CONTRACT VS RELAX
• Muscles work by contraction (or shortening).
• When they do they pull on the bone, causing
movement. The muscle that is responsible for the
movement is called the agonist.
• When a muscle contracts, it has an opposing muscle
that relaxes (or lengthens) at the same time. This is
called the antagonist.
• Muscles can be agonists or antagonists, depending on
the direction of the movement.
• Muscles can also be stabilisers. This means the
muscles act at a joint to hold it still or stable. This
provides a fixed strong base for muscle movement.
The main muscles involved in
• Upper body
deltoid, pectorals, biceps, triceps, latissimus
dorsi, trapezius, rectus abdominis, external
obliques, erector spinae
• Lower body
quadriceps, hamstrings, gluteus maximus,
gastrocnemius, soleus, tibialis anterior
WHERE YOU AT?
• Skeletal muscles attach to bones. They span
across a joint (ie are attached to at least 2
• They can attach directly to a bone or attach by a
• The point of attachment that to the more
stationary bone is the origin of the muscle. It is
usually closer to the trunk.
• The point of attachment to the movable end is
the insertion. It is usually further from the centre
of the body.