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PubMed1988

A review of the literature related to trunk muscle performance.

In the past, there has been no comprehensive review of the literature pertaining to different methods of assessing trunk muscle strength. This review describes the different studies that have been performed, and determines the hierarchy of strength values and agonist/antagonist strength ratios for the trunk musculature. In general, the strength hierarchy consists of, from strongest to weakest: extension, flexion, side bending, and rotation. The agonist/antagonist ratio for extension/flexion is 1.30 and for rotation and side bending, motion to the right approximately equals motion to the left. Changes in the relative strengths of the different trunk muscle groups is affected by spinal pathology, and this is discussed. Possible clinical implications and direction for future research are delineated based on the findings of this review.

Back↗
PubMed1985

Energetic aspects of skeletal muscle contraction: implications of fiber types.

In this chapter fundamental energetic properties of skeletal muscles as elucidated from isolated muscle preparations are described. Implications of these intrinsic properties for the energetic characterization of different fiber types and for the understanding of locomotion have been considered. Emphasis was placed on the myriad of physical and chemical techniques that can be employed to understand muscle energetics and on the interrelationship of results from different techniques. The anaerobic initial processes which liberate energy during contraction and relaxation are discussed in detail. The high-energy phosphate (approximately P) utilized during contraction and relaxation can be distributed between actomyosin ATPase or cross-bridge cycling (70%) and the Ca2+ ATPase of the sacroplasmic reticulum (30%). Muscle shortening increases the rate of approximately P hydrolysis, and stretching a muscle during contraction suppresses the rate of approximately P hydrolysis. The economy of an isometric contraction is defined as the ratio of isometric mechanical response to energetic cost and is shown to be a fundamental intrinsic parameter describing muscle energetics. Economy of contraction varies across the animal kingdom by over three orders of magnitude and is different in different mammalian fiber types. In mammalian skeletal muscles differences in economy of contraction can be attributed mainly to differences in the specific actomyosin and Ca2+ ATPase of muscles. Furthermore, there is an inverse relationship between economy of contraction and maximum velocity of muscle shortening (Vmax) and maximum power output. This is a fundamental relationship. Muscles cannot be economical at developing and maintaining force and also exhibit rapid shortening. Interestingly, there appears to be a subtle system of unknown nature that modulates the Vmax and economy of contraction. Efficiency of a work-producing contraction is defined and contrasted to the economy of contraction. Unlike economy, maximum efficiency of work production varies little across the animal kingdom. There are difficulties associated with the measurement of maximum efficiency of contraction, and it has yet to be determined unequivocally if the maximum efficiency of contraction varies in different fiber types. The intrinsic properties of force per cross-sectional area, economy, and Vmax determine the basic energetic properties of skeletal muscles. Nonetheless, the mechanics and energetics of skeletal muscles in the body are profoundly influenced by muscle architecture, attachment of muscles to the skeleton, and motor unit organization.(ABSTRACT TRUNCATED AT 400 WORDS)

Actomyosin↗
PubMed1988

Static exercise--physiologic dangers and proper training techniques.

Static exercise is commonly encountered occupationally and in normal activities of daily living. In addition, weight training, a form of static exercise, is one of the fastest growing physical activities in the United States. Static exercise is a stressor to the cardiovascular system. At high intensities it produces immediate and profound systolic and diastolic hypertension, moderate tachycardia and enhanced contractility resulting in a moderate increase in cardiac output without an increase in stroke volume. Static exercise is well tolerated in healthy people. People with cardiovascular disease appear to tolerate static exercise of low intensity if they have normal left ventricular fraction and reserve. However, in people with impaired left ventricular function and reserve, the exercise stress causes tachycardia, a hypertensive state, increased systemic vascular resistance, and left ventricular end diastolic pressure. If the exercise stress persists, stroke volume and ejection fraction decline. This article helps nurse practitioners in wellness and preventive patient education. An analysis of current research covers the relationship between client variables and the cardiovascular effects of static exercise. Nurse practitioners learn how to identify and advise clients who should avoid static exercise. The proper selection of a health fitness club and the proper components of a basic weight-training program are comprehensively reviewed.

Cardiovascular Physiological Phenomena↗
PubMed1988

Stretching, strengthening, and conditioning for the competitive tennis player.

For an athlete to be competitive at the highest levels of tennis, he or she must possess an optimal level of flexibility, strength, and cardiovascular conditioning. He or she also must be at a maximum level in areas including upper and lower extremity selective endurance, isolated muscular strength patterns of repetitive activities, and agility. To achieve this, a great deal of time and effort must be spent off the tennis court strengthening the appropriate muscle groups and improving overall agility and pattern responses. It is hoped that these programs will allow the American junior tennis player to return to a level competitive with the rest of the world.

Humans↗
PubMed1987

[Mechanism of self-regulation and the inotropic reaction of the rat myocardium during aging].

The experiments on rat papillary muscles revealed that in ageing rats myocardium has a decreased distension ability. The curves of shortening value/length and force/velocity for the myocardium of old animals are shifted downwards. The alterations in isotonic contraction parameters had a distinct age differentiation, while the age did not affect the inotropic effects of increased frequency, paired stimulation and external calcium. It is suggested that changes in biomechanical properties of ageing myocardium are associated with alterations in calcium transport in sarcoplasmic reticulum.

Aging↗
PubMed1986

[Autoregulation of the contractile function of the myocardium in response to changes in the concentration of the activating cation].

In guinea-pig isolated papillary muscles, dependence of the isotonic contraction velocity on the perfusate Ca++ concentration was studied. The dependence was the steepest at the lowest rate of stimulation. At a high rate (2 Hz), changes in contraction velocity as well as in extent of the muscle shortening were minimal. Replacement of a half of Ca++ ions by Sr++ resulted in an augmentation of steepness of the dependence on sum of [Ca++] and [Sp++], and in a more prominent fall in relaxation velocity as compared with contraction velocity. Replacement of a half of Ca++ ions with Ba++ or depletion of [Na+] in usual solution to 25 mM resulted in a prominent fall in relaxation velocity while the contraction velocity increased. This dissociation coincided with signs of cellular Ca++ overload and a more steep restitution of contraction velocity during diastole. Results are discussed in terms of participation of Na+-Ca++ exchange in these self-regulatory phenomena.

Animals↗
PubMed1979

[Action of acetylcholine on the mammalian auricle influenced by verapamil].

The action of acetylcholine (ACh) and verapamil (VePa) on the action potential (V(t)), phase plane trajectories of V(t) (dV/dt--V(t) -- plot) and isotonic contractions were investigated using an isolated vegal innervated preparation from rabbit atrium (method I) and investigating action potentials from atrial trabeculae by means a modified sucrose gap technique (method II). If the VePa-concentration increases to 4 mg/1 the duration of the action potential decreases at 20 and 90% repolarization (driving frequencies 2 s-1). In the VePa-solutions phase plane trajectories of the action potential did not change significantly. ACh application favours the disappearance of a region in the repolarization phase plane plot showing anomalous rectification (d(--dV/dt)/dV less than 0) both by control conditions and verapamil. The electrotropic ACh-and vagal effects will be unchanged by verapamil. The inotropic ACh-and vegal action (method I) increases by VePa (2 mg/1). The action of ACh and verapamil will be analysed using a mathematical model for reconstructing the repolarization phase of mammalian atrial myocardium action potentials.

Acetylcholine↗
PubMed1983

Exercise therapies in peripheral neuropathies.

The treatment of peripheral neuropathies should be aimed at maintaining the range of motion of the joints, re-educating the patient in skilled activities and optimizing the recovery of strength. Many techniques have been described to substitute for, to strengthen and to improve the function of residual innervated muscle; however, not all of these techniques are of unquestioned value. Specifically, electrical stimulation does not appear to enhance reinnervation of totally denervated muscle. Similarly, overstretching weakened muscle may impair the use of paretic muscle. Because overwork may damage partially denervated muscle, brief isometric or isotonic contractions may be more beneficial for increasing strength than a program of habitual exhausting activities.

Cold Temperature↗
PubMed1984

Evaluating the cardiac patient for exercise therapy. Role of exercise testing.

Several types of exercise tests and their use are reviewed. Suggestions are made for modification of tests to enhance their value in the counseling of normal individuals and patients with cardiac problems regarding occupational, recreational, and training activity. Also discussed are indications and contraindications to testing, end points in testing, and evaluation of test results.

Arm↗
PubMed1978

[Study of the silent period during the post-stimulus histogram method].

Isotonic contractions of human hand muscles were elicited by nerve stimulation and the silent period was studied on single motor units employing post-stimulus histograms. At submaximal M-response (up to 70% of M-maximum) the motoneurons under study were not stimulated and thus the after-hyperpolarization was excluded from the experiment. Under these conditions the latency of the silent period was not less than 60 ms and the silent period parameters were similar to those after subthreshold for M-response nerve stimulation and to those after skin stimulation. The experiments proved that neither recurrent inhibition nor spindle unloading affected the spinal centres of muscles under study.

Electromyography↗
PubMed1978

Influence of internal shortening on time course of active state in rat papillary muscle.

In order to investigate internal shortening effects upon time course of active state, a study on rat papillary muscle has been carried out. Internal (or CE) shortening was evaluated according to a mechanical muscle model in which parallel elastic (PE), series elastic (SE), contractile (CE) elements are represented. CE force-velocity-shortening-time relationships have been used to describe time course of muscle active state in isometric, completely isotonic, afterloaded, and stopped isotonic contractions. The results obtained suggest that, regardless of type of contraction utilized, the parameters of muscle active state are strongly influenced by the amount of CE shortening.

Animals↗