Disease relevance of Workload

• Nifedipine and propranolol were equally effective in relieving exertional ischemia as shown by improvement in radionuclide ejection fraction at identical work loads [1].
• In congestive heart failure, the low activity of aerobic enzymes is likely to impair energy production and lead to lactate acidosis at low workloads [2].
• We conclude that the failure of other workers to observe insulin effects on glucose uptake and lactate release under physiological workloads [preparation (ii)] may be a consequence of intracellular hypoxia in their preparations [3].
• OBJECTIVE: Racemic propranolol attenuates cardiac hypertrophy secondary to abdominal aortic banding-induced pressure overload by a mechanism independent of its effect on cardiac work load [4].
• Resting metabolic rate and the energy cost of performing a specific (light work load on a bicycle ergometer were measured in nine subjects susceptible to malignant hyperpyrexia (MHS) and nine control subjects, both fasting and following a 600-kcal meal [5].

Psychiatry related information on Workload

• We found that exercise at equal perceived exertion was associated with the choice of a nearly equal absolute work load after sleep deprivation as after normal sleep (17.1 vs. 17.5% grade; p = n.s.). In addition, after 10 min of exercise at the self-selected intensity, subjects displayed identical ventilation, oxygen uptake, and CO2 production [6].
• The effects of variations in work load (indexed by paid work hours) on psychological well-being, cortisol, smoking, and alcohol consumption were examined in a sample of 71 workers (44 women, 27 men) in the retail industry [7].

High impact information on Workload

• This response is believed to be mediated by increased phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) and is hypothesized to reduce the work load imposed on the folding machinery during stress [8].
• Low-intensity exercise was performed for 60 min at a work load equal to 50% of the lactate threshold, and high-intensity exercise was performed for 30 min at a work load between the lactate threshold and maximal work capacity for the individual [9].
• Thus, alterations in skeletal muscle carnitine metabolism, characterized by an increase in acylcarnitines and a decrease in free and total carnitine, are dependent on the work load and, therefore, the metabolic state associated with the exercise, and are poorly reflected in the plasma and urine carnitine pools [9].
• Myosin isoenzyme expression can be altered by changes in work load but is still responsive to increased levels of thyroid hormone [10].
• These data confirmed that "work load," in addition to luminal nutrition, maintains intestinal mass [11].

Chemical compound and disease context of Workload

• Since ischemia can cause changes in phosphorylated compounds similar to those during catecholamine stimulation, this study tested the hypothesis that the exaggerated depletion of PCr and accumulation of Pi during high workloads in LVH is the result of impaired myocyte oxygenation [12].
• The workloads were adjusted to approximately 70% of peak O2 consumption (VO2peak) measured either in hypoxia for the HT group or in normoxia for the NT group [13].
• Epinephrine responses to hypoglycemia and to identical relative work loads have been shown to be higher in endurance-trained athletes than in untrained subjects [14].
• The non-linear release of Bohr protons over the range of Hb-O2 saturation in the blood reduces HCO3- dehydration at the gills during greater work loads elevating arterial P(CO2) levels, leading to an increase in HCO3- buffer capacity of the blood and tissues [15].
• 6N-cyclopentyladenosine (CPA; selective A1 adenosine receptor agonist) induced bradicardia and negative inotropic effects, reduced work load (i.e., decreased HR, VPSP, +dP/dtmax, +dP/dtmax/VPSP and HR x VPSP) and inhibited endotoxin-induced tachycardia and renin release [16].

Biological context of Workload

• During submaximal exercise at a fixed work load, diltiazem decreased the average heart rate response from 119 +/- 17 to 107 +/- 14 beats/min (p less than 0.01), systolic blood pressure from 182 +/- 15 to 175 +/- 15 mm Hg (p less than 0.05) and the rate-pressure product from 21.8 +/- 4.2 to 18.8 +/- 3.2 x 10(-3) units (p less than 0.01) [17].
• In addition, total body oxygen consumption during similar workloads was lower after dobutamine infusion than before.(ABSTRACT TRUNCATED AT 250 WORDS)[18]
• Arterial and femoral venous lactate levels were markedly reduced during submaximal exercise after training, even though cardiac output and leg blood flow were unchanged at these workloads [19].
• Amiodarone treatment caused a significant rise in pulmonary capillary wedge pressure from 22 +/- 8 to 37 +/- 9 mm Hg (p less than .001) at the highest identical workloads and from 26 +/- 10 to 37 +/- 9 (p less than .005) at maximal symptom-limited workloads [20].
• Multiple enrichment of the tissue glutamate pool with 13C as an index of metabolic turnover within the tricarboxylic acid cycle was readily observed as a function of work load [21].

Anatomical context of Workload

• The total 2-deoxy[3H]glucose trapped in the myocardium was proportional to the glucose uptake which was varied by the mechanical work load and availability of other oxidizable substrates [22].
• To examine whether catecholamines have a direct effect on myosin heavy chain expression of heart myocytes or whether they act via an altered work load, myocytes from neonatal rat hearts were cultured in thyroid hormone-free media containing various positive inotropic and chronotropic agents [23].
• Univariate analysis showed that gender (chi-square = 5.1), exercise work load (chi-square = 3.1), extent of coronary artery disease and left ventricular ejection fraction (chi-square = 14.8) and thallium variables (chi-square = 22.7) were prognostically important [24].
• This exchange was monitored at baseline and at high workloads by comparing (13)C enrichment between the products of alpha-KG oxidation (succinate) and alpha-KG efflux from mitochondria (glutamate) [25].
• At similar workloads, oxygen consumption, blood flow, and glucose uptake were lower in the obese than the nonobese subjects when expressed per kilogram of muscle, but similar when expressed per quadriceps femoris muscle mass [26].

Associations of Workload with chemical compounds

• Both peak work load (1,100 +/- 60 versus 1,400 +/- 40 kpm/min) and peak O2 uptake (1.85 +/- 0.10 versus 2.38 +/- 0.07 l/min) were lower in the older men (p < 0.05) [27].
• Lactate levels during moderate exercise were significantly lower after propranolol than after either atenolol or placebo (p = 0.03), but were similar at heavy work loads [28].
• The increases in antecubital venous norepinephrine concentrations were greater in the older men at each work load (p < 0.05), although the plasma epinephrine responses were similar in the two groups [27].
• The average submaximal work load at which significant ST-segment depression (0.1 mV) first appeared was increased from 355 +/- 142 to 525 +/- 143 seconds (p less than 0.01) after diltiazem [17].
• Furthermore, marked increases in basal work load and wall stress induced by angiotensin II infusion (in four additional studies) did not reproduce this behavior [29].

Gene context of Workload

• To determine the role of TR beta 1 in detail, we compared contractility in isolated perfused hearts from wild-type (WT) and TR beta knockout mice under normal and increased work load [30].
• Basal and exercise-stimulated plasma GH and PRL concentrations were similar in the three groups tested at similar relative workloads, suggesting that physical training induces adaptive changes whereby higher absolute workloads induce similar hormonal and metabolic changes [31].
• We conclude that physical training causes adaptive changes in highly trained runners so that identical GH and PRL responses to exercise are recorded at higher absolute workloads [31].
• The results suggested a closer relationship between CS activity (oxidative potential) and work load than between Mb content and work load [32].
• One hour of acute exercise (Ex) (70% VO2 max relative work load) decreased hepatic homogenate catalase (-12%, P less than 0.02) and increased hepatic m-Mn SOD (+28%, P less than 0.03) [33].

Analytical, diagnostic and therapeutic context of Workload

• Consequently, dipyridamole echocardiography should be considered a complementary tool in the presence of high work load positivity or ambiguous exercise ECG results [34].
• Transplant recipients achieved a significant lower exercise work load than did the volunteers (42 +/- 16 vs. 128 +/- 22 W), but a higher venous lactate concentration (31.3 +/- 14.9 vs. 13.7 +/- 4.1 mg/100 ml) [35].
• Such triggers include biomechanical stress (e.g., work load, compensation for ischemic damage), sarcomeric protein mutations, cytoskeletal protein mutations, abnormal energetics, G protein-coupled receptors for ligands (including angiotensin II and endothelin-1), or their signal transducers within cells [36].
• In interpreting isoproterenol stress tests it should, however, be kept in mind that these changes are realized at a lower work load for the heart [37].
• In the steady state, aerobic lactate output is largely independent of cardiac work load, but increases slightly when octanoate is included in addition to pyruvate in the perfusion fluid [38].

References