Are you Fast or Slow?



If you had to choose which would you
prefer: Sprinting or Distance Running? 

Understanding how skeletal muscle works is
essential for aspiring athletes and their physical therapists and sports
coaches.  But it’s also good for us to
understand so that we can improve our own physical fitness, regardless of what
level we’re at.

Muscle Composition:

The human skeleton is surrounded by bundles
of muscle fibers called myocytes.   These
contain lots of strands of protein (actin and myosin) called myofibrils.  These strands are able to pull by grabbing
hold of each other, which shortens the muscle and causes it to contract.

Slow twitch muscle fibers are dark red in
color because they contain lots of blood vessels.  They rely on oxygen supplied by these blood
vessels for energy and although they fire more slowly than fast twitch muscle
fibers they take much longer to tire. 
Slow twitch fibers are great for marathon runners and long distance

By comparison, fast twitch muscle fibers
are lighter in color because they use anaerobic metabolism to create fuel so
they can fire quickly and repeatedly in short bursts.  These short bursts of concentrated energy
produce the incredibly fast running of a sprinter.

Your soleus muscles, in your lower leg, and
your back muscle are unusually made of mainly slow twitch fibers.  Your other muscles are made of both.  Your eyes have fast twitch muscle fibers.

If you were a chicken…

Did you know that the dark meat of a
chicken, i.e. in the legs, is made up of slow twitch muscle fibers?  White meat, like the wings and breasts, is
made up of fast twitch muscle fibers. 
Chickens spend most of their time walking and standing on their legs
which doesn’t require much energy.  But
when they launch into short bursts of flight, they use up lots of energy
flapping their wings and using muscles to get them airborne, even if only
briefly, and that requires fast twitch muscle fibers.

Whilst most of us have an equal amount of
fast and slow twitch muscle fibers (50/50) it’s been noted that Olympic
athletes tend to have significantly higher proportion of one or the other.  Olympic sprinters tend to have around 80%
fast twitch muscle fibers whilst Olympic marathon runners tend to have around
80% slow twitch fibers.

Plenty of research by sports scientists is
going into finding out whether specific training can change the fiber
type.  There is some evidence to suggest
that human skeletal muscle could switch fiber types from fast to slow due to
intensive training techniques.

Genetics plays a large part in
what percentage of muscle fibers we have but consistent training efforts do pay
off.  If you stick to a regular training
program you will see results and improve your performance.  Being sensible about eating a balanced diet,
learning how good nutrition can improve your overall health, taking regular
and following stretching and relaxation techniques will all help to
improve your overall physical condition. 

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