Key Area 3: Movement analysis 3.1: Muscle contractions
Knowledge Application
Muscle contractions – muscles can only
contract to produce movement. There are two
types of muscle contraction.
Skeletal muscles – work in pairs and are
connected to the skeleton by a tendon to help
move limbs.
Concentric contraction –
this is the shortening of the
muscle when it is under tension
(contracting).
Isotonic contraction
Isotonic contraction - are when
the muscle changes length when
it is under tension. The length of
a muscle can shorten or lengthen
producing a concentric or eccentric
contraction.
Isometric contraction - is when the muscle
stays the same length when under tension.
Eccentric contraction – this is
the lengthening of the muscle
when it is under tension.
Isometric contraction
Example: An isotonic concentric is when
you perform bicep curls as part of a
training session.
Example: An concentric contraction
during a bicep curl. This is when you lift
the weight and the bicep muscle shortens
(contracts).
Example: An eccentric concentric is
when you lower the weight during a bicep
curl and the bicep lengthens.
Example: An isometric concentric is,
when performing bicep curls, if you hold
the movement half way.
The bicep holds the tension without any
shortening or lengthening of the muscle.
Example: During the lifting phase
when performing a bicep curl, the
bicep is the agonist (prime mover).
The bicep is contracting to control
the movement.
Example: During the lifting of the
weight when performing a bicep
curl, the tricep is the antagonist.
The muscle will relax and extend to
allow exion at the elbow.
Example: During a tricep extension the roles
change. The tricep becomes the agonist and the
bicep becomes the antagonist.
Muscle actions – muscle pairs called agonistic pairs, work across joints to perform movement by
pulling on bones via the muscle tendon.
Agonist (prime mover) – this is
the muscle that is controlling the
movement. It is sometimes called the
prime mover.
Antagonistic pairs – this is what we
call two muscles that work together
to perform a movement.
It is when one muscle contracts
(shortens) and the other one
relaxes (lengthens).
Antagonist – during the
movement this is the muscle
that relaxes to allow the
movement to be controlled.
