摘要:

SARIS, W.H.M. Habitual physical activity in children: methodology and findings in health and disease.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 253-263. 1986. Habitual physical activity in children has become a major field of interest for many exercise and sport scientists as well as for pediatric clinicians who specialize in the prevention of and rehabilitation from hypokinetic diseases. This paper discusses the state of the art concerning the measurement of habitual physical activity, identifies factors which may cause hypo-activity in children, and outlines specific problems on which research should be focused. The areas addressed include: the use of different field methods to measure physical activity and methodological constraints in young children; the level of daily activity in healthy children; and, finally, some aspects of reduced habitual physical activity in pediatric diseases.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

INBAR, O. and O. BAR-OR. Anaerobic characteristics in male children and adolescents.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 264-269, 1986. Only sparse information has been published on the effects of growth,development, and maturation on the ability to perform high intensity, short-term “anaerobic” tasks. Cross-sectional studies on Italian, African, British, and American females and males have indicated an age-related progression in the performance of the Margaria step-running test. Children had a distinctly lower mechanical power output than adolescents and young adults, both in absolute terms and when divided by body weight, or by fat-free mass. Data are presented on some 300 10- to 45-yr-old Israeli males who performed the Wingate anaerobic test by cycling or by arm cranking. Both the peak power at any 5-s period and the mean power throughout the test were lowest in the children, whether expressed in absolute power units or corrected for body weight. Performance progressed with age and reached the highest values at the end of the third decade for cycling and at the end of the second decade for arm cranking. This pattern is unlike that described for maximal O2uptake per kg body weight which, in males, remains virtually unchanged from childhood to young adulthood. In females, maximal O2uptake per kg is even higher in children than among adolescents or adults. Biochemical correlates of such a low anaerobic performance in children are their lower maximal lactate concentration in muscle and blood, lower rate of anaerobic glycolysis, and lower levels of acidosis at maximal exercise. The mechanisms for the relatively deficient anaerobic characteristics of children are not clear.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

RUTENFRANZ, J. Longitudinal approach to assessing maximal aerobic power during growth: the European experience.Med. Sci. Sports, Exerc.,Vol. 18, No. 3, pp. 270-275, 1986. This review deals with the principle and constraints of conducting longitudinal studies on exercise in children. As with cross-sectional studies, longitudinal ones have advantages and constraints: the different types of such designs as mass studies, population studies, or prospective cohort studies should be therefore selected to minimize their possible drawbacks. Other problems of longitudinal studies, such as the age span studied, time and sequential measurement effects, or interventional effects, have to be controlled by statistical measures and study design. In longitudinal studies ad hoc research groups working in field laboratories are for many reasons more flexible than permanent teams using institutional laboratories.Only direct determinations of maximal aerobic power should be used in longitudinal studies. These should be accompanied by such measurements as body height, body mass, lean body mass, and peak height velocity and by such health indicators as daily physical activity, blood pressure, smoking habits, and blood lipids. Examples for this approach are given in this paper, and general issues of longitudinal studies are discussed from the economic and ethical point of view.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

BAR-OR, O. Pathophysiological factors which limit the exercise capacity of the sick child.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 276-282, 1986. While deficient exercise performance of sick children results from hypoactivity and detraining, it can also be caused by specific pathophysiological factors. These can affect one or more components of physical fitness. A low maximal aerobic power will result from a low maximal stroke volume, as in aortic stenosis or cardiomyopathy; a low maximal heart rate, as in congenital complete heart block or intake of β-blockers; a low O2content of the arterial blood, as in anemia or advanced cystic fibrosis; and a high O2content of mixed-venous blood, as in muscle atrophy or severe malnutrition. A high O2cost of locomotion, as in advanced obesity or cerebral palsy, will cause the patient to exert at a high percentage of his maximal aerobic power and thus fatigue easily. A subnormal muscle strength, as in progressive muscular dystrophy or juvenile rheumatoid arthritis, is sometimes the primary factor that limits the walking ability or other daily functions. Recent data suggest that local muscle endurance, as assessed by the Wingate anaerobic test, is particularly deficient in some neuromuscular diseases. Examples are muscular dystrophies and spastic cerebral palsy. The ratio of peak anaerobic power to peak aerobic power seems lower in such patients than in able-bodied controls.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

LOWEY, S. Cardiac and skeletal muscle myosin polymorphism.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 284-291, 1986. Skeletal muscles, unlike cardiac tissue, express several myosin isozymes during development which differ in primary structure from adult myosin. Monoclonal antibodies have shown the presence of at least two embryonic myosins, followed by a post-hatch myosin that persists until the appearance of adult myosin in chicken pectoralis muscle. Although the two major cardiac isozymes differ in enzymatic activity, the avian skeletal myosin isozymes all share the same high level of ATPase activity found for adult pectoralis myosin. The functional basis for the extensive myosin polymorphism in skeletal muscles thus remains to be determined.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

KELLY, A. M. and N. A. RUBINSTEIN. Development of neuromuscular specialization.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 292-298, 1986. This review outlines recent advances in understanding the program of muscle specialization during development and discusses some of the controls over this process. The scheme of fiber heterogeneity is laid down very early in myogenesis and, at least in the chicken, it appears to be intrinsically determined by the limb, independent of neuromuscular contact. In mature muscle, specialized fibers are usually intermingled in a mosaic. This results from the pattern of muscle assembly from primary and secondary generation cells as these distinct generations commonly express different phenotypes. The muscle develops in this way as secondary cells use the walls of primary myotubes as a scaffold to support their differentiation. This process may be regulated by transient expression of N CAMs. Myoblasts left after N CAMs are no longer expressed may become the satellite cells of mature muscle. In the rat, primary cells all initially express slow myosin, whereas most secondary cells are fast in phenotype. Post-partum, the initial plan of fiber specialization is modulated. In developing slow muscles many secondary generation fibers convert from a fast to a slow phenotype, whereas in developing fast muscles, primary slow fibers transform to a fast phenotype. Hormones, particularly thyroid hormone, play a significant role in this modification. The role of the nerve is less well understood.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

MAHDAVI, V., E. E. STREHLER, M. PERIASAMY, D. F. WIECZYOREK, S. IZUMO, and B. NADAL-GINARD. Sarcomeric myosin heavy chain gene family: organization and pattern of expression.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 299-308, 1986. The sarcomeric myosin heavy chains (MHCs), which exhibit different levels of ATPase activity, are encoded by a closely related multigene family from which seven members have been identified and characterized in the rat. The MHC genes appear to map to a single chromosome, and at least two of them, α and β-cardiac, are closely linked in the genome. Each of these genes is ˜25 kilobases long, and their coding sequences are interrupted by 40 introns. Each MHC gene displays a pattern of expression that is tissue-specific and developmentally regulated, with more than one MHC gene expressed in each muscle and developmental stage. Moreover, with the exception of the extra-ocular muscle MHC gene that has a very specific pattern of expression, the other genes are all expressed in more than one tissue.The expression of all MHC genes can be modulated by thyroid hormone. Surprisingly, however, the same myosin heavy chain gene can be regulated by thyroid hormone in highly different modes, even in opposite directions, depending on the tissue in which it is expressed. Furthermore, the skeletal embryonic and neonatal myosin heavy chain genes, so far considered specific to these two developmental stages, can be re-induced by hypothyroidism in specific adult muscles.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ALPERT, N. R. and L. A. MULIERI. Functional consequences of altered cardiac myosin isoenzymes.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 309-313, 1986. This is a review of work dealing with the contribution of myocardial myosin isoenzymes to the performance of the heart muscle. Isoenzyme composition is altered in rabbit hearts by banding the pulmonary artery (increase in %V3) and thyroid hormone injection (increase in V1). Both treatments result in myocardial hypertrophy. The performance of the hearts rich in V3or V1myosin isoenzyme is assessed by simultaneous analysis of the myothermal and mechanical output of papillary muscles isolated from the right ventricle. Initial and tension dependent heat per tension time integral are decreased in the pressure overload and increased in the thyrotoxic hypertrophied hearts. Thus, the economy of isometric contraction is high in the hearts with the V3myosin and low in the hearts with the V1myosin. This change in performance is explained in terms of alterations in the cycling frequency and tension time integral of the myosin cross-bridge. In the pressure overload hearts the cross-bridge cycling frequency is decreased, while the tension time integral is increased. Conversely, in the thyrotoxic preparations the cycling frequency is increased and the tension time integral is decreased.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

SLY, R. M. History of exercise-induced asthma.Med. Sci. Sports Exerc.,Vol. 18, No. 3, pp. 314-317, 1986. Strenuous exercise prolonged for several minutes can cause airway obstruction in asthmatic subjects. Initial obstruction becomes most extreme 5-10 min after the completion of exercise and usually remits within a few minutes but may recur 3-6 h later. The response to exercise depends upon the type of exercise. Swimming is less likely to cause exercise-induced asthma than running. Recent exercise or pretreatment with a bronchodilator or cromolyn can inhibit exercise-induced asthma. Nasal breathing or inhalation of warm, fully humidified air during exercise can minimize exercise-induced asthma. Local changes in osmolarity or cooling of mast cells probably causes release of mediators that cause airway obstruction.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID