USAWA

By Dan Wagman, Ph.D., C.S.C.S.

THE GUESSING GAME – BOX SQUATS

Part II: Less Guesswork

“The progressive evolution of athletic performance and specific conditioning techniques is dependent on a thorough understanding of those mechanisms underlying dynamic muscular function.”(2)

In Part I, I presented someone’s guess that has huge intuitive appeal—that the box squat will enhance your squat strength and power for driving out of the hole. I made a guess, too, and to derive at it I asked what is perhaps the most important question anybody can ask about any training concept: by what physiological mechanism would that idea work? I could find none. The question is, might there be something going on that’s less well understood about muscle contraction mechanisms that might render the box squat a useful tool after all?

Our knowledge of how important the coupling and amortization phases (see Part I) are to you being able to produce maximal strength goes back to research published in 1931.(1) Back then, however, those phase-terms were not used. Since then research has built upon itself and advanced our knowledge of what we now term the stretch-shortening cycle. What all this scientific study would suggest is that the promise that performing box squats will enhance your regular squat is nonsense. But I wanted to verify or refute my “guess” based specifically on research that looked at the squat and box squat.

A First Look

I believe the best starting point to be research published in 1998.(2) The researchers recruited 40 athletes of various sports. They all had a minimum of 1 year squatting experience and could squat a minimum of 1.5 times their body weight. The entirety of testing methods are too complex to mention here, but to briefly illustrate included a modified Smith machine that measured and controlled speed of movement, among other things; a force plate to gather much data on force, power, work, etc.; electromyography to measure muscle contractions; and more.

The subjects were tested in three conditions: 1. They had to squat from the bottom position up, similar to a box squat. What was dissimilar to a box squat was that they had to first hold an isometric contraction for no more than 1.5 seconds before exploding upward; 2. The “stretch-shortening squat” was tested, which you may view as a normal competition squat with an intact coupling and optimized amortization phase; 3. The subjects had to perform a maximal isometric contraction against an immovable bar for 100 to 200 milliseconds before it automatically released and allowed the athletes to explode out of the hole.

Among many data points analyzed, the most important consideration for the strength athlete is that the greatest effect on the squat was achieved in the stretch-shortening condition, i.e., a regular squat. That was followed by the squat preceded by a maximal isometric contraction and lastly by squatting from the bottom up as in a box squat, which resulted in the weakest readings. In fact, the readings generated from the standard squat were more than twice that compared to the box squat style. The research team concluded that the quicker you transition from lowering the bar to exploding upward, the more strength you’ll be able to demonstrate. This finding is entirely in line with what you would expect considering the basics of muscle contraction mechanisms/physiology. Bottom line, you must have an intact coupling phase along with the briefest amortization phase possible. Only then can you expect to demonstrate maximal strength and power.

Still, because this was initial work done on the squat and how different methods of commencing the ascent might influence strength and power, there were a lot of methodological controls put in place. Researchers place a great deal of control into their studies in an effort to eliminate extraneous variables that might influence the outcome. In doing so, they obtain very specific and accurate information. From there, future research builds and looks at additional variables that might have an impact. And so it could be argued that since in this initial work the squat was performed with an empty bar and the speed of ascent could not exceed the 0.4 meters per second set by the modified Smith machine, no matter how hard each athlete tried, the squatting was not as specific to a regular competition squat as necessary for an accurate comparison. Of course the research team acknowledged this while outlining in painstaking detail the reasons for their approach. Moreover, it could be argued that when the subjects commenced the squat from a dead stop without pre-stretch or isometric contraction first, that movement pattern was not exactly the same as what’s generally advised in doing a box squat.

So far things don’t look good for the box squat, but the above concerns may or may not be valid, which means I had to dig deeper into the research advancements. Part III will look at comparisons between the actual box squat and standard squat.

References

1. Fenn, W.O., et al. The tension developed by human muscles at different velocities of shortening. American Journal of Physiology. 97:1–14, 1931.
2. Walsche, A., et al. Stretch-shorten cycle compared with isometric preload: contributions to enhanced muscular performance. Journal of Applied Physiology. 84(1):97–106, 1998.

By Dan Wagman, Ph.D., C.S.C.S.

THE GUESSING GAME – BOX SQUATS

Part I: Two Guesses

Like most guys and gals that got bit by the iron bug, I used to read all sorts of stuff about training. Once I came across something that seemed promising, I couldn’t wait to put it to practice in the gym, not to mention the torture I went through trying to manage the anticipation of huge gains. Of course those huge gains never happened, not until I learned about an area of scientific investigation called exercise physiology and started to apply what I learned. You see, that stuff isn’t based on guesses and conjecture. What I would like to share with you is a perfect example of why what might seem like really good training advice, when looked at from the perspective of human physiology, it couldn’t deliver as promised. My hope is that you’ll then be able to make more educated decisions about from whom to take training advice and what sort of questions to ask in your assessment of that advice.

The First Guess

It seems beyond obvious; for you to squat a ton of weight you have to be able to descend to below parallel in a controlled manner and once you hit depth you need to explode out of the hole in an effort to complete the movement. Nearly every lifter will tell you that the hardest part of the squat is blasting out of the hole. Naturally, this begs the question: might there be a method of training that’ll enhance your strength and power for getting out of the hole? Decades ago one very passionate powerlifter and coach came up with box squats for that very purpose.

The guess he made is that if you could squat down to a box that’s just the right height to break parallel, and you literally sat on it while rocking back, pausing on the box for one to five seconds or so, then blasted off it with all your might, you’d be able to increase the power you need to get out of the hole in a regular squat. This sounds really good. And so decades after the box squat idea was conceived tons of lifters still use it to increase their overall squat strength (though other purported benefits are said to exist). My guess, however, is that what seems to be such a good idea is far less than that when viewed through the lens of exercise physiology.

The Second Guess

The origin of my guess is based on the physiology of muscle contractions. Therefore, it’s really not a guess, but just humor me and let’s stay with the guessing theme.

When you squat down to depth your quad and glute muscles elongate, this is called an eccentric contraction (note that other muscles are involved, too, but addressing the entirety of functional anatomy and biomechanics is beyond the point of this article). When you reverse direction out of a deep squat, those same muscles shorten in what is termed a concentric contraction. For a very brief moment, as your muscles switch from eccentric to concentric, they contract isometrically. The linking of these contractions is referred to by some scientists as the coupling phase. Now, a fascinating thing occurs in your muscles during the eccentric phase of the squat—your muscles store elastic energy. As you reverse direction that stored elastic energy is released resulting in a powerful completion of the lift. The singular moment of switching directions is called the amortization phase and the entirety of what occurs here is often referred to as the stretch-shortening cycle. And here’s where another fascinating thing occurs; the longer the amortization phase, the more elastic energy is lost for the subsequent concentric contraction. Simply put, the longer the time you spend sitting on a box, the weaker you’d be during the ascent.

The above represents perhaps the most important amortization phase mechanism—reutilization of stored energy. Other proposed mechanisms include a stretch reflex, muscle-tendon interactions allowing muscles to remain at optimal lengths and to shorten at the best velocities, optimized muscle activation patterns, and increasing pre-force before the concentric contraction. Regardless of the mechanism(s) involved, it seems clear to me that the basics of muscle physiology deeply contradict the stated benefit of the box squat; as you sit on the box you’re increasing the amortization phase and ostensibly breaking the coupling phase, thus squandering valuable elastic energy. How could that possibly result in increased squatting abilities?

With that in mind, it’s well and good enough to reject the box squat. But is it possible that there is some component within the neuromuscular system that scientists have as of yet not discovered that would indeed warrant employing the box squat in your training? Could the original guess have accidentally hit on something? The way to get answers is to test the box squat hypothesis via controlled research. That’s what I’ll discuss in Part II.

Reference

Stone, M.H., M. Stone, and W. Sands. Principles and Practice of Resistance Training. Human Kinetics, 2007.