Rolling of the arm/elbow during tricep extension

Question

Much to my frustration, my arm/elbow rolls inward towards the end of each movement when doing tricep extension exercises. Is this to be expected, or is there something I can do to prevent this?

To elaborate: On a seated machine, the resting position has the arms curled & inside of the elbow pointing towards the ceiling, parallel to each other. As I extend/straighten my arm against the weight, during the last ~1/3 of the movement, my upper arm & elbow rotate such that the inside of the elbows start to point towards one another. Total rotation probably doesn't exceed 30°, but i can feel how the loading in my tricep shifts as the arm rotates.

Answer 1

I don't think there's anything wrong with what you're doing. I'm writing this while sitting at the seated tricep extension machine.

If your machine is similar to this one, the handles are pointing straight at you. When you grip the handle, your grip is on the inside of your elbows. In the last third of the movement this means the handle and your arm aren't perfectly inline and so your arm rotates. The machine's handles would need to be angled out about 45° for your arm to remain straight, or pointed outward like this style of machine (using a supinated grip). You can try something like a reverse grip tricep extension on a cable machine to feel what it would be like perfectly inline.

The loading on your tricep you're feeling is probably the tricep moving through its full extension.