Biomedical subjects

K Roecker

Publications and source records attributed to K Roecker.

11 recordsLinked to original sources

PubMed2005

Determining anaerobic capacity using treadmill ergometry.

The determination of anaerobic capacity (AC) using treadmill ergometry is problematic from a methodological, as well as a technical standpoint. In this study, a procedure from Monod and Scherrer was modified to examine whether realistic magnitudes of AC could be determined using three subject groups with different levels of anaerobic training. The subject groups consisted of 10 untrained (UT), 10 aerobic-trained runners (AeT), and 10 anaerobic-trained 400-meter sprinters (AnT). In two separate test series, first the VO2max was determined and second the so-called individual anaerobic threshold (IAT) was used to determine the aerobic power for all subjects. Then all subjects completed a series of sprints with increasing speeds above the VO2max, from which the work output from each test was calculated. Through linear regression, the point of intersection of the regression line with the y-axis was defined as global AC. The results show typically higher VO2max and IAT for AeT (62.2 ml x kg(-1) x min(-1), 14.7 km x h(-1)) compared to UT (53.2 ml x kg(-1) x min(-1); 11.2 km x h(-1)) and AnT (56.7 ml x kg(-1) x min(-1); 11.8 km x h(-1)). AC was significantly higher in AnT (4.1 +/- 0.58 kJ) compared to AeT (1.8 +/- 0.65 kJ) and UT (3.2 +/- 0.68 kJ). The determined absolute values of AC are considerably lower than of comparable examinations using bicycle ergometry. One reason for such an underestimation of AC could be that the horizontal work done during exercise on a treadmill was not taken into enough consideration. Another explanation is that the magnitude of the calculated AC values shows a dependency on the duration of each sprint test. In addition, the critical velocity for all subjects was found to be higher than for IAT, which consequently leads to an underestimation of AC. Moreover, the absolute level of the AC values appears to depend on the endurance of the comparison groups. It can then be concluded that the applied procedure allows for a differentiation amongst a variously trained collective, but does not allow a correct absolute determination of the AC.

Adult↗

PubMed2005

Gas exchange measurements with high temporal resolution: the breath-by-breath approach.

Respiratory gas analysis as an indicator for metabolic strain during exercise has a long history. First introduced in the 18th century, huge gas collectors served for the determination of oxidative energy delivery. While still being accepted as accurate, this particular method delivers data of low temporal resolution only. Further developments of gas analysis techniques therefore focused on a higher density of data. When algorithms became available for indispensable calculations, the so-called "breath-by-breath" (BBB) method was established some decades ago. Thereby, the term BBB in the narrower sense means that a particular physiologic value is determined for each of a subject's single respiratory cycles. Reliable application of this approach depends on the performance of available computer systems, the quality of the analyzing software routines, and the responsiveness of the gas analyzers. Thus, it appears that even nowadays technical progress is continuing in this area. This review describes technical aspects and prerequisites of the BBB approach and its specific areas of application.

Breath Tests↗

PubMed2003

Heart-rate recommendations: transfer between running and cycling exercise?

With the expanding use of portable heart rate (HR) monitors in endurance sports, HR is increasingly used as a marker for exercise intensity. Hereby, HR at the so-called individual anaerobic threshold (IAT) is one possible reference point. However, once determined, it is often attempted to apply HR recommendations from one type of ergometry to different kinds of exercises. We examined whether HR at IAT and at 4 mmol x l -1 blood lactate is predictable from cycling to running and vice versa. Data of 371 subjects (304 male, 67 female) were analyzed. All subjects underwent an incremental test on a treadmill (TR, starting speed 6 or 8 km x h -1, increments 2 km x h -1 every 3 min) and on a bicycle ergometer (BE, start at 50 Watt, increments 25 or 50 Watt every 3 min). IAT was determined at a net increase of lactate concentration of 1 - 5 mmol x l -1 above lactate concentration at lactate threshold for running (as in: Med Sci Sports Exerc 1998, 30 (10); 1552 - 1557) and 1.0 mmol x l -1 for cycling. A maximum time span of three weeks was allowed between the tests. We found that heart rate at IAT or at 4 mmol x l -1 blood lactate did not correlate between cycling and running. A sports specific test seems to be a prerequisite for reliable heart rate recommendations.

Adult↗

PubMed2003

Individual differences in self-reported heat tolerance. Is there a link to the cardiocirculatory, thermoregulatory and hormonal response to endurance exercise in heat?

AIM: Tolerance to exercise in heat exhibits great interindividual variability. We questioned whether individual differences in self-reported heat tolerance within a group of endurance trained athletes are linked to the cardiocirculatory, thermoregulatory and hormonal response to endurance exercise in heat. METHODS: Using a rating scale to assess the individual degree of tolerance to exercise in heat we allocated 12 non-heat-acclimated trained runners into two groups of 5 highly heat tolerant (HHT) and 7 less heat tolerant (LHT) athletes. Both groups performed a 60-min treadmill run (velocity 90% of individual anaerobic threshold, room temperature and humidity 28 inverted exclamation mark C and 50%, respectively). RESULTS: Sweating rate did not differ between HHT (mean +/- SEM: 0.44+/-0.02) and LHT (0.40+/-0.02 ml x kg(-1) x min(-1)). Compared to LHT, exercise-induced rises in core temperature (39.3+/-0.2/40.0+/-0.2 inverted exclamation mark C), heart rate, plasma norepinephrine and cortisol were significantly lower in HHT, while epinephrine did not exhibit differences between the groups. In contrast, response of human growth hormone (hGH) was significantly more pronounced in HHT. CONCLUSION: Our initial results, obtained in a small group of endurance-trained runners, show that self-reported tolerance to exercise in heat is associated with an attenuated rise in body core temperature during prolonged exercise under elevated ambient temperatures. This finding in heat tolerant athletes is paralleled by a lower stress response as reflected by lower rises in heart rate and stress hormones such as norepinephrine and cortisol. The functional significance (i.e. with respect to sweating function) of the more pronounced response of hGH in heat tolerant athletes warrants further research.

Body Temperature↗

PubMed2001

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.

Adaptation, Physiological↗

PubMed2001

First-pass effect of an intravenous bolus of [13C]bicarbonate displayed breath-by-breath.

The dilution of an intravenous bolus dose of [13C]bicarbonate is used as an estimate for the metabolic rate under certain conditions. It is a consistent finding in all studies that the total amount of intravenous [13C]bicarbonate cannot be recovered as breath 13CO2. In this study, we used a breath-by-breath analysis of 13CO2 to depict the washout of 13CO2 at a high temporal resolution to analyze the extent to which a probable first-pass effect is responsible for the reduced recovery. Eight healthy men were tested at seated rest and with bicycle exercise at a constant load relative to 40 and 75% maximal O2 consumption VO2 max). [13C]bicarbonate (0.0125 g/kg body wt) was administered as an intravenous bolus in each test. Respiratory mass spectrometry was used to derive the course of the end-tidal 13CO2-to-12CO2 ratio from the breath-by-breath data. Approximately 2 min after 13C administration, the washout curve could be fitted well by a two-exponential curve describing a two-compartment mammillary model. Immediately after administration of the bolus dose, an excess peak in the end-tidal 13CO2-to-12CO2 ratio appeared. This peak could not be included in the two-exponential fitting. The area under the first peak resulted in 3.8 +/- 1.3% of the total [13C]bicarbonate dose at rest, 11.5 +/- 2.9% at moderate exercise (40% VO2 max), and 16.9 +/- 4.0% at intensive exercise (75% VO2 max). The first-pass effect had an increasing impact of up to about two-thirds of the lacking bicarbonate with higher exercise intensity. The "loss" of tracer via this first-pass effect must be considered when the results of studies with parenteral administration of [13C]bicarbonate are considered, especially when it is given as a bolus dose and during exercise.

Adult↗

PubMed2000

Increase characteristics of the cumulated excess-CO2 and the lactate concentration during exercise.

The so-called excess-CO2 in physical exertion results stoichiometrically directly from the quantity of protons bound in bicarbonate buffering. This situation is used in determining the ventilatory threshold (VT). However, the extent to which the degree and increase characteristics of excess-CO2 can be used as an equivalent to blood lactate concentrations is uncertain. To investigate this relationship, 21 healthy men exercised on a cycle ergometer (starting at 50 watt, increases of 50 watt every 3 minutes) to subjective exhaustion. To evaluate the characteristics of this increase, a slope constant lambda was calculated in relation to performance for both the blood lactate concentration (lambda lactate) and the cumulated excess-CO2 (lambda CO2 excess). The start of the lactate increase (LT) and excess-CO2 (VT) showed good intercorrelation (VT=2.27+0.98 x LT; r=0.914; P<0.001). Mean lambda lactate and lambda CO2 excess were of similar dimensions in all subjects (69.3 +/- 39.8 watt vs. 80.11 +/- 15.7 watt), but a minority of the subjects (n=7) showed a considerably more gradual increase for the excess-CO2 to the maximum. Since in addition there was no significant correlation between the absolute values for maximum lactate concentrations and the cumulative excess-CO2, an interindividual prediction of lactate concentrations from the excess-CO2 would be difficult. It is an open question, however, whether perhaps additional performance-limiting factors, such as the ventilation or the buffering capacity, may be included when measuring the excess-CO2 so that this parameter could be more a measure for the formation rate of new lactate than the blood lactate concentration alone.

Adult↗

PubMed1998

Predicting competition performance in long-distance running by means of a treadmill test.

PURPOSE: The purpose of this study was to examine the power of 16 parameters beside the individual anaerobic threshold (IAT) in predicting performance in various competition distances. METHODS: This study examined 427 competitive runners to test the prediction probability of the IAT and other parameters for various running distances. All runners (339 men, 88 women; ages, 32.5 +/- 10.14 yr; training, 7.1 +/- 5.53 yr; training distance, 77.9 +/- 35.63 km.wk-1) performed an increment test on the treadmill (starting speed, 6 or 8 km.h-1; increments, 2 km.h-1; increment duration, 3 min to exhaustion). The heart rate (HR) and the lactate concentrations in hemolyzed whole blood were measured at rest and at the end of each exercise level. The IAT was defined as the running speed at a net increase in lactate concentration 1.5 mmol.L-1 above the lactate concentration at LT. RESULTS: Significant correlations (r = 0.88-0.93) with the mean competition speed were found for the competition distances and could be increased using stepwise multiple regression (r = 0.953-0.968) with a set of additional parameters from the training history, anthropometric data, or the performance diagnostics. CONCLUSIONS: The running speed at a defined net lactate increase thus produces an increasing prediction accuracy with increasing distance. A parallel curve of the identity straight lines with the straight lines of regression indicates the independence of at least a second independent performance determining factor.

Adult↗

PubMed1998

Effects of intensive endurance exercise on DNA damage in leucocytes.

OBJECTIVE: It has been shown that highly intensive anaerobic exercise induces DNA damage in leucocytes (LEU). The present study was designed to investigate whether intensive endurance exercise is capable of inducing comparable effects. EXPERIMENTAL DESIGN: A prospective study. PARTICIPANTS: Twelve men (aged 27.3 +/- 4.1 years) who undertook a regular training of different extent (running volume 45 +/- 25 km.week-1) volunteered in the study. INTERVENTIONS: The subjects competed in a half marathon (HM) of 21.1 km, 93.0 +/- 10.4 min. MEASUREMENTS: Blood was taken at rest, 1 and 24 hrs after HM for determination of creatine kinase, neutrophil (PMN), lymphocyte and monocyte counts. DNA damage in LEU at rest and 24 hrs after HM was quantified using the single cell gel-electrophoresis (SCG) assay. RESULTS: PMN increased from 2.81 +/- 0.69 to 13.13 +/- 2.91 1 hrs after HM (p < 0.01) and returned to 3.26 +/- 0.47 10(9) cells.l-1 by 24 hr recovery. DNA migration (image length, IL) reflecting the extent of DNA damage was elevated significantly in 10 of 12 subjects one day after HM. IL rose from 32.7 +/- 2.2 to 40.7 +/- 3.9 microns (p < 0.01). Correlation analysis revealed a relationship between DNA migration 24 hrs after HM and PMN count 1 hr post-exercise (r = 0.67, p < 0.05). CONCLUSIONS: The results confirm the hypothesis that DNA damage in LEU occurs after intensive endurance exercise. We suppose our observation of exercise-induced DNA damage in LEU is affected by reactive oxygen species which are released from PMN. It is quite unclear whether DNA damage in LEU is causal involved in exercise-induced modifications of the immune system.

Adult↗

PubMed1996

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.

Adaptation, Physiological↗

PubMed1996

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.

Adaptation, Physiological↗