Muscle Physiology 101 + HBBS vs. LBBS

Stole this from this thread. Read the whole thing for funsies if you’re inclined.

1) On force production: Why a lighter load moved at the same velocity as a heavier load CANNOT require the same (or certainly not more) force production by the skeletal muscles.

Statement: Force production as measured at the bar is less with the lighter load, of course. But it [force production] increases when one is pushing “harder” against the same load with less leverage.

No it doesn’t. Muscle physiology dictates that this is not the case. Pushing harder, i.e. producing more force through a series of muscular actions- which only pull technically, requires more force to be produced by both temporal (rate) and amount (number) of motor units firing.

These motor units, which make up the muscle fibers comprising the muscle belly, are either on or they’re off…period. To recruit them you either need to move the weight faster or add more resistance, both of which require MORE force production.

If there’s less weight being moved than a heavier weight at the same speed there is less total force being produced. There will, however, be some muscles that are creating “more” force in a HBBS than they would in an equally weighted LBBS due to the improved efficiency of the LBBS as compared to the HBBS. These muscles’ motor units, however, will not produce more force when compared to a heavier load- regardless of the leverage advantage/disadvantage. A 700lb half squat requires more force production than a 500lb ATG squat if they move at the same velocity- however it (the half squat) leaves muscle mass untrained and that doesn’t appear to be optimal. The HBBS both leaves muscle mass untrained AND reduces force into the bar.

2) On the bottom of the HBBS vs. the LBBS:

Statement: Not true. The bottom of the HBBs is less mechanically efficient on account of the more acute knee angle.

I don’t think you could actually say that the bottom of the HBBS is less mechanically efficient due to the acute-ness of the knee angle. The quadriceps are very strong…stronger than the hamstrings if we’re talking pure force production. Obviously joint angle, velocity of movement, etc. needs to be taken into consideration but the point is in a HBBS the quadriceps are lengthened MORE than in a LBBS and have a longer moment arm acting about the knee joint- potentiating more torque. This- coupled with a less horizontal back angle might be interpreted at being a more advantageous position except it doesn’t use the hamstrings and adductors as well as the LBBS, which is one of the reasons we can lift more weight using that squatting style- in general.

3) On general muscle recruitment when force production increases

Statement: Riddle me this. . . Let’s agree that LBBS allows for moving a heavier load than HBBS because it [the LBBS] places you in a position to recruit more muscle fiber (and it is not just a mechanical advantage). Now, an Oly lifter has to stand up a heavy clean. How does training that extra muscle fiber that is not used in standing the weight up — via the LBBS — help you?

A trained muscle can be recruited when the load is heavy enough (or velocity fast enough) to exceed that specific motor units threshold- and then it fires to perform it’s action(s). Strength, ie force production is a general adaptation that can be applied specifically. For instance, it your bench press goes up, you can swing a golf club faster because your force production of some of the muscles utilized to swing the club have been trained to produce more force. Somehow, these two activities are different.

Motor unit threshold is a muscle physiology principle, Henneman’s size principle to be exact, stating that larger size and higher threshold motor units are recruited sequentially (smallest to largest) when force output demands are increased. Thus there is a certain threshold of force generation required to move the load that is the impetus for recruiting the highest threshold (and largest sized) motor units. Heavy weight and/or high velocity are what does this, however the Westside percentages oft-repeated of 55-65% are woefully inadequate for getting these motor units to fire.

tl;dr> heavier squat (regardless of leverages)= more motor unit recruitment that are either 100% on or off based on the threshold either being met (or not) for their recruitment. More motor unit recruitment= more muscle trained= more gainzZz.

Golf Stuff:

Gordon et al., 2009 investigated the relationship of strength, power and flexibility to club head speed. The results showed a significant correlation between chest strength and club head speed

“These results are similar to those reported by Hetu et al., 1998 and Westcott et al., 1996 who studied changes in golf performance following a strength (Table 2) and flexibility training program. Significant increases in several physical fitness measurements (+6.2% grip, +14.2% chest press, +18.1% leg extension and +47.3% trunk rotation) were related to an improved drive performance (+6% in CHS)”

4) On muscle contraction, i.e. muscles only contract (shorten) and pull. NO muscles push and NO muscles radially expand to create force.

No muscles push or expand to create force. They shorten or create tension via cross-bridging in an isometric function. The muscle cells tend to draw things intracellularly in response to training, thus expanding- but this is on the micro level and is more of a hypetrophic stimulus vs. a force producing stimulus.

Statement about the heart radially expanding to create force: In essence, doesn’t the heart do exactly that? The heart “expands” every piece of itself “out” (in the direction of its own interior space), pushing blood along. The use of “expand” is interesting here — looking at the transverse thickness of the muscle rather than it’s length. But if you’ll remember, that was *PRECISELY* the comment (from Dave Paauwe) that got me talking about the heart.
 

The heart expands during diastole (both in atrial and ventricular diastole, which are separate events). When the atria relax (diastole) and expand, the ventricles are contracting (pulling from z line to z line of the sarcomere) to push blood out of the ventricle and into either the aorta or pulmonary trunk (as explained below). Radial expansion and increased pressure (to a point) of the ventricle itself stretches the muscle fibers eccentrically of the cardiac tissue, which optimizes their sarcomeric length at ~2.2um (Starling’s Law). If the heart becomes overfilled, the actin-myosin cross bridges are less abundant and the contractility is compromised. This is part the mechanism behind dilated cardiomyopathy/CHF. None of this has to do with a muscle fiber expanding to create force, however.

The heart “pushing” is actually a pull. The myofibrils are laid in series and contract in unison via gap junctions connecting cells, which turns them into a syncitium. The force of a radially constricting (not expanding) ventricle increases ventricular pressure to a point where it overcomes the pressure in the aorta, thus creating blood flow from ventricle to aorta. This is why when a person has aortic stenosis from either a calcified valve or congenital bicuspid aortic valve that left ventricular hypetrophy occurs, as this is an adaptation to the requirements for increased force production,(similar to skeletal muscle but no one ever asks me to flex my heart 😦

Interestingly, after the ejection (systole) of blood into the aorta (or pulmonary trunk from the right ventricle) occurs in 2 phases, a quick initial phase and a slower second phase. The second phase is driven mostly by the negative pressure (venturi effect) created by the 1st phase and quite literally, this pressure “pulls” the blood up thru the aortic valve. Similarly, the negative pressure also helps pull blood from the atrium into the ventricle as the aortic valve closes.

5) On specializing for Olympic lifting for the genetically average….
 
Statement: If I were trying to specialize in Olympic lifting, I might switch to primarily high bar, while obviously working on my front squat as well. That would allow me to use more weight than the front squat, without being quite as far from the catch position, since I am indeed a motor moron in many ways.
 

The logic involved in reasoning that the LBBS messes up the recovery of the clean is, in my mind, analogous to me making the argument that front squatting messes up the recovery of the snatch or, similarly, that doing the snatch messes up the clean with respect to receiving positions, grip, etc. They are markedly different, right?

 
I would also make the argument that if an athlete has a problem not being able to maintain a vertical-ish torso OR, more importantly, overcome a forward lean in a heavy clean recovery (like virtually all Internationally competitive WL’ers can and do when it actually gets heavy) that a LBBS would be more advantageous than a HBBS in improving this ability.

Statement on HBBS for average Oly enthusiasts: That’s obviously not conclusive, but I can see someone making the argument, especially if they want to do Olympic lifting, even though they don’t have the natural talent/aptitude to be elite.
 

That’s fair. Although just to be a contrarian (go figure), I would argue that a non elite, non athlete, is unlikely to have the genetic predisposition – and thus the explosive ability (e.g. Power) that he or she needs to be competitive. Since power is force/time- and they are lacking in the time department , it behooves THAT person- the genetically handicapped- to seek improvements in force production with greater vigilance than the “athlete”. Can you guess how I’d go about doing that?

 
-barbellmedicine