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At least 19 recordsLinked to original sources

PubMed2005

Comparison between maximal power in the power-endurance relationship and maximal instantaneous power.

The purpose of this study was to analyze the relevance of introducing the maximal power (P(m)) into a critical-power model. The aims were to compare the P(m) with the instantaneous maximal power (P(max)) and to determine how the P(m) affected other model parameters: the critical power ( P(c)) and a constant amount of work performed over P(c)(W'). Twelve subjects [22.9 (1.6) years, 179 (7) cm, 74.1 (8.9) kg, 49.4 (3.6) ml/min/kg] completed one 15 W/min ramp test to assess their ventilatory threshold (VT), five or six constant-power to exhaustion tests with one to measure the maximal accumulated oxygen deficit (MAOD), and six 5-s all-out friction-loaded tests to measure P(max) at 75 rpm, which was the pedaling frequency during tests. The power and time to exhaustion values were fitted to a 2-parameter hyperbolic model (NLin-2), a 3-parameter hyperbolic model (NLin-3) and a 3-parameter exponential model (EXP). The P(m) values from NLin-3 [760 (702) W] and EXP [431 (106) W] were not significantly correlated with the P(max) at 75 rpm [876 (82) W]. The P(c) value estimated from NLin-3 [186 (47) W] was not significantly correlated with the power at VT [225 (32) W], contrary to other models ( P <0.001). The W' from NLin-2 [25.7 (5.7) kJ] was greater than the MAOD [14.3 (2.7) kJ, P < 0.001] with a significant correlation between them (R = 0.76, P <0.01). For NLin-3, computation of W (P > P c), the amount of work done over P(C), yielded results similar to the W' value from NLin-2: 27.8 (7.4) kJ, which correlated significantly with the MAOD (R = 0.72, P <0.01). In conclusion, the P(m) was not related to the maximal instantaneous power and did not improve the correlations between other model parameters and physiological variables.

Adult↗

PubMed2002

A non-invasively determined surrogate of cardiac power ('circulatory power') at peak exercise is a powerful prognostic factor in chronic heart failure.

OBJECTIVES: This study was designed to assess the prognostic value of a new variable derived from a cardiopulmonary exercise test, the circulatory power, a surrogate of cardiac power, at peak exercise, in patients with chronic heart failure. BACKGROUND: Peak exercise cardiac power and stroke work are invasive parameters with recently proven prognostic value. It is unclear whether these variables have better prognostic value than peak oxygen uptake (VO(2)). METHODS: The study population comprised 175 patients with chronic heart failure (ejection fraction <45%) who underwent a cardiopulmonary exercise test. Circulatory power and circulatory stroke work were defined as the product of systolic arterial pressure and VO(2) and oxygen pulse, respectively. Prognostic value was assessed by survival curves (Kaplan-Meier method) and uni- and multivariate Cox analyses. RESULTS: With a mean follow-up of 25+/-10 months, ejection fraction, heart rate, systolic arterial pressure, peak VO(2), VCO(2), the anaerobic threshold, minute ventilation, the ventilatory equivalents of oxygen and carbon dioxide, the half times of VO(2) and VCO(2) recoveries, and the circulatory stroke work and power predicted outcome. Multivariate analysis demonstrated that the peak circulatory power (chi-square=19.9, P<0.001) (but not peak circulatory stroke work) was the only variable predictive of prognosis. CONCLUSION: The prognostic value of cardiopulmonary exercise tests in heart failure patients can be improved by assessing a new variable, the circulatory power - a surrogate of cardiac power - at peak exercise.

Adult↗

PubMed1985

The power to pollute and the power to preserve: perceptions of female power in a Hindu village.

In traditional Hindu village society, women are seen as having the power to pollute men. Such beliefs denigrate certain aspects of female sexuality. A detailed examination of these beliefs reveals that female sexuality is only associated with pollution and negative forces when women become estranged from men through their biology or other circumstances. When associated with pollution women are perceived as being in danger as well as endangering others. In contrast when women identify their interests with men's they are not in danger and can exercise positively valued powers such as the power to preserve life. The nexus of beliefs connected with female pollution and other mystical powers encourages women to subordinate their interests to men's.

Ethnicity↗

PubMed2005

Medicare program; conditions for payment of power mobility devices, including power wheelchairs and power-operated vehicles. Interim final rule with comment period.

This interim final rule conforms our regulations to section 302(a)(2)(E)(iv) of the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (Pub. L. 108-173). This rule defines the term power mobility devices (PMDs) as power wheelchairs and power operated vehicles (POVs or scooters). It sets forth revised conditions for Medicare payment of PMDs and defines who may prescribe PMDs. This rule also requires a face-to-face examination of the beneficiary by the physician or treating practitioner and a PMD prescription and pertinent parts of the medical record that the durable medical equipment supplier maintains in records and makes available to CMS or its agents upon request. Finally, this rule discusses CMS' policy on documentation that may be requested by CMS or its agents to support a Medicare claim for payment, as well as the elimination for the Certificate of Medical Necessity for PMDs.

Certificate of Need↗

PubMed2006

Medicare program; conditions for payment of power mobility devices, including power wheelchairs and power-operated vehicles. Final rule.

This final rule conforms our regulations to section 302(a)(2)(E)(iv) of the Medicare Prescription Drug, Improvement, and Modernization Act of 2003. This rule defines the term power mobility devices (PMDs) as power wheelchairs and power operated vehicles (POVs or scooters). It sets forth revised conditions for Medicare payment of PMDs and defines who may prescribe PMDs. This rule also requires a face-to-face examination of the beneficiary by the physician or treating practitioner, a written prescription, and receipt of pertinent parts of the medical record by the supplier within 45 days after the face-to-face examination that the durable medical equipment suppliers maintain in their records and make available to CMS or its agents upon request. Finally, this rule discusses CMS' policy on documentation that may be requested by CMS or its agents to support a Medicare claim for payment, as well as the elimination of the Certificate of Medical Necessity (CMN) for PMDs.

Centers for Medicare and Medicaid Services, U.S.↗

PubMed2001

Effects of external loading on power output in a squat jump on a force platform: a comparison between strength and power athletes and sedentary individuals.

The aim of this study was to determine the effects of external loading on power output during a squat jump on a force platform in athletes specializing in strength and power events (6 elite weight-lifters and 16 volleyball players) and in 20 sedentary individuals. Instantaneous power was computed from time-force curves during vertical jumps with and without an external load (0, 5 or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Peak instantaneous power corresponded to the highest value of instantaneous power during jumping. Average power throughout the push phase of the jump was also calculated. A two-way analysis of variance showed significant interactions between the load and group effects for peak instantaneous power (P< 0.01) and average power (P< 0.001). Peak instantaneous power decreased significantly in sedentary individuals when moderate external loads were added. The peak instantaneous power at 0 kg was greater than that at 5 and 10 kg in the sedentary individuals. In contrast, peak instantaneous power was independent of load in the strength and power athletes. Mean power at 0 kg was significantly lower than at 5 kg in the athletes; at 0 kg it was significantly higher than at 10 kg in the sedentary males and at 5 and 10 kg in the sedentary females. In all groups, the force corresponding to peak instantaneous power increased and the velocity corresponding to peak instantaneous power decreased with external loading. The present results suggest that the effects of external loading on peak instantaneous power are not significant in strength and power athletes provided that the loads do not prevent peak velocity from being higher than the velocity that is optimal for maximal power output.

Adult↗

PubMed1990

Factors in maximal power production and in exercise endurance relative to maximal power.

The relationship of muscle fiber type and mass to maximal power production and the maintenance of power (endurance time to exhaustion) at 36%, 55%, and 73% of maximal power was investigated in 18 untrained but physically active men. Power output was determined at constant pedalling rate (60 rev.min-1) on a cycle ergometer instrumented with force transducers and interfaced with a computer. Maximal power was determined for each subject as the highest one-revolution average power. Fat-free mass was determined by hydrostatic weighing, fat-free thigh volume by water displacement and skinfold measurement, and percentage and area of type II fibers from biopsy specimens taken from the vastus lateralis. Maximal power averaged 771 +/- 149 W with a range of 527-1125 W. No significant correlations were found among percentage of type II fibers, relative area of type II fibers, or fat-free thigh volume and maximal power or endurance times to exhaustion at any percentage of maximal power. Weak but significant relationships were found for fat-free mass with both maximal power (r = 0.57) and endurance time at 73% of maximal power (r = -0.47). These results show maximal power to be more dependent on factors related to body size than muscle-fiber characteristics. The low correlations for so many of the relationships, however, suggest that individuals employ either different combinations of these factors or utilize other strategies for the generation of high power.

Ergonomics↗

PubMed2001

The impact of emission power on the destruction of echo contrast agents and on the origin of tissue harmonic signals using power pulse-inversion imaging.

The purpose of this study was to determine the impact of emission power on ultrasound (US)-induced destruction of echocontrast microbubbles during real-time power pulse inversion imaging (PPI) in myocardial contrast echocardiography (MCE) and to evaluate the magnitude of noncontrast PPI signals arising from myocardial tissue at variable emission power to define the cut-off emission power for optimal MCE using low power technologies. In vitro studies were performed in a flow phantom using Optison, Definity and AFO 150. PPI signal intensity during real-time imaging at 27 Hz was compared with intermittent imaging at 0.1 Hz to evaluate bubble destruction at variable emission power (MI: 0.09 to 1.3). In healthy volunteers, PPI signal intensities during constant infusion of Optison(R) was studied in real-time PPI 22 HZ and during intermittent imaging triggered end-systolic frames every, every 3rd and every 5th cardiac cycle. In addition, the impact of emission power on nonlinear PPI signals from myocardial structures was studied. In vitro, there was a 40% decrease of real-time PPI signal intensity for Optison and AFO 150 at lowest emission power (0.09), whereas no signal loss was observed for Definity. Increase of emission power resulted in a faster decay for Optison(R) and AFO 150 as compared to Definity. In vivo, real-time PPI during continuous infusion of Optison(R) resulted in a 40% decrease of myocardial signal intensity as compared to intermittent imaging every 5th cardiac cycle, even at lowest possible emission power (mechanical index = 0.09). There was a strong positive relationship between MI and noncontrast myocardial PPI signals in all myocardial segments. PPI signal intensity was found to be lower than 1 dB only for extremely low emission power (MI < 0.2). Destruction of microbubbles during real-time imaging by use of PPI at low emission power varies considerably for different echo contrast agents. However, bubble destruction and the onset of tissue harmonic signals focus the use of real-time perfusion imaging to very low emission power.

Adult↗

PubMed2005

Low power vs standard power transpupillary thermotherapy in patients with age-related macular degeneration and subfoveal choroidal neovascularization ineligible for photodynamic therapy.

AIM: To assess the effect of standard power vs low power transpupillary thermotherapy (TTT) in patients with active subfoveal choroidal neovascularization secondary to age-related macular degeneration ineligible for photodynamic therapy (PDT) by original treatment of age-related macular degeneration with photodynamic therapy (TAP) study group recommendations. METHODS: Retrospective review of 79 patients with active predominantly occult subfoveal choroidal neovascularization or predominantly classic subfoveal choroidal neovascularization but Snellen visual acuity <20/200. All patients were treated with TTT administered via a Mainster wide field fundus contact lens with a retinal power/diameter coefficient of 248 mW/mm in the standard power (n=27) and 181 mW/mm in the low power group (n=52). The primary outcome was stabilization (<1 Snellen line change) or improvement (two or more Snellen lines) in visual acuity. Clinical and fluorescein angiographic resolution of overlying exudation was documented. RESULTS: At 24 month follow-up, 17 patients (63%) in the standard power and 36 patients (69%) in the low power group achieved stable or improved vision. Improved vision (mean three lines) was observed in 22% of the standard power and 23% of the low power group. Overlying exudation was reduced clinically with minimal or no leakage on fluorescein angiogram in 85% of standard power and 90% of low power group. Subgroup analysis in the low power group demonstrated a visual benefit in patients with subfoveal lesions, which had any classic component. CONCLUSIONS: Low power TTT is as effective as standard power in stabilizing or improving vision and reducing overlying exudation in patients with active subfoveal choroidal neovascularization ineligible for PDT.

Aged↗

PubMed2001

Interconverting the matrix and principal meridional representations of dioptric power in general including powers with nonorthogonal and complex principal meridians.

The principal meridians of the powers of thick astigmatic systems, like the eye, are not necessarily at right angles. The consequence is a class of phenomena included in the category commonly described as irregular astigmatism. The conventional principal meridional representation of power, however, is unsuited to quantitative analysis. This paper presents equations for converting from the principal meridional form of power to a representation, the dioptric power matrix, which is amenable to quantitative analysis. It generalizes an earlier paper which treated only powers of a conventional form in which the principal meridians are always at right angles. It copes in particular with what are known as asymmetric powers. A routine is also presented for converting in the reverse direction, from the power matrix to the principal meridional form of power. The principal meridional form of power turns out not always to be unique, there being distinct powers (they are asymmetric) with the same principal powers and meridians. Thus, in general, the dioptric power matrix is a satisfactory representation of power while the principal meridional representation is not.

Data Interpretation, Statistical↗

PubMed1993

Investigation of circadian rhythms in peak power and mean power of female physical education students.

The aim of this investigation was to establish if there were characteristic circadian rhythms in peak power and mean power. Thirteen female physical education undergraduate students, aged from 18-21 years, were measured for peak power and mean power (Wingate Anaerobic Test) at four time points: 0300, 0900, 1500, and 2100 hours. Peak power was defined as the highest mechanical power that is elicited during a 5-sec period and mean power was defined as the average power that is sustained throughout a 30-s period. A significant circadian rhythm was found for the peak power (F = 3.22, p = 0.030). The mean peak power at 1500 h was about 7% higher (p < .05) than at 0300 h. Also a tendency to circadian rhythm was observed in mean power (F = 3.99, p = 0.01) being about 16% and 15% higher respectively (p < 0.05) at 1500 h and 2100 h than at 0300 h. Based upon the particular protocol used, it was concluded that there are characteristic circadian rhythms in peak power and mean power.

Adolescent↗

PubMed2003

Dialogue and power: a critical analysis of power in dialogical therapy.

This article explores the relationship between dialogue and power in the practice of dialogue-oriented, "not-knowing" forms of therapy. It is argued that power of a dynamic and reversible kind infuses much ordinary social dialogue, and that the joint processes of power and resistance work together to render an interaction dialogical. In contrast, in dialogical therapy, overt exercises of power threaten the interaction's dialogical status, and power is deferred and denied by the therapist through not-knowing practices. A case study of Harlene Anderson's (1997) is used to illustrate that it is precisely power's presence that informs the practices of not knowing and uncertainty that characterize dialogical therapies. It is suggested that the not-knowing therapist withholds aspects of his or her voice as a condition for dialogicity. Instead, special speaking arrangements are required, in which the therapist's not-knowing is continuously communicated to the client, for the therapeutic conversation to remain dialogical. Without these speaking arrangements, I argue that therapy moves toward monologue. Therapists inherit powerful speaking positions from the institutional and sociocultural context, and the rejection of power within therapy serves only to conceal this aspect of power, which nevertheless pervades the therapeutic relationship. Finally, it is suggested that power is a "common factor"--shared by all therapies--and that our status as "inheritors" of power needs to be included in our understanding of the therapeutic process. This expanded view of therapy requires the re-theorization of dialogue, such that it includes, rather than excludes, considerations of power.

Communication↗

PubMed2001

When power does not corrupt: superior individuation processes among powerful perceivers.

To examine whether powerful people fail to individuate the less powerful, the authors assigned participants to either a high-power or low-power role for a computer E-mail role play. In 3 studies, participants in the high-power role made decisions and determined the outcomes of interactions; low-power role players had no power and relied on high-power targets for outcome decisions. Studies I and 2 found that high-power perceivers better individuated low-power targets. Study 3 demonstrated that high-power role players' superior judgment can be impaired by including a task that directs their responsibility toward organizational rather than interpersonal concerns. In all, results suggest that the effect of power on social judgment may be more complex and multifaceted than has previously been acknowledged.

Female↗

PubMedDate not supplied

Increasing scientific power with statistical power.

A survey of basic ideas in statistical power analysis demonstrates the advantages and ease of using power analysis throughout the design, analysis, and interpretation of research. The power of a statistical test is the probability of rejecting the null hypothesis of the test. The traditional approach to power involves computation of only a single power value. The more general power curve allows examining the range of power determinants, which are sample size, population difference, and error variance, in traditional ANOVA. Power analysis can be useful not only in study planning, but also in the evaluation of existing research. An important application is in concluding that no scientifically important treatment difference exists. Choosing an appropriate power depends on: a) opportunity costs, b) ethical trade-offs, c) the size of effect considered important, d) the uncertainty of parameter estimates, and e) the analyst's preferences. Although precise rules seem inappropriate, several guidelines are defensible. First, the sensitivity of the power curve to particular characteristics of the study, such as the error variance, should be examined in any power analysis. Second, just as a small type I error rate should be demonstrated in order to declare a difference nonzero, a small type II error should be demonstrated in order to declare a difference zero. Third, when ethical and opportunity costs do not preclude it, power should be at least .84, and preferably greater than .90.

Data Interpretation, Statistical↗

PubMed2003

Acute effect of alternating heavy and light resistances on power output during upper-body complex power training.

This study investigated the effect on upper-body power output of manipulating resistances during contrast or complex power training. This power-training strategy typically entails the athlete alternating sets of a heavy resistance in a strength-oriented exercise with sets of lighter resistances in a power-oriented exercise. Sixteen rugby league players, who were experienced in power training and who performed complex training on a regular basis, served as subjects for this study and were divided equally into a control (Con) or experimental (Exp) group. Both groups were pre- and posttested for power output while performing explosive bench press throws in a Smith machine with a resistance of 50 kg (BT P50). The Exp group performed an intervention strategy of a 6-repetition set of bench presses with a resistance of 65% of 1 repetition maximum (65% 1RM) between tests. At the pretest occasion, no differences were observed between the groups in power output; however, at the posttesting, a significant difference in power output was observed between the groups in the BT P50. The 4.5% increase in the power output recorded during the posttesting BT P50 for the Exp group was determined to be significantly different from all other scores (p < or = 0.05). These data indicate that the performance of a set of heavy resistance strength training exercise between power training sets will acutely enhance power output in the second power training set. This effect has been previously theorized as possibly due to some combination of acute neural or mechanical adaptations.

Analysis of Variance↗

PubMed1991

Statistical inference on mean dioptric power: asymmetric powers and singular covariance.

Methods have been developed recently for testing hypotheses on mean dioptric power and for constructing confidence regions in situations that are most likely to be encountered. In this paper the methods are extended to make the analysis complete. A new situation covered specifically is that of dioptric power not of the form sphere/cylinder x axis. Such powers, termed asymmetric powers because the dioptric power matrices are asymmetric, include the equivalent power of a thick obliquely crossed bitoric lens. A second situation is that in which the covariance matrix of the sample of powers is singular. Symmetric dioptric power (the more familiar form of power) can be represented by a point in three-dimensional space. In general, however, dioptric power is four dimensional in character. Singularity of covariance arises when variation in the sample is limited to a subspace of dimension less than the full three or four. The space spanned by the sample is called the range space of the sample. The dimension of the range space may be four, three, two, one or zero. Each case is considered in turn. Numerical examples of hypothesis testing are presented in range spaces of dimension four to one. The test statistic devised for each case also gives the equation of the confidence region about the mean of a sample of dioptric powers. Singularity can sometimes be avoided merely by taking larger samples and by taking more accurate readings. The problem of near singularity is briefly discussed. The paper allows basic hypothesis testing on mean dioptric power and the construction of confidence regions in all possible circumstances.

Multivariate Analysis↗

PubMed2001

Mechanical efficiency and user power requirement with a pushrim activated power assisted wheelchair.

The objective of this study was to quantify the difference in mechanical efficiency and user power generation between traditional manual wheelchairs and a pushrim activated power assisted wheelchair (PAPAW). Ten manual wheelchair users were evaluated in a repeated measures design trial with and without the PAPAW for propulsion efficiency. Subjects propelled a Quickie GP equipped with the PAPAW and their own chair on a computer controlled wheelchair dynamometer at five different resistance levels. Power output, user power with the PAPAW hubs, subjects' oxygen consumption per minute and mechanical efficiency were analyzed. Metabolic energy and user power were significantly lower (p<0.05), and mechanical efficiency significantly higher with the PAPAW than with subjects' own chairs. Subjects needed to generate on average 3.65 times more power when propelling their own wheelchairs as compared to PAPAW. Mean mechanical efficiency over all trials was 80.33% higher with the power assisted hubs. PAPAW provides on average 73% of the total power when subjects propel with power assistance. Significantly increased efficiency and reduced requirement of user power is achieved using the PAPAW. With use, the PAPAW may contribute to delaying secondary injuries of manual wheelchair users. In addition, it may be suitable for people who have (or at risk for) upper extremity joint degeneration, reduced exercise capacity, low strength or endurance who currently use electric powered wheelchairs.

Adult↗

PubMed1994

Need for power and women's careers over 14 years: structural power, job satisfaction, and motive change.

Previous findings by D. G. Winter (1988) relating the need for Power to choice and attainment of power-relevant careers (teaching, including college; psychotherapy; journalism; and business management) were successfully replicated among 118 female collage seniors, 69 of whom returned mailed questionnaires 14 years later. High n Power women reported both more power-relevant job satisfaction and dissatisfaction; n Power predicted career progression only for women in power-relevant careers. Those women holding relational power jobs and those in structural power roles who reported higher overall job satisfaction increased in n Power over 14 years. Power-motivated women in different structural power roles reported contrasting satisfactions and career progression.

Adult↗