T Nation

MU Recruitment Patterns and Fatigue

Here’s a question I’m hoping someone can help me with. When multiple sets are performed each to concentric failure with high intensity (high weight) e.g. six sets of five RM are the high threshold MU’s that where recruited in set one still being recruited in set six where accumulated fatigue results in the use of much lighter weight, or, with the lighter weight are only lower threshold MU’s recruited? Its got to be one of two possibilities either the higher threshold MU’s are still activated but the fatigue they have accumulated in the previous sets results in the lower weight, or, the accumulated fatigue prevents the higher threshold MU’s from being recruited and instead the work is performed by lower threshold MU’s hence the lower weight. Which one is it?

First off I don’t know many people that need to do 6 sets of 5 reps if your goal is fatiguing the high threshold MU’s (type IIB’s). See how many sets it takes you to hit what Poliquin calls the “critical drop off point”, using the starting weight, where performance decreases significantly from one set to the next, for most people it’s 4 or 5. From there, move on to a new exercise. But do NOT lower the weight and continue to squeeze out lower tension sets of 5. You are not turning off the HTMU’s, the accumulated fatigue requires you to lower the weight, but these are merely low tension “junk sets” and are a waste of your time. If you were to lower the weight significantly and follow up your 5’s with a moderate-high rep set, that could aid in hypertrophy of some of the other fiber types, but once you can no longer perform sets of at least 3-4 with your starting weight, provided adequate rest and or antagonist training between sets, you have significantly fatigued the IIB’s with that exercise. Remember strength is highly neural, and the N.S. takes far longer to recover than the muscular system.

Thanks for the answer Marc, I was beginning to wonder if anyone would reply. In the intervening time between posting and your response I was able to source an answer to the MU recruitment under fatigue conditions question, but your information regarding critical drop off point was new to me, is this detailed in Poliquin’s Principles book? Or was it in an article? Your recommendation to keep the weight fixed rather than lowering it and performing junk sets seems a valid one, a simple comparison test of the two regimens and the gains I make will provide the final answer. Tell me though, would this rationale apply to sets of 10RM? When hypertrophy is the goal would it be better to keep the weight fixed and perform successive sets of lower reps, or lower the weight and expose the targeted MU’s to a possible higher volume of work? (relative to individual differences in tolerance to lactic acid build up determining how much the weight would have to be decreased).

Craig, Poliquin has discussed his critical drop-off point numerous times, it’s been a while since I’ve read “Poliquin Principles”, but as I recall it is described with percentages given. Ian King echos this concept (without the catch phrase) by reccomending moving on to a new exercise before lowering the weight, more total movements=more angles to stimulate the fibers=more hypertrophy. I would not lower the weight even in 10RM sets unless you are adding reps (ex. 2x10@225lbs, 1x15@195lbs)or using drop sets. It sounds to me like you may be using to many sets per exercise, I used to do the same. Generally speaking (exceptions apply) for strictly hypertrophy purposes I would not reccomend more than 2 or 3 sets per exercise unless you are trying to improve neural adaptions to that specific movement (i.e. training for a bench press contest, or specificaly targeting the type IIB’s). Achieve your higher volume through adding exercises, drop sets, or Tellekinetics methods (if you haven’t read Beyond 2001 by Jerry Telle, make that your next book). Think of it like this: you go to a bar with your girlfriend and some guy grabs her ass, not knowing you’re a T-man. So instinctualy, you drop him. While your fist was in flight, another guy grabs her ass. Guy #1 is out cold, do you sit on his chest and pummel his face into a coma, or do you drop guy #2? Hopefully you’d drop guy #2, and if there’s a guy #3, you’d move on to him instead of wasting time with the unconscious fellas on the floor. Hint Hint- the guys represent muscle fibers, so hit 'em hard, leave 'em alone, and move onto the next ones! Then take your T-vixen home and have rowdy sex with her!
One of my best methods for inducing hypertrophy is by starting the workout with strength/neural training- heavy weight, low reps(1-5), higher sets, long rest with compound movements, then dedicating the second half of the workout to the opposite, high reps, low rest, low sets, isolation movements. Motor Units are activated from low threshold to high threshold, so after the first half of your workout, you’ve activated a large pool of Type I’s, IIA’s, IIX’s and IIB’s, but only properly fatigued the B’s and some X’s. The second half will trash the remaining fibers to leave you with a great hypertrophic response assuming your nutrition is up to speed. Definately use a during workout drink for this one. Let me know what you think.

my understandin is IIBs and IIXs are two dif names for the same thing… also poliquin describes the drop off at 7% strength drop off…

Hi Marc, sorry for the late reply but it’s been a public holiday/long weekend here in Australia and I’ve been away from the computer for a couple of days. I was looking back through the files I’ve copied and pasted from t-mag and I came across the following, it’s from one of Charles’s Q&A columns back when he was still writing for testosterone net, I didn’t copy the issue no. though so I can’t tell you which one.

Q:Could you settle an argument that I had with my training partner about drop sets? I would just kick my partner’s ass, but I married her a few years ago and wish to get laid in the new millennium. When using drop sets on the Scott curl, I say that you should perform about four reps, and then drop the weight. But my wife says to do the usual 8-12 reps to failure, and then lower the weight for another set. If our main goal is size, which method is best? Should we just alternate between the two?

A: The truth of the matter is that you’re both right. Each of the methods will work. There are many synonyms for this training technique: down the rack, railroading, suicide sets, etc. Even in the earliest scientific literature on determining the best loading parameters for strength development, drop sets were found to be superior to standard sets for increasing maximal strength. Exhaust the higher threshold fibers first and, as you lower the weight, prolong the time under tension of the worked muscle groups.
Mode A
Drop sets for a fast-twitch person

  1. Perform four rep maximums.
  2. Drop the weight by 10-15% and perform as many reps as possible (probably one or two).
  3. Drop the weight by another 10-15% and perform as many reps as possible (probably one or two).
  4. Rest, then do another two to three drop sets.
    Mode B
    Drop sets for a fast-twitch person
  5. Perform two rep maximums.
  6. Drop the weight by 5-7% and perform as many reps as possible (probably only one).
  7. Drop the weight by another 5-7% and perform as many reps as possible (probably only one).
  8. Drop the weight by another 5-7% and perform as many reps as possible
    (Probably only one).
  9. Rest, then do another three to four drop sets.
    Mode C
    Drop sets for a normal fiber distribution type
  10. Perform eight rep maximums.
  11. Drop the weight by 5-10% and perform as many reps as possible (probably three or four).
  12. Drop the weight by another 5-10% and perform as many reps as possible (probably three or four).
  13. Rest, then do another two to three drop sets.
    Mode D
    Drop sets for a normal fiber distribution type
  14. Perform six rep maximums.
  15. Drop the weight by 20% and perform as many reps as possible (probably 12).
  16. Drop the weight by 20-25% and perform as many reps as possible (probably 25).
  17. Rest, then do another one to two drop sets.

As I interpret it Charles sees no problem in dropping the weight when doing RM sets (by sets 3 or 4 you would have to to complete the requisite no. of reps). The concept of the critical drop off point you introduced me to would refer to the point where volume becomes counterproductive.
As I’ve just started with this type of RM lifting regimen, I’ve yet to determine what will be my own optimum no. of sets,(an easy enough thing to determine, start with a fixed no., then lower it and compare results), theory gets anyone only so far, then individual differences necessitate trial and error to see what is optimal. Strange you hardly ever here any of the experts say that though, it’s usually a case of my way or the highway, I guess because much of their writing is geared towards the program in a can reader.
Are you familiar with “Designing Resistance Training Programs” by Fleck and Kraemer? They identify an RM continuum citing it as the best guide to developing a particular feature of muscular performance, e.g. <6RM for 1RM strength development, 6-12RM for Hypertrophy, 12-20RM for local muscular endurance. Using the exact resistance that allows only a specific number of repetitions to be performed is superior to using a % of 1RM, they state, to illustrate this they give the example of a trainees who varied in there performance on a leg press machine with reps ranging from 12-22reps when asked to perform a set to concentric failure at 80% of their 1RM. Those trainee’s who where able to perform 22 reps would if using that % of 1RM for strength development be in fact training lower threshold MU’s more conducive to local muscular endurance training.
RM training is obviously not the only type of training that produces results, but maybe the most optimal? Charles states in the above that it has been shown to be superior to straight sets (e.g. fixed weight reaching failure on last rep of last set) at least in the incarnation of drop sets.
Me I couldn’t say. Straight sets and simple periodization alternating on a weekly basis between sets with reps of 5 or 8 or 12 saw my dumbbell bench press go from 6x5x22kg to 6x5x40kg naturally. So I know they work, at least for me. But then I plateaued and despite trying numerous strategies with volume and/or intensity manipulation could progress no further. Hence my interest in RM set workouts. Will it work? Only time will tell.
You say you do both high and low rep workouts in the same session to exhaust all your muscle fibres? I’ve heard of tacking a back off/up set on to low rep workouts to add an element of hypertrophy to a strength workout but not much beyond that, mostly because of the sub-optimal performance when undertaking the 2nd mode of training due to accumulated fatigue/energy substrate depletion etc. The questions of excessive volume and the diminishing effectiveness of the periodization of rep ranges when the muscle is exposed to the whole range of reps all the time (something I.K. has written of) also come to the fore. But as I said earlier theory takes you only so far, then trial and error must take place, and if this style of training is producing results for you great. Given my own recovery ability though I’m not sure my body would be able to handle it. The concept you mention of multiple exercises for a body part when training with high reps is one I’m familiar with.
Thanks for your replies Marc. I was going to say, obviously either no one else knew the answer to my original question or they couldn’t give a stuff, but if you ask a simple question like what your favourite bicep exercise is you get a gazillion replies!
But that was before dman’s reply, but still, two respondents out of the thousands that access the forum, jeez!
So many thanks both of you for your replies dman and especially Marc, they have both been of tremendous help and I greatly appreciate it.