The flexor muscles are used when bending forward at the waist. The flexor muscles are located in the cervical and lumbar spine.
There are several muscles in the human body that are not located above the waist. For example, the brevis and longus muscles are not above the waist, as they are located in the legs.
your muscles are not streched out so they get used to not being used
Muscles within the brachium are responsible for the extension of the elbow. These muscles also work for the flexing of the arm as well.
The muscles used in the leg press exercise are your Quads primarily. Hamstring gets a good work out too.
There are five muscles worked when doing a triceps extension. The main muscle is, obviously, the triceps. Secondary muscles that are worked are the deltoid, pectorals major, latissimus dorsi, and teres major.
The muscles that produce extension of the finger joints and wrist are the extensor muscles. In the forearm, the specific extensor muscles responsible for extension of the fingers and wrist include the extensor digitorum and extensor carpi radialis muscles.
extension, contraction
Extension of the arm at the shoulder is due to:Latissimus DorsiPosterior fibers of the DeltoidTeres MajorExtension of the elbow joint is almost entirely due to triceps brachi
supraspinatus, infraspinatus, subscapularis, teres minor
The antagonists would be those muscles that cause knee flexion. Hamstrings (biceps femoris, semimembranosus, semitendonosis) are the primary knee flexors, and would thus be antagonists to knee extension.
By putting your body in different positions you can workout almost all muscles including your back muscles by doing a back extension with dumbbells or the most common exercise squats which workout your legs