Muscles move joints, to which they are joined, by shortening
and pulling one end of the muscle closer to the other end.
A muscle is made up of lots and lots of muscle fibres which
are held together in bundles. The muscle fibres are activated
by the brain sending electrical impulses to each muscle fibre
via the nerves. These impulses cause the muscle fibre to
contract and shorten so moving the joint over which the muscle
works. If a muscle can not work, due to injury or illness,
each little muscle fibre gets thinner and the whole muscle
gets weak. Muscles are capable of both power and endurance.
If one washes one's hair in the shower or blow it dry one
needs endurance to hold arms up for a period of time.
heavy suitcases onto a roof rack or putting them away in
the top cupboard requires power to be able to lift them up.
Power is for doing movements against resistance. Moving limbs,
walking up stairs, getting up from a chair lifting a heavy
shopping bag all calls for power. Muscle endurance allows
the muscle to work at a lower level for long periods. The
muscles that help us to maintain a certain posture need endurance.
Having been in bed for a week with flu one would feel a bit
weak at the knees when first up. This is partly because the
Quadriceps have not been working and have become weak. Gradually
asking the legs to stand and do more walking the muscles
quickly regain some of their strength and endurance. Lets
assume that the muscles that bend the index finger have 1000
muscle fibres. To beckon with the finger might ask say 10
fibres to work. Wanting to lift an empty bucket on the one
finger might use 100 fibres. Whereas lifting a bucket that
was full of water would ask most of the thousand fibres to
work. By trying to lift a little more water each time would
eventually train the muscle to lift a full bucket of water.
When a muscle is damaged the muscle fibres are torn and the
connective tissue around the muscle
is also damaged. When the fibres are damaged fluid seeps out
of torn fibres and causes localised swelling. This works like
glue when squeezed from a tube. The glue tries to repair the
damage and in its enthusiasm sticks everything to everything
else. The individual fibres of the muscle, which are normally
free to glide slightly one on the other, become stuck together
and are irritated by the pull of even the slightest contraction
in the muscle. It is important that the ends of the muscle
fibres stick together but not that they stick along their
whole length. Sprains and strains are not helped by "working
through them" or by exercising and 'keeping it moving'.
It is advisable to seek the help of a Chartered Physiotherapist
as soon as possible. In the meantime resting and keeping the
leg up if its a lower limb problem will allow the body to
do its own repair job much quicker than if you try to carry
on as though nothing had happened.