Arthur’s Misadventures with Acceleration On the Human Knee
by Ken Hutchins
Slamming Into Lockout
In 1982, Arthur Jones created much excitement with the Nautilus DuoSquat machine. He motivated Jim Flanagan and several other large men to experiment with high-repetition sets of 50 repetitions per leg. Putting the nonsense of such repetition schemes aside, I was more appalled with the violence Arthur permitted in form.
Arthur decreed that the seat be set so that the subject could straighten each of his legs under the selected load. As Arthur pushed Jim Flanagan and others through their DuoSquat routines in the prototype shop, they habitually fired out of every stretched position and slammed into every lockout. As a result of Arthur’s insistence in the gym, these subjects (employees) echoed his dictum to “completely straighten the legs” to Nautilus customers.
At Nautilus Seminars I instructed customers to set the seat so that lockout was impossible.
I established lockout as a serious liability concern. I also declared that lockout was discordant with Nautilus Philosophy. It unloaded the desired musculature, excessively compressed the spine, excessively loaded the neck musculature, and was unduly dangerous.
Arthur’s closer henchmen reported to him that I was countermanding his protocol regarding the DuoSquat. I did not fear Arthur’s wrath, because I was his only willing and eligible pigeon slated for guard duty at the Nautilus-funded Osteoporosis Research Study.
As a result, Jim Flanagan orchestrated my trip to the woodshed, so to speak. As Jim and others observed from a distance, Arthur patiently explained and justified his recommended protocol for the DuoSquat. This meeting occurred just before commencement of the Osteoporosis Study in late 1982. I now surmise that it was crucially important that I be on board with Nautilus marketing of the DuoSquat if it were to be a financial success.
I admit that I did learn from Arthur during this mild cross examination. He showed me how he had designed the cam radius—reduced only so far (force increased) as to not exceed bone integrity. He calculated a safety margin and stayed on the safe side of that margin. (1,174#?)
Arthur also explained that he had designed the seat tilt at such an angle (approximately 30 degrees) to the movement-arm line of force so that approximately 1/2 of the force (Sine 30 degrees) was supported through the pelvis and backpad, not the spine, shoulders, and shoulder pads. This I had not considered.
I then presented Arthur with my reservations of lockout. I also raised a question: “Are we using the machine to defeat the machine or to fatigue the muscle?” [Note that this was my first intellectual consideration and expression of the Assumed vs Real Objective Argument.] He then threw a rhetorical question at me: “Ken, do you realize, upon reaching lockout, that the force doesn’t suddenly jump from the muscles onto the bones? The bones are supporting the load throughout the movement, not just suddenly at lockout?”
I replied that I had not considered the possibility that such a fear was lurking in my mind and affecting my bias. And I promised to reflect on the matter for a while to examine his protocol recommendations in light of this possibly irrational fear as well as his other points recently shared.
Indeed, The Force Does Jump From the Muscles Onto the Bones at Lockout!
I left for the Osteoporosis Project in October 1982. After unsuccessfully incorporating the DuoSquat into the workouts for our study subjects for 6-8 months I wrote Arthur the following memo sometime in mid-1983:
Approximately a year ago, we discussed my reservations regarding the safety of lockout during the performance of the DuoSquat. You speculated that my bias was the result of an unacknowledged and irrational assumption. The supposed fear: the resistance force suddenly jumps from the muscles onto the bones at lockout.
Although this notion may or may not have been lurking beneath my conscious process, you certainly planted the seed for its complete fruition. Note that five sources of force converge at lockout:
Disconnect the chain from the movement arms on the Duo Squat. Then place the subject as you dictate—seat so close that he can just barely lockout his legs against the frame of the machine. Here the subject encounters maximum force from body compression, movement arm flexion, pad compression, etc. Denote this machine force.
Once reconnected, the negative cam is at its smallest radius, hence its greatest resistance provision at lockout. Denote this cam force.
At lockout the quadriceps are no longer effecting knee rotation. They exert a force encouraging translational movement of the tibia into the femur. Denote this quad force.
At lockout the hamstrings are no longer effecting hip rotation. They exert a force encouraging translational movement of the tibia into the femur. Denote this hamstrings force.
The screw-home property of the knee results in maximum stability at lockout. This occurs in part because the cruciate ligaments contract as they twist on one another akin to twisting the opposite ends of a dish rag. This tightly approximates the ends of the tibia and femur. But if the knees are violently extended, this contraction is so forceful that the cruciates are commonly avulsed, carrying sizable chunks of their moorings with them. Denote this cruciate force.
As a result of lockout in the DuoSquat, five forces promoting translational shortening of the body converge at lockout. Therefore—in effect—these forces do suddenly jump from the muscles onto the bones at lockout.
As usual, no reply came from Arthur. But his reaction to my letter was unmistakable at the next Nautilus Seminar. He and his henchmen—other than me—began to warn customers to set the seat as I had detailed. A protocol involving lockout was no longer permissible or deemed safe. No one mentioned or dared to remember that it was once recommended.
My letter to Arthur was much too sanitized. It did not mention or account for acceleration forces resulting from the recklessly ballistic behavior that I observed by Arthur’s closest associates while using the DuoSquat.
Acceleration was the Big One. Acceleration forces accounted for the greatest threat to the human body during the DuoSquat. And acceleration accounts for the greatest force threat generated during all human movement, even that during a weightless environment. By this I do not mean to entirely distract the reader away from the points I belabored in my letter to Arthur. In fact, those issues so mentioned are more glaringly egregious because of the acceleration!
I did not mention acceleration in the letter, because I intended a purely static analysis, and because I knew that the subject of acceleration would cause tremendous defensiveness on the part of Arthur. He already considered himself extremely sensitive to acceleration effects, while I saw through his weakness on the subject.
The effects of acceleration indicate that subjects encounter excessive force merely by slamming their knees into lockout when under no external load. The wide-spread ignorance of this fact often engenders false critical analysis of the proper design and use of all exercise equipment. Specific to this discussion are exercises involving the knees: knee extension, knee flexion, and leg press or squat.
As I have belabored for over 20 years, that without the speed being controlled consistently at excursions of 8-12 seconds, camming, body placement, load points, attitude, alignment, and other factors are of secondary consequence.