Contractility: The Ability To Shorten A Muscle

To perform isokinetic contractions expensive equipment is needed that increases the load as the muscle contraction speed increases.

2. In strength training and rehabilitation, emphasis should be given to both the concentric and eccentric phases of the movement. During the concentric phase, the muscle shortens from a lengthened position and during the eccentric phase the muscle lengthens from a shortened position. For example, in the execution of the

This activity is the critical driving force of muscle contraction. The stream of action potentials along the muscle fiber surface is terminated as Acetylcholine at the neuromuscular junction is broken down by acetyl cholinesterase. The release of Calcium ions is ceased. The action of the myosin molecule heads is obstructed because of the change in the configuration of troponin and tropomyosin due to the absence of calcium ions. This will eventually cause the contraction to be ceased. Together with these physical processes, an external stretching force such as gravity pulls the muscle back to its normal length.

Isometric contractions appear when there is no change in the length of the contracting muscle. This occurs when carrying an item in front of you. As the weight of the item is pulling your arms down, but your muscles are contracting to hold the items at the same level. Isokinetic contractions are really similar to isotonic, in that the muscle changes length during the contraction. Where they are different is that Isokinetic contractions produce movements of a constant speed. What you need to measure this is something called a isokinetic dynamometer. Concentric contractions are those which cause the muscle to shorten. An example is bending the elbow from straight to fully extended, causing a concentric contraction of the Bicep muscle. Eccentric

Muscles are specialised tissues which respond to nervous stimulation by contracting, which means that the muscle shortens and thickens. Muscle tissue is also elastic, which means that it can be stretched by weight, and when the weight is removed the muscle will return to its normal length.

Contractility is the pumping of the heart muscle. It is measured as the ejection fraction. Contractility directly influences stroke volume. Increased contractility will increase stroke volume with any amount of preload. Diseases that disrupt myocyte activity reduce contractility. Myocardial infarction is the most common. Others include, but are not limited to, cardiomyopathies, degenerative valve disease, and myocarditis (Francis & Tang, 2003). Secondary causes of decreased contractility, such as myocardial ischemia and increased myocardial workload, contribute to neurohumoral , immune, and inflammatory changes and can cause ventricular remodeling. Ventricular remodeling occurs when the size, shape, and function of the affected chamber is distorted. Ventricular remodeling causes hypertrophy and dilation of the heart muscle and causes progressive myocyte contractile dysfunction over a period of time. When contractility is decreased, stroke

Summary… A condition which is characterized by an inability of the muscles to function at their full strength; a vague complaint of debility, fatigue, or exhaustion attributable to weakness of various muscles. The weakness can be characterized as subacute or chronic, often progressive, and is a manifestation of many muscle and neuromuscular diseases.

Muscles contract when they are stimulated; when a muscle contracts and produces movement this is called an isotonic contraction. An isotonic contraction can be either concentric or eccentric.

Isometric muscle contractions occur when the muscle contracts but there is no movement. For example when someone holding a wall sit position. Isotonic muscle contractions result in movement. There are two types of isotonic muscle contraction, Concentric and Eccentric. Concentric muscle contractions are the most common form of contraction. These occur when the muscle shortens in length in order to make the bone move. These contractions occur when the body is working against

A motor unit is made up of a single motor neuron and the associated muscle fibers it innervates. The size of the motor unit defines the level of control. It varies in size because there is an inverse association between the size of the motor unit and the level of control. Large body masses have motor units that are made up of additional muscle fibers and small body masses are made up of less muscle fibers. The muscles that have more motor units (example the muscles in the eye) are able to harness more power. Muscles that contain little muscle fibers are not able to control as accurately. The motor unit is distributed throughout the muscle and not contained to one central location of the muscle.

A muscle contraction is when the muscle length changes during contraction. Contractions occur when a muscle has been stimulated by a nerve impulse that has reached a muscle fibre. When a muscle contracts it is called an isotonic contraction and generates force by changing the length of the muscle. Isotonic muscles are either concentric or eccentric contractions. Concentric contractions cause the muscles to shorten whilst generating force and the angle of the joints which are attached to the muscle to change. An isometric contraction is where contractions generate force without the length of the muscle altering resulting in no movement.

muscles in movement.” Voluntary muscles are muscles that you can control such as biceps, but,

Most of these contractions you will need specialised equipment to measure the rate of the consistency of the work out. A practical example of isokinetic contractions would be bench pressing at a low weight but a high repetition, this would be isokinetic as you would need to do it at a constant speed so therefore you would need it at a suitable weight to do these contractions correctly. If you had it at a high weight you would get worn out and start struggling at the end of the set of repetitions. An everyday example of isokinetic example would be doing your teeth as you would be doing it at the same pace and contractions and shortenings would take

The type of stretching I chose to research is proprioceptive muscular facilitation, or PNF stretching. PNF stretching is defined as stretching techniques used to enhance both active and passive range of motion in order to improve motor performance. PNF stretching is often used by physical therapist to aid in rehabilitation. PNF stretching techniques can passive, meaning there is no muscle contraction, or the techniques can be active, meaning there is a voluntary muscle contraction. One thing that all of these variations of PNF stretching have in common is muscular inhibition. Muscular inhibition is when the muscles on one side of a joint relax to accommodate contraction on the other side. PNF stretching is used to help muscular strengthening,

During prolonged activity, muscles show a decline in ability to respond to stimulation with optimal levels of contractile activity; this is a phenomena denoted as muscle fatigue (MF) (1). The causes of MF are not yet understood, however there are many observations of associations between metabolic and biochemical factors with MF. In order for force to be generated by muscles, calcium ions which are released from the sarcoplasmic reticulum bind to troponin. The new troponin-Ca2+ complex cause’s tropomyosin to change shape, exposing the binding site on actin. Myosin then binds to actin, causing cross bridge tilting, and generating contraction (1).