Re: Re: Explosive Strength deficit clarification

[Guest guest]

Ken Vick

> IMHO this one of the most under utilized and unrecognized areas in

> strength training today. Using Explosive Strength Deficit and Rate

> of Force Development measures can allow us to better design

> individual training programs that meet the athletes needs.

Unfortunately, not everyone has access to a force platform to measure

RFD and the more common position transducer type devices (IMO) are

virtually useless for assessing RFD.

> Which brings me to the need to use this at different stages of

> training. With a young athlete, or athlete with litle physical

> training background, the training is likely more GPP making use of

> the ESD (Explosive Strength Deficit) concept less/non important.

>

> A question I still have, and am not aware of much research on, is;

> Is ESD a plastic quality and to what degree?

>

> I have seen the ESD (measured by force plate) change over time, but

> only to a limited degree. Is this a basic quality of the neuro-

> mucular system that is set within some range of ESD?

The question is, if you have an athlete training in an " explosive

manner " for most (or all) of their training, regardless of the load

used, wouldn't you expect that all strength related qualities improve

proportionately? For example, if I can perform a squat with 200kg in x

number of seconds, and train for 8 weeks, and perform a squat with 220kg

in the same amount of time, my peak and average force production has

increased, but so has my ability to produce force rapidly, therefore you

wouldn't expect a (large) change in ESD. Research by Hakkinen et al.

(Acta Physiol. Scand. 1985) has found that typical weight training

improves force expression but not explosive force expression, however,

maximal acceleration weight training improves both force and explosive

force expression.

> Some authors have speculated that this is almost entirely related to

> muscle fiber type. I suspect that much of the literature is correct

> and fiber type has a very strong influence, but wonder if their

> aren't also neurological qualities that play an important role?

Good questions. All of the published research in human performance over

the past 20 or so years regarding RFD has only calculated the maximal

RFD (based on Viitasalo et al. Electromygr. Clin. Neurophysiol. 1980).

Although Zatsiorsky and others have proposed that other portions of the

force-time curve are important, no one has bothered to measure them, let

alone compare them to sporting movements. An abstract by Schilling et

al. (JSCR 2001) found correlations between isometric RFD and myosin

heavy chain expression and an abstract I was presenting at the IOC World

Congress (now rescheduled as part of the 2002 ACSM) compared RFD

variables with EMG variables. Both of these abstracts have looked at

RFD as an average, and as the " S- " and " A- " curves (based on Zatsiorsky

1995)

Komi (Intl. Conference on Weightlifting, Lahti, Finland 1998) suggested

that there was a " parallelism " between the force-time curve and the

EMG-time curve.

Recent work by B Macintosh has found that phosphorylation of the

regulatory myosin light chain (ie. muscle force potentiation) increases

RFD.

So RFD is affected by both muscle and neural factors, but so are other

force-time variables (and velocity and power variables as well). As a

scientist, I'm interested these relationships, but as an athlete, I'm

more concerned about the trainability of these variables (just in case I

have a lot of type I fibres , and I think it's fairly well established

that RFD is a trainable quality regardless of muscle fibre makeup.

Loren Chiu

Graduate Assistant

Exercise Biochemistry Laboratory

Human Performance Laboratories

The University of Memphis

[Guest guest]

Loren Chiu:

<The question is, if you have an athlete training in an " explosive manner " for

most (or all) of their training, regardless of the load

used, wouldn't you expect that all strength related qualities improve

proportionately? For example, if I can perform a squat with 200kg

in x number of seconds, and train for 8 weeks, and perform a squat with

220kg in the same amount of time, my peak and average force production

has increased, but so has my ability to produce force rapidly, therefore

you wouldn't expect a (large) change in ESD.>

Ken Vick wrote:

<<I see what you're saying, and think this is true for much of the movement in

the strength training continuum, but aren't there

some that don't fall in that range? Plyometrics are going to have

different effects from hypertrophic methods which will still be

different than maximal strength movements.>>

Force expression is much more complicated than simply looking at the

peak force (or average or RFD - Rate of Force Development - or whatever) for

similar movements. For

example, let's calculate ESD (Explosive Strength Deficit) for an athlete,

comparing their Fm (maximal force) from adepth jump to their

Fmm (force maximum maximorum) from a squat. Let's say we've done a great deal

of

pilot work and find that for this athlete, they produce maximal force

during an isometric contraction at x degrees hip, knee and ankle

extension. Then we measure their Fm performing a drop jump from a 50cm

box (because this is " specific " to their sport). We then calculate ESD,

as suggested by Zatsiorsky.

Here are the questions I would have:

1. Where did Fm occur during the drop jump? During the eccentric

landing, isometric pre-movement period, or the concentric rebound?

2. Did Fm occur at the same joint angles as when Fmm was measured?

3. If these biomechanical factors are not the same for measurement of Fm

and Fmm, can we compare them, knowing that force expression is more than

just the force production of the muscle (and involves a myriad of

factors such as the SEC (Series Elastic Component) stiffness of the muscles

(see GJ , various pubs), lever arm lengths, etc.)?

Similarly, I couldn't compare the RFD recovering from a snatch in the

full squat position to RFD during a vertical jump because the hip and

knee angles are different. So different training methods train

different muscle actions and portions of the force-time curve,

therefore, we can't simply use ESD to compare these changes to a

" standard " movement (Fmm). So ESD may provide a rough guide of " useable

force, " but unless we " clean up the system, " the apparent value may be

less than proposed

<<I was disappointed that was cancelled as I was presenting also

in a semi-related area. We did some investigations of professionals

hockey players and the relationship of different on-ice speed

qualities to jump performance in different conditions and also

evaluated the force time characteristics of the jumps with a force

platform. I believe you're right that this more in-depth analysis

will yield important information related to sport. Keep up the good work. >>

I received an e-mail last week that the IOC World Congress was

rescheduled to be held in conjunction with the ACSM conference this year

(the same message is now on the website:

http://www.iocworldcongress.com

Myself and a colleague will be presenting our abstracts there. I would be

interested in seeing your

results.

Loren Chiu

Graduate Assistant

Exercise Biochemistry Laboratory

Human Performance Laboratories

The University of Memphis

[Guest guest]

Loren Chiu wrote:

Force expression is much more complicated than simply looking at the

peak force (or average or RFD - Rate of Force Development - or whatever) for

similar movements. For

example, let's calculate ESD (Explosive Strength Deficit) for an athlete,

comparing their Fm (maximal force) from adepth jump to their

Fmm (force maximum maximorum) from a squat. Let's say we've done a great deal

of

pilot work and find that for this athlete, they produce maximal force

during an isometric contraction at x degrees hip, knee and ankle

extension. Then we measure their Fm performing a drop jump from a 50cm

box (because this is " specific " to their sport). We then calculate ESD,

as suggested by Zatsiorsky.

Here are the questions I would have:

1. Where did Fm occur during the drop jump? During the eccentric

landing, isometric pre-movement period, or the concentric rebound?

Casler writes:

Hi Loren, I would suggest that the Fm would occur in the " isometric moment "

between eccentric and concentric actions. This is the moment when all

external forces (in this case gravity/momentum) and all internal forces

(muscle tension, elastic tension, skeletal flexion, etc) are maximized. We

have to consider that measurable RFD on a force plate is always going to be

the graph of the external force plotted with the internal power forces and

the resulting relationship.

During the eccentric action the RFD (force plate) measurement can only rise,

but cannot peak until the external force is " equaled " (which happens during

the isometric transition moment) by the body's summed forces. So in the

contractile/tension " sandwich " the isometric is RFD winner as far as peak

force.

Loren Chiu wrote:

2. Did Fm occur at the same joint angles as when Fmm was measured?

Casler writes:

Only if the transition took place at exactly the same joint angles.

IF, care is taken to reproduce the same or essentially similar ROM for both,

then the translation of that profile will surely offer benefits and the

joint angles WILL probably see the similar numbers. This, of course is

entirely dependant on the " matching " of the external loading. The momentum

force of the jump would have to be calculated to produce the same force as

the weight load to see exact similarity.

[What do you mean by " momentum force " ? Momentum and force are two entirely

different physical quantities. Mel Siff]

Loren Chiu wrote:

3. If these biomechanical factors are not the same for measurement of Fm

and Fmm, can we compare them, knowing that force expression is more than

just the force production of the muscle (and involves a myriad of

factors such as the SEC (Series Elastic Component) stiffness of the muscles

(see GJ , various pubs), lever arm lengths, etc.)?

Similarly, I couldn't compare the RFD recovering from a snatch in the

full squat position to RFD during a vertical jump because the hip and

knee angles are different. So different training methods train

different muscle actions and portions of the force-time curve,

therefore, we can't simply use ESD to compare these changes to a

" standard " movement (Fmm). So ESD may provide a rough guide of " useable

force, " but unless we " clean up the system, " the apparent value may be

less than proposed

Casler writes:

I agree. I think the complexity of the external force, muscular force

(inclusive of SEC) the biomechanical effectiveness in the a particular ROM

and any existing or preconditioned Motor Activation Profile will ultimately

have to be considered in this equation.

Take for example the RFD of a clean with " RFD peaks " in the initial lifting

phase " and " the second pull.

I find this very interesting and the above are only my opinions. The reason

I have an opinion is not because I am a researcher (sure you can tell) but

because I have been working on a project that " explores " improving RFD as

one of its properties.

One of the " key " elements in " training " for maximum RFD is not losing site

of the fact that RFD is developed *against* something. The only way to

improve RFD is to provide an opposition force that provides a " stimulus " in

ALL areas that can be improved or trained.

[There is no situation in biological life where force or RFD are NOT developed

against something, either internal or external to the organism involved. Even

in

non-biological situations, Newton's Laws of Motion stress the same point. Mel

Siff]

Proprioceptively, it (RFD) can only be developed in an opposing relationship

and only in proportion to that relationship. If RFD has a limitation it is

that not all Ranges of a Motion are maximally opposed and thus not trained

(stimulated) maximally.

Additionally the another limit to RFD is in our ability to maximally

" preload " . The loading phase determines to a large degree the overall

characteristics and potential of the remaining action. It is not difficult

to adequately " load " the eccentric and isometric aspects, just slightly

dangerous if care is not taken since in many cases we are working on the

" outer limits " of tissue strength .

I think there are loading improvements that can certainly be made with

regards to the " least " maximized concentric muscle action. To realize these

improvements we need a method of " loading " that will require the force

generation in that concentric dominant ROM to be maximized. This will train

and improve the motor impulse profile and subsequently greater RFD (greater

acceleration) in these ranges.

This is rather simple in a totally vertical lift (clean, snatch, pull, etc)

by using CAT, but is virtually impossible in any weight-loaded angular

action, which are the majority of sports moves that require acceleration and

RFD. It is also difficult in submaximal or repetitive effort exercises

that require a portion of the action be reserved for " deceleration " which

sacrifices a potentially important segment. There are those already

addressing these " shortcomings " and results seem to be favorable. I would

also suggest that it " may " be possible to train, even the vertical lifts, in

another way that will offer RFD improvements.

I can guarantee that this method will lead to higher " readings " in RFD on a

force plate in the shortened concentric ranges I am referring to. I would

surmise from that, that eventually we would realize an increased (trained)

CNS response leading to greater " body " force in those ranges.

Interesting area.

Regards,

A. Casler

TRI-VECTOR 3-D Force Systems

Century City, CA

http://sites.netscape.net/summitfitnessco/homepage

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