Cobra and Sphinx look similar — both are gentle prone backbends — but they differ meaningfully in arm position and how much extension they ask of the lower back.
Sphinx: forearms down, gentler curve
In Sphinx, the forearms stay on the mat with elbows under the shoulders, which limits how far the chest lifts and produces a milder, more sustainable spinal extension — often used as the gentler entry point.
Cobra: hands down, more lift
Cobra presses through the hands with elbows bent, allowing (though not requiring) a deeper lift of the chest and a stronger extension through the lower back.
Which to choose
Sphinx is generally the more accessible starting point for sensitive lower backs, since the extension is smaller and easier to sustain; Cobra can be introduced once Sphinx feels comfortable and more extension is wanted.
Can you switch between the two in the same session?
Yes — many gentle back-focused sequences use Sphinx as a warm-up extension and Cobra as a slightly deeper follow-up once the lower back has warmed up a little.