Muscular contractions are divided into different categories based upon its action, Concentric, Eccentric, Isotonic and of course Isometric. Today we talk about Isometrics, which is loosely defined as a contraction, taking place without movement of the joint. Much like a bodybuilder flexing a muscle, this is a type of isometric contraction. But how can we use this technique and secondly why would we even want to do this.
Two words, physiologic overload. Discovered by Tim Kent when looking at isometric contractions on the knee found that by holding the contraction at 90 degrees and ad gradually increasing the force for 10 seconds, he found that the subject didn’t just get stronger at the 90 degrees (which was expected) they also got stronger at the 10 degrees above and below 90 degrees. So we can apply that to nearly all joints in the body, not just in the knee. The key is to train various joint ranges and if you stay in a pain free ROM you can begin to strengthen the entire joint.
We can use this in a post rehab setting when managing the client after physical therapy. They may still show functional deficits in a particular joint, let say the shoulder, and they may illicit pain in certain points of the ROM. By stopping and performing an isometric contraction just before and beyond the painful area we can “sneak up” on the muscle and begin strengthening it without putting the client in pain. In a Core Stix External Rotation place you as the trainer will have to put the Rod under resistance and then have the client hold the contraction. Begin with you holding 100% of the resistance and their hand is just basically resting on the rod. Then slowly for the entire 10 seconds you release the resistance slowly and they are now taking it up. By the end of the 10 seconds they should be holding the entire resistance.
For our active aging client we can use isometrics the same way but we can also use it to increase workload in nearly any exercise. One of my favorites to do this with is the Core Stix Scapular Stabilizing Presses. With the rods in C3, initiate the move by performing an external rotation, then when their arms are perpendicular to their body have them perform a press. Then perform a unilateral press with the right arm while the left arm is performing a scapular stabilizing isometric hold. Alternate sides. One of the best advantages to this is that when the body is performing this contraction, the amount of spinal stability will be magnified.
This is a simple way to not only rehab the client but also turn up the volume of one of our core upper extremity exercise