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View Full Version : Neural "Overload": A Mechanism?



PowerManDL
08-18-2003, 03:09 PM
I happened across these two on Pubmed:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8786037&dopt=Abstract

Synaptic feed-backs mediated by potassium ions.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6913470&dopt=Abstract

Muscle fatigue due to changes beyond the neuromuscular junction.

It looks like they explain our mechanism for the "overload" effect on the peripheral nervous system when maximal reps are performed.

The muscle releases K+ ions when the nerve impulse reaches the end-plate, releases acetylcholine, and stimulates Na+ release in the muscle.

This process, which changes the membrane potential, is mediated through the muscle by the T-tubules. This change in membrane potential stimulates the release of Ca++ ions from the sarcoplasmic reticulum.

Apparently, what we're looking at is a mechanism by which the K+ released causes inhibition in the release of acetylcholine from the axon end-plate, especially during high-frequency stimulation. Additionally, it seems there's some mechanism by which the T-tubules or sarcoplasmic reticulum become damaged as well during high-frequency stimulation.

High-frequency stimulation is what occurs during maximal reps, I should add....when the CNS is firing impulses rapidly in order to recruit the maximal amount of fibers.

So...it appears we've got a conditionally-inhibitive factor here. I would postulate that the damage to the T-tubule or sarcoplasmic reticulum, along with possible damage to the end-plate by K+ ions, is the mechanism behind the extended recovery time in maximal repetitions.

WillKuenzel
08-19-2003, 10:24 AM
So its saying that K+ ions are extending the recovery period (well not really just that but the process that follows)? So if there were a way to reduce the amount of K+ ions released then recovery might be quicker?

Fix the links and that might help too. ;)

chris mason
08-19-2003, 11:56 AM
Homeyield, if you reduce the potassium, which is integral to neural propagation, don't you think that might hamper the old contraction a bit?

PowerManDL
08-19-2003, 01:38 PM
Ok, fixed the links.

I'm not so sure if the inhibitory effect on the synapse and end-plate results in any significant "damage"-- I remember reading something about it awhile back, but I'm looking for info on it now.

And yeah, inhibiting K+ isn't something you want to do, since as Chris noted it's pretty key to transmitting the impulses.

However, it does appear that the T-tubule and/or sarcoplasmic reticulum, both of which are downstream from the junction and inside the muscle fiber, undergo some structural changes that inhibit their capacities after being exposed to high-frequency impulses.

My thinking is that one of those factors, or a combination, is responsible for the "neural shock" effect of maximal reps. In other words, its compelling evidence (in addition to the empirical) to keep maximal reps infrequent....and that, by avoiding the high-frequency neural output of max reps, you could train a *lot* more frequently without experience negative effects.

WillKuenzel
08-19-2003, 02:01 PM
Gotcha.

What are you meaning by maimal reps? Training to failure (max effor) or one rep maxes?

PowerManDL
08-19-2003, 02:02 PM
Any rep-maximum. From the body's standpoint, the effect is nearly identical.

WillKuenzel
08-19-2003, 02:11 PM
Aight but by not training towards failure you lose those positive results of training that close right?

Even though recovery is quicker and you can train more often, are you still getting all the benefits of training towards failure? I guess what I'm wanting to know is the cost analysis (or pro's and con's) to training sub-maximal.

Where would the line be drawn to get the best of both worlds?

PowerManDL
08-19-2003, 02:23 PM
Well, the only real benefit of hitting failure is the increase in strength that occurs during the maximal rep. In terms of hypertrophic response, it doesn't really do anything.

So for someone concerned with sheer size, you'd ideally want to avoid it as much as possible. As hypertrophy tends to be brought about best by a gradual increase in loading, working to a RM every 3-4 workouts would be an option.

For someone concerned with strength, you'd want to find a way to sequence in max sets with submax sets.

What I'm doing is varying the assistance work over the 4-week waves I use for my core movements. Start out submaximal, multiple sets, increasing the weight and decreasing the sets until the final week, when I work up to a new RM.

An approach for someone not interested in my esoteric methods would be to simply have a light day and a heavy day each week. The light day would have 4-6 sets, submaximal, and the heavy day would have 1-2 maximal sets.

WillKuenzel
08-19-2003, 02:31 PM
I can understand the wave approach better based just on how my body would want to respond although I'll admit the technicalities elude me.


Say for sheer size then, does this lend more support for HST or is there another option that you might recommend?

Blood&Iron
08-19-2003, 04:24 PM
Originally posted by HomeYield

Say for sheer size then, does this lend more support for HST or is there another option that you might recommend?

What he outlines here is completely in line with HST. Leaves out a few things which HST advocates (the strategic deconditioning, decreasing rep ranges, etc some of which are advocated for injury prevention as much as anything) but it doesn't contradict anything.

Also, while using HST, I've found it quite effective to use a higher number of sets at lesser %s of my rep maxes, and decrease them as I approach my maxes (as he's outlined for someone more concerned with strength)


Originally posted by PowerManDL
Well, the only real benefit of hitting failure is the increase in strength that occurs during the maximal rep. In terms of hypertrophic response, it doesn't really do anything.

So for someone concerned with sheer size, you'd ideally want to avoid it as much as possible. As hypertrophy tends to be brought about best by a gradual increase in loading, working to a RM every 3-4 workouts would be an option.

For someone concerned with strength, you'd want to find a way to sequence in max sets with submax sets.

What I'm doing is varying the assistance work over the 4-week waves I use for my core movements. Start out submaximal, multiple sets, increasing the weight and decreasing the sets until the final week, when I work up to a new RM.

JuniorMint6669
08-28-2003, 02:00 PM
Originally posted by PowerManDL
Any rep-maximum. From the body's standpoint, the effect is nearly identical.

Hey powerman- very interesting stuff. I had two questions though.

1. Is failure due to lactic acid buildup (pain) the same? I assume not, but I really have no idea. Ive been incorporating light weight high rep sets at the end of some workouts for lactic acid tolerance, and it seems to carry over well to my heavier sets, but I take it to "failure" and beyond sometimes. Ouch it burns ;)

2. Isolation vs. Compound failure. Do K+ ions affect total recovery, or are they muscle specific? ie If I reach failure on calf raise, will it extend the recovery time of the entire body, or just calves? Also, does failure on an Isolation movements release the same amount of K+ ions? eg bicep fails = failed curl vs. quads fail, hams come in and fail, glutes come in and fail, adductors come in and fail = failed squat.

Thanks for your time :D

PowerManDL
08-28-2003, 03:00 PM
Originally posted by JuniorMint6669
Hey powerman- very interesting stuff. I had two questions though.

1. Is failure due to lactic acid buildup (pain) the same? I assume not, but I really have no idea. Ive been incorporating light weight high rep sets at the end of some workouts for lactic acid tolerance, and it seems to carry over well to my heavier sets, but I take it to "failure" and beyond sometimes. Ouch it burns ;)

No...failure due to lactate accumulation is a totally different animal. H+ ions build up and cause electrochemical interference with the propogation of the nerve impulse. Its not the same effect.


2. Isolation vs. Compound failure. Do K+ ions affect total recovery, or are they muscle specific? ie If I reach failure on calf raise, will it extend the recovery time of the entire body, or just calves? Also, does failure on an Isolation movements release the same amount of K+ ions? eg bicep fails = failed curl vs. quads fail, hams come in and fail, glutes come in and fail, adductors come in and fail = failed squat.

No no...nothing like that. This is a purely local effect, occuring at the junction between the muscle fiber and the neuron connected to it.

eatdirt40
08-28-2003, 03:40 PM
so what does this all mean in a conclusion

PowerManDL
08-28-2003, 04:52 PM
You're not good at this whole "reading comprehension" thing, are you?

JuniorMint6669
08-28-2003, 08:45 PM
Thanks powerman. You're such a smarty... i really enjoy reading your posts on AL and FI boards. Do you see anything wrong with me doing lactic acid training- as far as hindering my gains?

eatdirt-- your sig is really... really long... just thought id let you know ;) And in conclusion, dont take things to failure very often, especially if you are concerned with hypertrophy.

Oh powerman- one more question. How does this relate to someone not loooking for hypertrophy, but rather looking to maintain LBM while dieting? Would it be OK to reach failure at this time, or would it be more catabolic? If it was okay, maybe doing strength cycles while cutting to maintain LBM and strength? Thanks again :D

Scott S
08-28-2003, 09:09 PM
By rep-maxes, are you talking about 1RM, or of taking a low-rep set to failure?

If it were the latter, then (assuming hypertrophy were the goal) it wouldn't be very advisable at all to push for that last rep, would it?

JuniorMint6669
08-28-2003, 10:19 PM
Scott S:


Originally posted by PowerManDL
Any rep-maximum. From the body's standpoint, the effect is nearly identical.

Good question still... if you squeeze out that last rep, you didnt really hit failure, did you? Or maybe you did and then stabilizers came in and took over. I guess ill shut up and let powerman answer our questions :D

PowerManDL
08-28-2003, 10:20 PM
Originally posted by JuniorMint6669
Do you see anything wrong with me doing lactic acid training- as far as hindering my gains?

Not really, no.


Oh powerman- one more question. How does this relate to someone not loooking for hypertrophy, but rather looking to maintain LBM while dieting? Would it be OK to reach failure at this time, or would it be more catabolic? If it was okay, maybe doing strength cycles while cutting to maintain LBM and strength? Thanks again :D

Its about stimulus. If you're maintaining LBM, you'd ideally want to be sending your calories towards muscle as much as possible, meaning you'd still want a frequent growth stimulus.

PowerManDL
08-28-2003, 10:21 PM
Originally posted by Scott S
By rep-maxes, are you talking about 1RM, or of taking a low-rep set to failure?

If it were the latter, then (assuming hypertrophy were the goal) it wouldn't be very advisable at all to push for that last rep, would it?

Failure is failure. The only difference between a 1RM and an 8RM, in terms of the last rep, is the fact that the weight on the bar is higher.

Scott S
08-29-2003, 01:02 AM
Okay. Guess I should've read HomeYield's question more carefully.