The fitness world is fraught with ill-defined terms. It is possible that “strength training” is the most egregious offender in this realm. Ask ten fitness professionals and you will most likely get some variation of weight training. Ask a yogi and you’ll get a different answer. Most unfortunate is the public, and to a certain extent the medical community,when equating strength training with traditional weight lifting and bodybuilding. The deeper this mindset sets into a community, the less likely understanding and appreciation of subtle strength training techniques are.
The physiology and kinesiology community recognize three main types of muscular contraction: concentric, eccentric, and isometric. They are defined as follows:
- Concentric Muscle Contraction: When a muscle becomes shorter in length (and increases in girth) as a result of neural stimulation. Typical example – upward phase of an arm curl.
- Eccentric Muscle Contraction: When a muscle increases in length (and decreases in girth) despite being activated by neural stimulation. Typical example – controlled downward phase of an arm curl.
- Isometric Contraction: When a muscle experiences no change in length where the neural stimulation is insufficient to overcome a given resistance. Typical examples: halting and holding an arm curl in the middle range of motion or attempting to arm curl the bumper of a big truck.
This seems pretty simple right? If not I will provide clarification by categorizing the movements presented in the exercise catalog by these terms so that as you progress through the material you will develop a better understanding.
To optimize the gains in functional strength it is necessary to emphasize all three of these types of contractions. Specifically training only one of them provides only minimal cross-over to another. To illustrate this we turn to the arm curl once again:
Perhaps you were to do arm curls in a manner that eliminated the downward, eccentric phase of the movement. A partner could take the weight from the top of the movement after completing the concentric phase (thigh to chest) and hand it back to you at the thigh, where you would complete the next concentric repetition. In this instance you would, over time, enhance your capacity in the upward, concentric phase, and likewise your partner would gain in the eccentric strength required in the lowering phase.
A functional application of this would be seen in placing and removing an object from a shelf. After three months of training, you and your hypothetical partner were passing back and forth a weight with a maximal single repetition capacity of a little over 100 pounds. When you and your partner are both faced with a 98 pound object, a shelf at chest height, and a chair at thigh height. You would easily be able to lift this package up onto the shelf; your partner would not. When removing the object from the shelf, your partner would be able to lower it to the chair easily, where as you would likely pull the object from the shelf and it would proceed to drop like a stone. You may suffer trauma and strain if you fully engaged against this resistance. This is an example of specificity of training and a real world effect.
It is also important to note that the eccentric phase partner would experience much more muscle soreness after each training session.
Provided the previous description of muscle contraction is both clear and interesting to you, ask us a question, or check back with us to further understand some of the variability that can be applied to these types of contractions.