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Free weights or machines?

(HealthDay)—Resistance or strength training isn't just for bodybuilders—it's for everyone, and it's essential to combat the natural tendency to lose muscle mass with age.

Cranky crabs in broken shells often have the upper claw in fights

Sheer aggression rather than pure muscle strength often gives hermit crabs living in broken shells the edge during a fight. Broken shells constrain crabs' activities because they are heavy and a large portion of them unusable. ...

Video: Phone book physics

Myth-buster fans have likely heard of the phenomenon of interlocking pages of two phonebooks and discovering that they are impossible to pull apart.

Tiger genome to help big-cat conservation

South Korean scientists said on Tuesday they had carried out the first DNA analysis of the tiger and four other great felines in a project to help critically-endangered cats to survive.

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Muscle

Muscle (from Latin musculus, diminutive of mus "mouse") is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause either locomotion of the organism itself or movement of internal organs. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples are the contraction of the heart and peristalsis which pushes food through the digestive system. Voluntary contraction of the skeletal muscles is used to move the body and can be finely controlled. Examples are movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers: slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force while fast twitch fibers contract quickly and powerfully but fatigue very rapidly.

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