something to share with u guys,
“The velocity of the muscle contraction depends on the relation between the maximum isometric force capacity of the fiber and the magnitude of the force applied to the fiber. For forces less than the isometric force, the fiber will shorten. Conversely, the lenght of the fiber will increase when the applied force is greater than the isometric force.” (pg 258, Neuomechanics of Human Movement, Enoka)
So, does that mean a concentric contracrion is actually a “successfull” isometric contraction.
And an eccentric contraction is a “failed” isometric contraction???
TNT
not really…
but all movement either eccentric or concentric begins with an isometric, and the switch from eccentric to concentric and viceversa is seperated by and isometric muscle contraction.
Agreed. Interesting reading, I haven’t gotten to my Enoka text just yet still working on Siff’s Supertraining!
P.S. Is this why you think Shroeder has isometrics has a mainstay in his program?
SVS,
The more I see your questions along this line of training and interest in what Jay’s system is, it suprises me that you dislike DB Hammers Neuro-Dynamics Training System. Have you read through his book, and if so, did you understand it? I ask because your questions are geared towards topics that DB goes into depth on and explains the need for their placement within a training system. It seems, for as much as you seem to Dog on his style, you would already have an understanding on these topics.
the use of iso by jay schroeder is different from the reason that db uses them.
Taken from Supertraining:
" As muscle tension increases, intramuscular pressure also increases and
metabolism is unable to meet the physiological demands of the exercise,
resulting in a hyhperbolic drop in performance and marked increase in fatigue."
“Maintenancce of a maximal isometric contraction, however, depends ultimately on
autonomic repsonses produced by muscle fatigue or protective relfexes elicited
in the muscles or connective tissues. Motivation may overcome the negative
feedback from these tissues for sometwhat longer, but voluntary activation of
the muscles eventually becomes impossible and rest becomes necessary.”
"Isometric endurance with resistance exeeding 10-15 percent of a muscle’s
maximal strength is very short compared with that of dynamic exercise, because
of metabolic demands and the impairment in blood flow to the exercising muscles
by the intense muscle contraction (Petrofsky & Phillips, 1986).
Clearly, the value and utilization of the isometric regime leaves much to be explored, as much of what was initiated in the east has (to my knowledge) yet to be translated.
Interestingly enough, it would appear that a true isometric contraction is only able to exist at relative short durations.
As the duration of contraction increases (either under loadless or loaded conditions) the nature of the contraction will inevitably end in muscle relaxtion as fatigue will set in and result in the inability to maintain the static contraction.
Thus, under loadless isometric action (eg pulling/pressing against immoveable object) the end result is relaxation, and under loaded isometric action (eg weights) the sequence is eccentric action followed by relaxation.
James Colbert,
I know DB’s reasoning for using ISO’s, so please explain how Jay’s differs. I understand at time he uses longer duration holds, but beyond that, how do they differ in understanding, philosophy, and application.
the east? are asain countries doing research into isometrics our are u talking about easter block countries.
James, I was referring to the former USSR/Eastern bloc Europe
James, what do you think of this? Could ISO’s be thought of as similar to EMS? Say 10 sec contractions for sprinters and six seconds for very strong athletes like throwers or lineman? Of course this comparison can only be in terms of muscular contraction, because EMS bypasses the CNS.
I do not have any sold answers for use of isometrics but I think one way Jay uses the is to fatigue the slow twitch muscle fibers so your body calls upon more powerful muscle fibers to complete the lift…for example in a dynamic iso-bench press when the athlete pushes up against someone holding the bar at their chest their weaker muscle fibers fatigue, then the stronger fibers kick in and when the bar is released the stronger fibers complete the lift…not sure but I think this is what Jay talks about in his video. 
In addition to what James posted; Also, from Supertraining
Pg 46 “Ligaments become stronger and stiffer when subjected to increased stress, and weaker and less stiff when the stress is decreased”
45, “Tendons, together with other series elastic components, particularly after termination of powerful isometric or eccentric contractions, play a vital role in storing elastic energy during locomotion and other motor acts, thereby saving energy and increasing muscular efficiency.”
I could be wrong in my intrepretation about the post on pg 45 concerning energy efficieny and muscular efficieny but I believe other “motor acts” are the crucial words.
Pg 46, " With more specific reference to muscle tissue, it has been proposed that ST fibres may be able to sustain cross-bridge attachments for a longer period of than FT fibres…Therefore, the former would utilize the elastic energy stored in their cross-bridges more efficiently during slow movements. In addition, this process may be augmented by the behaviour of the connective tissue in each given muscle in determining the ability of the slow and fast muscles to perform different types of work… Slow muscles with their greater content of strongly cross-linked collagen would then be more adapted to slow contraction, since the fairly rigid collagenous connective tissue would resist fast contraction. The less rigid connective tissue in fast muscle, on the other hand, would facilitate fast movements with greater changes in form."
I could be wrong but the above quote implies,
- Using isometrics will incoporate more ST Fibres then doing a regular con-ecc contraction. So that afterwards, when one goes back to the normal con-ecc lifting he will be stronger at the bottom (i.e. bench press) bc now he will be able to utilize more ST fibres then before. The reason for this is simply that normal lifting does not trigger all of these fibres only a percentage of them. Using isometrics will allow the lifter to utilize more of the ST fibres. And since we all know that ST fibres are recruited before FT fibres then this has great implications; however, I could be wrong and that more overall fibres are incoporated in isometrics then normal con-ecc lifting. This would mean more ST and FT fibres overall as opposed to one or the other. In either case the athlete benefits and its a win-win situation!
You posted while I was replying to funny! 
no ems is not the same thing or even close in similarity to isometrics. althougth ems as perscribed by charlie francis ( 10 sec on 50 off) is an isometric contraction. this type of ems can only be used apart from other types of training. with proper machines ems can be applied while performing other activities. For example ems while bench pressing. the muscle is not “frozen” up as in convential ems application.
the concept of slow twitch fibers being recruited before fast maybe a outdated one. there has been research showing that fiber recruitment is more dependent on the task, and pyschological state. for example if you perform a ballistic action the first fiber to be recruited will be the fastes. as motor patterns become more effecient this phenomnon is even more prevalant ie it is more likly that during balistic actions the proper fiber type. i believe u were eluding to jays EDI excercises. involvement of slow twitch fiber in explosive activities is not desiarable type IIb fibers trained in oxyget debt is the goal of this type of training, that and maximal motor unit involvment.
elars21, I agree with James Colbert in that the comparison between EMS and short duration high intensity Isometrics is not a wise one, despite your reference to comparing the muscular contraction.
EMS elicits an involuntary muscle response and the variablity of the pulse frequency cannot be compared to the volitional muscular contraction as expressed by isometrics.
Additionally, I feel that it is important to note the motor tasks performed/developed by varying the muscular effort during various isometrics.
As Siff states; when considering short duration high intensity isometric contractions one may develop absolute strength or explosive strength.
As Siff states the ‘rise or attack time’ (duration to reach peak force) is a key determinant as to defining the muscular effort. A ‘slow’ rise/attack time lends itself to absolute strength development. A brief or rapid rise/attack time will yield greater developments in explosive strength.
Which fibers are you referring to in your first sentence here?
How much do we know about the ability of ST fibers to reach and sustain tension?
slow twtich fibers do maintain their filamint attachment slightly longer but their endurance comes more from available energy substrates.