摘要:

Knowledge of the mechanical and electrical output from skeletal muscle is of interest to investigators from several disciplines including physiology, biomechanics, neuroscience, orthopedics, and physical rehabilitation. Estimates of muscle output (i.e., force) have generally been made using indirect calculations. Forward solution (e.g., EMG) and optimization models have recently been developed using of a wide variety of input parameters to estimate force output of individual muscles. These estimates, however, have lacked comparison values necessary for validation.In vivomeasurements of muscle force have been made in both animals and humans using a “buckle” type tendon transducer surgically implanted on the tendons of the muscles under study. Investigations utilizing these transducers have addressed a wide range of questions regarding muscle function. This review examines the use of this technology and discusses the significance of the future use of “buckle” transducers in studies exploring load sharing among muscles and in the validation of existing models that estimate muscle force.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Low mechanical efficiency values in wheelchair propulsion are usually explained on the basis of the supply of force and power generated during the push phase. The purpose of this study is to analyze the movement and muscular activity pattern in handrim wheelchair propulsion, focusing on both the push and recovery phases. Data on cardiorespiratory and propulsion technique parameters were obtained from 40 wheelchair basketball players with extensive experience in wheelchair propulsion in six situations: two exercise levels (60% and 80% of individual &OV0312;O2peak), and three velocities (1.11, 1.67, and 2.22 m·s−1) with constant power output on a treadmill. A two-factor analysis of variance with repeated measurements was applied with “exercise level” and “speed” as the main factors. A significant effect on gross mechanical efficiency was found when the velocity was increased from 1.67 to 2.22 m·s−1. Decreased mechanical efficiency could be explained by a significant change in the acceleration of the wheelchair-user system during recovery, caused by arm and trunk movements, inducing inertial forces to act on the wheelchair. Consequently, mechanical work increased significantly during the recovery phase. These findings indicate that studies on mechanical efficiency in wheelchair propulsion should not only be focussed on power supply during the push phase, but also on the movement pattern during recovery.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This paper has two purposes. It first prefaces a symposium titled “Exercise adherence and behavior change: prospects, problems, and future directions.” The symposium describes the progress made during the past 5 years toward understanding the adoption and maintenance of physical activity and exercise. Specifically, research is discussed that has tested the applicability to physical activity of four psychological models of behavior: Reasoned Action, Planned Behavior, Social-Cognitive Theory, and the Transtheoretical Model of stages of change. Recent exercise interventions in clinical/community settings also are discussed to illustrate how theoretical models can be implemented to increase and maintain exercise. The second purpose of this paper is to provide a brief summary of the contemporary literatures on the determinants of physical activity and interventions designed to increase and maintain physical activity. The summary focuses on the measurement problems that have limited the advances made in theory and application in these areas of research. Progress toward resolving the measurement problems during the past 5 years is contrasted with earlier scientific consensus.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The following paper gives a summary of the published studies that have applied the theories of reasoned action and planned behavior to the prediction of exercising intentions and behavior. The paper focuses primarily on the knowledge gained from the application of these theories and how these theoretical frameworks could potentially be used in guiding the development of exercise promotion programs.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This paper presents Bandura's social cognitive theory as a utilitarian framework to study the determinants of physical activity. I provide an overview of social cognitive theory assumptions and stress the importance of studying self-efficacy in concert with other key cognitive processes. Research addressing when there is a cognitive-behavioral relationship is identified. The paper concludes with the practical implications of social cognitive theory.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The transtheoretical model has been used to understand the stages individuals progress through, and the cognitive and behavioral processes they use while changing health behaviors. The model postulates that individuals engaging in a new behavior move through the stages of Precontemplation, Contemplation, Preparation, Action, and Maintenance. Movement through these stages does not always occur in a linear manner, but may also be cyclical as many individuals must make several attempts at behavior change before their goals are realized. The amount of progress people make as a result of intervention tends to be a function of the stage they are in at the start of treatment. Instruments have been developed to measure the stages and processes of exercise adoption and maintenance and the related constructs of exercise specific self-efficacy and decision making. Psychometric data on these instruments are reviewed. Additionally, data collected on these measures from worksites in the U.S. and Australia are presented along with data from interventions aimed at increasing the adoption of physical activity among community volunteers and worksite employees. Applications of the transtheoretical model for the initiation, adoption, and maintenance of exercise behavior from clinical, community, and public health perspectives are discussed.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Research in the exercise adherence area over the past several decades has resulted in the identification of a number of promising methods for influencing physical activity on the individual level. The substantial prevalence of underactivity across most sectors of the American population, however, demands that higher-level approaches to physical activity promotion that include environmental, organizational, and policy-level strategies be increasingly brought to bear on this problem. This paper compares individual and community approaches to physical activity intervention and provides examples of how the community/public health approach to physical activity promotion can be implemented to facilitate increases in population-wide physical activity.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Controversy persists regarding the mechanism underlying the lactate threshold. It has recently been argued that there is in fact no “threshold” and that blood lactate increases as a continuous function during exercise (HughsonJ. Appl. Physiol.62:1975–1981, 1987). In comparing continuous and threshold models, questions have been raised regarding the ramp rate, data sampling, and the mathematical models employed (MortonJ. Appl. Physiol.67:885–888, 1989). To address some of these concerns, we evaluated 61 subjects (mean age 45 ± 15), who underwent maximal ramp treadmill tests with the ramp rate individualized such that test duration was approximately 10 min for each subject. The relationship between changes in blood lactate and oxygen uptake were evaluated using a modification of the log-log transformation model described by Beaver (J. Appl. Physiol.59:1936–1940, 1985) and a continuous exponential plus constant model described by Hughson et al. (J. Appl. Physiol.62:1975–1981, 1987). Model fitting, using mean squared error (MSB) and coefficient of determination (CD) for each method were as follows:

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID