Cause of Weakness 3
IDENTIFY – The cause of my weakness, lack of explosive power in my legs, is due
to the lack of fast twitch glycolytic fibres in my leg muscles. Power = Force x
Velocity so fast twitch fibres are directly linked to power.
EXPLAIN – My weakness is due to the proportion of high to slow twitch muscle
fibres in my leg. Power relies on a higher proportion of fast twitch muscle fibres to be
effective. My proportion of fast twitch muscle fibres to slow twitch is too low and I
therefore need to increase it if I want to improve explosive power in my legs.
Muscles are made up of thousands and thousands of individual muscle fibres, which
are held together by connective tissue. However, these fibres differ in physiological
makeup and it is the type of muscle fibre which exists that explains the difference in
performance. E.g. a marathon runner and a weight lifter. The individual muscle fibres
are made up of hundreds of smaller elements called myofibrils. These myofibrils
contain the proteins responsible for muscle contraction, actin and myosin; together
with the components necessary for energy production and the control of movement
(namely mitochondria, glycogen and fat deposits, and muscle spindles).
Skeletal muscle has two main fibre types; fast twitch and slow twitch. I lack fast
twitch fibres and therefore cannot jump as high as other netballers, because of this I
often lose out in the air when I am jumping to collect a lob pass or when I am jumping
for a rebound. Slow twitch fibres are red in colour, they contract slowly, are more
effective during aerobic endurance based activities, they can contact repeatedly but
exert less force than fast twitch fibres. Although fast twitch fibres exert a greater force
they are easily exhausted. They are white in colour, contract rapidly and are most
effective for anaerobic, speed/strength based activities. Fast twitch and slow twitch
fibres vary in different muscles and in different individuals; these proportions tend to
be inherited however, through specific training a performer can change the
proportions. E.g. a lot of aerobic training will increase the amount and effectiveness
of the slow twitch muscle fibres.
Fast twitch muscle fibres can be subdivided into type 2a and type 2b;
 Type 2a – Fast Oxidative Glycolytic Fibres (FOG); these fibres pick up certain
type one characteristics through endurance training. They therefore tend to
have a greater resistance to fatigue and are most effective for activities of high
intensity and of relatively short periods of time, e.g. tracking an opposing
player when playing centre for an extended period of defending.
 Type 2b – Fast Twitch Glycolytic Fibres (FTG); these are used for activities of
very high intensity and have a much stronger force of contraction. This is
because the motor neuron that carries the impulse is much larger; there are
generally more fibres within a fast twitch motor unit; and the muscle fibres
themselves are larger and thicker. These fibres are most effective for activities
of high intensity (explosive) for very short periods of time, e.g. jumping to
intercept a pass over my head or making a strong lunge to one side in order to
send the defender the wrong way.
 FTG fibres differ from FOG fibres in their pure fast-twitch properties. They
have few mitochondria and high levels of stored glycogen and the enzymes
necessary for producing energy without oxygen. The FOG fibres have the
stored glycogen and enzymatic properties of FG fibres, in addition to high
levels of oxidative enzymes which assist aerobic metabolism. They have the
best of both worlds.
ANALYSE/JUSTIFY – If I were to increase the effectiveness and proportion of my
type 2b fast twitch muscle fibres it would enable me to improve my vertical jump and
therefore increasing my chance of intercepting high balls. This would mean that as the
balls were not going over me as much I would keep aroused and alert and it would
raise my entire game.
Corrective Practice
IDENTIFY – As I do not have enough power in my legs to intercept high balls, this
indicates that I need to partake in a training programme specifically designed to
improve and increase the proportion of type 2b fast twitch muscle fibres in my legs.
EXPLAIN – I will combine fartlek training with some specific weight ‘stations’ as the
programme goes on to encourage hypertrophy of the muscles. This hypertrophy
(splitting) of the muscles increases the amount of type 2b fibres in the muscle as the
mass of the muscle increases. The more I train the more effective the fibres will
become and the higher I will be able to jump. Plyometric exercises are the rapid
deceleration and acceleration of muscles that create a stretch-shortening cycle. The
exercises train the muscles, connective tissue and nervous system to effectively carry
out the stretch-shortening cycle, thereby improving an athlete's performance. Muscles
generate more force in contraction when they have been previously stretched.
Plyometrics enables this to occur through an eccentric (lengthened) phase before a
powerful concentric (shortened) phase. This stimulates adaptation within the
neuromuscular system whereby the muscle spindles within the muscle cause a stretch
reflex, which prevents muscle damage and produces a more powerful contraction of
the muscle group. Exercises that I
will perform as part of my
Plyometrics
session
include;
bounding (as can bee seen in the
diagram to the right), hopping,
leaping, skipping and depth jumps as
they are all specific to increasing
power in my legs.
The training will therefore improve the power in my legs and will enable me to jump
higher as the training goes on. Before I start the test I will complete the vertical jump
test and every 4 weeks redo the test to monitor my improvement. This test is
extremely valid as it is just testing explosive power in my legs and as long as put
maximum effort into each test it should be very reliable to. This allows me to
continually assess my progress as the training programme goes on.
ANALYSE – my training programme will follow the principle of SPORT;
Specificity; the programme is specifically designed to improve the power in my legs
so it therefore very specific. Progression; though kinaesthetic feedback and the
ongoing evaluation I will be able to assess whether I need progress some of the
stations. E.g. for leaping I will increase the height of the barriers, for depth jumps I
will hold weights and increase them as I feel necessary and I may add in weighted
squat thrusts as my body becomes accustomed to the circuit. Overload; as I am
pushing myself to my maximum potential and continuously progressing, my body is
being constantly, but safely, overloaded. Reversibility; I will complete the training
programme 3 times a week with a 1 day gap in between in order to improve recovery,
due to muscle hyperplasia of the skeletal muscles in my legs. Tedium; to reduce
tedium I will train with a partner and play music whilst completing it. To comply with
health and safety regulations I will ensure that all equipment is properly set up, the
ground is dry and not slippery, that I wear the correct attire and that there is no-one
else that could be injured near me. I will complete a suitable warm up and cool down
to ensure that I do not injure my muscles.
JUSTIFY – The plyometrics training will improve the power in my legs and will
enable to intercept more of the overhead balls that are passed over me. This will
increase my confidence and maintain my arousal levels as well as increasing stamina
as I don’t have to continuously move around my player. My team-mates will all feel
confident in my ability and as there is now no weak link in the team we will cohese
more and this will result in more wins.