Effects of acute exercise and training status on glucocorticoid-induced leucine zipper (GILZ) expression in human skeletal muscle

Interactions between statin therapy and physical exercise complicate effective cardiovascular prevention. Emerging evidence suggests that muscle strain related changes in the expression of the glucocorticoid-induced leucine zipper (GILZ) may be involved. Therefore, we measured GILZ mRNA expression levels in M. vastus lateralis samples of 32 healthy individuals before and after a standardized bout of strength or endurance exercise. Overall, we found a highly significant downregulation of GILZ after exercise training (p < 0.001). Within-subgroup changes were statistically significant only after strength training, supporting the role of muscle (as opposed to cardiocirculatory) strain. If confirmed, this may help fitting training recommendations and medication.

BaSAlt - A mixed-methods study protocol on setting-based physical activity promotion and counseling in nursing homes

Introduction

Physical activity (PA) is a major contributor to healthy aging. However, physical inactivity is prevalent among the elderly in Germany, particularly in institutionalized settings such as nursing homes. This paper aims to describe the study objectives, design, methods, assessment types, collection schedules and considerations for analyzing the data within the BaSAlt study on facilitators and barriers for PA promotion in nursing homes.

Methods

We designed the BaSAlt study as a participatory intervention study with multiple measurement points in six to eight nursing homes with a total of approx. 200 residents using four main modules: (1) setting-level analysis of physical activity patterns, physical activity-related climate and physical activity-related interaction with ‘significant others,’ and organizational facilitators and barriers to physical activity, (2) physical-activity related individual-level analysis of objective and self-reported physical activity and sedentary behavior, a geriatric assessment with established procedures, assessment of people's activity and health biographies (biographical mapping) as well as their motivational, subjective well-being and distress status, and (3) a counseling module that integrates counseling at the setting level as well as individual physical activity counseling for residents. In module (4) evaluation, the effects of integrated counseling with regard to the implementation of PA promotion strategies are analyzed.

Discussion

This study will extend our knowledge of physical activity promotion in German nursing homes. Its findings will inform governmental authorities, care professionals, and academics on how to reach a particular group, characterized by inactivity, multimorbidity, and a high prevalence of dementia, residing in nursing homes, a setting that will gain further relevance in the future.

Acute and long term effect of compression stockings in athletes with venous insufficiency

Venöse Rezirkulationskreisläufe mit daraus resultierender kapillärer Hypertension beeinflussen möglicherweise den oxidativen Stoffwechsel der Skelettmuskulatur. Ziel dieser Studie war, den Einfluss der chronischen venösen Insuffizienz (CVI) und deren Therapie durch medizinische Kompressionstrümpfe auf Leistung, Laktatspiegel und subjektives Befinden von Langstreckenläufern und Radsportlern zu untersuchen. Studienteilnehmer, Methoden: 24 gesunde Läufer (13 Männer und 11 Frauen) und 20 gesunde Radsportler (18 Männer und 2 Frauen) wurden in einer offenen prospektiven, randomisierten Kohortenstudie über 40 Tage untersucht. Die venöse Insuffiziez der Läufer entsprach Stadium C2–4EC,P,SAS,PPR, die der Radsportler C2–3EPAS,PPR. Die Kompressionstherapie erfolgte mit Unterschenkelkompressionsstrümpfen nach Maß (Venotrain Champion A-D compression class 2, Bauerfeind Germany). Standardisierte Laufbandergometer- bzw. Fahrradergometer-Mehrstufentests mit Bestimmung der kapillären Laktatspiegel wurden durchgeführt und subjektive Beschwerden pro- und retrospektiv mittels Fragebögen erhoben. Ergebnisse: Die medizinische Kompressionstherapie führte zu keinem akuten Effekt auf Leistung, Herzfrequenz und Laktatspiegel, wenn Leistungstests mit und ohne Kompression verglichen wurden. Ebensowenig fand sich kein signifikanter Unterschied zwischen Leistungstests ohne Kompression vor und mit Kompression nach einer vierwöchigen Kompressionstherapie. Die Kompressiontherapie führte jedoch zu einer signifikanten Abnahme von CVI-typischen Beschwerden im Alltag und nach dem Training. Schlussfolgerung: Bei Läufern und Radfahrern mit CVI konnte keine messbare Leistungssteigerung nach einer akuten oder mehrwöchigen Therapie mit Kompressionstrümpfen nachgewiesen werden. Ebensowenig wurde die sportliche Leistungsfähigkeit durch die Kompressionstherapie beeinträchtigt. Subjektiv empfanden die Athleten das Tragen von Kompressionsstrümpfen als sehr vorteilhaft. Kompressionstrümpfe können Athleten mit CVI daher empfohlen werden.

A model case of a positive outcome in super-super obesity

For an increasing number of obese patients, bariatric surgery is considered as the treatment of choice after the failure of conventional strategies. While numerous studies on bariatric surgery have shown substantial health benefits, there is a broad inter-individual variation in the long-term outcome, which is insufficiently understood. Here we show a favourable long-term outcome following multidisciplinary care in a super-super-obese patient. The patient suffered from numerous typically obesity-associated comorbidities and limitations. He underwent multidisciplinary care including two-step bariatric intervention. Endoscopic intragastric balloon positioning was followed by gastric sleeve surgery without Roux-en-Y gastric bypass. His body weight dropped from 260 kg (body mass index [BMI] 79.4 kg m(-2) ) to 85 kg (BMI 25.9 kg m(-2) ) within 16 months and continued to be stable at 90 kg (BMI 27.8 kg m(-2) ) at the end of the follow-up period of 48 months. The loss of excess body weight was associated with the remission of numerous obesity-related comorbidities and with a concomitant pronounced increase in the quality of life and in the socioeconomic status. Eventually, the patient was able to lead a normal life with a decreased risk of long-term complications. We attribute the positive long-term outcome to the following potential determinants: individualized bariatric surgery, multidisciplinary care, the patient's long-term compliance, adequate adherence to the aftercare, physical exercise after surgery, family support, the cooperation of the primary care physician and the financial coverage by the health insurance. Some of these factors remain to be evaluated as predictors of a favourable long-term outcome in prospective trials.

[Relation between pelvis malposition and functional knee pain by long distance running]

PURPOSE

During endurance run knee problems often appear. This study wants to show the connection between a one- sided malposition of the pelvis and knee joint pain during endurance running.

METHOD

We tested endurance runners which had pelvis malposition and knee pain. Therefore 100 athletes were tested, 50 with knee pain and 50 without knee pain. Manual examination and clinical instruments were used for examination of sacroiliac joints for measurement of vertical distances between spinae iliacae anteriores superiores. Collected data were analyzed by appropriate statistical methods.

RESULTS

The results show that there is a connection between a one- sided pelvic malposition and knee pain during endurance running. These relations are probably realized by changes in lower extremity dysfunction as a result of pathological chains. The one sided pelvis malposition was in the control group significant higher (0.9 ± 0.4 cm) than in the control group (0.3 ± 0.2 cm).

CONCLUSION

There is a correlation between knee pain and os coxae malposition. (It is necessary in examine and treat the the cause- and effect chain to prevent injuries).

Exercise dependent pleurisy in a soccer athlete

Except for traumatic or spontaneous pneumothorax, little information is known about exercise associated pleural pathologies. We present the case of a 22-year-old athlete with symptoms of musculoskeletal disorders of his upper back after a first league soccer match. Clinical examination initially showed a blockage of the costotransversal joints six and seven with subsequent muscular tension representing an interscapulovertebral pain syndrom. Temporary complete pain relief with following severe reoccurrence of symptomes led to further diagnostic procedures after 3 days. Contrast Enhanced Magnetic Resonance Images (CE-MRI) surprisingly revealed an intrathoracic tumenescence in front of the cardiac apex with surrounding pleural effusion. After excluding all alternative diagnosis for unclear pleurisy we assumed an exercise dependent local pleurisy with subsequent pleural effusion due to local friction by a posttraumatic intrathoracic hematoma. Several invasive and non-invasive therapeutical options were discussed in this rare case with a final decision for a conservative strategy. Seven weeks after injury the player was able to return to play. Even if musculoskeletal problems are most likely in high impact athletes, referred pain due to less common disorders has always to be kept in mind.

High cardiorespiratory fitness is an independent predictor of the reduction in liver fat during a lifestyle intervention in non-alcoholic fatty liver disease

OBJECTIVE

Lifestyle intervention with diet modification and increase in physical activity is effective for reducing hepatic steatosis in patients with non-alcoholic fatty liver disease (NAFLD). However, for a similar weight loss, there is a large variability in the change in liver fat. We hypothesised that cardiorespiratory fitness may predict the response to the intervention.

DESIGN

Longitudinal study with increase in physical activity and diet modification.

SETTING

University teaching hospital.

PATIENTS

50 adults with NAFLD and 120 controls at risk for metabolic diseases.

MAIN OUTCOME MEASURES

Total-, subcutaneous abdominal- and visceral adipose tissue by magnetic resonance tomography, liver fat by 1HMR spectroscopy and cardiorespiratory fitness (VO(2,max)) by a maximal cycle exercise test at baseline and after 9 months of follow-up.

RESULTS

In all subjects total-, subcutaneous abdominal- and visceral adipose tissue decreased and fitness increased (all p<0.0001) during the intervention. The most pronounced changes were found for liver fat (-31%, p<0.0001). Among the parameters predicting the change in liver fat, fitness at baseline emerged as the strongest factor, independently of total- and visceral adipose tissue as well as exercise intensity (p = 0.005). In the group of subjects with NAFLD at baseline, a resolution of NAFLD was found in 20 individuals. For 1 standard deviation increase in VO(2,max) at baseline the odds ratio for resolution of NAFLD was 2.79 (95% confidence interval, 1.43-6.33).

CONCLUSIONS

Cardiorespiratory fitness, independently of total adiposity, body fat distribution and exercise intensity, determines liver fat content in humans, suggesting that fitness and liver fat are causally related to each other. Moreover, measurement of fitness at baseline predicts the effectiveness of a lifestyle intervention in reducing hepatic steatosis in patients with NAFLD.

Sequentially based analysis versus image based analysis of Intima Media Thickness in common carotid arteries studies - do major IMT studies underestimate the true relations for cardio- and cerebrovascular risk?

Background

Image-based B-mode ultrasound has gained popularity in major studies as a non-invasive method of measuring cardio- and cerebrovascular risk factors. However, none of the major studies appears to have paid sufficient attention to the variation in end diastolic wall process. By using sequentially based analyses (SBA) of Intima-Media Thickness (IMT), the general purpose of this study was to show that the current image based (ECG tracked) analysis (IBA) has some major variations and might underestimate the true relations for cardiovascular events and stroke for IMT measurement.

Method

The study group consisted of 2500 healthy male subjects aged between 35 to 55 years. 4 sequences (300 images) were analyzed per subject. 750,000 images were analysed throughout the course of this study.

Results

IBA showed significantly lower mean, maximal, and minimal values for IMT in CCA than for SBA. The correlation analysis between IBA and SBA with the cardio- and cerebrovascular risk factors showed a higher correlation of SBA for all risk factors. The Pearson coefficient was 0.81, p < 0.01, for SBA versus Framingham CHD risk level (FCRL) and 0.49, p = 0.01, for IBA versus FCRL.

Conclusion

IBA did not measure the true maximal values of the IMT in this study. Together with the correlation analysis, this indicates that IBA might underestimate the true relations for IMT and risk factors.

Lifestyle intervention in individuals with normal versus impaired glucose tolerance

BACKGROUND

Lifestyle intervention is effective in the prevention of type 2 diabetes in individuals with impaired glucose tolerance (IGT). It is currently unknown whether it has beneficial effects on metabolism to a similar extent, in individuals with normal glucose tolerance (NGT) compared to individuals with IGT.

MATERIALS AND METHODS

Data from 181 subjects (133 with NGT and at risk for type 2 diabetes and 48 with IGT) who participated in the Tuebingen Lifestyle Intervention Program with increase in physical activity and decrease in caloric intake were included into this study. Body fat distribution was quantified by whole-body magnetic resonance (MR) tomography and liver fat and intramyocellular fat by (1)H-MR spectroscopy. Insulin sensitivity was estimated from an oral glucose tolerance test (OGTT).

RESULTS

After 9 +/- 2 months of follow-up, the diagnosis of IGT was reversed in 24 out of 48 individuals. Only 14 out of 133 participants with NGT developed IGT. Body weight decreased in both groups by 3% (both P < 0.0001). Two-hour glucose concentrations during an OGTT decreased in individuals with IGT (-14%, P < 0.0001) but not with NGT (+2%, P = 0.66). Insulin sensitivity increased both in individuals with IGT (+9%, P = 0.04) and NGT (+17%, P < 0.0001). Visceral fat (-8%, P = 0.006), liver fat (-28%, P < 0.0001) and intramyocellular fat (-15%, P = 0.006) decreased in participants with IGT. In participants with NGT these changes were significant for visceral fat (-16%, P < 0.0001) and liver fat (-35%, P < 0.0001).

CONCLUSIONS

Moderate weight loss under a lifestyle intervention with reduction in total, visceral and ectopic fat and increase in insulin sensitivity improves glucose tolerance in individuals with IGT but not with NGT. In individuals with NGT, the beneficial effects of a lifestyle intervention on fat distribution and insulin sensitivity possibly prevent future deterioration in glucose tolerance.

Computer-based quantification of the mean Achilles tendon thickness in ultrasound images: effect of tendinosis

BACKGROUND

B-mode measurement of the sagital diameter of the Achilles tendon based on a manual tracing (MT) procedure is partly dependent on the subjectivity of the reader. The aim of this study is to establish a standardised automatic procedure to differentiate between normal and chronically degenerated tendons. For this comparison, the tracing results of the tendon boundaries of an automatic identification (AI) process, already established with the detection of intima-media thickness, are compared with computer-assisted MT.

METHODS

The detection of the tendon boundaries was performed in 115 ultrasound images including the cranial border of the calcaneal tuberosity. The measured section (starting point 4 cm away from the anterior boundary of the calcaneal tuberosity) amounted to 3 cm, and was divided into three sub-segments (1 cm each). Intra- and inter-reader/observer variability for mean and maximum Achilles tendon thickness (ATT) with AI and MT were evaluated. A normal group and a group with clinically diagnosed chronic tendon degeneration had mean and maximum ATT readings compared.

RESULTS

Using MT, the intra- and inter-reader variability was 3.0% and 6.8%, respectively, using AI the variability was 1.6% and 3.9%, respectively. Mean and maximum ATT were measured systematically lower by AI compared to MT in all regions by 0.4 mm. The AI procedure was most accurate in the second segment. The mean ATT and maximum ATT were correctly detected in 93.9% and 96.6% of the images.

CONCLUSION

The AI procedure detected the ATT with a high level of precision in all three segments. The most robust measurement was reached in the second segment. It eliminates most of the inter-/intra-reader variability in ATT measurement using MT. We suggest this new method could be a new gold standard for quantification of chronic disorder in Achilles tendons.

[Obesity--an interdisciplinary task]

In industrial nations, over the last five decades conditions concerning nutrition and physical exercise as well as socio-economic circumstances have changed radically. One of the consequences following from this development has been a rapid increase in the prevalence of obesity. Studies have shown that currently 20 percent of the German adult population suffer from obesity. Investigations into the etiology of obesity have to address complex interactions between genetic, socio-economic and psychosocial factors. A year ago, at the University Hospital Tübingen different departments joined to set up the "Plattform Adipositas". Endocrinologists, obesity surgeons, professionals in sports medicine and psychosomatic medicine as well as dieticians are collaborating to develop scientifically based therapy programs and treatment pathways for obese patients. The following article gives an account of this exemplary interdisciplinary cooperation.

Exercise-induced, persistent and generalized muscle cramps. A case report

We are reporting on a 46-year-old man who has suffered of muscle cramps for 4 years, occurring immediately after jogging and playing tennis and lasting for 7-8 hours. Repeated neurological, orthopedic, internal medical and endocrinological examinations showed no pathological findings. Physiotherapy, supplementation of fluids and electrolytes had no effect, nor did medication therapy with muscle relaxants. During spiroergometry without medication, there was an overproportional increase of heart rate and respiratory rate with delayed pCO2 increase after exercise with otherwise normal blood gas levels. This reaction was considerably reduced during spiroergometry under beta-blockade (metoprolol 100 mg); at the same time, the muscle cramps could no longer be induced. Both excessive respiratory regulation and direct hyperadrenergic stimulation should be discussed as the primary cause of the muscle cramps. According to recent findings, b-blockers with intrinsic sympathocomimetic activity should be avoided in therapy.

Metabolic reaction after concentric and eccentric endurance-exercise of the knee and ankle

PURPOSE

Power training plays an essential part in many sport disciplines. The importance of eccentric power training remains a matter of controversial discussion. The objective of this study was therefore to investigate the difference in metabolic reaction between eccentric and concentric stress in comparable work.

METHODS

Sixty-four men between 22 and 60 yr of age performed maximum isokinetic 1-min endurance tests of the knee and ankle each in concentric (180 degrees.s-1) and eccentric (60 degrees.s-1) modes with comparable total area of contraction-time curve (NS). Higher strength values (mean peak torque, P < 0.01), lower fatigue (fatigue index, P < 0.001), lower increase in lactate (P < 0.01), and lower ammonia production (P < 0.01) were found in eccentric than in concentric exercise, independent of the joint. The eccentric form of stress showed lower decrease and thus age-dependence in maximum strength and in fatigue than the concentric form.

RESULTS

The results permit the conclusion that eccentric exercise leads to less fatigue and lower lactate and ammonia reaction than concentric exercise in comparable work levels. Variable visco-elastic properties of the muscle fibers themselves with additive passive strength in eccentric mode is considered as the cause.

CONCLUSIONS

It remains uncertain whether the lower metabolic stress might be useful during the training process. A greater scope of training and increased number of training stimuli might be applied in primarily eccentric forms of exercise.

Metabolic and cardiocirculatory reactions after concentric and eccentric exercise of the shoulder

Lower metabolic and cardiocirculatory reactions to eccentric compared to concentric exercise are known for large muscle groups. The extent of exercise reaction depends on the muscle mass involved and moreover differs between the various muscle groups, while it is unclear to which extent cardiovascular and metabolic reactions and differences between the types of work exist in the shoulder, also it is not known whether these reactions differ according to training status. Lactate production (LA), heart rate (HR), and blood pressure (BP) were examined following eccentric and concentric shoulder movements in 16 male gymnasts (GN) and 15 male untrained subjects (US). Differentiation was made according to the types of work for peak torque (PT) and local muscle endurance (LME). Following eccentric exercise, the increase of LA and HR was clearly lower than following concentric exercise (p<0.05). No difference was observed between the groups. Diastolic BP showed no changes, whereas systolic BP was higher following concentric exercise. Eccentric PT was higher than concentric PT in GN within a test-retest variability of 15%. LME showed a lower degree of fatigue under eccentric conditions, independent of the group. It is concluded that eccentric exercise of the shoulder leads to lower metabolic and cardiocirculatory reactions than concentric exercise, in spite of higher peak torque and less fatigue. Exercises consisting of a high proportion of eccentric movement may thus be beneficial in the therapy of shoulder complaints, especially in patients with cardiovascular disease.

Muscular fatigue, maximum strength an stress reactions of the shoulder musculature in paraplegics

In paraplegic patients, shoulder complaints attributable to muscle dysbalances arising from the particular daily form of exercise are often observed. The goal of therapy is to correct these imbalances through muscular training, whereby eccentric exercise might offer advantages due to lower fatigue with concurrent higher maximum strength. This study therefore examines muscle fatigue, maximum strength, and suitability for paraplegics of eccentric exercise of the shoulder. Muscle fatigue, isokinetic peak torque, and EMG activity were determined eccentric (Ecc) and concentric (Con) in 41 paraplegic subjects (13 early rehabilitants; 16 trained in wheelchair sports; 12 untrained). Serum CK, myoglobin, and subjective pain were collected for one week after exercise. In eccentric exercise, there was less muscle fatigue in all groups. Highest Ecc/Con peak torque ratio was found in trained subjects in all movements, followed by the untrained and the early rehabilitants. EMG-activity was lower in eccentric compared to concentric exercise (Ecc/Con ratio <1). CK and myoglobin concentrations, like pain symptoms, showed a marked increase after exercise. It is concluded that the Ecc/Con strength patterns among paraplegics are altered. Eccentric exercise offers advantages on the basis of lower muscular fatigue independent of training status and lesion time and higher maximum strength with increasing duration of paraplegia and additional athletic training. However, due to structural damage and subjective pain eccentric exercise can only be recommended with reservations in therapy and training.

Ventilatory, lactate-derived and catecholamine thresholds during incremental treadmill running: relationship and reproducibility

Anaerobic threshold as a basic criterion of training recommendation can be estimated by various parameters. The purpose of this study was to investigate the relationship and the reproducibility of ventilatory, lactate-derived and catecholamine thresholds of an incremental treadmill exercise. Therefore, 11 male subjects underwent two incremental treadmill tests within 7 days. The lactate threshold (LT) was determined at the lowest value of the lactate-equivalent (ratio lactate/performance). The individual anaerobic threshold (IAT) was calculated at LT+1.5 mmol/L lactate. The ventilatory thresholds, using mass-spectrometry, were defined by the V-slope method (AT) and at the deflection point of end-tidal CO2 (ET-CO2) concentration (RCP). The thresholds of epinephrine (TE) and norepinephrine (TNE) were calculated in the manner of LT. The running velocities were highly reproducible at LT (test-retest correlation coefficient r=0.90), IAT (r=0.97), AT (r=0.88) and RCP (r=0.95). By contrast TE (r=0.49) and TNE (r=0.46) showed a poor reproducibility. TE and TNE occurred 5-11% below LT and AT with a low correlation to LT and AT. LT was found 4% below AT, both were correlated with r=0.70 (p<0.01, test 1) and r=0.95 (p<0.01, test 2). IAT occurred 7-8% above RCP, in both tests a close correlation was found between IAT and RCP of r=0.97 (p<0.01). In summary, the ventilatory and lactate-derived thresholds show a high and similar reproducibility, but the catecholamine threshold does not. In the present exercise protocol, there are systematic differences between the lactate-derived and ventilatory thresholds, in spite of a close relationship, and these must be taken into account in recommendations derived for training.

The echocardiographic determination of volume and muscle mass of the heart

One- and two-dimensional echocardiography permits assessment of left ventricular size and muscle mass, whereas the validity and reliability differ. It is comparable to other methods, such as angiography, scintigraphy and magnetic resonance imaging, but has the advantage of being noninvasive and of lower cost. It therefore appears particularly well-suited for applications in sports medicine. However, changes of 10%-20%, depending on the parameter, are necessary in individual cases to permit assumption of a proven change. A further methodical improvement, especially in respect to reliability but also to validity may be expected in the future from three-dimensional, computer-supported examination techniques. Enlargement of the heart due to endurance sports is harmonic and affects all four cardiac chambers. Limits to the increase in left ventricular volume and muscle mass can be recognized in relation to body weight. They usually do not exceed 70% of the baseline value or the value obtained for untrained persons. Power training, even in extreme forms, results in no or only minimal dimensional changes.

Effect of combined parasympathetic and sympathetic blockade on left ventricular relaxation at rest and during exercise in trained and untrained men

We investigated the influence of autonomic blockade (AB) on the left ventricular (LV) diastolic function at rest (R) and during bicycle exercise (EX) in eight endurance-trained (TR) and ten untrained subjects (UT). Two-dimensional and M-mode echocardiography at the parasternal long axis were performed at rest and during an exercise protocol, which consisted of two stages of 50 and 100 W. Using the digitized data from the M-mode echocardiogram, the normalized maximal increase in LV dimension during the rapid filling phase (nmD) was calculated according to Hörtnagl. Additionally the ECG was recorded at R and during Ex 60 min after this first test. 0.02 mg.kg body mass-1 propanolol and 0.04 mg.kg body mass-1 atropine were injected intravenously over a 5-min period and the test procedure was repeated as described above. Before AB nmD increased significantly from resting values to 100 W in both groups, whereas nmD tended to be lower in UT compared to TR. During AB nmD of UT was rather unchanged at R and during EX compared to pre-blockade conditions. In contrast nmD of TR was slightly reduced and this difference was significant at 100 W. No major difference in nmD between the TR and UT group could be observed during AB. Before and during AB HR of TR were significantly lower at rest, 50 and 100 W compared to UT. We conclude that the enhanced diastolic relaxation observed in endurance athletes seems to be due to a training-induced adaptation of the autonomic nervous system.

Breath-by-breath measurements for the analysis of exogenous glucose oxidation during intense endurance exercise using [13C]-isotopes

Up to now only the analysis of 13CO2 in separate breath-gas samples after administration of [13C]-labelled carbohydrates with intervals of several minutes in between has been available for analyses of the exogenous glucose oxidation during exercise. Our studies show the use of rapid respiratory mass spectrometry for breath-by-breath analysis to determine exogenous glucose utilization. Six male triathletes performed two exercise tests of 100-min duration each on a cycle ergometer. In both tests 5 min after the beginning of cycling glucose was administered. In test 1 30 g natural glucose was given, in test 2 a mixture of 1.5 g [13C1]-glucose and 28.5 g natural glucose. The work rate was regulated to keep constant 90% of the VO2 at the VO2 levelling off (VO2max) measured in a short ramp test. The resulting work rate was at 260.2 +/- 9.5 watts in test 1 and at 276.3 +/- 12.1 watts in test 2. Respiration gases and the end-tidal concentrations of 12CO2 (12C) and 13CO2 (13C) were calculated breath-by-breath online. The course of the ratio [13C/12C] reflects the course of exogenous glucose utilization. Onset of utilization was 10.5 +/- 5.5 min following oral administration. Maximum utilization was attained at 53.1 +/- 9.8 min with a maximal rate of oxidation of 0.36 +/- 0.05 g/min. The beginning of the energy supply of exogenous glucose could be determined quite soon after oral administration.