Just think about it for a moment: all the muscles in your body have a job to do, there are no useless muscles!
In order for your muscles to do their job they must travel a specific motion which cannot be changed; for example, the bicep which is located at the humerus bone can only be flexed and extended which is the lengthening and shortening of the muscle. Each and every muscle is lengthened and shortened through different ranges of motion.
In order to get the best out of any given exercise, you must know its motion and how the anatomy of the muscle works. The basic movements of the body are pulling and pushing movements using both arms and legs yet involve a multitude of muscles.
Pushing movements involve the pectoralis major (chest), minor as well as latissimus dorsi (back), anterior deltoid (front shoulder) and all 3 heads of the tricep.
The arms must press in front of the body or above the body in order to perform the concentric part of the repetition which is called arm extension. On the negative part of the repetition the arms are drawn back to the sides of the body or head meaning the arms are put back into flexion and the muscles in use are lengthened. These muscles are involved in all pressing movements using the same range of motion meaning the arms will only flex and extend when pressing either in front or above head.
Pulling movements involve a large amount of muscles. The main muscles are a group called the spinal erectors which run from top to bottom of the posterior of the body and in the midline around the spinal cord.
The latissimus dorsi which is lateral to the spinal erectors control the majority of pulling movements with a secondary antagonist muscle being the biceps, brachialis and radial brachialis. Again the main functions of the body when pulling are the arms extending and flexing on movements such as lat pulldowns, shoulder retraction on row movements but also the torso extending and flexing on movements such as deadlifts and T-bar rows which also involve flexion and extension of the arms and retraction of the shoulder blades.
Leg movements involve the muscles; semitendinosus, semimembranosus and biceps femoris in the hamstrings.
The quads consist of the rectus femoris, vastus lateralis, vastus medialis and vastus intermedius.
The primary movement of the quads are extension of the leg using the knee hinge joint. That is the shortening of the muscle on the concentric part of the repetition and involve the leg being straight rather than flexed. The quads then are lengthened on the eccentric phase of the repetition which is when the knee hinge goes back into flexion.
The main movement of the hamstring muscles is flexion (bringing your heel in closer to your body).
This is pronounced in exercises such as leg curls, lunges which use hip flexion and standing leg curls. When involved in compound movements such as squats and leg presses, both agonist and antagonist muscles work together. On the eccentric part of a squat, the hamstrings are being worked and then to push the legs back up to extension, the quads are being fully contracted. This is a prime example of both muscles working together at the same time rather than an isolation movement such as leg extension or leg flexion.
To understand how to get the best out of your muscles you must understand how they work and what range of motion they go through. This short article will help you understand how to work specific muscles and helps you understand how they are working through a given exercise. If you are new to exercise and want to know how to hit each muscle effectively, use this article to your advantage and follow the basic movements outlined.