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PubMed1995

[A comparative study of external respiration, gas exchange and circulation during static and dynamic muscular loads].

Indices of external breathing, gas exchange, and circulation were studied during bicycle ergometry and static ergometry of 19 healthy male volunteers which were stopped at critical levels of heart rate, arterial pressure, ECG or subjective fatigue. The bicycle workload maximum averaged 210 Watts, the static ergometric, 224 kg/s. Both types of exercises were characterized by unidirectional shifting of the external breathing and gas exchange indices; however, they were less pronounced at static loads. Arterial pressure and resistance of the peripheral vessels were the only indices of the array the dynamics of which complied with and even exceeded that during bicycling. In contrast to the dynamic muscular load, the maximal dynamics of gas exchange and external breathing during static ergometric workload was observed in the rehabilitation period following restoration of muscle blood flow; this must be taken into account in interpretation of test results. It is concluded that high information virtues of the static ergometric test in the context of predicting aerobatic load tolerance, and similarity of dynamics in the period of rehabilitation hold much promise for using the tests with static muscular loading in aviation and space medicine.

Adult↗
PubMed1993

Is group physical therapy superior to individualized therapy in ankylosing spondylitis? A randomized controlled trial.

PURPOSE: To study the effects of adding supervised group physical therapy to unsupervised individualized therapy in ankylosing spondylitis. METHODS: One hundred forty-four patients were randomized to exercises at home, or the same plus weekly group physical therapy for 9 months. Endpoints were spinal mobility, fitness (maximum work capacity by ergometry), functioning (Sickness Impact Profile, Health Assessment Questionnaire for the Spondylarthropathies, and Functional Index), and patient's global assessment of change on a 10-cm visual analogue scale. RESULTS: Thoracolumbar flexion and extension increased by an average of 0.5 cm (9%) after home exercises, and by 0.9 cm (16%) after group therapy. Maximum load in ergometry decreased by 2 W (1%) after home exercises, but increased by 7 W (4%) after group therapy. Global assessment improved by 0.3 (6%) after home exercises, and by 1.7 (34%) after group therapy. These three differences were statistically significant. There were no significant differences in chest expansion, cervical rotation, or the self-assessments of functioning. CONCLUSIONS: Group physical therapy proved superior to individualized therapy in improving thoracolumbar mobility and fitness, and had an important effect on global health reported by the patients.

Activities of Daily Living↗
PubMed1987

Comparison of arm and treadmill exercise at 85% predicted maximum heart rate.

Both treadmill exercise and arm exercise are used for evaluating coronary artery disease, but arm exercise has lower diagnostic sensitivity. We compared the two exercise modalities with respect to the rate-pressure product at 85% predicted maximal heart rate, a parameter frequently used to denote performance of sufficient exercise to derive clinical conclusions. At this heart rate, treadmill exercise resulted in a significantly greater systemic oxygen consumption (2.7 +/- .8 vs. 2.1 +/- .6 l/min) and rate-pressure product (30.6 +/- 4.4 X 10(3) vs. 28 +/- 3.3 X 10(3)) than arm ergometry. An inability to generate sufficient imbalance of myocardial oxygen supply and demand may account for the relatively higher incidence of false negative exercise tests seen with arm ergometry, especially if the exercise test is stopped when the patient attains 85% predicted maximal heart rate.

Adult↗
PubMed1993

Comparison of the effects of terazosin and enalapril on laboratory stress testing blood pressure in patients with essential hypertension.

It is the current opinion that an ideal antihypertensive drug should reduce blood pressure (BP) not only at rest but also during stressful situations. The current study was aimed to compare the effects of the selective alpha 1-adrenergic blocker terazosin (5 mg once daily) and of the angiotensin-converting enzyme inhibitor enalapril (20 mg once daily) on cardiovascular response to a set of standardized laboratory stressors, such as mental arithmetic, handgrip test and cycle ergometry, in a group of 16 essential hypertensive patients. The study was a randomized, double-blind, cross-over trial preceded by a placebo run-in period. Terazosin and enalapril had a comparable effect on resting BP, reducing systolic (SBP) and diastolic (DBP) blood pressure from 159.5 +/- 13.9/101.6 +/- 8.8 mm Hg during placebo by 7.8%/6.7% and by 11.3%/10.2%, respectively. The "response" rate to the two treatments was approximately the same, being 69% and 75% after terazosin and enalapril, respectively. During mental arithmetic, from an average of 181.6 +/- 17.8/118.6 +/- 11.5 mm Hg during placebo, BP was reduced by 11.5%/7.9% after terazosin and by 13.6%/8.5% after enalapril; during handgrip test, BP decreased from 207.2 +/- 22.2/142.2 +/- 13.6 mm Hg by 7.3%/8.4% after terazosin and by 7.7%/7.1% after enalapril; finally, during cycle ergometry, terazosin and enalapril lowered BP by 5.4%/6.7% and 7%/3.1%, respectively, from a placebo value of 215.5 +/- 17.3/127.6 +/- 11.2. No significant difference in antihypertensive efficacy was observed between the two drugs, either at rest and during stress testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed2006

Continuous ratings of breathlessness during exercise by children and young adults with asthma and healthy controls.

Although it is recommended and common practise for adults with respiratory disease to rate symptoms (e.g., dyspnea and/or leg discomfort) during exercise testing, there are no reports on whether children can rate their perception of breathlessness during exercise. Our aims were to evaluate the ability of children and young adults with asthma to continuously rate breathlessness on the 0-10 category-ratio (CR-10) scale with a computerized system during cycle ergometry, and to compare their results with those of healthy subjects. At an initial visit, subjects were familiarized with equipment and exercise protocol, and practised rating breathlessness while cycling. At a follow-up visit (2-4 days later), subjects performed incremental exercise and rated breathlessness using a computer system, mouse, and monitor. Changing the position of the mouse caused movement of a vertical bar located adjacent to the CR-10 scale to indicate the severity of breathlessness. Baseline characteristics of the 14 subjects with asthma (age, 15 +/- 3 years) and 33 healthy subjects (age, 16 +/- 2 years) were similar. The two groups had comparable levels of fitness as measured by peak oxygen consumption (VO(2)). Correlations between exercise physiologic variables (power production, VO(2), and minute ventilation) and breathlessness ratings were >0.90. Subjects reported progressively more ratings of breathlessness with increasing exercise intensities. There were no differences between groups for slopes, x-intercepts, and absolute thresholds relating physiologic variables and breathlessness. In conclusion, children and young adults with asthma as well as healthy individuals of comparable age successfully used the computerized system to rate breathlessness continuously during cycle ergometry. Both groups reported more ratings of breathlessness with this technique as exercise progressed.

Adolescent↗
PubMed1988

Changes in beta-adrenoceptors and leucocyte subpopulations after physical exercise in normal subjects.

Seven healthy volunteers were subjected to standardized bicycle ergometry. Before and at the end of exercise, leucocyte and lymphocyte subset distribution was assessed by immunofluorescence labelling with monoclonal antibodies and the cytofluorograf. Competition binding studies were performed on mononuclear leucocytes with a fixed amount of the radioligand 125I-(-)-cyanopindolol (125I-CYP) and increasing concentrations of the hydrophilic ligand (-)4-(3-tertiary-butylamino-2-hydroxypropoxy)-benzimidazol-2-one hydrochloride (CGP-12177). Total numbers of beta-adrenoceptors per cell and the receptor-ligand affinities were then derived by computer analysis. In separate experiments with blood obtained from resting subjects, beta-adrenoceptor numbers of lymphocyte subsets, which had been sorted by the fluorescence activated cell sorter, were determined by saturation binding of 125I-CYP. During exercise there was a twofold increase in total leucocyte numbers. The ratio between monocytes (4%) and lymphocytes (55%) remained constant, but the composition of lymphocyte subsets had changed. A twofold increase was observed for the lymphocyte population carrying the Leu-7 and the CD8 antigens or only the Leu-7 antigen, whereas the number of B cells and CD4 positive T cells increased only slightly. The lymphocyte phenotype changes appeared after 3 min, reached a maximum at the end of ergometry and had disappeared 30 min after exercise. Exercise led to a doubling of the number of beta-adrenoceptors in unseparated mononuclear leucocytes from 240 +/- 46 to 535 +/- 190 sites per cell (SD, n = 6). beta-Adrenoceptor numbers were higher on sorted Leu-7 positive cells (KD 14 +/- 6 pmol/l, Bmax 1174 +/- 233 sites/cell) and on CD8 positive cells (KD 145 +/- 79 pmol/l, Bmax 1577 +/- 670 sites/cell) than on monocytes (KD 39 +/- 31 pmol/l, 647 +/- 91 sites/cell). Very low specific 125I-CYP binding was found on Leu-7 and CD8 negative cells (less than 0.2 pmol/l). Before exercise the displacement curves with CGP-12177 fitted best a single site model, whereas after exercise 12% of the receptors were in a low affinity state for CGP-12177 indicating internalized receptors. (ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Serum creatine kinase as an indicator of local muscular strain in experimental and occupational work.

Serum creatine kinase (SCK) was measured in ten subjects in the laboratory before and after the performance of bicycle ergometry and a lifting task. SCK was significantly increased 24 h and 48 h after the lifting work but not after the bicycle ergometry, although the work performed on the latter was four-times as great as on the former. The lifting work resulted in muscle pain and tenderness and, for six subjects, in clinical signs of shoulder tendinitis. In a field study, an increase in SCK was noted among assemblers/welders and cash-register operators, but not among controllers and forklift-truck drivers. A health interview revealed that musculo-skeletal complaints were most often located in the upper extremity in the cases of the assemblers/welders and the cash-register operators. It is proposed that the SCK increase during work is a result of a high local muscular load due to fatigue and energy depletion of muscle cells producing a greater efflux of muscle enzymes. The evaluation of SCK changes during work may be an important tool in occupational health for early detection of work tasks producing local muscular strain.

Adult↗
PubMed1985

Thermoregulation during prolonged actual and laboratory-simulated bicycling.

Thermoregulatory and cardiorespiratory responses to bicycling 55 km (mean speed 9.7 m X s-1) outdoors (15 degrees C DB) were compared to equivalent cycle ergometry (90 min at 65% VO2max) in the laboratory (20-23 degrees C DB, 50% RH) in 7 trained cyclists. Outdoor environmental conditions were simulated with fans and lamps, and were contrasted with standard no-wind, no-sun laboratory conditions. Sweating rate was similar during outdoor and laboratory simulated outdoor cycling (0.90 and 0.87 to 0.94 1 X h-1 respectively). During outdoor bicycling, mean heart rate (161 bt X min-1) was 7-13% higher (p less than .05) than under laboratory conditions, suggesting a greater strain for a similar external work rate. The increase in rectal temperature (0.8 degrees C) was 33-50% less (p less than 0.05) at the cooler outdoor ambient temperature than in the laboratory. Thermoregulatory stress was greater under the no-fan, no-lamp laboratory condition than during simulated outdoor conditions (36-38% greater (p less than 0.05) sweating rate, 15-18% greater (p less than 0.01) mean skin temperature, 6.4 to 7.8 fold greater (p less than 0.01) amount of clothing-retrained sweat). The cooling wind encountered in actual road bicycling apparently reduces thermoregulatory and circulatory demands compared with stationary cycle ergometry indoors. Failure to account for this enhanced cooling may result in overestimation of the physiological stress of actual road cycling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Plasma volume changes during submaximal swimming.

The hemodynamic and diuretic responses of six swimmers were evaluated during 35 min of resting immersion, free swimming, and land bicycle ergometry at approximately 70% exercise specific maximal oxygen uptake. Venous blood, sampled at 0, 5, 10, 15, 25, and 35 min of each trials, was analyzed for hemoglobin. hematocrit, and total plasma protein concentration. Urine output was also measured. Resting immersion resulted in a significant (p less than 0.05) hemodilution (plasma volume = +2.5 +/- 1.5%) during the first 25 min and a return towards resting levels at the termination. During swimming exercise, plasma volume decreased by -15.9 +/- 1.3% (p less than 0.01). A similar -17.0 +/- 1.3% decrease was also evident during cycle ergometry. Urine output averaged 3.1 +/- 0.9 ml x min-1 during resting immersion, significantly greater than either swimming (1.0 +/- 0.1 ml x min-1) or cycling (0.4 +/- 0.2 ml x min-1). Total plasma protein concentration increased less during cycling compared to swimming (p less than 0.05) and was unchanged (p greater than 0.05) during resting immersion. It was concluded that the hemodynamic and renal responses to immersion are suppressed during swimming. It was also apparent that, despite possible differences in hemodynamics, plasma shift during exercise may be similar on land and in the water. It appears that the amount of plasma lost from the intravascular space during exercise may be independent of the muscle mass involved, but related to a combination of the ratio of active to total mass for each individual and body position.

Adult↗
PubMed1985

Receptor binding of propranolol is the missing link between plasma concentration kinetics and the effect-time course in man.

In a double-blind, placebo-controlled study in 6 healthy volunteers, the correlation between beta-adrenoceptor binding, the time course of the effect and plasma concentration kinetics was investigated from 0 to 48 h after a single oral dose of propranolol 240 mg. First, the in vitro beta-adrenoceptor interaction of propranolol was investigated. Propranolol inhibited beta-adrenoceptor binding to rat parotid (beta 1) and reticulocyte (beta 2) membranes in the presence of pooled human plasma with a Ki of about 8 ng/ml plasma. After oral administration of 240 mg propranolol, concentration kinetics in plasma could be described by a Bateman function with a fictive concentration at time 0 of 275 ng/ml plasma, and a mean elimination half-life of 3.5 h. Using the concentration kinetics of propranolol in plasma together with its in vitro beta-adrenoceptor binding characteristics in the presence of placebo plasma from each individual, the time course of antagonism against beta-adrenoceptor mediated effects was predicted. The latter was in agreement with the time course of propranolol-induced inhibition of tachycardia due to orthostasis. After bicycle ergometry, however, the time course of inhibition of tachycardia was shorter than was predicted. Plasma sampled at various times after propranolol administration inhibited beta-adrenoceptor binding of the radioligand 3H-CGP 12177 to rat reticulocyte membranes in a fashion reflecting the time course of inhibition of exercise tachycardia observed in the volunteers. A direct, linear relation was shown between the in vitro inhibition of beta-adrenoceptor binding by the plasma samples withdrawn after propranolol administration and the inhibition of exercise tachycardia observed in parallel. The results show that the concentrations of antagonist present in plasma are representative of the concentrations in the effect compartment. Deep compartments of drug distribution appear irrelevant to the effects of the drugs. The relation between the plasma concentration of propranolol and the reduction in heart rate at various levels of physical effort shows no significant inhibition at rest and increasing IC50-values from orthostasis to 2 min and to 4 min of ergometry. IC50-values after orthostasis are in the range of the Ki-values from in vitro receptor binding studies, whereas the IC50-values after exercise are shifted 2- to 3-fold to the right relative to the Ki-values. This finding is in agreement with increased beta-adrenoceptor stimulation with increasing effort (release of endogenous noradrenaline), which shifts the antagonist concentration-effect curve to the right.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

The influence of inspired oxygen on the oxygen uptake response to ramp exercise.

The relation between VO2 and work rate (WR) was examined in seven male subjects who performed ramp (1 W.3s-1) two-legged cycle ergometry to exhaustion while inspiring either hypoxic (12% O2), normoxic (21% O2), or hyperoxic (40% O2) air. The anaerobic threshold was estimated from respiratory gas exchange threshold (RGET). Prior to the RGET, the delta VO2/delta WR was greater under normoxic [mean (SD); 10.19(1.04) ml O2.min-1.W-1] and hyperoxic [10.44 (0.72)] conditions compared with hypoxia [9.34 (0.89)]. Above the RGET, the delta VO2/delta WR for hypoxia [8.91 (0.63)], normoxia [10.40 (0.77)], and hyperoxia [11.08 (0.48)] were all significantly different from each other. These data indicated that for two-legged, cycle, ramp ergometry in normoxia below the RGET, both the delta VO2/delta WR and response time was constant. Above the RGET, the normoxic VO2 response was the net result of a declining delta VO2/delta WR and a longer response time to the unsteady state character of a ramp exercise protocol.

Adult↗
PubMed1985

Blood lactate vs. exhaustive exercise to evaluate aerobic fitness.

This study compared the predictive power of a lactate-related index determined during submaximal cycle exercise to that of an exhaustive cycle ergometer test for evaluating the endurance exercise capacity of soldiers. The subjects (n = 48 males) performed a continuous exercise test to voluntary exhaustion on the cycle ergometer. Power output (PO) increased by 50 W steps each fourth min, with determinations of heart rate (HR), RPE and blood lactate concentrations (HLa) just prior to each PO increase. The PO at a 4 mmol L(-1) HLa concentration (WOBLA) was interpolated; based on the time to exhaustion the maximal PO that could be maintained for 6 min (Wmax6) was calculated from previously documented formulae. Subjects were timed during a 3000 m cross-country run. Both the cycle test and the run were performed again 3 months later, as was an additional 3000 m run with full military equipment weighing about 21 kg. All 3000 m times were significantly correlated (p less than 0.05) with both Wmax6 and WOBLA; similar predictive power was demonstrated for both Wmax6 and WOBLA, suggesting that accuracy in evaluation would not be sacrificed by substituting the submaximal for the exhaustive exercise test. HR and RPE-related indices showed markedly lower predictive power. The results extend the previously documented relationship between HLa during treadmill ergometry and running performance to include the use of cycle ergometry for the evaluation of running performance. The results also proved applicable to running performance while load carrying.

Adult↗
PubMed2001

[Lactate in cardiac rehabilitation].

BACKGROUND: Training increases work capacity and concomitantly quality of life, and also, according to new data, the life expectancy of patients with coronary heart disease and heart failure. At the same time, the importance of adequate training intensity increases aiming at low complications and high efficacy. ASSESSMENT OF EXERCISE CAPACITY: The objective of the present work is to define objective training guidance parameters in cardiac rehabilitation. Maximal exercise capacity must be distinguished from the performance without symptoms of oxygen deficit. The latter used to be early surpassed in untreated stabile angina pectoris. Within the last decade optimized therapy often yields a cardiac performance limit above the anaerobic threshold derived from lactate measurements. The concepts of aerobic and anaerobic thresholds derived from the lactate performance curve are introduced and modified leaving the 4 mmol/l lactate threshold concept to meet the criteria for performance capacity and breaking point in cardiac patients. The relationship to threshold concepts derived from spirometric data is mentioned as well as from stress hormones. The heart rate at the anaerobic threshold measured at treadmill ergometry systematically lies above the one from bicycle ergometry. Lactate increases faster with advancing age and the anaerobic threshold is earlier reached and progressively so because of the reduced muscle mass and reduced endurance capacity of people of the industrialized countries. IMPORTANCE: The determination of the anaerobic threshold as an objective criteria independent of motivation leads to training control, as shown by an example. Ineffective training above the threshold giving rise to catecholamines can be avoided by lactate performance diagnostic. Additionally, the success of rehabilitation measures can objectively be quantified and documented much better from the threshold work capacity than from maximal exercise tolerance. Preliminary reports indicate the importance of lactate diagnostics for rehabilitation guidance in heart failure.

Adult↗
PubMed1998

["Cox/Maze-III operation" as surgical therapy of chronic atrial fibrillation during mitral valve and atrial septal defect II operation].

PROBLEM: Atrial fibrillation is associated with significant morbidity and mortality. The increased risk of thromboembolism makes constant anti-coagulation necessary, while the absence of atrial contraction worsens the hemodynamic situation. In this study we examined the results of simultaneous surgical treatment of chronic atrial fibrillation through "Cox/Maze-III-procedure" while mitral valve surgery and atrial septal closure. PATIENTS AND METHODS: Between February 1995 and July 1997 sixteen patients aged 50 to 72 y (mean: 59 y) underwent open heart surgery (mitral valve replacement n = 10, reconstruction n = 3; mitral valve reconstruction and atrial septal closure n = 1, atrial septal closure n = 1, thrombectomy from left atrium n = 1) and "Cox/Maze-III-procedure" in one session. Preoperative duration of chronic atrial fibrillation was between 2 and 12 y (mean: 5.0 y). The patients were examined preoperatively and postoperatively 3, 6, 12, and 24 months after surgery using the following methods: transesophageal echocardiography (TEE), ECG, long-term ECG, and stress ergometry. RESULTS: During the early postoperative period (< 7 d) all of the patients were in sinus rhythm or atrial pacing; eight patients intermittently had atrial fibrillation. In the follow-up period from 1 to 27 months (mean 14 months), 15 patients have a stable sinus rhythm (94%). One patient, preoperatively known to have intermittent tachybradycardia, received a pacemaker 2 months postoperatively for sinus bradycardia. Postoperatively in TEE patients showed left atrial contraction with improvement of hemodynamic situation. Stress ergometry 6 months postoperatively showed lower increasements of heart rate, at 12 months normal frequency. CONCLUSION: The surgical treatment of chronic atrial fibrillation through "Cox/Maze-III-procedure" can be performed combined with other heart operations without increased perioperative or postoperative risks. The Maze-procedure is an effective surgical therapy of chronic atrial fibrillation. Postoperatively there is an improvement of the hemodynamic situation because of sinus rhythm and synchrone atrioventricular contraction.

Aged↗
PubMed1999

[Papillary muscle rupture during stress ECG after myocardial infarct].

The case of a 57 year old patient is reported, who suffered from an acute myocardial infarction with maximum CK and CKMB values of 821 and 84 U/l, respectively. The patient underwent bicycle exercise testing 9 days after a myocardial infarction in 25 W steps every 2 min starting with 50 W. The ergometry was interrupted at 125 W because of ST segment depression of 0.28 mV in V6. Systolic blood pressure dropped to 55 mm Hg, combined with severe angina and shock. Volume substitution and catecholamines did not elevate blood pressure. Immediate M-mode and Doppler echo revealed a "stiletto"-shaped mitral regurgitation profile typical of acute mitral valve insufficiency. The transesophageal echocardiogram showed a distinct mass moving between the left ventricle and left atrium, diagnostic of papillary muscle rupture. Despite of shock, mitral valve replacement was performed successfully. To our knowledge, this is the first report of a papillary muscle rupture during exercise testing after myocardial infarction. Papillary muscle rupture can be induced by exercise. This fateful event may not be predicted by the course of the ergometry. In case of hypotension during exercise, papillary muscle rupture should be considered. The diagnosis is to be established by transesophageal echocardiography.

Echocardiography, Doppler↗
PubMed2001

[Anti-ischemic efficacy of sustained-release isosorbide-5-mononitrate: echocardiography during mental and physical stress].

This double-blind, placebo-controlled study investigated the anti-ischemic efficacy of sustained-release isosorbide-5-mononitrate (IS-5-MN) 100 mg/day on the basis of stress echocardiography and stress ECG in patients subjected to physical (bicycle ergometry) and mental stress (mental stress test). Forty male patients with a stress-induced ST segment depression of > 0.1 mV during bicycle ergometry who received beta blocker background therapy were randomized into the 14-day treatment phase (IS-5-MN: 20 patients, placebo: 20 patients). After 2 weeks of treatment, a significant prolongation of the time to 0.1 mV ST segment depression and of the time to stress-induced anginal attacks could be demonstrated for IS-5-MN in the stress echocardiography. A significantly greater reduction in the wall motion score determined via stress echocardiography was found in IS-5-MN-treated vs. placebo-treated patients relative to baseline. There were only 4 patients who developed ST segment depression during mental stress; however, the echocardiography demonstrated a significantly greater reduction of the wall motion score after 2 weeks of treatment vs. baseline in the IS-5-MN vs. the placebo group. The efficacy of sustained-release IS-5-MN 100 mg/day was proved in this study both by stress echocardiography, and stress electrocardiography in situations of physical and mental stress. It was found that echocardiography is more sensitive for detecting ischemic reactions induced by mental stress than ECG.

Adult↗
PubMed2006

Lactate increase and oxygen desaturation in mitochondrial disorders--evaluation of two diagnostic screening protocols.

BACKGROUND: Mitochondrial disorders are characterized by an accumulation of lactate and an insufficient oxygen extraction from blood during exercise. Therefore, both parameters (lactate and oxygen saturation) can be used as screening tests in mitochondrial disorders. However, conflicting results regarding sensitivities and specifities of both tests have been reported. METHOD: We examined 27 patients with genetically defined mitochondrial disorders (single deletions n = 15, multiple deletions n = 5, A3243G mutation n = 7), patients with other neuromuscular disorders, and healthy controls. In the first test subjects performed intermittent isometric handgrip exercise (0.5 Hz) at 80% (3 minutes) and 30% (3 and 15 minutes) of maximal contraction force (MCF). Oxygen saturation and partial pressure in cubital venous blood from the exercising arm were measured. In the second test subjects underwent cycle ergometry at 30 W for 15 minutes. Venous lactate at rest, during and 15 minutes postexercise was determined. RESULT: Both tests showed specificities of 92-96%. Sensitivities for changes of venous oxygen partial pressure and oxygen saturation ranged from 21-26% at 80% MCF for 3 minutes to 47-58% at 30% MCF for 15 minutes. Sensitivities for venous resting, peak, and post-exercise lactate was 33%, 58%, and 67%, respectively. The degree of deoxygenation, however,was independent of the intensity and duration of the applied forces. Oxygen desaturation and lactate increase in patients with mitochondrial disorders were not different in patients with and without clinical symptoms of myopathy. There were significant correlations between the heteroplasmy and both the degree of oxygen desaturation and lactate increase in patients with single deletions. In patients who performed both protocols (n = 16) a combination of both tests increased sensitivity up to 87%. CONCLUSION: Oxygen desaturation in forearm exercise tests and lactate increase in cycle ergometry tests show a high specifity but only moderate sensitivity. Combination of the two screening test clearly increases the sensitivity.

Adolescent↗
PubMed2002

Maximal lactate steady state concentration (MLSS): experimental and modelling approaches.

It is assumed that the maximal lactate steady state (MLSS) can be used to establish the highest workload that can be maintained over time without continual blood lactate accumulation. In untrained subjects, and in both elite and junior athletes, MLSS occurs at different blood lactate concentrations (BLC) for different exercise modes. This suggests that MLSS depends on the motor pattern of exercise and may be a function of the relationship between power output per unit muscle mass and the mass of the muscle primarily engaged in the activity. A computer model has been developed that takes account of current theories relating to the effect of exercise on BLC and to the factors that limit oxygen transport to the muscle cell. Simulations using this model support the suggestion that load per unit of engaged muscle mass accounts for task-specific levels of MLSS. Simulated differences in MLSS appear because the MLSS does not necessarily reflect the real maximal equilibrium between lactate formation and utilization, the LLSS. The higher difference between MLSS and LLSS measured in rowing ergometry compared to cycle ergometry seems to indicate a greater task sensitivity of the BLC response to given changes of exercise intensity during rowing. Whether such a difference may be relevant for a deeper understanding of task-specific training strategies remains a matter for further investigation.

Homeostasis↗