It’s not often I call exercises worthless, but in this case, I have no problem with it.
This exercise makes ZERO SENSE.
If you want to do a side plank, do a regular side plank. That engages the core muscles in the “anti lateral flexion” function as it’s called
Adding in an straight leg or bent leg isometric hold is flat out STUPID.
Not only is this position completely removed from any real life activity, it does a terrible job of training the adductors in the first place. And it’s immense valgus stress on the knee in a position it was NEVER meant to bear weight in.
The best way to strength the adductors directly is to use an adductor machine. Train their actual anatomical function.
If you do want to train them isometrically, Do a wide stance squat.
Even standing on one leg trains the adductors’ stabilization function.
If you don’t have an adductor machine, try this Cossack lunge. Or a conventional Wide stance squat.
This isn’t an “exercise”. It’s contrived hot garbage fitness industry horse**** that people are doing because they no ability for critical or independent thinking.