description of a new 8-register heartbeat integrator for recording the heart rate over a long period (24-h or more) in order to assess daily physical activity in children and adults.

1. In studying forearm skeletal muscle substrate exchange, an often applied method for estimating skeletal muscle blood flow is strain gauge plethysmography. A disadvantage of this method is that it only measures total blood flow through a segment of forearm and not the flow through the individual parts such as skin, adipose tissue and muscle. 2. In the present study the contribution of forearm subcutaneous adipose tissue blood flow to total forearm blood flow was evaluated in lean (% body fat 17.0 ± 2.2) and obese males (% body fat 30.9 ± 1.6) during rest and during infusion of the non-selective β-agonist isoprenaline. Measurements were obtained of body composition (hydrostatic weighing), forearm composition (magnetic resonance imaging) and of total forearm (venous occlusion plethysmography), skin (skin blood flow, laser Doppler), and subcutaneous adipose tissue blood flow (133Xe washout technique). 3. The absolute forearm area and the relative amount of fat (% of forearm area) were significantly higher in obese as compared to lean subjects, whereas the relative amounts of muscle and skin were similar. 4. During rest, the percentage contribution of adipose tissue blood flow to total forearm blood flow was significantly higher in lean compared with obese subjects (19 vs 12%, P < 0.05), whereas there were no differences in percentage contribution between both groups during isoprenaline infusion (10 vs 13%). Furthermore, the contribution of adipose tissue blood flow to total forearm blood flow was significantly lower during isoprenaline infusion than during rest in lean subjects (P < 0.05), whereas in the obese this value was similar during rest and during isoprenaline infusion. 5. In conclusion, although the overall contribution of adipose tissue blood flow to total forearm blood flow seems to be relatively small, the significance of this contribution may vary with degree of adiposity. Calculations on the contribution of adipose tissue blood flow and SBF to total forearm blood flow indicate that the contribution of non-muscular flow to total forearm blood flow may be of considerable importance and may amount in lean subjects to 35–50% of total forearm blood flow in the resting state.

The aim of the present study was to compare data on 24-h energy expenditure (EE24 h) in nine boys and ten girls (mean age 9.3 and 8.1 years, respectively) by heart rates (fc) combined with energy expenditure obtained from a 1-day stay in an indirect calorimeter (EEcal) and a 2-week period of normal living using the doubly labelled water method (EEdlw). Individual calibration curves were derived fromfc and oxygen uptake measured during sleep (in the calorimeter), standing and walking on a treadmill. An estimation of energy expenditure based on 24-hfc, monitoring (EEfc) was made during the stay in the calorimeter and on a normal school-day. Mean results showed an overestimation in EEfc compared to EEcal and EEdlw of 10.4% and 12.3% respectively, varying from 6.3% to 16.2%. These results confirmed earlier observations in adults that for a group thefc method overestimates EE24 h by about 10%.

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. The circulating concentration of several GI hormones was measured and several were found to be significantly elevated (P<0.05) after the race [mean values: gastrin 159.6 (SEM 17.8) ng·l-1; vaso-active intestinal peptide 224.3 (SEM 20.1) ng·l-1; peptide histidine isoleucine 311.1 (SEM 27.5) ng·l-1 ; motilin 214.1 (SEM 15.1) ng·l-1] but larger increases were not found to be significantly correlated with GI symptoms. Plasma cortisol, adrenaline, and noradrenaline concentrations were significantly higher after the race compared to resting values (P<0.05). There was a trend for post-race noradrenaline values to be lower in sufferers of GI disturbance. The post-race plasma noradrenaline concentration was significantly lower specifically in those runners with intestinal cramps. Also, the resting plasma cortisol concentration was significantly lower in those individuals who developed intestinal cramps during the race. Plasma creatine phosphokinase, alanine aminotransferase and aspartate aminotransferase activities were increased following the race, which may indicate that there was tissue damage. An increase in plasma potassium concentration was observed after the race in individuals with GI complaints [0.29 (SEM 0.07) mmol·l-1 increase], whereas no increase was observed in individuals without GI symptoms. An inability of the Na+-K+ pump to keep pace with the needs of skeletal muscle (as well in the intestinal tract) may have accounted for the high plasma potassium values immediately following exercise and may have played a role in the development of GI disorders. However, many other sources of K+ release may have accounted for the elevated plasma K+ (skeletal muscle, liver and red blood cells) in such sufferers and the correlation between the increase in K+ and GI symptoms may be an indirect one.

Two experiments were done at rest to examine gastric residue and secretion volume and electrolyte composition after ingestion of beverages of varying composition. In the first experiment the effects of two different sport drinks, one isotonic (7 carbohydrate, primarily sucrose) (I) and one hypertonic (18 carbohydrate, primarily maltodextrin) (H), and a control beverage (0.08 g.1−1aspartame in water) (C) on titratable acid, pH, osmolality, gastric emptying and secretion volume, and Na+, K+, and Cl−content were measured. In a second experiment five solutions were tested all containing 150 g.1−1maltodextrin, with 28 meq.1−1Na+(low Na), 140 meq.1−1Na+(high Na), 28 mcq.I-1K+(K), or 140 meq.1-1Na+and 28 meq.1−1K+(high NaK). Beverages H and C, and distilled water (W) were also tested. Samples were taken via a nasogastric tube. A dye dilution technique for serial sampling was employed to determine beverage and secretion volumes. After receiving a bolus of 8 ml.kg−1body weight, samples of gastric residue were taken at 0, 10, 20, 30, 40, 60, and 80 min. Gastric secretion of Na, K+, and Cl−was fairly constant despite large differences in beverage composition. Changes in gastric residue pH, titratable acid, osmolality, and electrolyte composition reflected the increasing proportion of the residue that was from gastric secretions. The effects of varying concentrations of Na+and K+(in a 150 g.1−1maltodextrin solution) on gastric emptying were not significant. The high carbohydrate concentration and/or the large volume ingested may have overridden any effect of sodium or potassium. No differences were observed between W and C. Secretion was decreased in these two solutions versus all the others. Although nonsignificant, there was a trend for greater secretion in H versus the other carbohydrate containing solutions in experiment 2. This may be a result of the higher pH maintained after ingestion of this beverage.

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 21 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<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.

REHRER, N. J., E. BECKERS, F. BROUNS, F. TEN HOOR, and W. H. M. SARIS. Exercise and training effects on gastric emptying of carbohydrate beverages. Med. Sci. Sports Exerc., Vol. 21, No. 5, pp. 540–549, 1989. 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-1glucose (G), 15 g·100 ml-1maltodextrin plus 3 g·100 ml-1fructose (MD), 7 g·100 ml-1sucrose (1)) and artificially sweetened water were compared during rest and 50 and 70 Wmaxbicycling. 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< 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 Wmaxexercise; 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.

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 ≥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 crossover study was designed. Sixteen subjects ingested 8 ml·kg BW−1of 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°C or by intermittent sauna exposure at 100°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< 0.05). ANOVA revealed significant effects of dehydration (P< 0.05) and exercise (P< 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. Core body temperature was significantly higher after the dehydration-exercise regime (39.1°C) than after the rest-dehydration regime (37.9°C) (P< 0.05). It is concluded that dehydration and/or thermal effects delay GE and may be related to a higher prevalence of GI disturbance.

Jeukendrup, A. E., M. Mensink, W. H. M. Saris, and A. J. M. Wagenmakers. Exogenous glucose oxidation during exercise in endurance-trained and untrained subjects. J. Appl. Physiol.82(3): 835–840, 1997.—To investigate the effect of training status on the fuel mixture used during exercise with glucose ingestion, seven endurance-trained cyclists (Tr; maximum O2uptake 67 ± 2.3 ml ⋅ kg−1⋅ min−1) and eight untrained subjects (UTr; 48 ± 2 ml ⋅ kg−1⋅ min−1) were studied during 120 min of exercise at ∼60% maximum O2uptake. At the onset of exercise, 8 ml ⋅ kg−1⋅ min−1of an 8% naturally enriched [13C]glucose solution was ingested and 2 ml/kg every 15 min thereafter. Energy expenditure was higher in Tr subjects compared with UTr subjects (3,404 vs. 2,630 kJ; P< 0.01). During the second hour, fat oxidation was higher in Tr subjects (37 ± 2 g) compared with UTr subjects (23 ± 1 g), whereas carbohydrate oxidation was similar (116 ± 8 g in Tr subjects vs. 114 ± 4 g in UTr subjects). No differences were observed in exogenous glucose oxidation (50 ± 2 g in Tr subjects and 45 ± 3 g in UTr subjects, respectively). Peak exogenous glucose oxidation rates were similar in the two groups (0.95 ± 0.07 g/min in Tr subjects and 0.96 ± 0.03 g/min in UTr subjects). It is concluded that the higher energy expenditure in Tr subjects during exercise at the same relative exercise intensity is entirely met by a higher rate of fat oxidation without changes in the rates of exogenous and endogenous carbohydrates.