An iso-hold, in muscular training, is about maintaining muscle contraction under pressure. In other words, it is about holding the position at the peak of the contraction against the force (whichever it is between the good old gravity, a band, a pulley or anything else) that wants to return the weight to its starting point. That “peak” of contraction will normally be in the middle of the movement, between the end of the contraction and the beginning of the controlled release.
As an example, the iso-hold of a pull-up would be to hold yourself at the “top” position, where you are closer to the bar (or farther from the ground).
So if you’ve been following, an iso-hold rep would be to do an iso-hold at the peak of each rep. Taking back our pull-up example, you would lift yourself to the bar, hold for a few seconds, drop back down, and restart those steps until you’re too tired to continue.
I know, there is nothing revolutionary about this, in fact, you probably already knew all that, the longer you hold, the harder it gets.
But I thought that the subject deserved to be talked about, because it can be interesting for a few things like raising mind-muscle connection, increasing difficulty and just exhausting the targeted muscles even more.
I use this technique for movements that I feel weak at. If I take the pull-up again, I can only do 5 or 6 of them, so adding an iso-hold to each rep make me work a little more. The logic behind this is that it increases the time that the involved muscles are under tension, and more tension means more damage to the muscles. Consequently, this damage will be turned into gains, whether it be more endurance, more strength or more muscle fibers. So in the case of my pull-ups, because I’m not able to do as many reps as I should, adding iso-holds with each rep lets me work the muscles a little more without the need for more reps.
The other time I use it is for muscles that need special attention. For example, I tend to have knee pain when walking/running for long distances (by “long distances” I mean more than a few kilometers without breaks, which is generally exceptional circumstances for most people). So I try to strenghten the VMO muscle (Vastus Medialis Oblique, a part of the quadriceps which is sometimes called the “water drop”) which often grows slower than its counterpart and disrupts the knee mechanics. The exercises I choose for this part are the split-squat and other similar movements such as the reverse lunge.
So when a muscle is lagging behind, like my VMO in this example, it will also be harder to “feel”. But then, using a movement that is known to solicite the said muscle and holding it at the toughest point (the peak) will make it come forward because it will start to “burn”. That burn will confirm that you are indeed using the appropriate movement for what you are looking to achieve. Repeat the process for long enough will slowly resensibilize the muscle and someday it will probably act like it should.
In some cases, an iso-hold may be useless, like in the case of biceps curls, where the peak contraction is also at the easiest point. To obtain the same effect, we just have to use an elastic band.
Iso-holds are a nice way to crank up the difficulty of a training without the need for any specialized equipment. It can be incorporated into any workout program as it won’t necessitate any change to it other than just holding reps for longer when doing them. However, don’t go crazy about it by adding holds to every exercise in your program because it will probably become more of an annoyance than anything. Like I said ealier, choosing movements that you feel the need for a little more work would probably be the right choice. Try it and see if it helps.