Date: 10/11/01 12:40 PM
Author: Angel Face (no profile)
Subject: Intensity and Failure
Now this is where we start to get to the nitty gritty, but first I will
have to cover some background stuff on fatigue...for this I am assuming
that you have knoweldge of how energy is formed...if not let me know and
I will post some info...
ATP/Pc factors: Intramuscular levels of ATP fall rapidly during
exercise...this is thought to be one of the major factors in fatigue...
Creatine Phosphate levels fall rapidly at the onset of exercise, after a
period of roughly 30 secs levels may be as low as 5% of the prexercise
concentration. Consequenlty there wont be optimal levels of CP to
replenish ATP stores.
Creatine Phosphate fuels the ADP/ ATP conversion, as levels of CP
decline levels of ATP get depleted.
The ATP/PC system fuels the first few seconds of exercise...after which
anaerobic glycolysis takes place... a buy product of glycolysis is
Lactic acid, which casues a build-up in the muscle cells of Hydrogen
ions (H+) raising the p.H.... Which affects the process that exposes
actin cross-bridging sites (troponin) and permit muscle contraction. ATP
formation is also affected.
calcium ions (Ca++) are released from the sarcoplasmic reticulum by the
T tubules during muscle contraction and returned by the Ca-Pump.
Reduced sarcoplasmic Ca++ concentrations has been linked to fatigue.
Declines in force that can be produced have been linked to declined
levels of CA++ (Calcium ions). This is because decreased Ca++ released
reduces the number of actin/myosin cross-bridges that can be formed.
This is most likely to be due to impairement of the T-tubule. While
exercising potassium ions (K+)build up in the T-tubules, this is due to
the inability of the Na+K+ ATPase (breaks down ATP) Pump (sodium,
potassium atpase pump) to maintain the proper Na+/K+ balance at the
T-tubules. This affects the conduction of the action potential (these
cause movement to occur...like an electrical impulse) to the
sarcoplasmic reticulum, consequently Ca++ release is inhibited affecting
one's capacity to contract a muscle. lactic acid again builds yup here
and once again intracellular H+ concentrations increase, this then slows
the uptake of Ca++ by the sarcoplasmic reticulum, because the H+ affects
the pump. Therefore there is a marked reduction in levels of Ca++
As should be obviuos ATP is broken and provides the energy for
contraction (into ADP and Pi)this inorganic phosphate (Pi) builds up.
Increased Pi levels are thought to inhibit further cross-bridges being
formed between the filaments. As ATP is used to fuel the muscle
contraction, Pi is released from the myosin head. Increased
concentrations of Pi affects this from happening.
(
http://www.mesomorphosis.com/forums/...essage_ID=4723)
Date: 10/11/01 02:02 PM
Author: Angel Face (no profile)
Subject: RE: Intensity and Failure
That being said I can now continue...HIT popularized by Mike mentzer
(hope this doesnt open up the proverbial can of worms!)is based on the
premise that If you don't take your sets to failure, then you are not
presenting your body with the stimulus to adapt because you can
perform the appropriate amount of reps. Therefore as you take your
reps to failure, you are presenting the stimulus by forcing your body
to cope with something that it cannot do (remeber the original post!).
Consequently you adapt because you have forced yourself to do
something that it simply cannot do...seems logical and simple right!
But you have to ask yourself, why are so many powerlifters muscular if
they dont train to failure? as with olympic lifters!
...I take you back to the theory of rate coding..essentially you fail
in an exercise because there are not sufficiently rested muscle fibres
to perform the task...at the end of the set the only fibres that arent
fatigued are the low threshold high endurance motor units..which dont
have the neccessary force producing capabilities to perform the work.
I take you back now to the theory of supercompensation and the
subesequent breakdown and buildup theory that dictates that muscle
damage (catabolism) has to occur for the increase in proetin synthesis
to occur!...
...Research has shown that the most muscle damage occurs during the
negative paotion of the exercise (sarcomere popping!)...this is
because less muscle fibres are recruited to perform the eccentric
movemnt resulting in a greater stress on those fibres...consequently
by increasing the time that the muscle fibres are under tension (most
tension is generated during -ve portion) there in theory is a better
stimulus for muscle growth! ... from this it seems that more tension
can be generated by taking a set to failure than stopping short
because it would take longer to perform! keep this in mind!
...Back to rate coding (seems pretty important doesnt it?) as the
moment of failure draws closer the CNS will innervate all the motor
units it can to perform the reps and fire them as often as it
can...however as fatigue sets in there is a reduction in firing
frequency (up to around 70-80% I think!), consequently the rate of
twitching is not high enough to continue the exercise...thus failure
occurs.
...back to neural factors...as a nueron fires it has to release the
neurotransmitter Acetyl Choline so that the message can be
carried...as mentioned previoulsy the electrical current is passed
down the axon due to the na+ and K+ (when people refer to electrolites
in sports drinks like gatorad, lucozade, these is what they are
refering to), and the K+ Na+ atp ase pump... as failure approaches
(lack of firing) the electrolites become taxed...as failure occurs
these are virtually depleted...it is speculated that another of the
major factors in fatigue is the inability of the motor neurons to
create and release acetylcholine (ACh) fast enough so that
transmission of the action potential can be maintained from the neron
to the muscle...
It can be said that ability to produce force is dependant on power
speed and frequency of the 'electrical impulse elicited by the CNS to
contract a muscle...as fatigue develops there is a mared decrease in
the speed of these signals, as this occurs inhibitory mechanisms
(mentioned previuos) stop further contrcations occuring....
...However due to emotional factors lke psyching oneself up it is
possible to extend the time until these inhibitory mechanisms take
effect(fight or flight syndrome)...there is a ditinct relationship
between this and catecholamine levels...
...Therfore I hope that you can see that failure may not occur due to
the peripheral (muscle) factors but the Central ones...failure may not
be due to muscular fatigue but neural inhibition...the CNS does this
for one simple reason: SO THAT IT CAN REST AND RECOVER!
...If we are to believe the supercompensation theory muscle fibers
need to produce appropriate tension for a long enough period of time
to cause damage breakdown...this has the effect of growth factors to
be released in the cells Calcium levels within the cell must increase
toperpetuate both Catabolism and the required anabolic effect. Growth
stimuli may also be provided by the fatigue metabolites building up
(phosphate and hydrogen ions) due to elevated levels of lactic acid .
Please not that any of these reactions occurs because of muscular
failure!
It may become evident that failure is actaully detrimental (note to
John this would neccessiate the two factor theory, that has always
been rejected by bodybuilders) because too much stress occurs
(especially if inadequate rest intervals are used)...this would
facilitate the increasing levels of fatigue resulting in a faster
establishment of the Overtraining syndrome!
Probably the main point to take away from this is intensity and rest
should be monitored so to prevent the build up of fatigue and OTS
...Hope that wasnt too heavy I am drawing to a close soon on this
thread...It could keep going on forever...but I hope that at least its
made at least one person sit up and think about how they train and
that its not as simple as going into the gym and picking up a few
pieces of iron a few times....I hope you can bump this thread to keep
it active so that other people get to read it!
(
http://www.mesomorphosis.com/forums/...essage_ID=4748)