SEARCH · PubMed Health

Results for “Workload”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89Linked to original sources

PubMed1996

Determination of maximal lactate steady state response in selected sports events.

Maximal lactate steady state (MLSS) refers to the upper limit of blood lactate concentration indicating an equilibrium between lactate production and lactate elimination during constant workload. The aim of the present study was to investigate whether different levels of MLSS may explain different blood lactate concentration (BLC) levels at submaximal workload in the sports events of rowing, cycling, and speed skating. Eleven rowers (mean +/- SD, age 20.1 +/- 1.5 yr, height 188.7 +/- 6.2 cm, weight 82.7 +/- 8.0 kg), 16 cyclists and triathletes (age 23.6 +/- 3.0 yr, height 181.4 +/- 5.6 cm, weight 72.5 +/- 6.2 kg), and 6 speed skaters (age 23.3 +/- 6.6 yr, height 179.5 +/- 7.5 cm, weight 73.2 +/- 5.6 kg) performed an incremental load test to determine maximal workload and several submaximal 30-min constant workloads for MLSS measurement on a rowing ergometer, a cycle ergometer, and on a speed-skating track. Maximal workload was higher (P < or = 0.05) in rowing (416.8 +/- 46.2 W) than in cling (358.6 +/- 34.4 W) and speed skating (383.5 +/- 40.9 W). The level of MLSS differed (P < or = 0.001) in rowing (3.1 +/- 0.5 mmol.l-1), cycling (5.4 +/- 1.0 mmol.l-1), and in speed skating (6.6 +/- 0.9 mmol.l-1). MLSS workload was higher (P < or = 0.05) in rowing (316.2 +/- 29.9 W) and speed skating (300.5 +/- 43.8 W) than in cycling (257.8 +/- 34.6 W). No differences (P > 0.05) in MLSS workload were found between speed skating and rowing. MLSS workload intensity as related to maximal workload was independent (P > 0.05) of the sports event: 76.2% +/- 5.7% in rowing, 71.8% +/- 4.1% in cycling, and 78.1% +/- 4.4% in speed skating. Changes in MLSS do not respond with MLSS workload, the MLSS workload intensity, or with the metabolic profile of the sports event. The observed differences in MLSS and MLSS workload may correspond to the sport-specific mass of working muscle.

Adult↗

PubMed2001

Prolonged stage duration during incremental cycle exercise: effects on the lactate threshold and onset of blood lactate accumulation.

The aim of this study was to investigate whether increasing the duration of workloads from 3 min to 8 min during incremental exercise would influence workload (W), oxygen consumption (VO2) and heart rate (HR) at the lactate threshold (LT) and the onset of blood lactate accumulation (OBLA). Two groups of six male cyclists were assigned to a well-trained (WT) and recreational (REC) group on the basis of their performance in a maximal incremental ramp test. Each subject then performed two incremental lactate tests (EXT) consisting of six workloads of either 3 min (EXT3-min) or 8 min (EXT8-min) duration. At the completion of each workload whole capillary blood samples were obtained for the determination of blood lactate (BLa) concentration (mM). Power output (Watts, W), HR and VO2 were averaged in the final minute of each workload as well as in the third minute of the EXT8-min. The workload, HR and VO2 at the LT and OBLA were subsequently determined from the data of EXT3-min and EXT8-min. The results demonstrate that workload and VO2, but not HR, at the LT and OBLA were higher in the WT cyclists. At the same time, the workload at the LT obtained from the results of the EXT3-min was significantly (P < 0.05) higher then the value obtained in the EXT8-min in the WT subjects but not the REC subjects. However, the workload, VO2 and HR at the OBLA, together with the VO2 and HR at the LT were not significantly different when calculated from data obtained from EXT3-min or EXT8-min. The data obtained in this study suggest that incremental exercise protocols using workloads of duration longer than 3 min have the effect of increasing the workload at the LT in well-trained cyclists. However, the OBLA determined in exercise tests using stage increments of either 3 min or 8 min is similar in cyclists of different training status.

Adaptation, Physiological↗

PubMed2005

Maximal lactate steady state concentration independent of pedal cadence in active individuals.

The maximal lactate steady state (MLSS) is defined as the highest blood lactate concentration that can be maintained over time without a continual blood lactate accumulation. The objective of the present study was to analyze the effects of pedal cadence (50 vs. 100 rev min(-1)) on MLSS and the exercise workload at MLSS (MLSS(workload)) during cycling. Nine recreationally active males (20.9+/-2.9 years, 73.9+/-6.5 kg, 1.79+/-0.09 m) performed an incremental maximal load test (50 and 100 rev min(-1)) to determine anaerobic threshold (AT) and peak workload (PW), and between two and four constant submaximal load tests (50 and 100 rev min(-1)) on a mechanically braked cycle ergometer to determine MLSS(workload) and MLSS. MLSS(workload) was defined as the highest workload at which blood lactate concentration did not increase by more than 1 mM between minutes 10 and 30 of the constant workload. The maximal lactate steady state intensity (MLSS(intensity)) was defined as the ratio between MLSS(workload) and PW. MLSS(workload) (186.1+/-21.2 W vs. 148.2+/-15.5 W) and MLSS(intensity) (70.5+/-5.7% vs. 61.4+/-5.1%) were significantly higher during cycling at 50 rev min(-1) than at 100 rev min(-1), respectively. However, there was no significant difference in MLSS between 50 rev min(-1) (4.8+/-1.6 mM) and 100 rev min(-1) (4.7+/-0.8 mM). We conclude that MLSS(workload) and MLSS(intensity) are dependent on pedal cadence (50 vs. 100 rev min(-1)) in recreationally active individuals. However, this study showed that MLSS is not influenced by the different pedal cadences analyzed.

Bicycling↗

PubMed1995

Anaerobic threshold, individual anaerobic threshold, and maximal lactate steady state in rowing.

Anaerobic threshold, also termed 4.0 mmol.l-1 threshold (AT4), and individual anaerobic threshold (IAT), presumably indicate the workload corresponding to maximal lactate steady state (MLSS) during an incremental workload test. MLSS is the highest blood lactate concentration (BLC) resulting in a steady state during constant workload. The purpose of the present investigation was to ascertain the validity of AT4 and IAT as related to MLSS during rowing ergometry. Nine rowers (mean +/- SD age 20.2 +/- 1.6 yr; HT 187.2 +/- 4.9 cm; WT 81.1 +/- 6.3 kg) performed an incremental load test to determine AT4, IAT and maximal workload and several 30 min constant workloads for MLSS measurement on a mechanical rowing ergometer. The incremental load test was conducted at 215 W and increased by 35 W every 3.0 min. The first 30 min constant workload was conducted at 60% of maximal workload (363.3 +/- 45.1 W). If a constant load test resulted in a steady state of BLC subsequent constant load tests were performed and workload increased by 3% to 10% after each constant load test until no steady state of BLC could be observed. AT4 (287.0 +/- 20.5 W), IAT (287.1 +/- 25.1 W), and BLC at IAT (4.2 +/- 0.8 mmol.l-1) were higher (P < 0.001) compared to MLSS workload (255.1 +/- 17.5 W) and MLSS (3.0 +/- 0.6 mmol.l-1), respectively. Independent of the practical application of AT4 and IAT, in rowing AT4 and IAT do not represent MLSS workload.

Anaerobic Threshold↗

PubMed2001

Measuring the academic radiologist's clinical productivity: applying RVU adjustment factors.

RATIONALE AND OBJECTIVES: To improve understanding of academic radiologists' clinical workloads, the Society of Chairmen of Academic Radiology Departments (SCARD) performed surveys to collect workload data for radiologists in 20 departments; workload was measured in relative value units (RVUs) per full-time equivalent (FTE). Although they were useful for comparisons within some subspecialties, the workload data proved inadequate for comparisons across sections, and adjustment factors were needed for each Current Procedure Terminology (CPT) code. MATERIALS AND METHODS: All CPT codes for examinations were divided into groups with similar radiologist work effort. Focusing on radiologists who worked almost exclusively in each group, the authors created adjustment factors by using data from the individual radiologists at each institution. RESULTS: The adjustment factors are 0.50 for angiography, 0.58 for computed tomography and magnetic resonance imaging, and 1.0 for nuclear medicine, plain radiography, and special procedures (no adjustment needed for these groups). These factors are multiplied by the work RVUs for each examination to create the adjusted workload RVUs. CONCLUSION: The SCARD survey provided very useful clinical workload data, with workload measured in work RVUs per FTE for specific subspecialty sections. The new adjusted workload RVUs allow comparison of radiologists' workload across subspecialties.

Academic Medical Centers↗

PubMed2004

Short-term low-carbohydrate diet dissociates lactate and ammonia thresholds in men.

A low-carbohydrate (L-CHO) diet has been shown to shift the lactate threshold toward higher workloads. The aim of the present study was to examine the effect of an L-CHO diet on the ammonia threshold and to compare it with the lactate threshold in men. The plasma catecholamine threshold was also measured. Eight young, untrained men participated in the study. Two exercise tests with graded workload were performed. The workload was increased every 3 minutes by 40 W until volitional exhaustion. The first test was performed after 3 days of a controlled mixed diet. After the first test, the mixed diet was switched to a L-CHO diet. Three days later the same test was repeated. The blood concentration of lactate, ammonia, noradrenaline, and adrenaline was measured before and after each workload in both groups. It was found that the concentration of the examined compounds in the blood increases exponentially with graded workload after each kind of diet. This led us to calculate the blood ammonia, lactate, epinephrine, and norepinephrine thresholds. The thresholds were defined as points at which the concentration of a given compound starts to increase in a nonlinear fashion, which is calculated using 2 segmental linear regressions. After the mixed diet, the threshold for each compound occurs at the same workload. The L-CHO diet resulted in dissociation of the lactate threshold from the ammonia threshold: the lactate threshold was shifted toward a higher workload, whereas the ammonia threshold was shifted toward a lower workload. The norepinephrine threshold was also shifted toward a lower workload, and the epinephrine threshold remained unchanged. The results obtained indicate that an L-CHO diet accelerates production of ammonia and delays production of lactate during graded exercise, as well as that diet must be strictly controlled when ammonia and lactate thresholds are measured.

Adult↗

PubMed2005

Impact of UK colorectal cancer screening pilot on primary care.

BACKGROUND: The UK Colorectal Cancer Screening Pilot has recently been completed to evaluate the feasibility of screening using the faecal occult blood test. Screening will be phased in over the next several years, and it is important to consider the impact on the NHS workforce. AIM: To determine the impact of the UK Colorectal Cancer Screening Pilot on primary care workload. DESIGN OF STUDY: A retrospective survey and prospective audit of general practice staff. SETTING: General practice. METHOD: Workload impact was assessed using a postal questionnaire and a prospective audit of activity in participating practices. Questionnaires were sent to practices that had been involved in the Pilot between 6 weeks and 1 year previously. They were sent to a random sample of 59 practices in Scotland and 60 practices in England between February 2001 and March 2002. Audit forms were sent prospectively to 60 practices involved in the Pilot between May 2001 and September 2002. RESULTS: Sixty-seven per cent of GPs, 82% of practice managers, 69% of practice nurses, and 70% of receptionists responded to the questionnaire. Of 60 practices contacted to take part in the workload audit, 38 returned completed 'workload impact audit' forms. Most practice staff indicated they spent 2% or less of their time during the screening period on Pilot-related activities. Forty per cent of GPs thought that a national colorectal cancer screening programme would substantially impact on the workload in primary care. However, there were variations by country: practice staff in Scotland were more likely to think that it would substantially impact on workload than practice staff in England (44.7% versus 26.6%). CONCLUSIONS: The surveys and audit demonstrate that the Pilot has had a discernible, albeit modest, impact on workload in primary care. Workload of particular significance to primary care personnel includes increases in paperwork, administration, and information provision to patients. The majority of primary care staff support the introduction of a colorectal cancer screening programme. However, there is a strong perception, particularly among GPs, that a national programme of faecal occult blood test screening will impact significantly on workload in primary care, and that primary care-based activities generated through screening should be adequately resourced and remunerated.

Aged↗

PubMed2000

Maximal lactate-steady-state independent of performance.

PURPOSE: The maximal lactate steady state (MLSS) corresponds to the highest workload that can be maintained over time without a continual blood lactate accumulation. MLSS and MLSS intensity have been speculated to depend on performance. Experimental proof of this hypothesis is missing. METHODS: 33 male subjects (age: 23.7 +/- 5.5 yr, height: 181.2 +/- 5.3 cm, body mass: 73.4 +/- 6.4 kg) performed an exhausting incremental load test to measure peak workload and three to six 30-min constant load tests on a cycle ergometer to determine MLSS. RESULTS: MLSS (4.9 +/- 1.4 mmol x L(-1)) was independent of MLSS workload (3.4 +/- 0.6 W x kg(-1)) and peak workload (4.8 +/- 0.6 W x kg(-1)). MLSS intensity (71.1 +/- 6.7%) did not correlate with peak workload or MLSS (P > 0.05). A positive correlation was found between peak workload and MLSS workload (r = 0.82, P < 0.001). CONCLUSIONS: MLSS and MLSS intensity are independent of performance but subjects with higher maximum performance have higher MLSS workloads. The combination of various fitness related effects on both, the production and the disappearance of lactate during exercise, may explain that different MLSS workloads coincide with similar levels of MLSS and MLSS intensity.

Adolescent↗

PubMed2001

[Determining the extent of intensive physical performance in patients with coronary heart disease].

Intensive physical exercise improves cardiac perfusion, skeletal muscle function and risk factors in patients with coronary artery disease (CAD). Otherwise, overdosed intensity can induce training adaptation as well as cardiac events. Therefore, we tested whether exercise intensity corresponding to an equilibrium between lactate production and elimination from the blood during incremental exercise tests represented the blood lactate [Lac-]B steady-state intensity during constant physical training. Randomized into two groups with 30 CAD patients each (T1: 25 male, 5 female; 59 +/- 7 years; T2: 26 male, 4 female; 60 +/- 9 years), the patients initially performed two successive incremental exercise tests. In the first test, workload was increased stepwise until exhaustion or symptom limitation (maximal workload: T1 142 +/- 48 watts, T2 145 +/- 45 watts) with the corresponding [Lac-]B accumulation of up to 6.7 +/- 2.6 (T1) or 6.5 +/- 2.0 (T2) mmol/l, respectively. After a seven minute active rest the second test began with 25 watts, increased with 5 (maximum workload in first test < 100 watts) or 10 watts per minute, respectively. During lower intensities in the second test, [Lac-]B initially decreased to an individual lactate minimum intensity (workload at LMI 83 +/- 32 in T1 or 86 +/- 29 in T2 watts, respectively; [Lac-]B at LMI 4.6 +/- 2.2 and 4.9 +/- 1.8 mmol/l, respectively) and then increased again. To check if the individual LMI represented the [Lac-]B steady-state workload in constant workload exercise, the patients performed 30 min constant load tests with the LMI (CT1) or a 30 min constant load test with an intensity 10% above the LMI (CT2), respectively. The workload in CT1 was 83 +/- 32 watts with a mean exercise time of 29.0 +/- 1.7 min. After 10 min of exercise the [Lac-]B steady state was reached at 3.3 +/- 1.4 mmol/l with no further increase in the last 20 min. The mean workload in CT2 was 95 +/- 31 watts with an exercise time of 23.3 +/- 8.3 min (p < 0.01). [Lac-]B increased from 4.4 +/- 1.7 mmol/l after 10 min to 4.7 +/- 2.0 mmol/l at the end (p < 0.01). Fifty percent of patients stopped CT2 before the 30 minute end. The results indicates that the LMI, estimated during lactic acidosis in two successive incremental tests, represented the individual lactate steady-state intensity also during constant load exercise. Therefore, training regimens for CAD patients could be deduced from LMI.

Aged↗

PubMed2000

The effect of nonscreening smears on screening smear results: a statistical analysis with its implications for the NHS cervical screening programme.

This is a statistical analysis of individual NHS Cervical Screening Programme laboratories screening smear 'pick-up' rates (defined here as percentage low grade and percentage high grade of total adequate smears for ages 20-64 years derived from general practitioners and community clinics) in relation to their nonscreening smear workload proportion (here defined as percentage nonscreening smears of total laboratory workload from all sources for all ages). This was achieved by the use of three one way ANOVA models in order to receive a complete overview of the results. The models were applied to the following: (1) Laboratories with a total workload of less than 15000 general practitioner (GP) and community clinic smears; (2) laboratories with a total workload of greater than 15000 GP and community smears and; (3) all laboratories (i.e. a combination of 1 and 2). The 'test' groups within each of these models comprised three subgroups based on the percentage of laboratory workload that consisted of smears from a nonscreening source. This figure ranged from 2.8% to 82.6%. The subgroups were divided so as to contain approximately the same number of laboratories in each one (172 laboratories in total, 42 with workload < 15000 and 130 with > 15000). The results show that laboratories high and low grade pick-up rates have a positively correlated but variable relationship with the proportion of their workload that consists of nonscreening smears. The results show significance overall at the 5% level for high grade and the 10% level for low grade (high grade at P = 0.045 and low grade at P = 0.071). Significance for laboratories viewing less than 15000 screening smears at the 1% level (high grade P = 0.006 and low grade P = 0.005). They show no significance, however, for laboratories viewing more than 15000 screening smears (high grade P = 0.457 and low grade P = 0.622). There is an intriguing possibility that a greater exposure to abnormal smears results in a greater tendency to detect them. The current data provides no evidence to support the NHS Executive's use of 15000 as a designated figure when quality monitoring and service provision becomes a specific issue. The closure or amalgamation of laboratories with workloads less than this would appear to have no scientific evidence base.

Adult↗

PubMed1992

Effect of education, occupation and some lifestyle factors on common rheumatic complaints in a Swedish group aged 50-70 years.

The relation between common rheumatic diseases such as osteoarthrosis, arthralgia without definite signs of osteoarthrosis, subacromial shoulder pain, different forms of tendinitis, low back pain and neck pain, and the level of formal education, occupational workload and some lifestyle factors were examined in 502 of 900 randomly selected subjects aged 50-70 years. The group with rheumatic complaints had a higher proportion of subjects with a lower level of formal education (less than or equal to eight years) by bivariate analysis. In multivariate analysis, the major risk factors were: a self rated heavy workload (odds ratio (OR) 6.4), sleep disturbance (OR 3.6), and advanced age (OR 2.0 per five year increase) for osteoarthrosis; a self rated heavy workload for subacromial shoulder pain (OR 5.4) and low back pain (OR 4.8); and a self rated heavy workload (OR 8.0) and female sex (OR 4.8) for neck pain. A self rated heavy workload was strongly correlated with a low level of formal education. A heavy workload (i.e. previous or present principal occupation) could only be confirmed in the groups with neck pain and low back pain on the basis of available occupational classification data. Neck pain was thus associated with occupations entailing repetitive tasks and awkward posture with respect to the neck, shoulders, and back. Low back pain was associated with occupations entailing awkward posture with respect to the neck, shoulders, and back, and occupations entailing exposure to vibration and heavy manual work. It is concluded that, in a cross sectional sample of an elderly population, a low level of formal education and self rated heavy physical work are associated with the occurrence of adult rheumatic complaints, though the self rated heavy workload could only be verified in the groups with neck pain and low back pain. There correlations between heavy work and low back pain, and especially neck pain, suggest that successful prevention would mean a substantial economic gain to the community. Whether the level of education is a marker of risk factors other than a heavy occupational workload needs further evaluation.

Age Factors↗

PubMed2005

Who's overworked and who's underworked among radiologists? An update on the radiologist shortage.

PURPOSE: To use weighted data and information on hours worked to investigate further the market for radiology services by analyzing the extent to which radiologists wanted less or more work in 2003. MATERIALS AND METHODS: Weighted data were used from the American College of Radiology's 2003 Survey of Radiologists. A statement on the survey cover sheet indicated that responses would not be individually identified, and responses were processed by an outside contractor for enhanced assurance of confidentiality. The authors analyzed workloads and the desired workload changes for radiologists who wanted less work, those who wanted more work, and those who sought no change in their workload. Multivariate regression analysis was also used to identify the probable causal links between characteristics of radiologists and the practices they work in and their desire for a workload change. RESULTS: The net average workload change sought was approximately 0.1% of the current workload and was not significantly different from zero, indicating that the overall total workload is what is desired. However, radiologists working in academic or government practices sought 4% and 12% more work, respectively, while those in private practices sought 2% less. In addition, radiologists working in nonmetropolitan practices sought 3% less work than those in large metropolitan areas. CONCLUSION: There was an overall balance between the demand and the supply of radiologists in 2003. The authors found some imbalances, including surpluses in academic and government-owned practices, a shortage of radiologists in private radiology groups, and a shortage in nonmetropolitan areas. There were differences in radiologists' desired workload by sex, age, and type and location of practice.

Humans↗

PubMed1999

[Is the system of assigned general practitioners more demanding for female than male physicians?].

The Ministry of Health has tried out and evaluated the personal doctor system in four municipalities in Norway (1993-96). We have explored the reported workload, and whether there were any reporting differences between female and male doctors. We also explored some of the possible factors explaining the reported increased workload. The doctors reported their workload by a postal questionnaire survey. The information from the questionnaires was linked to the doctors' lists received from the National Insurance Administration and were analysed separately for male and female doctors. Female doctors had more women and children on their patient lists, male doctors more men and elderly people. 50% of all the doctors reported that their workload was too heavy. There were no significant differences between male and female doctors in reporting too heavy total workload. 52% of male doctors and 82% of female doctors reported an increase in workload after the introduction of personal doctor system (p < 0.05). Of the explaining factors analysed, only women-dominated lists were associated with reported heavy workload among female doctors (p < 0.05). If the personal doctor system is to be introduced as a national system, it would seem important to have some control over the generation of lists to avoid too heavy workloads.

Adult↗

PubMed1987

An experimental evaluation of psychophysical criteria for repetitive lifting work.

Two experiments were performed to test the reliability and validity of psychophysically determined maximum acceptable workloads for setting lifting standards. The perceived workload in a repetitive diagonal lifting task was found to be a positively accelerated function of the weight lifted and of the work pace respectively. A twofold increase in objective workload resulted in a four- to fivefold increase in perceived workload. This relation was independent of previous occupational experience of lifting work. The psychophysically assessed maximum acceptable workloads for this type of lifting task appeared to be satisfactorily reproducible when subjects had to adjust work pace or when they were left free to adjust both the weight and the work pace. However, the results raised several questions concerning the applicability of the psychophysical assessment of maximum acceptable lifting work. Slight changes in the instructions given to the subjects had a definite effect on the selection of workloads. Furthermore, the workloads selected by subjects with previous occupational experience of lifting work - i e, warehouse workers - were systematically lower than those selected by subjects without such previous experience - i e, office employees. At the same time, the warehouse workers rated perceived exertion higher than the office employees, indicating that previous occupational experience of lifting work enhanced the subjective assessment of physical effort. There were no consistent relations between the workloads found acceptable by the subjects and their physical characteristics and performance capacity.

Journal Article↗

PubMed1987

Metabolic and ventilatory responses during very low level exercise.

1. Nine male and six female healthy subjects were studied during supine bicycle exercise at workloads of 12 and 37 W; pedalling rates varied between 30 and 50 cycles/min at each workload. Measurements were made of oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), tidal volume (VT), respiratory frequency (fR), inspiratory and expiratory time (TI, TE) and mean inspiratory flow (VT/TI) using a non-invasive canopy-computer-spirometer system. 2. At rest, males had greater values of VE, VT, TI, inspiratory duty cycle (TI/TTOT), VCO2 and VO2, and a lower fR, than females. 3. At the lower workload, VO2, VCO2, VE, VT and VT/TI increased linearly with increasing pedalling rate, whereas at the higher workload there was a decrease in VO2 and little or no change in ventilatory parameters from 30 to 50 cycles/min except for an increase in fR in females. 4. While performing supine exercise, there was an effect of pedalling rate on ventilatory and metabolic parameters at the low workload (12 W) which diminished at the higher workload (37 W). An increase in pedalling rate appears to enhance efficiency at these low workloads. 5. Differences between the sexes during exercise generally include: (a) a higher breathing frequency, (b) a greater mechanical efficiency, and (c) lower ventilatory equivalents of O2 and CO2 (VE/VO2 and VE/VCO2) during the higher workload in females than males.

Adult↗

PubMed2002

Mechanical control of extracellular space in rabbit atria: an intimate modulator of the translocation of extracellular fluid and released atrial natriuretic peptide.

We have previously shown that extracellular fluid (ECF) is translocated by atrial contraction. Following on from this finding we have proposed a two-step sequential mechanism for the regulation of stretch-activated secretion of atrial natriuretic peptide (ANP): myocytic release of ANP into the surrounding paracellular space followed by the translocation of ECF with the released ANP into the bloodstream. This latter step is induced by atrial contraction, and is therefore controlled by atrial workload. However, the mechanism that regulates the changes in translocation of the ECF has not been defined. To define the relationship between the atrial workload, ECF translocation, size of the extracellular space (ECS) and ANP secretion, experiments have been performed in isolated perfused beating rabbit atria. Atrial workload, transendocardial translocation of the ECF and the secretion of ANP were quantified. Changes in the size of the atrium and the ECS were determined by a newly developed methodology in the beating atria. Atrial workload determined the translocation of the ECF and released ANP with waning of the translocation at higher myocardial workloads. Atrial workload inversely determined the size of the atrium and the ECS. The latter directly determined the translocation of the ECF in terms of atrial workload. From these data we suggest that the size of the ECS is an intimate modulator of the translocation of the ECF and released ANP, and that the phenomenon of waning of the transendocardial translocation that appeared at higher atrial workloads is closely related to the shrinkage of the ECS.

Animals↗

PubMed1984

Effects of physical conditioning on left ventricular ejection fraction in patients with coronary artery disease.

To address the hypothesis that physical conditioning may improve left ventricular function in patients with coronary artery disease, we performed first-pass radionuclide ventriculography in 53 patients at rest and during upright bicycle exercise before and after 6 to 12 months of exercise training. The peak bicycle workload achieved before the onset of fatigue, dyspnea, or angina increased by an average of 22% (p = .0001) after training, and mean heart rate at a workload equal to the pretraining maximum workload was decreased by 10 beats/min after training (p = .0002). Of 21 subjects with angina or exertional ST segment depression before training, 15 (71%) were able to exercise to the same workload without these manifestations of ischemia after training. Whereas neither mean resting left ventricular ejection fraction (LVEF) nor LVEF at peak exertion was significantly altered, mean LVEF at the pretraining maximum workload was increased from 0.50 to 0.54 (p = .002) after training. There was a significant correlation between the magnitude of training bradycardia and the increment in LVEF at the pretraining maximum workload (p = .009). We conclude that the relative bradycardia at comparable exercise workloads produced by exercise conditioning is associated with improvements in left ventricular performance as assessed by the LVEF. This observation is compatible with the hypothesis that training bradycardia in conditioned subjects with ischemic heart disease is associated with lower myocardial oxygen demand and lesser degrees of ischemia at comparable workloads. However, training effects on ventricular afterload or on ischemia contractile performance of the heart cannot be excluded.

Adult↗

PubMed2001

Measuring the academic radiologist's clinical productivity: survey results for subspecialty sections.

RATIONALE AND OBJECTIVES: The purpose of this project was to understand better the academic radiologist's clinical workload in order to determine faculty staffing requirements more accurately. MATERIALS AND METHODS: Surveys performed by the Society of Chairmen of Academic Radiology Departments (SCARD) collected data for radiologists in 20 departments in 1996 and 1998; the data included work relative value units (RVUs) per full-time equivalent (FTE). Radiologists in each subspecialty were compared with their counterparts in other departments. The data were collected for each radiologist. Summary statistics showing averages, medians, and quartiles were used to describe workload (in RVUs per FTE) for each department and each subspecialty. RESULTS: Overall, the average clinical workload was 4,458 RVU/FTE, with 0.62 RVU per procedure. In those sections for which the faculty performed similar types of procedures across departments, the results were useful. The workload data, however, proved inadequate to compare across subspecialty sections. Between 1996 and 1998, the workload increased from 3,790 to 4,458 RVU/FTE. CONCLUSION: The SCARD survey provided very useful clinical workload data, measured in work RVUs per FTE for specific subspecialty sections. At practically all surveyed institutions, increasing clinical workload is competing with academic activities.

Academic Medical Centers↗