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PubMed2004

Efficiency of walking and stepping: relationship to body fatness.

OBJECTIVE: To determine energetic efficiency of walking and stepping in a heterogeneous normal adult population and its association with body fatness and to assess within- and between-individual variations. RESEARCH METHODS AND PROCEDURES: Using a combination of a whole-room indirect calorimeter and a large precision force platform, we simultaneously measured minute-by-minute energy expenditure (EE) and mechanical work during walking and stepping in healthy adult men (n = 60) and women (n = 85). Efficiency was calculated as a ratio (percentage) of mechanical work and EE of activity. Efficiency of walking and stepping performed at various intensities was compared for reproducibility within the same day (morning and afternoon) and correlated with a subject's characteristics. RESULTS: The efficiency of walking was negatively correlated with body fatness in both men and women at 0.9 to 1.2 m/s but positively correlated with body fatness in men and not correlated in women at the slowest speed tested (0.6 m/s). Efficiency of walking and stepping of various intensities was reproducible during the same day. Compared at similar EE levels, walking was more efficient than stepping (26% to 27% vs. 18% to 22%, p < 0.01). Women were significantly (p < 0.01) more efficient than men during stepping. Age, sex, body mass, fat-free mass, fitness (maximal oxygen uptake), height, and speed variations contributed to the between-subject differences in efficiency. DISCUSSION: Obese individuals were less efficient than lean individuals during normal-speed walking. Significant interindividual variations in efficiency of walking and stepping may be attributed to habituation and physical characteristics such as age, sex, and fitness level.

Adult↗

PubMed2000

Effects of epidermal growth factor, transferrin, and insulin on lipofection efficiency in human lung carcinoma cells.

Poor transfection efficiency is the major drawback of lipofection. We showed previously that addition of transferrin (TF) to Lipofectin enhanced the expression of a reporter gene in HeLa cells by 120-fold and achieved close to 100% transfection efficiency. The purpose of this study was to determine whether TF and other ligands could improve the efficiency of lipofection in lung carcinoma cells. Confluent A549, Calu3, and H292 cells were transfected for 18 hours with a plasmid DNA (pCMVlacZ) using Lipofectin plus TF, insulin, or epidermal growth factor as the vector. The transfected cells were assessed for transfection efficiency by beta-galactosidase activity (light units/microg protein) and the percentage of blue cells following 5-bromo-4-chloro-3-indolyl beta-D-galactopyranoside staining. Lipofectin supplemented with epidermal growth factor yielded the largest enhancement of lipofection efficiency (< or =23-fold over that by Lipofectin alone) in all three cell lines. Insulin significantly enhanced the lipofection efficiency in A549 and Calu3 cells but not in H292 cells, whereas TF showed significant lipofection efficiency-enhancing effect in Calu3 and H292 cells but not in A549 cells. The transfection efficiency correlated well with the amounts of DNA delivered to the nucleus as well as the amounts of the receptor. These results indicate that the gene delivery strategy employing ligand-facilitated lipofection can achieve high transfection efficiency in human lung carcinoma cells. In addition, enhancement of the expression of the receptor may be a possible strategy for increasing the efficiency of gene targeting.

Cell Nucleus↗

PubMed1998

Possible effects of fatigue on muscle efficiency.

The efficiency of energy transduction is defined as the ratio of the work done by a muscle to the free energy change of the chemical processes driving contraction. Two examples of the experimental measurement of muscle efficiency are: (1) the classical method of Hill which measures the value during a steady state of shortening, (2) measuring the overall efficiency during a complete cycle of a sinusoidal process, which comes closer to the situation during natural locomotion. The reasons why fatigue might lower efficiency are the following. (1) The reduction in PCr concentration and increase in Pi and Cr concentration which are characteristic of fatigued muscle, reduce the free energy of PCr splitting. This will reduce the efficiency of the recovery process. It is not known whether the efficiency of the initial process is increased to compensate. (2) There is a general conflict between efficiency and power output when motor units are chosen for a task or when the timing of activation is decided. During fatigue more powerful units have to be used to achieve a task which is no longer within the scope of less powerful units. (3) The slowing of relaxation that is sometimes found with fatigue may make it impossible to achieve the short periods of activity required for optimum efficiency during rapid cyclical movements. A reason why fatigue might increase efficiency is that muscles are thought to be more efficient energy converters when not fully activated than when fully active. Full activation is often not achieved in muscle which is considerably fatigued. Available observations do not allow us to find where the balance between these factors lies. The conclusion is thus that experiments of both the types discussed here should be performed.

Animals↗

PubMed2001

Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes.

The results of previous studies suggest that the maximum mechanical efficiency of rat papillary muscles is lower during a contraction protocol involving sinusoidal length changes than during one involving afterloaded isotonic contractions. The aim of this study was to compare directly the efficiency of isolated rat papillary muscle preparations in isotonic and sinusoidal contraction protocols. Experiments were performed in vitro (27 degrees C) using left ventricular papillary muscles from adult rats. Each preparation performed three contraction protocols: (i) low-frequency afterloaded isotonic contractions (10 twitches at 0.2 Hz), (ii) sinusoidal length change contractions with phasic stimulation (40 twitches at 2 Hz) and (iii) high-frequency afterloaded isotonic contractions (40 twitches at 2 Hz). The first two protocols resembled those used in previous studies and the third combined the characteristics of the first two. The parameters for each protocol were adjusted to those that gave maximum efficiency. For the afterloaded isotonic protocols, the afterload was set to 0.3 of the maximum developed force. The sinusoidal length change protocol incorporated a cycle amplitude of +/-5% resting length and a stimulus phase of -10 degrees. Measurements of force output, muscle length change and muscle temperature change were used to calculate the work and heat produced during and after each protocol. Net mechanical efficiency was defined as the proportion of the energy (enthalpy) liberated by the muscle that appeared as work. The efficiency in the low-frequency, isotonic contraction protocol was 21.1+/-1.4% (mean +/- s.e.m., N=6) and that in the sinusoidal protocol was 13.2+/-0.7%, consistent with previous results. This difference was not due to the higher frequency or greater number of twitches because efficiency in the high-frequency, isotonic protocol was 21.5+/-1.0%. Although these results apparently confirm that efficiency is protocol-dependent, additional experiments designed to measure work output unambiguously indicated that the method used to calculate work output in isotonic contractions overestimated actual work output. When net work output, which excludes work done by parallel elastic elements, rather than total work output was used to determine efficiency in afterloaded isotonic contractions, efficiency was similar to that for sinusoidal contractions. The maximum net mechanical efficiency of rat papillary muscles performing afterloaded isotonic or sinusoidal length change contractions was between 10 and 15%.

Animals↗

PubMed1988

Efficiencies from consumed O2 and pressure-volume area to work of in situ dog heart.

We studied the efficiencies from oxygen consumption (VO2) to external mechanical work (EW), from VO2 to the systolic pressure-volume area (PVA), and from PVA to EW, and the effects of cardiac output and contractility index (Emax) on these efficiencies in the left ventricle of open-chest, right-heart-bypassed dogs. PVA is an intermediate form of energy between VO2 and EW. PVA, EW, and Emax were determined by an abrupt occlusion of the ascending aorta. The right-heart bypass allowed us to collect all coronary venous return for VO2 measurement. The EW/VO2 efficiency ranged between 4 and 21%, the PVA/VO2 efficiency ranged between 5 and 27%, and the EW/PVA efficiency ranged between 60 and 95%. At a given Emax, EW/PVA efficiency was independent of cardiac output, but PVA/VO2 and EW/VO2 efficiencies increased with cardiac output. An increase in Emax by dobutamine increased EW/PVA efficiency, but decreased PVA/VO2 and EW/VO2 efficiencies. We could theoretically account for these changes in EW/PVA, PVA/VO2, and EW/VO2 efficiencies of the in situ heart by the VO2-PVA relation and its dependence on Emax that we had observed.

Animals↗

PubMed2004

Different measures of energetic efficiency and their phenotypic relationships with growth, feed intake, and ultrasound and carcass merit in hybrid cattle.

Residual feed intake (RFI) has been proposed as an index for determining beef cattle energetic efficiency. Although the relationship of RFI with feed conversion ratio (FCR) is well established, little is known about how RFI compares to other measures of efficiency. This study examined the phenotypic relationships among different measures of energetic efficiency with growth, feed intake, and ultrasound and carcass merit of hybrid cattle (n = 150). Dry matter intake, ME intake (MEI), ADG, metabolic weight (MWT), and FCR during the test averaged 10.29 kg/d (SD = 1.62), 1,185.45 kJ/(kg0.75 x d) (SD = 114.69), 1.42 kg/d (SD = 0.25), 86.67 kg0.75 (SD = 10.21), and 7.27 kg of DM/kg of gain (SD = 1.00), respectively. Residual feed intake averaged 0.00 kg/d and ranged from -2.25 kg/d (most efficient) to 2.61 kg/d (least efficient). Dry matter intake (r = 0.75), MEI (r = 0.83), and FCR (r = 0.62) were correlated with RFI (P < 0.001) and were higher for animals with high (>0.5 SD) RFI vs. those with medium (+/-0.5 SD) or low (<0.5 SD) RFI (P < 0.001). Partial efficiency of growth (PEG; energetic efficiency for ADG) was correlated with RFI (r = -0.89, P < 0.001) and was lower (P < 0.001) for high- vs. medium- or low-RFI animals. However, RFI was not related to ADG (r = -0.03), MWT (r = -0.02), relative growth rate (RGR; growth relative to instantaneous body size; r = -0.04), or Kleiber ratio (KR; ADG per unit of MWT; r = -0.004). Also, DMI was correlated (P < 0.01) with ADG (r = 0.66), MWT (r = 0.49), FCR (r = 0.49), PEG (r = -0.52), RGR (r = 0.18), and KR (r = 0.36). Additionally, FCR was correlated (P < 0.001) with ADG (r = -0.63), PEG (r = -0.83), RGR (r = -0.75), and KR (r = -0.73), but not with MWT (r = 0.07). Correlations of measures of efficiency with ultrasound or carcass traits generally were not different from zero except for correlations of RFI, FCR, and PEG, respectively, with backfat gain (r = 0.30, 0.20, and -0.30), ultrasound backfat (r = 0.19, 0.21, and -0.25), grade fat (r = 0.25, 0.19, and -0.27), lean meat yield (r = -0.22, -0.18, and 0.24), and yield grade (r = 0.28, 0.24, and -0.25). These phenotypic relationships indicate that, compared with other measures of energetic efficiency, RFI should have a greater potential to improve overall production efficiency and PEG above maintenance, and lead to minimal correlated changes in carcass merit without altering the growth and body size of different animals.

Adipose Tissue↗

PubMed2006

Longevity and efficiency associated with age structures of female pigs and herd management in commercial breeding herds.

Annual performance measurements, age structures of female pig inventories, and by-parity culling rates were abstracted from data files of 110 herds that participated in a data-share program in Japan. Parity at culling was used as a prime measurement of longevity, whereas pigs weaned x mated female(-1) x year(-1) (PWMFY) was a prime measurement of reproductive efficiency. High or low longevity herds were based on the greatest 50% of the herds or the remaining herds ranked by parity at culling, whereas high or low reproductive efficiency herds were grouped according to the greatest 50% of the herds or the remaining herds ranked by PWMFY. Measurements were analyzed as a 2 x 2 factorial arrangement, using the main effects of the 2 herd groups of longevity (high or low) and reproductive efficiency (high or low). Means of parity at culling and PWMFY were 4.6 (SD = 0.82) and 21.2 (SD = 3.02), respectively. The high longevity group had 1.27 greater parities at culling than the low longevity group (P < 0.05), but no differences between the high and low longevity groups were found in PWMFY (P = 0.21). No differences between the high and low efficiency groups were found in parity at culling (P = 0.50). No interactions between the longevity and efficiency groups were found on any longevity or efficiency measurement (P > 0.20). In herd management, the percentage of reserviced females and the percentage of multiple matings were associated with the longevity group and the efficiency group (P < 0.05). The high longevity group had lower culling rates in parity 0 to 6 than the low longevity group (P < 0.05), whereas no differences between the low and high efficiency groups were found in culling rates in parity 0 to 2 (P > 0.20). This study suggests that measures to achieve longevity and high reproductive efficiency in breeding herds do not conflict and that high reproductive efficiency and high longevity can be achieved.

Aging↗

PubMed2003

Efficiency of converting nutrient dry matter to milk in Holstein herds.

Production of milk from feed dry matter intakes (DMI), called dairy or feed efficiency, is not commonly measured in dairy herds as is feed conversion to weight gain in swine, beef, and poultry; however, it has relevance to conversion of purchased input to salable product and proportion of dietary nutrients excreted. The purpose of this study was to identify some readily measured factors that affect dairy efficiency. Data were collected from 13 dairy herds visited 34 times over a 14-mo period. Variables measured included cool or warm season (high ambient temperature <21 degrees C or >21 degrees C, respectively), days in milk, DMI, milk yield, milk fat percent, herd size, dietary concentrations (DM basis) and kilograms of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and forage. Season, days in milk, CP % and forage % of diet DM, and kilograms of dietary CP affected dairy efficiency. When evaluated using a model containing the significant variables, dairy efficiency was lower in the warm season (1.31) than in the cool season (1.40). In terms of simple correlations, dairy efficiency was negatively correlated with days in milk (r = -0.529), DMI (r = -0.316), forage % (r = -0.430), NDF % (r = -0.308), and kilograms of forage (r = -0.516), NDF (r = -0.434), and ADF (r = -0.313), in the diet, respectively. Dairy efficiency was positively correlated with milk yield (r = 0.707). The same relative patterns of significance and correlation were noted for dairy efficiency calculated with 3.5% fat-corrected milk yield. Diets fed by the herds fell within such a small range of variation (mean +/- standard deviation) for CP % (16.3 +/- 0.696), NDF % (33.2 +/- 2.68), and forage % (46.9 +/- 5.56) that these would not be expected to be useful to evaluate the effect of excessive underfeeding or overfeeding of these dietary components. The negative relationships of dairy efficiency with increasing dietary fiber and forage may reflect the effect of decreased diet digestibility. The results of this study suggest that managing herd breeding programs to reduce average days in milk and providing a cooler environment for the cows may help to maximize dairy efficiency. The mechanisms for the effects of the dietary variables on dairy efficiency need to be understood and evaluated over a broader range of diets and conditions before more firm conclusions regarding their impact can be drawn.

Animal Feed↗

PubMed2002

The development of mental processing: efficiency, working memory, and thinking.

This Monograph aims to contribute to the information processing, the differential, and the developmental modeling of the mind, and to work these into an integrated theory. Toward this aim, a longitudinal study is presented that investigates the relations between processing efficiency, working memory, and problem solving from the age of 8 years to to the age of 16 years. The study involved 113 participants, about equally drawn among 8-, 10-, 12-, and 14-year-olds at the first testing; these participants were tested two more times spaced one year apart. Participants were tested with a large array of tasks addressed to processing efficiency (i.e., speed of processing and inhibition), working memory (in terms of Baddeley's model, phonological storage, visual storage, and the central executive of working memory), and problem solving (quantitative, spatial, and verbal reasoning). Confirmatory factor analysis validated the presence of each of the above dimensions and indicated that they are organized in a three-stratum hierarchy. The first stratum includes all of the individual dimensions mentioned above. These dimensions are organized, at the second stratum, in three constructs: processing efficiency, working memory, and problem solving. Finally, all second-order constructs are strongly related to a third-order general factor. This structure was stable in time. Structural equation modeling indicated that the various dimensions are interrelated in a cascade fashion so that more fundamental dimensions are part of more complex dimensions. That is, speed of processing is the most important aspect of processing efficiency, and it perfectly relates to the condition of inhibition, indicating that the more efficient one is in stimulus encoding and identification, the more efficient one is in inhibition. In turn, processing efficiency is strongly related to the condition of executive processes in working memory, which, in turn, is related to the condition of the two modality-specific stores (phonological and visual). Finally, problem solving is related to processing efficiency and working memory, the central executive in particular. All dimensions appear to change systematically with time. Growth modeling suggested that there are significant individual differences in attainment in each of the three aspects of the mind investigated. Moreover, each of the three aspects of the mind as well as their interrelations change differently during development. Mixture growth modeling suggested that there are four types of developing persons, each defined by a different combination of performance in these aspects of the mind. Some types are more efficient and stable developers than others. These analyses indicated that processing efficiency is a factor closely associated with developmental differences in problem solving, whereas working memory is associated with individual differences. Modeling by logistic equations uncovered the rates and form of change in the various dimensions and their reciprocal interactions during development. These findings are discussed from the point of view of information processing, differential, and developmental models of thinking, and an integrative model is proposed.

Age Factors↗

PubMed2005

Luminous efficiency and the measurement of daytime displays, signals, and visors.

PURPOSE: Measurements concerning the usability or safety of optical equipment are based on assumptions regarding luminous efficiency. The current luminous efficiency functions are derived from human sensitivity experiments taken at low light levels compared with the outdoor daytime environment. The amount of error induced by extrapolating from low light level data to high light level applications is not known. We sought to determine whether standard luminous efficiency curves CIE V(lambda) and CIE Heterochromatic Brightness Matching are appropriate for measuring day-use optical equipment such as display phosphors, lasers, LEDs, and laser eye protection, which are becoming more common in aviation. METHODS: Flicker photometry and successive heterochromatic brightness matching were used to measure changes in luminance efficiency functions with increasing levels (1, 10, 100, and 1000 fL) of light adaptation. RESULTS: Luminous efficiency was found to depend on both the method and the reference intensity with which the measurements were taken. For heterochromatic brightness matching, luminous efficiency increased for longer wavelengths as reference intensity increased. Peak luminous efficiency shifted from approximately 540 nm to greater than 600 nm with increasing intensity. Peak luminous efficiency was constant for flicker photometry across all intensities, but the function narrowed slightly at 100 fL. CONCLUSION: Luminous efficiency curves measured at high reference intensities are substantially different from the standard luminous efficiency functions. Caution should be used when measuring spectrally narrow and bright sources such as lasers and LEDs with a V(lambda) corrected photometer because the measured luminance may correlate poorly with perceived brightness.

Adult↗

PubMed1995

Mechanical efficiency of stunned myocardium is modulated by increased afterload dependency.

OBJECTIVE: Oxygen consumption (MVO2) of stunned myocardium is relatively high compared to, and poorly correlated with, systolic contractile function. The aim of this study was to investigate whether an increased afterload dependency, induced by the decreased contractility of the stunned myocardium, contributes to the large variability in the mechanical efficiency data. METHODS: In 13 anaesthetised open thorax pigs undergoing two cycles of 10 min occlusion of left anterior descending coronary artery and 30 min reperfusion, segment shortening, the slope of end systolic pressure segment length relationship (Ees), external work (EW, derived from the area inside the left ventricular pressure segment length loop), the efficiency of energy conversion (EET, = EW/PLA x 100%, where PLA = total pressure-segment length area), mechanical efficiency (EW/MVO2), and their dependency on left ventricular end systolic pressure (Pes) were determined before and after induction of stunning, and during subsequent inotropic stimulation with dobutamine (1 and 3 micrograms.kg-1.min-1 over 15 min). RESULTS: The stunning protocol not only caused significant decreases in segment shortening, external work, energy conversion efficiency, and EW/MVO2 but also increased the afterload dependency of these variables. Before stunning an increase in Pes from 100 to 160 mm Hg decreased segment shortening from 18(SEM 1)% to 14(2)% (P > 0.05) and increased external work from 206(18) to 254(32) mm Hg.mm (P < 0.05). After induction of stunning the same increase in Pes caused a decrease in segment shortening from 9.5(1.8)% to -4.6(2.1)% (P < 0.05) and in external work from 149(21) to -11(10) mm Hg.mm (P < 0.05). The afterload dependency of the PLA was not altered by stunning, but the afterload dependency of energy conversion efficiency increased, since efficiency decreased from 67(3)% to 59(5)% as Pes was increased from 100 to 160 mm Hg before stunning, but from 57(5) to -7(5)% after induction of stunning (P < 0.05). Furthermore, the same increase in Pes resulted in an 8% decrease of EW/MVO2 before stunning and 107% after induction of stunning. Infusion of dobutamine not only restored segment shortening, external work, energy conversion efficiency, and EW/MVO2 of the stunned myocardium, but also attenuated their afterload dependency to pre-stunning levels. CONCLUSIONS: Myocardial stunning increases the afterload dependency of segment shortening, external work, energy conversion efficiency, and mechanical efficiency, which can be attenuated by inotropic stimulation with dobutamine. However, the decrease in left ventricular end systolic pressure, which accompanies the induction of stunning, counteracts the decrease in these variables. These two mechanisms can explain most of the reported scatter in mechanical efficiency.

Animals↗

PubMedDate not supplied

Masticatory efficiency and ability in relation to occlusion and mandibular dysfunction in girls.

PURPOSE: This study investigated the masticatory efficiency and ability in girls with normal occlusion and Class II malocclusion. Furthermore, it investigated the association between masticatory efficiency and ability on one hand and signs and symptoms of temporomandibular disorders (TMD) on the other hand. MATERIALS AND METHODS: A total of 183 girls, aged 11 to 15 years, were included in this study. Sixty subjects had normal occlusion and 123 subjects had Class II malocclusion. The examination included registration of signs and symptoms of TMD. Masticatory efficiency was evaluated with a masticatory efficiency test, while masticatory ability was self-assessed on a visual analog scale. RESULTS: Subjects with normal occlusion presented statistically significantly better masticatory efficiency and ability than subjects with Class II malocclusion. Thirty percent of the variation in masticatory efficiency was explained in a multiple regression analysis. Few occlusal contacts and a large overjet predicted a reduced masticatory efficiency. Subjects who reported frequent temporomandibular joint clicking and subjects who estimated their overall symptoms of TMD as moderate or severe also had reduced masticatory efficiency. CONCLUSION: The authors concluded that masticatory efficiency and ability were partly dependent on the occlusion and that symptoms of TMD influenced the masticatory efficiency and ability.

Adolescent↗

PubMed1993

The association between chewing efficiency and occlusal contact area in man.

Chewing is influenced by a number of factors, which include jaw and tongue movements, the activity of circumoral muscles, bite force and hard oral surfaces, but it is not clear which of these factors is most crucial to efficiency. The mere presence of surfaces such as the hard palate, or teeth, does not insure that chewing will be efficient. The purpose of this study was to explore the relationship between occlusal contact area, and chewing efficiency and to observe the influence of chewing-side preference on efficiency. These variables were recorded for both left- and right-hand sides, in a sample of 26 normal young adults. Chewing efficiency was estimated by the size of food particles collected after a predetermined number of chewing strokes. The particles were measured using image analysis and the median size calculated. Comparisons were made, firstly within subjects, between the left- and right-hand side, and secondly between subjects. Correlations were found between chewing efficiency and occlusal contact area which were more pronounced within, than between, subjects. It was concluded that while occlusal contact area influenced chewing efficiency within the same individual, it could not account for the differences in chewing efficiency found between individuals. Differences in the movement of the jaw and in the bite force may have a greater influence on chewing efficiency than occlusal contact area.

Adult↗

PubMed2004

Day surgery and hospital efficiency: empirical analysis of Norwegian hospitals, 1999-2001.

Day surgery has gained increasing significance in Norwegian health care during the 1990s, and now constitutes more than 50% of all elective surgery. Although the underlying general assumption is that this mode of delivering surgery will increase the efficiency of hospitals, most former studies have focused only on the cost-efficiency for specific types of surgical operations. The present study therefore uses data from Norwegian hospitals to test whether the proposition that day surgery spells efficiency also holds true at the hospital level. Hospital efficiency is measured as the technical efficiency of hospitals. This indicator captures how efficient hospitals are in utilising their total resources, and builds on a variety of hospital inputs (inpatient care, outpatient care) and hospital outputs (physician full-time equivalents (FTEs), other labour equivalents, medical expenses). Our empirical analysis is based on a simple decision model where the hospitals maximise utility functions of income, patients and effort under the constraint of the budget and various structural characteristics. The empirical model thus controls for several other important determinants of efficiency, such as hospital budget, the outpatient revenue share, irregularly long length of stay, hospital type and the share of emergency admissions. After accounting for these variables, our results document significant effects of day surgery on technical efficiency. The results furthermore show that the positive effect of day surgery is contingent upon hospital budget, as hospitals with large budgets experience stronger efficiency effects of day surgery.

Ambulatory Surgical Procedures↗

PubMed1998

Efficiency evaluation of skilled nursing facilities.

This study employs Data Envelopment Analysis (DEA) to determine technical efficiency using skilled nursing facilities in the United States, using a 10% national sample of 324 skilled nursing facilities stratified by ownership and size cluster groupings. Results show that nonprofit and for-profit firms operate using significantly different modes of production, thus allowing the best of the for-profits to achieve a level of technical efficiency .86 times higher than the most efficient nonprofit homes. The best larger nursing homes are .89 times more efficient than the best smaller facilities, also indicating a difference in production goals and technologies. A rationale for these differences is sought through an analysis of DEA generated slacks and a logistic regression. Controlling for size and ownership in the DEA, a higher percentage of Medicare patients leads to lower efficiency, while higher occupancy and greater percentage of Medicaid patients lead to greater efficiency. Regional characteristics do not impact efficiency. It is concluded that reimbursement policies should account for differences in organizational goals created by size and ownership differentials. The great variations in efficiency demonstrate tremendous potential for cost-savings through imitation of efficient firms.

Data Interpretation, Statistical↗

PubMed2001

The efficiency of the delivery of neonatal care in the UK.

BACKGROUND: A recent paper in Journal of Public Health Medicine (O'Neill et al., 2000; 22(1): 108-115) used regression modelling to determine the average costs of neonatal care services for a sample of 49 units in the United Kingdom in 1990-1991, and concluded that economies of scale were present in the sample as a whole. Although this form of modelling is useful, analysis of the efficiency of production for individual units is also important. METHODS: Data envelopment analysis (DEA) was used to analyse the data set published by O'Neil et al., to determine technical efficiency of neonatal units, measuring efficiency compared with a benchmark efficient frontier, and estimating economies of scale for each unit. Potential cost savings if units were to operate efficiently are estimated. RESULTS: There is evidence of substantial levels of technical inefficiency. Economies of scale varied between units, with increasing returns in the 36 inefficient units, and mainly constant returns in the 13 efficient units. This suggests that the presence of technical inefficiency was as important as scale inefficiencies. Total cost savings, if all units were operating efficiently, are estimated at ł10.4 million, equivalent to 10 extra units producing 57,000 additional days of care. CONCLUSIONS: DEA is a technique of great potential value in analysing the efficiency of health care production. As well as inefficiencies in the production of neonatal care in the United Kingdom due to differences in the scale of production, there appears to have been considerable technical inefficiency, which was not due to differences in case mix. The potential cost savings from efficiency gains are large.

Data Interpretation, Statistical↗

PubMed1975

Muscular efficiency during steady-rate exercise: effects of speed and work rate.

In a comparison of traditional and theoretical exercise efficiency calculations male subjects were studied during steady-rate cycle ergometer exercises of "0," 200, 400, 600, and 800 kgm/min while pedaling at 40, 60, 80, and 100 rpm. Gross (no base-line correction), net (resting metabolism as base-line correction), work (unloading cycling as base-line correction), and delta (measurable work rate as base-line correction) efficiencies were computed. The result that gross (range 7.5-20.4%) and net (9.8-24.1%) efficiencies increased with increments in work rate was considered to be an artifact of calculation. A LINEAR OR SLIGHTLY EXPONENTIAL RELATIONSHIP BETWEEN CALORIC OUTPUT AND WORK RATE DICTATES EITHER CONSTANT OR DECREASING EFFICIENCY WITH INCREMENTS IN WORK. The delta efficiency (24.4-34.0%) definition produced this result. Due to the difficulty in obtaining 0 work equivalents, the work efficiency definition proved difficult to apply. All definitions yielded the result of decreasing efficiency with increments in speed. Since the theoretical-thermodynamic computation (assuming mitochondrial P/O = 3.0 and delta G = -11.0 kcal/mol for ATP) holds only for CHO, the traditional mode of computation (based upon VO2 and R) was judged to be superior since R less than 1.0. Assuming a constant phosphorylative-coupling efficiency of 60%, the mechanical contraction-coupling efficiency appears to vary between 41 and 57%.

Adult↗

PubMed1984

Exercise efficiency during arm ergometry: effects of speed and work rate.

The purpose of this investigation was to determine the effects of increasing work rate and speed of movement on efficiency during steady-state arm crank ergometry (ACE). Ten men exercised at speeds of 50, 70, and 90 rpm and four power outputs (15, 30, 45, and 60 W). O2 uptake determinations were made using open-circuit spirometry and energy expenditure was calculated from the respiratory exchange ratio. Gross (work accomplished/energy expended), work (unloaded cranking as base-line correction), and delta (measurable work as base-line correction) efficiencies were computed. A curvilinear relationship was found to exist between work rate and energy expenditure, which dictates that both delta and work efficiency will decrease with increments in work. Work (range 20-29%) and delta (range 14-30%) efficiencies decreased with increases in power output. The result that gross efficiency (range 6-15%) increased with increments in work was due to the decreasing effect of the resting metabolic rate on the total energy expended. Gross, work, and delta efficiencies were lower (P less than 0.05) at 90 rpm when compared with the same work rate at 50 and 70 rpm. Although all of the exercise efficiencies tended to be lower at 70 rpm compared with work at 50 rpm, the difference was significant (P less than 0.05) only at 45 and 60 W. These data suggest that delta and work efficiencies during ACE are decreased with increments in either speed or power output. However, gross efficiency increases as a function of power output but decreases as a function of speed of movement.

Adult↗