Eccentric Quasi-Isometrics (EQIs) (Siff 1994) are not your ordinary type of strength training. Or stretching. (Yes, both are happening during this exercise!)
As such, they may be able to deliver results and benefits that you won’t see with any other type of training.
Please notice that I say, may be able to. This statement means that no DIRECT research that I know of has been done on the effects of this specific type of muscle action.
All of the information I’m presenting to you here is based on either published research on topics indirectly related to EQIs or on anecdotal evidence gathered from the real-world application of EQIs with athletes, and from my own experience.
Make no mistake about it, the effects of EQIs have not been written about in many places, but know that everything I’m sharing with you is theory, based on direct anecdotal and indirect empirical evidence.
What are EQIs?
EQIs are essentially just what the name says:
- Eccentric: The muscles are lengthening as they are contracting.
- Quasi-Isometrics: The action is very slow (nearly static).
First, some basic muscle physiology that forms the basis for EQIs.
The three element muscle model says this: Muscle is made up of, or constituted by a CONTRACTILE element (CC), and two ELASTIC (aka spring) components, one in series with the CC (SEC) and the other in parallel (PEC).
1. Contractile Component (aka element) (CC): what creates active tension in the muscle
2. Parallel Elastic Component (PEC): passive tension – works in parallel with the CC. The
PEC is responsible for passive flexibility.
3. Series Elastic Component (SEC): under tension whenever the CC is under tension, e.g.
works in series with the CC. The SEC is responsible for dynamic (active) flexibility.
A graphical representation of the 3-Element Muscle Model. (Source: “Tendinitis: its etiology and treatment” by Sandra Curwin and William D. Standish)
The graphic gives you a visual representation of how this looks.
What does this mean?
Let’s cover some basics in as simple terms as I can. (I’m going to include a few footnotes too, because I made a record of these when researching many moons
*Remember, when a muscle is lengthened, tension is produced (think of stretching a rubber band).
*Lengthened muscle represents the flexibility of that muscle.
*There are two types of flexibility (tension), passive and active.
• Active = moving. Muscle force or dynamic activity produced throughout a ROM.
• Passive= non-moving. Static, produced at a certain (usually extended) ROM.
As this relates to the CC, PEC, and SEC.
*Traditional stretching methods typically only stretch the PEC. If the emphasis is put on traditional methods of stretching, then primarily the PEC will become more flexible.
*When you stretch traditionally, the SEC are not lengthened or stretched. This worsens the ratio of passive (which the PEC is responsible for) to active flexibility (which the SEC is primarily responsible for).
**This is one reason why some experts/researchers have linked traditional stretching to increased injury risk (Lashvili 1982).