Ankle control for bodily tension
A slight tweak in the ankles might just help you garner the tension necessary to hold pristine form.
The first example would be the first love of every hand balancing initiate. In the frog stand, flexing your ankles will generate more tension in the glutes, allowing you to feel AND control the lower extremities more. Holding/altering the position in midair becomes easier when both the upper (especially those fingers in contact with the ground ) and lower body is tensed into one congruent piece.
Dorsiflexing in a side plank is a must for 3 reasons. There are only 2 points of contact with the ground in the side plank, it is paramount to have that ankle dorsiflexed at a minimum of 90 degrees for the best stable support. Secondly, having that leg by the ankle under tension facilitates the side plank hold as you fatigue. Thirdly, activating and loading the ankle from the side, builds the lateral fascia of the body in it’s entirety , essential in clients who have bow shaped legs (genu varum). Concentrically loaded or locked short muscles from the medial portions of the leg and thigh cause the legs to bow and thus cause elongation on the other (lateral) side.
When the ankles are plantarflexed, it increases glute engagement and renders it more tangibly. This translates to less forward swing when performing a pullup as the posterior muscles hold the legs back. In terms of fascia lines, dorsiflexing will make the abdominals and the whole front (anterior) of the body work harder and the glutes less.