Anatomy of a Maximum Contraction

Setting The Proper Joint Angle

Can you really get stronger on 5 to 11 10-second isometric contractions per week? There are many reasons I believe you can, some of which I’ll explain herein, more to come in later posts.

In 1985-86, I had the privilege of regularly participating in presentations by Arthur Jones, inventor of Nautilus, demonstrating his exercise-rehab technology to audiences consisting of orthopods, neurosurgeons, DCs, PTs, and various exercise/rehab professionals. Jones was on his way to inventing MedX, a predecessor to Nautilus spawned for spine rehab purposes.

I was a Nautilus employee (flunky) and my role in the presentations was to demonstrate a testing/rehab session on either the lumbar or leg extension machine. While making numerous attacks on exercise orthoddoxy, seldom, if ever, did Arthur get an argument from an attendee.

Isometric Testing

I also witnessed various iterations of experiments in which Jones wrestled with physiological factors that are darn-near impossible to control and thus factor out of force readings. In other words, in “testing” strength it’s difficult to gauge the effects of issues such as:

  • Body mass in relation to gravity.
  • Compression of body fat stores.
  • Inertia (momentum).

Jones was meticulous in demonstrating for purposes of strength assessment that dynamic movement (aka: a repeition) is erratic, as it depends on the millisecond-by-millisecond effort of the testee.

Although this may look like a shoulder press, the handles on Arthur Jones’ MedX Medical Lumbar machine are to keep the torso stabilized while the lumbar is extended (leaned back). The machine both tests statically at various points along a range of motion, and once the movement carriage is unlocked,  used for dynamic repetitions.

Since Jones’ objective was to measure and show improvement in force output, he utilized static testing at a sequence of angular positions. And at each angle the testee was first assessed without exertion, about the same as if a scale were weighing torso mass, or stored energy (bodyfat compression). This assessment was then deducted from the output of the testee’s exerted force. Repeatable results came rolling in. This is why I appreciate ViiV-Rx Prescription Strength. It confirms what I learned from Jones – with one slight adjustment.

The Prime Joint Angle?

Jones tested static contractions at about every 12-18 degrees along a range of motion. If you’re sitting upright in a chair with your feet on the floor, your knee figures to be about 90 degrees (the lower leg position in comparison to the thigh).

The illustration below shows a bottom angle of 108 degrees, cocked back some from 90, then extending to almost straight, stopping at 6 degrees. This illustrates Jone’s angular positions of isometric strength testing of the thigh muscles. Repeatability in measurement depended on precise joint angles. Researchers at the University of Florida tested thousands of subjects to establish age-and gender-matched normative data, along with the configuration of a “normal” strength curve. The peak reading on the thigh muscle, I belive, was either 60 or 42 degrees. Here’s where ViiV differs from Jones. Jones believed all the angles where necessary for both testing and strengthening.

About 20 years ago, Pete Sisco developed training methods he first called “Power Factor Training” and later “Static Contraction Training.” His contention is that placing the muscles in the joint angle at which it’s capable of producing the most force recruits the optimum amount of muscle fiber, and therfore produced strength gains. Sisco claims to have resarch showing that his max contraction at a single joint angle produces strength gains at all angles – and I find that plausible.

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