Toes to sky variations

In 2000 (and on a few other occasions) I published and claimed copyright on this exercise description (bolding added now):

Toes to sky variations :

Description – lay on your back, arms out on the ground at 90 degrees to the trunk, have your legs together, 90 degrees hip flexion so that legs are vertical.

Level One – lift the pelvis as far off the ground whilst maintaining totally vertical leg position (initially this may not be very far at all, at even at best the movement is limited in its range) and hold for 5-10 seconds

Level Two – as above, but bend one knee to 90 degrees at knee, alternate each rep which leg is bent, which is straight

Level Three – as above, but bend both knees so that the knees are bent to 90 degrees

I was conducting research and I came upon the following exercise in a publication copyright claimed by another 'author' at a subsequent date (bolding added):

Toes to sky variations :

Description – lay on your back, arms out on the ground at 90 degrees to the trunk, have your legs together, 90 degrees hip flexion so that legs are vertical.

Level One – lift the pelvis as far off the ground whilst maintaining totally vertical leg position (initially this may not be very far at all, at even at best the movement is limited in its range) and hold for 5-10 seconds.

Level Two – as above, but bend one knee to 90 degrees at knee, alternate each rep which leg is bent, which is straight

Level Three – as above, but bend both knees so that the knees are bent to 90 degrees

And I said to myself: “That looks familiar!” So I cross-referenced it and I said to myself: “Wow! No wonder that looked familiar!”

And I came upon this description another two more times by the same 'author' in different publications.

I noted that the use of this description was in the absence of credits or references to the origin or permission to use from the original author (myself), and that the 'author' claimed copyright....