That is correct, the muscle shortens as it contracts. E.g. A bicep curl, the bicep muscle as you lift the wight up is Isotonic contraction. :)
a concentric contraction- a concentric contraction involves the muscle length, shortening during a contraction! YA-trick-YA!
A concentric contraction is when the muscle shortens as it exerts force. This type of contraction is commonly associated with lifting weights or performing a bicep curl, for example.
An Isotonic contraction is when a muscle becomes longer or shorter to produce force and therefore an example is a bicep curl. During the downward phase your muscle (bicep) lengthens and during the upward phase your muscle (bicep) shortens.
A torn bicep muscle can usually occur when your bicep muscle is fully extended and under too much pressure. Weight lifters often get a torn bicep muscle when doing the preacher curl. The preacher curl can really strain the bicep muscle, and lead to a torn bicep muscle if you are lifting to much weight or have not warmed up correctly. Your bicep is a muscle on your arm. it is the muscle that you usually flex when trying to show off your srength. Most torn bicep muscle injuries occur when the arm is fully extended and the lifter is just about to pull the weight back up. When you get a torn bicep muscle you will feel an immediate sharp pain in your bicep near your elbow, followed by bicep muscle weakness and stiffness and eventaully bruising.
Agonist is bicep and other elbow flexors antagonist are all the elbow extensors ie triceps
The agonist (not angonist) muscle are the Biceps Brachii and the Brachioradialis and the antagonist is the Triceps Brachii.
When you preform an arm curl, you use your bicep muscle. it all depends on how you curl. If you curl straight up or do a twisting motion while curling. You use your shoulder and bicep and maybe a small portion of the pectoral muscle where it meets the shoulder.
Isotonic muscle contractions involve both concentric (muscle shortening) and eccentric (muscle lengthening) phases. In isotonic contractions, the muscle changes in length while maintaining a constant tension, such as when lifting a weight or performing a bicep curl.
Reactor muscles are the same for male and female. A reactor muscle are 2 muscles that do the opposite function (Ex. Bicep and triceps). To answer your question, the purpose of reactor muscles is to have a muscle that contracts and the other muscle stabilize. There are other terms I could use such as the muscle that is contracting is performing an concentric contraction (Contracting while shortening [Performing a bicep curl with a dumbbell]) and the muscle that is stabilizing is performing an eccentric contraction (Contracting while lengthening [Ex. Lowering a dumbbell with a bicep curl bar]). The reason this is important is because without the stabilizing muscle, also called an antagonist muscle, you would not have smooth controlled movement anywhere in your body. It would not be a good engineer and we would not be able to move are arms without looking weird. I hope this helps.
since the bicep curl is a flexion of the forearm at the elbow, the biceps brachii and brachialis are mainly used, especially in the supinated position. a prone bicep curl uses brachialis and brachioradialis more. the biceps brachii function is much less, since it is also a forearm supinator, so it is deactivated in the prone position.the triceps brachii are the antagonistic muscle group are not not involved in the bicep curl. the triceps extend the forearm at the elbow.
the bicep contracts in a concentric contraction which means the muscles has shortened. remember muscles can only pull they can not push. also the bicep curl can be described as elbow flexion and when the weight is lowered is called elbow extention. hope it helps