We are familiar with different modes of exercise: isometric, isotonic and isokinetic. Isometric exercises have a physiological overflow of 10 degrees on each side of the point of application (ie; to do the exercise at 20 degrees flexion, and you have strength gains from 10 to 30 degrees); isotonics and isokinetics, 15 degrees. Taking advantage of physiological overflow often allows us to bypass painful ranges of motion and still strengthen in that range of motion.
In this study, they looked at immediate and 45 minute later pain reduction (not function) comparing isometric (max voluntary quadricep contraction) and isotonic (single leg decline squat) exercises. They also looked at cortical inhibition (via the cortico spinal tract) as a result of the exercises.
Here is what they found: “A single resistance training bout of isometric contractions reduced tendon pain immediately for at least 45 min postintervention and increased MVIC. The reduction in pain was paralleled by a reduction in cortical inhibition, providing insight into potential mechanisms. Isometric contractions can be completed without pain for people with PT. The clinical implications are that isometric muscle contractions may be used to reduce pain in people with PT without a reduction in muscle strength.” These same results were not seen with the isotonic exercise.
Did the decrease in pain result in the decrease in cortical inhibition (muscle contraction is inhibited across an inflamed joint: Rice, McNair 2010; Iles, Stokes 1987)? Was it a play on post isometric inhibition (most likely not, since this usually only lasts seconds to minutes post contraction) ? Or is there another mechanism at play here? There has been one other paper we found here, that shows cortical inhibition of quadriceps post isometric exercise. Time will tell. In the meantime, start using those multiple angle isometrics!